WorldWideScience

Sample records for vlf emissions observed

  1. Numerical simulation of whistler-triggered VLF emissions observed in Antarctica

    Science.gov (United States)

    Nunn, D.; Smith, A. J.

    1996-03-01

    The British Antarctic Survey VLF database from Halley (L=4.3) and Faraday (L=2.3) stations, Antarctica, has been searched for clear examples of whistler-triggered emissions (WTEs). Dominant events were the triggering of risers or quasi-constant frequency emissions from the upper arm of a whistler. A fairly frequent occurrence was the triggering of steep fallers from the whistler upper arm. At Faraday most WTE events were the triggering of long steep risers from the lower whistler arm. A VHS/VLF Vlasov hybrid simulation code was run and successfully simulated the main categories of WTE: risers and fallers off the upper arm and risers from the lower arm. Agreement with observations was generally very good, although in the case of triggered fallers and risers from the lower arm, very high frequency sweep rates were not obtained. The Vlasov code is highly efficient and well suited to this problem.

  2. Numerical simulation of whistler-triggered VLF emissions observed in Antartica

    Energy Technology Data Exchange (ETDEWEB)

    Nunn, D. [Southhampton Univ., Southhampton (United Kingdom); Smith, A.J. [British Antarctic Survey, Cambridge (United Kingdom)

    1996-03-01

    The authors have extracted from VLF databases from British Antarctica Survey data taken at Halley and Faraday stations, examples of whistler-triggered emissions (WTE). The WTE are relatively narrow band emissions triggered by natural background whistlers undergoing nonlinear wave particle interactions generally in the equatorial regions. They occur with either rising or falling frequency relative to the triggering waves. Using a Vlasov type code the authors are able to simulate the types of emissions which are observed. 24 refs., 8 figs., 3 tabs.

  3. Some unusual discrete VLF emissions observed at a low-latitude ground station at Agra

    Directory of Open Access Journals (Sweden)

    B. Singh

    Full Text Available A detailed analysis of the VLF emissions data obtained during occasional whistler campaigns at the low-latitude ground station Agra (geomagnetic latitude 17°1' N, L = 1.15 has yielded some unusual discrete VLF emissions of the rising type. These include (1 emissions occurring at time intervals increasing in ge ommetrical progression, (2 emissions occuring simulta neously in different frequency ranges and (3 emissions observed during daytime. In the present study, the observed characteristics of these emissions are described and interpreted. It is shown that the increasing time delay between different components of the emissions match closely with the propagation time delays between different hops of a whistler of dispersion 19 s1/2, the unusual occurrence of the emissions in two different frequency ranges approximately at the same time may possibly be linked with their generation at two different locations, and the occurrence of emissions during daytime may be due to propagation under the influence of equatorial anomaly.

  4. Features of discrete VLF emissions observed at Gulmarg, India during the magnetic storm of 6–7 March, 1986

    Indian Academy of Sciences (India)

    R Singh; A K Singh; D Siingh; R P Singh

    2007-12-01

    During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147° 09′E, L = 1.28) during moderate magnetic storm activity ( $K^{−}_{P}$} = 32, index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain. In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions. In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions.

  5. VLF wave emissions by pulsed and dc electron beams in space. I - Spacelab 2 observations

    Science.gov (United States)

    Reeves, G. D.; Banks, P. M.; Neubert, T.; Bush, R. I.; Williamson, P. R.

    1988-01-01

    The properties of radio waves generated by electron beams in space were investigated using data from the wideband wave receiver on the Spacelab 2. The VLF observations were found to confirm the results of the STS 3/OSS-1 mission. It was found that a 1-keV electron beam injected from the orbiter produced copious broadband electromagnetic emissions. When the electron beam was square-wave modulated, narrow-band emissions at the pulsing frequency and harmonics of that frequency were produced along with the broadband emissions. The observations indicated that dc 50-mA electron beams and pulsed 50-percent duty-cycle 100-mA beams produce broadband radiation which is comparable in intensity and spectral shape at all points for which the wave field was sampled.

  6. Quasi-periodic VLF emissions observed during daytime at a low latitude Indian ground station Jammu

    Indian Academy of Sciences (India)

    K K Singh; J Singh; R P Patel; A K Singh; R P Singh; Rejesh Singh; P A Ganai

    2009-06-01

    This paper reports quasi-periodic pulsing hiss emissions recorded during daytime in the frequency range of 50 Hz –15 kHz at low latitude station Jammu (geomag.lat.=22° 26′N; =1.17). It is noted that pulsing VLF emissions are a rare phenomena at low latitudes.The various spectrograms of pulsing VLF hiss emissions presented in this paper clearly show band limited spectrums regularly pulsing with almost equal period of the order of few seconds in the frequency range of ∼3-8 kHz. Generation and propagation mechanism of these emissions are briefly discussed.

  7. Auroral pulsations and accompanying VLF emissions

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    V. R. Tagirov

    Full Text Available Results of simultaneous TV observations of pulsating auroral patches and ELF-VLF-emissions in the morning sector carried out in Sodankylä (Finland on February 15, 1991 are presented. Auroral pulsating activity was typical having pulsating patches with characteristic periods of about 7 s. Narrow-band hiss emissions and chorus elements at intervals of 0.3–0.4 s formed the main ELF-VLF activity in the frequency range 1.0–2.5 kHz at the same time. The analysis of auroral images with time resolution of 0.04 s allowed perfectly separate analysis of spatial and temporal variations in the auroral luminosity. Mutual correspondence between the behaviour of the luminous auroral patches and the appearance of ELF noise type hiss emissions and VLF chorus trains was found in two intervals chosen for analysis. While the hiss emissions were associated with the appearance of luminosity inside a limited area close to the zenith, the structured VLF emissions were accompanied by rapid motion of luminosity inside the area. The spatial dimension of the pulsating area was about 45–50 km and luminosity propagated inside it with velocity of about 10–12 kms. We discuss a new approach to explain the 5–15 s auroral pulsation based on the theory of flowing cyclotron maser and relaxation characteristics of ionosphere.

    Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions · Space plasma physics (wave-particle interactions

  8. Propagation properties of quasiperiodic VLF emissions observed by the DEMETER spacecraft

    Science.gov (United States)

    Hayosh, Mykhaylo; Němec, František; Santolík, Ondřej; Parrot, Michel

    2016-02-01

    Quasiperiodic (QP) emissions are electromagnetic waves in the frequency range of about 0.5-4 kHz observed in the inner magnetosphere that exhibit a periodic time modulation of the wave intensity, with modulation periods from a few seconds up to 10 min. We present results of a detailed wave analysis of nearly 200 events measured by the low-altitude Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft. Upper frequency range of studied emissions was limited to 1 kHz due to the sampling rate of the analyzed data. It is found that QP emissions propagate nearly field aligned at larger geomagnetic latitudes; they become more oblique at midlatitudes and eventually perpendicular to the ambient magnetic field at the geomagnetic equator and thus perpendicular to the Earth's surface, allowing their downward propagation through the ionosphere. The observed propagation pattern is consistent with the source of emissions located in the equatorial region at larger radial distances.

  9. Investigation of propagation properties of quasi-periodic (QP) VLF emissions observed by the DEMETER spacecraft.

    Science.gov (United States)

    Hayosh, M.; Santolik, O.; Nemec, F.; Parrot, M.; Hanzelka, M.

    2015-12-01

    Quasi-periodic (QP) emissions are whistler mode electromagnetic waves which are observed in the inner magnetosphere, either inside the plasmasphere or near the plasmapause. They exhibit a periodic time modulation of the wave intensity with the modulation periods from several seconds to minutes. The analysis of wave propagation properties of nearly 200 QP events measured by the low-altitude DEMETER spacecraft (altitude 700 km) shows that QP emissions generally propagate nearly field-aligned at larger geomagnetic latitudes (> 55 degrees) and they become more oblique at mid-latitudes (latitudes of 45 degrees). However, we have observed several QP events with unexpected variations of both wave and Poynting vectors directions over a short time/spatial interval at larger latitudes. These seem to contradict the general statistical results. We perform a detailed analysis of three such events. All these events were observed during quiet geomagnetic conditions (Kp < 2). A ray-tracing calculation is used to determine the wave paths and the locations of the generation regions. We also discuss the influence of the plasmapause on the wave propagation.

  10. Bispectrum Analysis of Non-linear wave-wave Interaction between VLF Transmitter signal and ELF emission on the Basis of DEMETER satellite observations

    Science.gov (United States)

    Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Kasde, Satish Kumar

    2016-07-01

    Symmetric sidebands are observed in the ionosphere by the DEMETER (Detection of Electromagnetic Radiation Transmitted through Earthquake Region) satellite, when it passes above the Indian VLF transmitter, named VTX (18.2 kHz), located near Kanyakumari, India. The spectral boarding phenomena may be divided into two types: (1) spectrally broadened components occurring without any association with ELF/VLF emissions under disturbed ionospheric condition, (2) Spectrally broadened components with predominant side band structure in association with ELF emission. Generally spectral analysis at second order (Power spectrum) is used to analyze the frequency component of signal, but it losses the phase information among the different Fourier components. To retain this information the bispectrum (third order) and/or the bicoherence (normalized bispectrum) are used. Results suggest a non-linear mode coupling between the transmitter signal and ELF emission which produces sidebands that are quasi-electrostatic in nature. However, faint spectral broadened components in both types 1 and 2 may be connected with Doppler shift of quasi-electrostatic, whistler mode waves with a broad spectrum near resonance cone, due to scattering of the transmitter signals from ionospheric irregularities in the F-region. Keywords: spectral boarding, wave-wave Interaction, whistler mode waves and Doppler shift

  11. Similar behaviors of natural ELF/VLF ionospheric emissions and transmitter signals over seismic Adriatic regions

    Directory of Open Access Journals (Sweden)

    M. Y. Boudjada

    2008-11-01

    Full Text Available We report on the analysis of ELF/VLF emissions observed by the Instrument Champ Electrique (ICE experiment onboard the DEMETER micro-satellite. We consider principally selected seismic events reported by Molchanov et al. (2006. These authors studied the VLF signals radiated by ground transmitters and received on board the DEMETER micro-satellite. They revealed a drop of the signals (scattering spot connected with the occurrence of large earthquakes. In our investigations, we proceed to a spectral analysis of ICE observations with the aim to find if the natural ionospheric VLF/ELF emissions show, or not, a similar ''drop'' in the intensity as it is the case of the VLF transmitter signal. We combine our results with those of Molchanov et al. (2006, and we discuss the origin of such interesting ionospheric features in the frame of the investigation of the pre-seismic electromagnetic emissions. We show that the geomagnetic activity is a key parameter which could disturb the natural VLF ionospheric emissions, and also the transmitter signal. We find that it is not possible to conclude the presence, or not, of a preseismic effect when the Kp-index is higher than one.

  12. Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters

    Energy Technology Data Exchange (ETDEWEB)

    Belov, A. S., E-mail: alexis-belov@yandex.ru; Markov, G. A.; Ryabov, A. O. [Lobachevsky Nizhni Novgorod State University (Russian Federation); Parrot, M. [Environment Physics and Chemistry Laboratory (France)

    2012-12-15

    The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

  13. Observations of the impenetrable barrier, the plasmapause, and the VLF bubble during the 17 March 2015 storm

    Science.gov (United States)

    Foster, J. C.; Erickson, P. J.; Baker, D. N.; Jaynes, A. N.; Mishin, E. V.; Fennel, J. F.; Li, X.; Henderson, M. G.; Kanekal, S. G.

    2016-06-01

    Van Allen Probes observations during the 17 March 2015 major geomagnetic storm strongly suggest that VLF transmitter-induced waves play an important role in sculpting the earthward extent of outer zone MeV electrons. A magnetically confined bubble of very low frequency (VLF) wave emissions of terrestrial, human-produced origin surrounds the Earth. The outer limit of the VLF bubble closely matches the position of an apparent barrier to the inward extent of multi-MeV radiation belt electrons near 2.8 Earth radii. When the VLF transmitter signals extend beyond the eroded plasmapause, electron loss processes set up near the outer extent of the VLF bubble create an earthward limit to the region of local acceleration near L = 2.8 as MeV electrons are scattered into the atmospheric loss cone.

  14. Prediction Capabilities of VLF/LF Emission as the Main Precursor of Earthquake

    CERN Document Server

    Kachakhidze, Manana

    2013-01-01

    Recent satellite and ground-based observations proved that in earthquake preparation period in the seismogenic area we have VLF/LF and ULF electromagnetic emissions. According to the opinion of the authors of the present paper this phenomenon is more universal and reliable than other earthquake indicators. Hypothetically, in case of availability of adequate methodological grounds, in the nearest future, earth VLF/LF electromagnetic emission might be declared as the main precursor of earthquake. In particular, permanent monitoring of frequency spectrum of earth electromagnetic emission generated in the earthquake preparation period might turn out very useful with the view of prediction of large (M 5) inland earthquakes. The present paper offers a scheme of the methodology according to which the reality of the above given hypothesis can be checked up. To prove the prediction capabilities of earth electromagnetic emission we have used avalanche-like unstable model of fault formation and an analogous model of ele...

  15. MAGNETOSPHERIC VLF LINE RADIATION OBSERVED AT HALLEY, ANTARCTICA

    OpenAIRE

    J. P., MATTHEWS; K., YEARBY

    1980-01-01

    Spectrograms of broad-band ELF/VLF goniometer data obtained from ground based measurements made at Halley, Antarctica (L=4.3,conjugate near St. Anthony, Newfoundland) have shown the presence of discrete line radiation of magnetospheric origin, in the frequency range 1-4 kHz. The properties of this radiation are broadly similar to Power Line Harmonic Radiation (PLHR), studied from ground based observations made at Siple, Antarctica (L=4.1,conjugate-Roberval, Quebec), although there are some in...

  16. Subionospheric VLF signatures and their association with sprites observed during EuroSprite 2003

    DEFF Research Database (Denmark)

    Mika, A.; Haldoupis, C.; Marshall, R.A.;

    2005-01-01

    national lightning detection network. The VLF observations were made in Crete, Greece with a narrowband receiver, and in Nancay, France with a broadband receiver. The storms were in the vicinity of a VLF transmitter (HWV) at Le Blanc, France, whose signal was received on Crete, arriving over a great circle...

  17. A parametric study of the numerical simulations of triggered VLF emissions

    Directory of Open Access Journals (Sweden)

    D. Nunn

    2005-12-01

    Full Text Available This work is concerned with the numerical modelling of VLF emissions triggered in the equatorial region of the Earth's magnetosphere, using a well established 1-D Vlasov Hybrid Simulation (VHS code. Although this code reproduces observed ground based emissions well there is some uncertainty regarding the magnitude of simulation parameters such as saturation wave amplitude, cold plasma density, linear growth rate and simulation bandwidth. Concentrating on emissions triggered by pulses of VLF radio waves from the transmitter at Siple Station, Antarctica (L=4.2, these parameters, as well as triggering pulse length and amplitude, are systematically varied. This parametric study leads to an understanding of the physics of the triggering process and also of how the properties of these emissions, particularly their frequency time profile, depend upon these parameters. The main results are that weak power input tends to generate fallers, intermediate power input gives stable risers and strong growth rates give fallers, hooks or oscillating tones. The main factor determining the frequency sweep rate - of either sign - turns out to be the cold plasma density, lower densities giving larger sweep rates.

  18. VLF observations of ionospheric disturbances in association with TLEs from the EuroSprite-2007 campaign

    DEFF Research Database (Denmark)

    NaitAmor, S.; AlAbdoadaim, M. A.; Cohen, M. B.;

    2010-01-01

    Two Very Low Frequency (VLF) AWESOME remote sensing systems located at Algiers, Algeria (36.45°N, 3.28°E) and Sebha, Libya (27.02°N, 14.26°E) monitor VLF signal perturbations for evidence of ionospheric disturbances. During the EuroSprite-2007 campaign a number of Transient Luminous Events (TLEs......-18 October and 17-18 December, 2007. The data from the two VLF receivers confirm the association between TLEs and early VLF signal perturbations with the perturbations amplitudes dependent on the observation configuration i.e. whether the TLE is near the receiver, near the transmitter, or far from both...... and the scattering process. The results also reveal that the early VLF perturbations can occur in the absence of a TLE....

  19. ELF/VLF wave propagation at subauroral latitudes: Conjugate observation between the ground and Van Allen Probes A

    Science.gov (United States)

    Martinez-Calderon, Claudia; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Keika, Kunihiro; Ozaki, Mitsunori; Schofield, Ian; Connors, Martin; Kletzing, Craig; Hanzelka, Miroslav; Santolik, Ondrej; Kurth, William S.

    2016-06-01

    We report simultaneous observation of ELF/VLF emissions, showing similar spectral and frequency features, between a VLF receiver at Athabasca (ATH), Canada, (L = 4.3) and Van Allen Probes A (Radiation Belt Storm Probes (RBSP) A). Using a statistical database from 1 November 2012 to 31 October 2013, we compared a total of 347 emissions observed on the ground with observations made by RBSP in the magnetosphere. On 25 February 2013, from 12:46 to 13:39 UT in the dawn sector (04-06 magnetic local time (MLT)), we observed a quasiperiodic (QP) emission centered at 4 kHz, and an accompanying short pulse lasting less than a second at 4.8 kHz in the dawn sector (04-06 MLT). RBSP A wave data showed both emissions as right-hand polarized with their Poynting vector earthward to the Northern Hemisphere. Using cross-correlation analysis, we did, for the first time, time delay analysis of a conjugate ELF/VLF event between ground and space, finding +2 to +4 s (ATH first) for the QP and -3 s (RBSP A first) for the pulse. Using backward tracing from ATH to the geomagnetic equator and forward tracing from the equator to RBSP A, based on plasmaspheric density observed by the spacecraft, we validate a possible propagation path for the QP emission which is consistent with the observed time delay.

  20. Case studies of quasi-periodic VLF emissions and related ULF fluctuations of the magnetic field

    Science.gov (United States)

    Hayosh, M.; Santolik, O.; Nemec, F.; Parrot, M.

    2014-12-01

    Quasi-periodic (QP) VLF emissions are observed in the inner magnetosphere mostly on the day-side. These waves exhibit a periodic time modulation of the wave intensity that is possibly a result of the whistler-mode wave growth being periodically modulated by compressional ULF magnetic field pulsations. We have analyzed 50 QP events measured by the DEMETER satellite at altitudes of about 700 km to verify their generation mechanism. The analyzed events have a modulation period between 15 s and 80 s, and they were observed during quiet geomagnetic conditions (Kp 30 keV) were observed by DEMETER and by the NOAA-17 satellite. We analyze possible links between these electrons, QP emissions, and ULF magnetic field pulsations.

  1. Observations of ionospheric ELF and VLF wave generation by excitation of the thermal cubic nonlinearity.

    Science.gov (United States)

    Moore, R C; Fujimaru, S; Kotovsky, D A; Gołkowski, M

    2013-12-01

    Extremely-low-frequency (ELF, 3-3000 Hz) and very-low-frequency (VLF, 3-30 kHz) waves generated by the excitation of the thermal cubic nonlinearity are observed for the first time at the High-Frequency Active Auroral Research Program high-frequency transmitter in Gakona, Alaska. The observed ELF and VLF field amplitudes are the strongest generated by any high frequency (HF, 3-30 MHz) heating facility using this mechanism to date. This manner of ELF and VLF generation is independent of naturally forming currents, such as the auroral electrojet current system. Time-of-arrival analysis applied to experimental observations shows that the thermal cubic ELF and VLF source region is located within the collisional D-region ionosphere. Observations are compared with the predictions of a theoretical HF heating model using perturbation theory. For the experiments performed, two X-mode HF waves were transmitted at frequencies ω1 and ω2, with |ω2-2ω1| being in the ELF and VLF frequency range. In contrast with previous work, we determine that the ELF and VLF source is dominantly produced by the interaction between collision frequency oscillations at frequency ω2-ω1 and the polarization current density associated with the lower frequency HF wave at frequency ω1. This specific interaction has been neglected in past cubic thermal nonlinearity work, and it plays a major role in the generation of ELF and VLF waves. PMID:24476285

  2. New type of ensemble of quasi-periodic, long-lasting VLF emissions at the auroral zone

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    J. Manninen

    2012-12-01

    Full Text Available A new type of the series of quasi-periodic (QP very low frequency (VLF emissions in frequency range of 1–5 kHz, and not associated with geomagnetic pulsations, has been discovered at auroral latitudes (L = 5.3 during the Finnish VLF campaign (held in December 2011. At least five unusually spectacular events, each with a duration of several hours, have been observed during the night under conditions of quiet geomagnetic activity (Kp = 0–1, although QPs usually occur during the daytime. Contrary to the QP emissions typically occurring during the day, the spectral structure of these QP events represented an extended, complicated sequence of repeated discrete rising VLF signals. Their duration was about 2–3 min each, with the repetition periods ranging from ~1 min to ~10 min. Two such nighttime non-typical events are reported in this paper. The fine structure of the separated QP elements may represent a mixture of the different frequency band signals, which seem to have independent origins. It was found that the periodic signals with lower frequency appear to trigger the strong dispersive upper frequency signals. The temporal dynamics of the spectral structure of the QPs studied were significantly controlled by some disturbances in the solar wind and interplanetary magnetic field (IMF. This finding is very important for future theoretical investigations because the generation mechanism of this new type of QP emissions is not yet understood.

  3. Statistical correlation of spectral broadening in VLF transmitter signal and low-frequency ionospheric turbulence from observation on DEMETER satellite

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    A. Rozhnoi

    2008-10-01

    Full Text Available In our earlier papers we have found the effect of VLF transmitter signal depression over epicenters of the large earthquakes from observation on the French DEMETER satellite that can be considered as new method of global diagnostics of seismic influence on the ionosphere. At present paper we investigate a possibility VLF signal-ionospheric turbulence interaction using additional characteristic of VLF signal-spectrum broadening. This characteristic is important for estimation of the interaction type: linear or nonlinear scattering. Our main results are the following:
    – There are two zones of increased spectrum broadening, which are centered near magnetic latitudes Φ=±10° and Φ=±40°. Basing on the previous case study research and ground ionosonde registrations, probably it is evidence of nonlinear (active scattering of VLF signal on the ionospheric turbulence. However occurrence rate of spectrum broadening in the middle-latitude area is higher than in the near-equatorial zone (~15–20% in comparison with ~100% in former area that is probably coincides with the rate of ionospheric turbulence.
    – From two years statistics of observation in the selected 3 low-latitude regions and 1 middle-latitude region inside reception area of VLF signal from NWC transmitter we find a correlation of spectrum broadening neither with ion-cyclotron noise (f=150–500 Hz, which possibly means poor representation of the turbulence by the noise due to its mixture with natural ELF emission (which correlates with whistler, nor with magnetic storm activity.
    – We find rather evident correlation of ion-cyclotron frequency noise, VLF signal depression and weak correlation of spectrum broadening with seismicity in the middle-latitude region over Japan. But in the low-latitude regions we do not find such a correlation. Statistical decrease of VLF signal supports our previous case study results. However rather weak spectrum broadening

  4. Ionospheric plasma Turbulence detection in the VLF data observed by DEMETER Satellite

    Science.gov (United States)

    Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Kumar, Sushil

    2016-07-01

    The electromagnetic wave data in the Very Low Frequency (VLF) range detected by DEMETER satellite has been analyzed, with special attention to the variation in spectral characteristics and non-linear effects, using the statistical and wavelet based techniques.The enhancement in statistical parameters shows the coherent structure and intermittent phenomenon which is the signature of turbulence. The characteristics features of VLF disturbances have further been studied using the wavelet and bispectral analysis tools which provide useful information on the plasma turbulence.A more interesting result emerges when the low-frequency turbulence emissions produce turbulence in VLF range. Finally, the relevance of the various turbulence mechanisms and their importance in ionospheric turbulence is discussed. Keywords:DEMETER, Earthquake, Phenomena of Intermittence, Coherent Structure.

  5. Statistical investigation of VLF quasiperiodic emissions measured by the DEMETER spacecraft

    Science.gov (United States)

    Hayosh, M.; Němec, F.; Santolík, O.; Parrot, M.

    2014-10-01

    We present a survey of quasiperiodic (QP) ELF/VLF emissions detected onboard the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite (altitude of about 700 km, nearly Sun-synchronous orbit at 10:30/22:30 LT). Six years of data have been visually inspected for the presence of QP emissions with modulation periods higher than 10 s and with frequency bandwidths higher than 200 Hz. It is found that these QP events occur in about 5% of daytime half orbits, while they are basically absent during the night. The events occur predominantly during quiet geomagnetic conditions following the periods of enhanced geomagnetic activity. Their occurrence and properties are systematically analyzed. QP emissions occur most often at frequencies from about 750 Hz to 2 kHz, but they may be observed at frequencies as low as 500 Hz and as high as 8 kHz. Modulation periods of QP events may range from about 10 to 100 s, with typical values of 20 s. Frequency drifts of the identified events are generally positive, but they are lower for events with larger modulation periods. The events are usually limited to higher L values (L > 2). The upper L shell boundary of their occurrence could not be identified using the DEMETER data, but they are found to extend up to at least L ~ 6. The occurrence rate of the events is significantly lower at the longitudes of the South Atlantic anomaly (by a factor of more than 2).

  6. Ionospheric effects of the Mt. Kirishima volcanic eruption as seen from subionospheric VLF observations

    Science.gov (United States)

    Rozhnoi, A.; Hayakawa, M.; Solovieva, M.; Hobara, Y.; Fedun, V.

    2014-01-01

    Data from the Pacific network of VLF receivers have been used to study the response of the lower ionosphere to the January 2011 Mt. Kirishima (South Japan) volcanic eruption. A major explosive eruption occurred on January 27, which was preceded by several small eruptions. Perturbations of nighttime subionospheric VLF signals have been detected on the day of the first small eruption on January 18 (UT) with the maximum observed about 1.5 h after the eruption. The nighttime signal remained disturbed during the subsequent pre-eruptive and eruptive activity of Mt. Kirishima. The daytime perturbations were not observed. The frequency of the maximum spectral amplitude was found to be in the range of periods of 6-30 min, which corresponds to the periods of internal gravity waves. These results suggest that the observed VLF ionospheric effects can possibly be produced by the penetration of gravity waves caused by the volcanic activity into the ionosphere.

  7. Combined ULF and VLF observations of seismo-electro-magnetic phenomena in Europe

    Science.gov (United States)

    Schwingenschuh, Konrad; Eichelberger, Hans; Wolbang, Daniel; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed Y.; Stangl, Günter; Magnes, Werner; Berghofer, Gerhard; Aydogar, Özer; Rozhnoi, Alexander; Solovieva, Maria; Vellante, Massimo; Villante, Umberto; Biagi, Pier F.

    2014-05-01

    A combined analysis of magnetic ultra-low-frequency (ULF) and electromagnetic very-low-frequency (VLF) fluctuations before, during and after earthquakes in south and south-east Europe is presented. The magnetic fluctuations are studied in the frame of the South European Geomagnetic Array (SEGMA) network. The fluxgate and searchcoil magnetometers, located in Italy, Bulgaria and Hungary perform measurements of fluctuations in the pico-Tesla and nano-Tesla range from milli-Hertz to 100 Hz. The properties of VLF radio links (10 kHz - 50 kHz) are studied in the frame of the European VLF/LF radio receiver network (INFREP). Single parameter studies of ULF and VLF variations in the vicinity of earthquakes in Europe have been performed in the last decade (Villante et al. 2010, Rozhnoi et al. 2009). We present the first results of a dual parameter study based on single parameter ULF and VLF observations. The proposed method provides the opportunity to decrease the number of false alerts. A dual parameter seismo-electro-magnetic reliability number is developed and compared with single parameter quality numbers. References: Rozhnoi, A., Solovieva, M., Molchanov, O., Schwingenschuh, K., Boudjada, M., Biagi, P. F., Maggipinto, T., Castellana, L., Ermini, A., and Hayakawa, M.: Anomalies in VLF radio signals prior the Abruzzo earthquake (M=6.3) on 6 April 2009, Nat. Hazards Earth Syst. Sci., 9, 1727-1732, doi:10.5194/nhess-9-1727-2009, 2009. Villante, U., De Lauretis, M., De Paulis, C., Francia, P., Piancatelli, A., Pietropaolo, E., Vellante, M., Meloni, A., Palangio, P., Schwingenschuh, K., Prattes, G., Magnes, W., and Nenovski, P.: The 6 April 2009 earthquake at L'Aquila: a preliminary analysis of magnetic field measurements, Nat. Hazards Earth Syst. Sci., 10, 203-214, doi:10.5194/nhess-10-203-2010, 2010.

  8. Meteorological effects in the lower ionosphere as based on VLF/LF signal observations

    Directory of Open Access Journals (Sweden)

    A. Rozhnoi

    2014-04-01

    Full Text Available Very low and low frequency (VLF/LF data recorded in the Far Eastern stations Petropavlovsk-Kamchatsky (158.92° E, 53.15° N, Yuzhno-Sakhalinsk (142.75° E, 46.95° N and Yuzhno-Kurilsk (145.861° E, 44.03° N are investigated to study the meteorological effects in the lower ionosphere. The results demonstrate the sensitivity of the VLF/LF signals to the variations of atmospheric pressure, humidity, wind velocity and temperature, and the VLF/LF record at the station of Yuzhno-Kurilsk is found to be most sensitive to those variations of atmospheric parameters. The region under consideration is characterized by high winter cyclonic activity in midlatitudes and strong summer and autumn typhoon activity in low latitudes. VLF/LF signal variations during 8 tropical cyclones (TCs with different intensity are considered. Negative nighttime anomalies in the signal amplitude that are most probably caused by TC activity are found for 6 events. Those anomalies are observed during 1–2 days when TCs move inside the sensitivity zones of the subionospheric paths. Perturbations of the VLF signal observed during 2 TCs can be caused by both the TC influence and seismic activity, but no correlation between TC intensity and magnitude of the signal anomalies is found. Spectral analysis of the typhoon-induced disturbed signals revealed the fluctuations with time periods in the range of 7–16 and 15–55 min that corresponds to the range of internal gravity waves periods.

  9. Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

    OpenAIRE

    Platino, M.; U. S. Inan; Bell, T.F.; Pickett, J.; Kennedy, E. J.; Trotignon, J. G.; Rauch, J. L.; Canu, P.

    2004-01-01

    It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere ill...

  10. Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

    Directory of Open Access Journals (Sweden)

    M. Platino

    2004-07-01

    Full Text Available It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990. One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere illuminated by the ELF/VLF waves. In an attempt to investigate this question further, ground-satellite conjunction experiments have recently been conducted using the four Cluster satellites and the HF heater of the High-Frequency Active Auroral Research Program (HAARP facility in Gakona, Alaska. Being located on largely closed field lines at L≈4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF wave-injection experiments, and will be increasingly used for this purpose as it is now being upgraded for higher power operation. In this paper, we describe the HAARP installation and present recent results of the HAARP-Cluster experiments. We give an overview of the detected ELF/VLF signals at Cluster, and a possible explanation of the spectral signature detected, as well as the determination of the location of the point of injection of the HAARP ELF/VLF signals into the magnetosphere using ray tracing.

  11. Subionospheric VLF Observations of Transmitter-Induced Precipitation of Inner Radiation Belt Electrons

    Science.gov (United States)

    Golkowski, M.; Inan, U.; Peter, W.

    2006-12-01

    Ionospheric effects of energetic electron precipitation induced by controlled injection of VLF signals from a ground based transmitter are observed via subionospheric VLF remote sensing. The 21.4 kHz NPM transmitter in Lualualei, Hawaii is keyed ON-OFF in a periodic sequence lasting 30 minutes. The same periodicity is observed in the amplitude and phase of the sub-ionospherically propagating signals of the 24.8 kHz NLK (Jim Creek, Washington) and 25.2 kHz NLM (LaMoure, North Dakota) transmitters measured at Midway Island. The NLM and NLK signal paths pass underneath the region of electron precipitation induced by the NPM transmitter, as predicted theoretically on the basis of cyclotron resonance interaction between energetic electrons and obliquely propagating whistler-mode waves injected by NPM. The ionospheric disturbances are consistent with that caused by conductivity enhancements resulting from secondary ionization produced by the precipitation of pitch angle scattered electrons in the 100-300 keV energy range. Periodic perturbations of the NLK signal observed at Palmer, Antarctica suggest that energetic electrons are scattered into both the bounce and drift loss cones. Utilizing a comprehensive model of magnetospheric wave-particle interaction, ionospheric energy deposition, and subionospheric VLF propagation, the precipitated energy flux is estimated to peak at L ~ 2 and ~ 3 x 10-4 [ergs s-1 cm-2

  12. On the possibility of precursors of earthquakes in VLF range observed by DEMETER Satellite

    Science.gov (United States)

    Sondhiya, D. K.; Kumar, S.; Gwal, A. K.

    2014-05-01

    Very Low Frequency (VLF) disturbances in the ionospheric electric field observed by DEMETER satellite prior to three different earthquakes that occurred during the years 2008-2009 have been presented. The electromagnetic wave data has been analyzed for few days before the earthquake with special attention to the variation in spectral characteristics and non-linear effects using the statistical and wavelet based techniques. Results indicate that the earthquake preparation process may disturb the ionospheric plasma and these disturbances can reach the non-linear stage leading to the strong variations in the electromagnetic field and plasma parameters. The enhancement in statistical parameters shows the coherent structure and intermittent phenomenon which is the signature of turbulence. The characteristics features of VLF disturbances have further been studied using the wavelet and bispectral analysis tools which provide useful information on the plasma turbulence.

  13. The quasi-periodical VLF/ELF emissions detected onboard the DEMETER spacecraft: statistical and theoretical analysis

    Science.gov (United States)

    Pasmanik, Dmitry; Hayosh, Mykhaylo; Demekhov, Andrei; Santolík, Ondřej; Nemec, František; Parrot, Michel

    2015-04-01

    We present a statistical study of the quasi-periodic (QP) ELF/VLF emissions measured by the DEMETER spacecraft. Events with modulation period larger than 10 s and frequency bandwidth more than 200 Hz were visually selected among the six year of measurements. Selected QP-emissions events occur mostly at frequencies from about 750 Hz to 2 kHz, but they may be observed at frequencies as low as 500 Hz and as high as 8 kHz. The statistical analysis clearly shows that QP events with larger modulation periods have lower frequency drift and smaller wave amplitude. Intense QP events have higher frequency drifts and larger values of the frequency bandwiths. Numerical simulation of the QP emissions based on the theoretical model of the flow cyclotron maser is performed. Calculations were made for wide range of plasma parameters (i.e. cold plasma density, L-shell, energetic electron flux and etc.) The numerical results are in good agreement with the observed relationship between different parameters of the QP emissions. The comparison between theoretical results and observations allow us to estimate the typical properties of the source of the QP emissions observed by the DEMETER satellite.

  14. VLF observation during Leonid Meteor Shower-2002 from Kolkata

    CERN Document Server

    Chakrabarti, S K; Acharyya, K; Mandal, S; Chakrabarti, S; Khan, R; Bose, B; Chakrabarti, Sandip K.

    2002-01-01

    Using a Gyrator-II Loop antenna tuned at 19.0Khz, we monitored the meteor shower during 17-24th November, 2002. We observe the primary peak at 3h58m (UT) on the 19th of November, 2002. We distinctly observed several `beadlike' and `exponentially dropping' signals. The `beadlike' signals were more in abundance on the 18th of November, 2002, one day prior to the actual encounter.

  15. Characteristic of Tweek Atmospherics Observed in Mid-latitude using AWESOME VLF Receiver

    OpenAIRE

    Norbayah Yusop; Nor Azlan Mohd Aris; S.A.M. Chachuli; Maizatul Alice Meor Said

    2014-01-01

    This study presents the analysis of tweek atmospherics received by AWESOME VLF receiver at station of Gakona (62.71°N, 143.99°W) during four months observation from January to April 2011. Tweek which originates from lightning discharge are used to monitor the nighttime D-region ionosphere using the fundamental cut-off frequency to measure the variations of the lower ionosphere’s reflection height, the equivalent electron density at the reflection height and the propagation distance travel by ...

  16. Characteristic of Tweek Atmospherics Observed in Mid-latitude using AWESOME VLF Receiver

    Directory of Open Access Journals (Sweden)

    Norbayah Yusop

    2014-03-01

    Full Text Available This study presents the analysis of tweek atmospherics received by AWESOME VLF receiver at station of Gakona (62.71°N, 143.99°W during four months observation from January to April 2011. Tweek which originates from lightning discharge are used to monitor the nighttime D-region ionosphere using the fundamental cut-off frequency to measure the variations of the lower ionosphere’s reflection height, the equivalent electron density at the reflection height and the propagation distance travel by tweeks. In this study, a total of 1316 tweeks are analyzed and from the analysis, it shows that equinox’s season has the highest tweek occurrence compared to winter season in March and April. The maximum harmonic (m of t weeks is found to be up to fourth ( m = 4 and tweeks with mode number one (m = 1 are more dominantly occurred. Our observations indicate that the equivalent electron densities for tweeks varies from 22-27 eL/cm3 in the altitude ranged of 75 to 91 km and demonstrate that these ELF/VLF signals travel considerable distances up to 6700 km from the causative lightning discharges. The ionospheric parameters for three locations (high, middle and low latitude respectively were compared and the results show that they are almost consistent for all the locations.

  17. Study of the effects of solar activities on the ionosphere as observed by VLF signals recorded at TNU station, Vietnam

    Science.gov (United States)

    Tan, L. M.

    2015-12-01

    A SuperSID monitor installed at Tay Nguyen University (TNU), Vietnam is used to detect the temporal variations of Very Low Frequency (VLF) signals during 2013 and 2014 to understand the responses of the ionosphere to sunset/sunrise transitions and solar flares. Two VLF station signals are tracked, JJI/22.2 kHz in Japan and NWC/19.8 kHz in Australia. Results show that the effects of sunrise, sunset and solar flares on the NWC signal are more significantly different than those on the JJI signal. Sunset and sunrise spikes only occur on the JJI-TNU path because of longitudinal differences between the receiver and transmitter. Two sunset dips and three sunrise dips appear on the NWC signal during summer season. During intense solar flares, the dips occur after the maximum disturbance of the VLF signals for the North-South path. The appearance of these dips is explained by modal interference patterns. Observing temporal variations of sunrise and sunset dips or spikes of VLF signals during different seasons enhances the understanding of the behavior of the ionosphere.

  18. Unusual attenuation events in the VLF range observed by the DEMETER spacecraft

    Science.gov (United States)

    Zahlava, Jan; Nemec, Frantisek; Parrot, Michel; Rodger, Craig J.; Santolik, Ondrej

    2015-04-01

    Results of a systematic study of unusual attenuation events observed by the DEMETER spacecraft in the VLF range are presented. In the frequency-time spectrograms of wave intensity, these attenuation events consist of several lines with significantly lower intensity. Detailed analysis of the events shows that they are formed by consecutive lightning generated whistlers. These whistlers are attenuated at some specific frequencies which vary continuously during the event, resulting in lines of lower intensity. We inspected all available DEMETER data for the presence of these attenuation events. Altogether, 1580 events have been identified. They occur exclusively during the nighttime. We compare the overall geographic distribution of the total event duration with the geographic distribution of the mean lightning occurrence. It is found that the event locations are closely related to the areas of enhanced lightning activity, but they are shifted by about 30 degrees westward. We present a simple model of a possible event formation based on a basic theory of wave propagation in the Earth-ionosphere waveguide. This model, however, does not explain the observed longitudinal shift. We believe that the shift is due to an azimuthal dependence of the wave attenuation in the Earth-ionosphere waveguide, which is not considered in the used simplified waveguide theory.

  19. Whistler-triggered emissions observed by ISIS satellites

    Science.gov (United States)

    Nakamura, Y.; Ondoh, T.

    1989-01-01

    A statistical examination has been conducted of the ducted and nonducted whistler-triggered emissions (WTEs) observed by the ISIS satellites in the 1979-1981 period. Most WTEs are observed with simultaneous lower hybrid resonance in the topside ionosphere. The VLF emissions triggered by ducted whistlers frequently occur at L of 2-3, while those triggered by nonducted whistlers occur in the wider latitudinal regions at L of 2.2-4.3.

  20. Multiple-Station Observation of Frequency Dependence and Polarization Characteristics of ELF/VLF waves generated via Ionospheric Modification

    Science.gov (United States)

    Maxworth, A. S.; Golkowski, M.; Cohen, M.; Moore, R. C.

    2014-12-01

    Generation of Extremely Low Frequency (ELF) and Very Low Frequency (VLF) signals through ionospheric modification has been practiced for many years. Heating the lower ionosphere with high power HF waves allows for modulation of natural current systems. Our experiments were carried out at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska, USA. In this experiment, the ionosphere was heated with a vertical amplitude modulating signal and the modulation frequency was changed sequentially within an array of 40 frequencies followed by a frequency ramp. The observed magnetic field amplitude and polarization of the generated ELF/VLF signals were analyzed for multiple sites and as a function of modulation frequency. Our three observation sites: Chistochina, Paxson and Paradise are located within 36km (azimuth 47.7°), 50.2km (azimuth -20°) and 99km (azimuth 80.3°) respectively. We show that the peak amplitudes observed as a function of frequency result from vertical resonance in the Earth-ionosphere waveguide and can be used to diagnose the D-region profile. Polarization analysis showed that out of the three sites Paxson shows the highest circularity in the magnetic field polarization, compared to Chistochina and Paradise which show highly linear polarizations. The experimental results were compared with a theoretical simulation model results and it was clear that in both cases, the modulated Hall current dominates the observed signals at Chistochina and Paradise sites and at Paxson there is an equal contribution from Hall and Pedersen currents. The Chistochina site shows the highest magnetic field amplitudes in both experimental and simulation environments. Depending upon the experimental and simulation observations at the three sites, a radiation pattern for the HAARP ionospheric heater can be mapped

  1. VLF/LF EM emissions as main precursor of earthquakes and their searching possibilities for Georgian s/a region

    Science.gov (United States)

    Kachakhidze, Manana; Kachakhidze, Nino

    2016-04-01

    Authors of abstract have created work which offers model of earth electromagnetic emissions generation detected in the process of earthquake preparation on the basis of electrodynamics. The model gives qualitative explanation of a mechanism of generation of electromagnetic waves emitted in the earthquake preparation period. Besides, scheme of the methodology of earthquake forecasting is created based on avalanche-like unstable model of fault formation and an analogous model of electromagnetic contour, synthesis of which, is rather harmonious. According to the authors of the work electromagnetic emissions in radiodiapason is more universal and reliable than other anomalous variations of various geophysical phenomena in earthquake preparation period; Besides, VLF/LF electromagnetic emissions might be declared as the main precursor of earthquake because it might turn out very useful with the view of prediction of large (M ≥5) inland earthquakes and to govern processes going on in lithosphere-atmosphere - ionosphere coupling (LAIC) system. Since the other geophysical phenomena, which may accompany earthquake preparation process and expose themselves several months, weeks or days prior to earthquakes are less informative with the view of earthquake forecasting, it is admissible to consider them as earthquake indicators. Physical mechanisms of mentioned phenomena are explained on the basis of the model of generation of electromagnetic emissions detected before earthquake, where a process of earthquake preparation and its realization are considered taking into account distributed and conservative systems properties. Up to these days electromagnetic emissions detection network did not exist in Georgia. European colleagues helped us (Prof. Dr. PF Biagi, Prof. Dr. Aydın BÜYÜKSARAÇ) and made possible the installation of a receiver. We are going to develop network and put our share in searching of earthquakes problem. Participation in conference is supported by financial

  2. Decrease of VLF transmitter signal and Chorus-whistler waves before l'Aquila earthquake occurrence

    Directory of Open Access Journals (Sweden)

    M. Y. Boudjada

    2010-07-01

    Full Text Available We investigate the VLF emissions observed by the Instrument Champ Electrique (ICE experiment onboard the DEMETER micro-satellite. We analyze intensity level variation 10 days before and after the occurrence of l'Aquila earthquake (EQ. We found a clear decrease of the VLF received signal related to ionospheric whistler mode (mainly Chorus emission and to signal transmitted by the DFY VLF station in Germany, few days (more than one week before the earthquake. The VLF power spectral density decreases of more than two orders of magnitude until the EQ, and it recovers to normal levels just after the EQ occurrence. The geomagnetic activity is principally weak four days before EQ and increases again one day before l'Aquila seismic event. Our results are discussed in the frame of short- and long-terms earthquakes prediction focusing on the crucial role of the magnetic field of the Earth.

  3. Lightning characteristics observed by a VLF/LF lightning detection network (LINET in Brazil, Australia, Africa and Germany

    Directory of Open Access Journals (Sweden)

    H. Höller

    2009-10-01

    Full Text Available This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency lightning detection network (LINET. The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere and TWP-ICE (Tropical Warm Pool-International Cloud Experiment during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses in W-Africa during June–November 2006.

    Regional and temporal characteristics of lightning are found to be dependent on orographic effects (e.g. S-Germany, Brazil, Benin, land-sea breeze circulations (N-Australia and especially the evolution of the monsoons (Benin, N-Australia. Large intra-seasonal variability in lightning occurrence was found for the Australian monsoon between the strong convection during build-up and break phases and the weak active monsoon phase with only minor lightning activity. Total daily lightning stroke rates can be of comparable intensity in all regions with the heaviest events found in Germany and N

  4. Lightning characteristics observed by a VLF/LF lightning detection network (LINET in Brazil, Australia, Africa and Germany

    Directory of Open Access Journals (Sweden)

    H. Höller

    2009-03-01

    Full Text Available This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency lightning detection network (LINET. The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere and TWP-ICE (Tropical Warm Pool – International Cloud Experiment during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses in W-Africa during June–November 2006.

    Regional and temporal characteristics of lightning are found to be dependent on orographic effects (e.g. S-Germany, Brazil, Benin, land-sea breeze circulations (N-Australia and especially the evolution of the monsoons (Benin, N-Australia. Large intra-seasonal variability in lightning occurrence was found for the Australian monsoon between the strong convection during build-up and break phases and the weak wet monsoon phase with only minor lightning activity. Total daily lightning rates can be of comparable intensity in all regions with the heaviest events found in Germany and N

  5. Horizontal Ionospheric Electron Density Gradients Observed by FORMOSAT-3/COSMIC TIP: Spatial Distributions and Effects on VLF Wave Propagation at Mid-Latitudes

    Directory of Open Access Journals (Sweden)

    Damien H. Chua

    2009-01-01

    Full Text Available We investigate the spatial variability of electron densities in the nightside ionosphere and its effects on very-low frequency (VLF wave propagation using a suite of instruments from the FORMOSAT-3/Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC spacecraft.We use observations from the Tiny Ionospheric Photometer (TIP instruments to infer the horizontal electron density gradients along each satellite track. We demonstrate that the OI 1356 _ radiance measured by the TIP instruments tracks the horizontal electron density structure well with high spatial resolution and unprecedented sensitivity. Accurate measurements of the horizontal electron density gradients are important for improving retrieved electron density profiles from GPS occultation and other tomographic remote sensing techniques. The processes underlying the variability in the large-scale, nightside electron density gradients are the main drivers of ionospheric weather. TIP observations reveal significant variability in both the small and large scale structure of the nightside ionosphere. The relative intensities, relative widths, and latitudinal separation of the northern and southern ionization crests of the Appleton anomalies show a high degree of longitudinal variation.We demonstrate how the TIP observations can be used to measure the horizontal gradient of the refractive index of whistler-mode VLF waves propagating in a cold, collisionless plasma. These measurements are critical for understanding how gradients in electron density associated with ionospheric structure such as depletions and the Appleton anomalies affect VLF wave propagation through the equatorial and mid-latitude ionosphere.

  6. Multispacecraft observations of quasi-periodic emissions

    Science.gov (United States)

    Nemec, Frantisek; Picket, Jolene S.; Santolik, Ondrej

    2014-05-01

    Quasi-periodic (QP) emissions are VLF electromagnetic waves in the frequency range of about 0.5-5 kHz which exhibit a periodic time modulation of the wave intensity. The modulation period is usually on the order of a few tens of seconds. The generation mechanism of these emissions is still not understood, but at least in some cases it appears to be related to ULF magnetic field pulsations which result in periodic modifications of the resonant conditions in the source region. We use multipoint measurements of QP emissions by the 4 Cluster spacecraft. The observations are obtained close to the equatorial region at radial distances of about 4 Earth radii, i.e. close to a possible generation region. A combined analysis of the high resolution data obtained by the WBD instruments and the ULF magnetic field data obtained by the FGM instruments allows for a detailed case-study analysis of these unique emissions. The presented analysis benefits from the recent close-separation configuration of three of the Cluster spacecraft (≡20-100 km) and a related timing analysis, which would be impossible otherwise.

  7. ELF/VLF signatures of sprite-producing lightning discharges observed during the 2005 EuroSprite campaign

    DEFF Research Database (Denmark)

    Greenberg, E.; Price, C.; Yair, Y.;

    2009-01-01

    in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites. The motivation for the present study was to identify the signature...... of the sprite-producing lightning discharges in the ELF and VLF electromagnetic frequency bands, to qualify and compare their parameters, and to study the influence of the thunderstorm-activated region on its overlaying ionosphere. For the 15 sprites analyzed, their causative positive cloud-to-ground (+CG......) discharges had peak current intensities between +8 and +130 kA whereas their charge moment changes (CMC) ranged from 500 to 3500 C km. Furthermore, the peak current reported by the Météorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation...

  8. Unique Observation of a Solar Flare by Lunar Occultation During the 2010 Annular Solar Eclipse Through Ionospheric Disturbances of VLF Signals

    Science.gov (United States)

    Maji, Surya K.; Chakrabarti, Sandip K.; Mondal, Sushanta K.

    2012-06-01

    Very Low Frequency (VLF) radio waves propagate through the Earth-ionosphere waveguide. Irregularities caused by excess or deficient extreme ultra-violet and X-rays, which otherwise sustain the ionosphere, change the waveguide properties and hence the signals are modified. We report the results of monitoring of the NWC transmitter (19.8 kHz) by a receiver placed at Khukurdaha (22°27'N, 87°45'E) during the partial solar eclipse (75 %) of 15th January, 2010. The propagation path from the transmitter to the receiver crosses the annular eclipse belt. We got a clear depression in the data during the period of the eclipse. Most interestingly, there was also a X-ray flaring activity in the sun on that day which reached its peak (C-type) right after the time when the eclipse reached its maximum. We saw the effects of the occultation of this flare in our VLF signal since a part of the X-ray active region was clearly blocked by the moon. We quantitatively compared by using analogies with previous observations and found best fitting parameters for the time when the flare was occulted. We then reconstructed the VLF signal in the absence of the occulted flare. To our knowledge, this is the first such incident where the solar flare was observed through lunar occultation and that too during a partial eclipse.

  9. Unique observation of a Solar Flare by Lunar Occultation during the 2010 Annular Solar Eclipse through ionospheric disturbances in VLF waves

    Science.gov (United States)

    Kanta Maji, Surya; Chakrabarti, Sandip Kumar

    2012-07-01

    Very Low Frequency (VLF) radio waves propagate through the Earth-ionosphere waveguide. Irregularities caused by excess or deficient solar extreme ultra-violet and X-rays, which otherwise sustain the ionosphere, changes the waveguide properties and hence the signals are modified. We report the results of monitoring of the NWC transmitter (19.8kHz) by a receiver placed at Khukurdaha (~80 km away from Kolkata) during the partial solar eclipse (75%) of 15th January, 2010. The receiving station and the transmitter were on two opposite sides of the annular eclipse belt. We got a clear depression in the data during the period of partial eclipse. Most interestingly, there was also a flaring activity in the sun on that day which reached its peak (C-type) just after the time when the eclipse was near maximum. We saw effects of the occultation of this flare in our VLF signal since a part of the active region was clearly blocking the moon. We model this occultation, and reconstructed the VLF signal in the absence of the flare. To our knowledge, this is the first such incident where the solar flare was observed through lunar occultation and that too during a partial eclipse.

  10. Hiss emissions during quiet and disturbed periods

    Indian Academy of Sciences (India)

    D K Singh; R P Singh

    2002-10-01

    The characteristic features of VLF hiss emissions during quiet and disturbed conditions observed at ground stations and on-board satellites are summarized. The increased intensity of the hiss emissions during magnetic storm period is explained by considering the enhanced flux of energetic electrons during magnetic storm period. The generation and propagation mechanism of VLF hiss are also briefly discussed.

  11. Longitudinal drift of substorm electrons as the reason of impulsive precipitation events and VLF emissions

    Directory of Open Access Journals (Sweden)

    A. A. Lubchich

    2006-10-01

    Full Text Available Using the data from satellite CRRES and three geostationary LANL spacecraft, the propagation of an electron cloud from midnight to the evening sector is investigated. An electron cloud was injected during a weak isolated substorm that developed on a quiet geomagnetic background. It is found that within the local time sector from 03:00 until at least 08:00 MLT, the propagation of electrons at perpendicular pitch-angles is well described by a simple model of drift in the dipole magnetic field. The flux levels in the field-aligned electrons increase simultaneously with the flux at perpendicular pitch angles, which is attributed to the pitch angle diffusion by the whistler mode. This pitch-angle diffusion leads to precipitation of electrons from a drifting cloud and an increase in the ionospheric electron density, simultaneously observed above Tromsø, Norway, by the EISCAT UHF radar in the morning sector (04:40–05:25 MLT. The precipitation develops as quasi-periodic pulses with a period of about 100 s. We discuss the models of pulsating precipitation due to the whistler cyclotron instability and show that our observations can be explained by such a model.

  12. Transionospheric VLF Propagation as an Ionospheric Diagnostic

    Science.gov (United States)

    Worthington, E. R.; Cohen, M.

    2015-12-01

    Very Low Frequency (VLF, 3-30 kHz) radio waves emitted from ground-based sources, such as VLF transmitters or lightning strokes, are attenuated as they travel through the D-region of the ionosphere, making measurements taken of the VLF energy that has escaped this region useful in estimating the electron density. It has been also been suggested that F-region irregularities may contribute additional attenuation to the VLF signal. Additionally, energy at these frequencies that escapes the ionosphere altogether strongly impacts the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributes to the formation of the slot region. We present an analysis of measurements captured by the DEMETER satellite over VLF transmitters. During its six-year mission, DEMETER completed hundreds of passes above well-characterized VLF transmitters while recording electric and magnetic field strengths. Statistically significant (daytime and nighttime) seasonal variations were observed in this data set. We compare observations with estimates obtained using a sophisticated full wave model of trans-ionospheric propagation, and discuss the viability of the International Reference Ionosphere in correctly predicting transionospheric VLF energy.

  13. VLF/LF signal studies of the ionospheric response to strong seismic activity in the Far Eastern region combining the DEMETER and ground-based observations

    Science.gov (United States)

    Rozhnoi, A.; Solovieva, M.; Parrot, M.; Hayakawa, M.; Biagi, P.-F.; Schwingenschuh, K.; Fedun, V.

    The paper presents the results of a joint analysis of ground-based and satellite observations of very low-frequency and low-frequency (VLF/LF) signals during periods of strong seismic activity in the region of Kuril Islands and Japan in 2004-2010. Ground and satellite data was processed using a method based on the difference between the real signal in nighttime and that of a model. The results of the analysis show a good correlation between ground-based and satellite data for several cases of strong (M ⩾ 6.8) earthquakes.

  14. Ionospheric turbulence from ground-based and satellite VLF/LF transmitter signal observations for the Simushir earthquake (November 15, 2006

    Directory of Open Access Journals (Sweden)

    Pier Francesco Biagi

    2012-04-01

    Full Text Available

    Signals from very low frequency (VLF/ low frequency (LF transmitters recorded on the ground station at Petropavlovsk-Kamchatsky and on board the French DEMETER satellite were analyzed for the Simushir earthquake (M 8.3; November 15, 2006. The period of analysis was from October 1, 2006, to January 31, 2007. The ground and satellite data were processed by a method based on the difference between the real signal at night-time and the model signal. The model for the ground observations was the monthly averaged signal amplitudes and phases, as calculated for the quiet days of every month. For the satellite data, a two-dimensional model of the signal distribution over the selected area was constructed. Preseismic effects were found several days before the earthquake, in both the ground and satellite observations.

     

  15. Modeling solar flare induced lower ionosphere changes using VLF/LF transmitter amplitude and phase observations at a midlatitude site

    Directory of Open Access Journals (Sweden)

    E. D. Schmitter

    2013-04-01

    Full Text Available Remote sensing of the ionosphere bottom using long wave radio signal propagation is a still going strong and inexpensive method for continuous monitoring purposes. We present a propagation model describing the time development of solar flare effects. Based on monitored amplitude and phase data from VLF/LF transmitters gained at a mid-latitude site during the currently increasing solar cycle no. 24 a parameterized electron density profile is calculated as a function of time and fed into propagation calculations using the LWPC (Long Wave Propagation Capability. The model allows to include lower ionosphere recombination and attachment coefficients, as well as to identify the relevant forcing X-ray wavelength band, and is intended to be a small step forward to a better understanding of the solar–lower ionosphere interaction mechanisms within a consistent framework.

  16. A generation mechanism for discrete very low frequency emissions observed at Varanasi

    Indian Academy of Sciences (India)

    A K Singh; S B Singh; R P Singh

    2005-12-01

    A new type of discrete VLF emissions recorded at the low-latitude ground station Varanasi (geomag. lat. 14° 55'$ N, geomag. long. 154°E; = 1.07) during the strong magnetic activity on 29–30 April 1990 have been reported. A generation mechanism for various temporal and spectral features of discrete VLF emissions recorded at Varanasi is presented on the basis of cyclotron resonance interaction between whistler mode wave and energetic electrons ejected by substorm electric fields. An attempt is also made to determine parallel energy and wave growth relevant to the generation process of discrete VLF emissions. Finally, our results are discussed with other published works.

  17. Variations of VLF/LF signals observed on the ground and satellite during a seismic activity in Japan region in May–June 2008

    Directory of Open Access Journals (Sweden)

    A. Rozhnoi

    2010-03-01

    Full Text Available Signals of two Japanese transmitters (22.2 kHz and 40 kHz recorded on the ground VLF/LF station in Petropavlovsk-Kamchatsky and on board the DEMETER French satellite have been analyzed during a seismic activity in Japan in May–June 2008. The period of analysis was from 18 April to 27 June. During this time two rather large earthquakes occurred in the north part of Honshu Island – 7 May (M=6.8 and 13 June (M=6.9. The ground and satellite data were processed by a method based on the difference between the real signal in nighttime and the model one. For ground observations a clear decrease in both signals has been found several days before the first earthquake. For the second earthquake anomalies were detected only in JJI signal. The epicenters of earthquakes were in reliable reception zone of 40 kHz signal on board the DEMETER. Signal enhancement above the seismic active region and significant signal intensity depletion in the magnetically conjugate area has been found for satellite observation before the first earthquake. Anomalies in satellite data coincide in time with those in the ground-based observation.

  18. Whistler-triggered VLF noise bursts observed on the DE-1 satellite and simultaneously at Antarctic ground stations

    Science.gov (United States)

    Smith, A. J.; Carpenter, D. L.; Inan, U. S.

    1985-01-01

    Simultaneous observations of whistler-triggered very low-frequency noise bursts on the ground at Anarctic stations, Halley and Siple, and on the high-altitude satellite DE-1 are reported. Results of a case study from June 25, 1982 in which the satellite data were recorded near 25 deg south magnetic latitude and the L = 4.7 magnetic shell, are presented. Analysis indicates that the chorus bursts that are triggered in whistler ducts travel downwards in the ducts to low altitudes in the ionosphere, and that propagation to DE-1 is by upward reflection into a nonducted mode. A means of estimating the propagation characteristics of the wave bursts is provided by comparisons of nonducted signals from the Siple transmitter and discrete periodic emissions. The ducted-nonducted mode conversion process is a mechanism for the large-scale spreading into the magnetosphere of coherent whistler-mode wave energy which is generated, amplified, or triggered in small localized ducts. The DE-1 data show that a strong interaction exists between whistler-triggered noise bursts and prevailing hiss levels.

  19. VLF and ELF effects in the upper ionosphere caused by large-scale acoustic waves in the lower ionosphere observed from AUREOL-3 satellite

    International Nuclear Information System (INIS)

    The active MASSA(or MARS) experiment concerning the study of the effects generated in the upper atmosphere and in the magnetosphere by a large-scale acoustic wave reaching ionospheric altitudes, was realized in such a way, that the AUREOL-3 satellite crossed the corresponding magnetic force tubes by the time of the development of the electromagnetic processes expected in the lower ionosphere E-region above the explosion. The measurements performed revealed, in the ionospheric and magnetospheric plasmas, electromagnetic effects generated by a large-scale acoustic wave produced as a result of chemical ground explosion with a kinetic energy 288 TNT(Tons). These effects include nearly electrostatic ELF and VLF-noises in the magnetic force tube based on the E-layer ionosphere above explosion, their area expands with a velocity of about 0.6 km/sec, that is, as of an acoustic wave in the lower ionosphere. Besides, an intense MHD wave was detected at the L = 1.31, that is, equator-wards form the explosion L-shell (L = 1.5). This electromagnetic signal has a steep front and than a slow decay. The results of the MARS experiment were confirmed and extended during further similar experiments when industrial ground explosions (barrages'construction, etc.) were conducted at the predetermined times to achieve the coordinated data from AUREOL-3 and from ground-based observations

  20. Strange VLF bursts in northern Scandinavia: case study of the afternoon "mushroom-like" hiss on 8 December 2013

    Science.gov (United States)

    Manninen, J.; Kleimenova, N. G.; Kozlovsky, A.; Kornilov, I. A.; Gromova, L. I.; Fedorenko, Y. V.; Turunen, T.

    2015-08-01

    We investigate a non-typical very low frequency (VLF) 1-4 kHz hiss representing a sequence of separated noise bursts with a strange "mushroom-like" shape in the frequency-time domain, each one lasting several minutes. These strange afternoon VLF emissions were recorded at Kannuslehto (KAN, ϕ = 67.74° N, λ = 26.27° E; L ∼ 5.5) in northern Finland during the late recovery phase of the small magnetic storm on 8 December 2013. The left-hand (LH) polarized 2-3 kHz "mushroom caps" were clearly separated from the right-hand (RH) polarized "mushroom stems" at the frequency of about 1.8-1.9 kHz, which could match the lower ionosphere waveguide cutoff (the first transverse resonance of the Earth-ionosphere cavity). We hypothesize that this VLF burst sequence could be a result of the modulation of the VLF hiss electron-cyclotron instability from the strong Pc5 geomagnetic pulsations observed simultaneously at ground-based stations as well as in the inner magnetosphere by the Time History of Events and Macroscale Interactions during Substorms mission probe (THEMIS-E; ThE). This assumption is confirmed by a similar modulation of the intensity of the energetic (1-10 keV) electrons simultaneously observed by the same ThE spacecraft. In addition, the data of the European Incoherent Scatter Scientific Association (EISCAT) radar at Tromsø show a similar quasi-periodicity in the ratio of the Hall-to-Pedersen conductance, which may be used as a proxy for the energetic particle precipitation enhancement. Our findings suggest that this strange mushroom-like shape of the considered VLF hiss could be a combined mutual effect of the magnetospheric ULF-VLF (ultra low frequency-very low frequency) wave interaction and the ionosphere waveguide propagation.

  1. ELF and VLF signatures of sprites registered onboard the low altitude satellite DEMETER

    Directory of Open Access Journals (Sweden)

    J. Błęcki

    2009-06-01

    Full Text Available We report the observation of ELF and VLF signature of sprites recorded on the low altitude satellite DEMETER during thunderstorm activity. At an altitude of ~700 km, waves observed on the E-field spectrograms at mid-to-low latitudes during night time are mainly dominated by up-going 0+ whistlers. During the night of 20 July 2007 two sprites have been observed around 20:10:08 UT from the observatory located on the top of the mountain Śnieżka in Poland (50°44'09" N, 15°44'21" E, 1603 m and, ELF and VLF data have been recorded by the satellite at about 1200 km from the region of thunderstorm activity. During this event, the DEMETER instruments were switched in the burst mode and it was possible to register the wave forms. It is shown that the two sprites have been triggered by two intense +CG lightning strokes (100 kA occurring during the same millisecond but not at the same location. Despite the distance DEMETER has recorded at the same time intense and unusual ELF and VLF emissions. It is shown that the whistler wave propagates from the thunderstorm regions in the Earth-ionosphere guide and enters in the ionosphere below the satellite. They last several tens of milliseconds and the intensity of the ELF waveform is close to 1 mV/m. A particularly intense proton whistler is also associated with these emissions.

  2. E.l.f./v.l.f. emissions observed on Ariel 4. [wave-particle phenomena in magnetosphere

    Science.gov (United States)

    Bullough, K.; Denby, M.; Gibbons, W.; Hughes, A. R. W.; Kaiser, T. R.; Tatnall, A. R. L.

    1975-01-01

    The Ariel 4 satellite was designed to study wave-particle phenomena in the magnetosphere by measuring the electromagnetic wave fields over a wide frequency range and the fluxes and pitch angle distributions of energetic particles. We describe here the results of a preliminary study of the various v.l.f./e.l.f. electromagnetic wave phenomena which are observed. These include man-made signals from v.l.f. transmitters, impulsive noise originating in thunderstorms and emissions arising from magnetospheric energetic charged particles.

  3. Possibility of Earthquake-prediction by analyzing VLF signals

    Science.gov (United States)

    Ray, Suman; Chakrabarti, Sandip Kumar; Sasmal, Sudipta

    2016-07-01

    Prediction of seismic events is one of the most challenging jobs for the scientific community. Conventional ways for prediction of earthquakes are to monitor crustal structure movements, though this method has not yet yield satisfactory results. Furthermore, this method fails to give any short-term prediction. Recently, it is noticed that prior to any seismic event a huge amount of energy is released which may create disturbances in the lower part of D-layer/E-layer of the ionosphere. This ionospheric disturbance may be used as a precursor of earthquakes. Since VLF radio waves propagate inside the wave-guide formed by lower ionosphere and Earth's surface, this signal may be used to identify ionospheric disturbances due to seismic activity. We have analyzed VLF signals to find out the correlations, if any, between the VLF signal anomalies and seismic activities. We have done both the case by case study and also the statistical analysis using a whole year data. In both the methods we found that the night time amplitude of VLF signals fluctuated anomalously three days before the seismic events. Also we found that the terminator time of the VLF signals shifted anomalously towards night time before few days of any major seismic events. We calculate the D-layer preparation time and D-layer disappearance time from the VLF signals. We have observed that this D-layer preparation time and D-layer disappearance time become anomalously high 1-2 days before seismic events. Also we found some strong evidences which indicate that it may possible to predict the location of epicenters of earthquakes in future by analyzing VLF signals for multiple propagation paths.

  4. Optimizing an ELF/VLF Phased Array at HAARP

    Science.gov (United States)

    Fujimaru, S.; Moore, R. C.

    2013-12-01

    The goal of this study is to maximize the amplitude of 1-5 kHz ELF/VLF waves generated by ionospheric HF heating and measured at a ground-based ELF/VLF receiver. The optimization makes use of experimental observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) Observatory in Gakona, Alaska. During these experiments, the amplitude, phase, and propagation delay of the ELF/VLF waves were carefully measured. The HF beam was aimed at 15 degrees zenith angle in 8 different azimuthal directions, equally spaced in a circle, while broadcasting a 3.25 MHz (X-mode) signal that was amplitude modulated (square wave) with a linear frequency-time chirp between 1 and 5 kHz. The experimental observations are used to provide reference amplitudes, phases, and propagation delays for ELF/VLF waves generated at these specific locations. The presented optimization accounts for the trade-off between duty cycle, heated area, and the distributed nature of the source region in order to construct a "most efficient" phased array. The amplitudes and phases generated by modulated heating at each location are combined in post-processing to find an optimal combination of duty cycle, heating location, and heating order.

  5. Multi Station Frequency Response and Polarization of ELF/VLF Signals Generated via Ionospheric Modification

    Science.gov (United States)

    Maxworth, Ashanthi; Golkowski, Mark; University of Colorado Denver Team

    2013-10-01

    ELF/VLF wave generation via HF modulated ionospheric heating has been practiced for many years as a unique way to generate waves in the ELF/VLF band (3 Hz - 30 kHz). This paper presents experimental results and associated theoretical modeling from work performed at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska, USA. An experiment was designed to investigate the modulation frequency dependence of the generated ELF/VLF signal amplitudes and polarization at multiple sites at distances of 37 km, 50 km and 99 km from the facility. While no difference is observed for X mode versus O mode modulation of the heating wave, it is found that ELF/VLF amplitude and polarization as a function of modulated ELF/VLF frequency is different for each site. An ionospheric heating code is used to determine the primary current sources leading to the observations.

  6. Radio emissions from double RHESSI TGFs

    Science.gov (United States)

    Mezentsev, Andrew; Østgaard, Nikolai; Gjesteland, Thomas; Albrechtsen, Kjetil; Lehtinen, Nikolai; Marisaldi, Martino; Smith, David; Cummer, Steven

    2016-07-01

    A detailed analysis of Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) terrestrial gamma ray flashes (TGFs) is performed in association with World Wide Lightning Location Network (WWLLN) sources and very low frequency (VLF) sferics recorded at Duke University. RHESSI clock offset is evaluated and found to experience changes on the 5 August 2005 and 21 October 2013, based on the analysis of TGF-WWLLN matches. The clock offsets were found for all three periods of observations with standard deviations less than 100 μs. This result opens the possibility for the precise comparative analyses of RHESSI TGFs with the other types of data (WWLLN, radio measurements, etc.) In case of multiple-peak TGFs, WWLLN detections are observed to be simultaneous with the last TGF peak for all 16 cases of multipeak RHESSI TGFs simultaneous with WWLLN sources. VLF magnetic field sferics were recorded for two of these 16 events at Duke University. These radio measurements also attribute VLF sferics to the second peak of the double TGFs, exhibiting no detectable radio emission during the first TGF peak. Possible scenarios explaining these observations are proposed. Double (multipeak) TGFs could help to distinguish between the VLF radio emission radiated by the recoil currents in the +IC leader channel and the VLF emission from the TGF producing electrons.

  7. Time-of-arrival analysis applied to ELF/VLF wave generation experiments at HAARP

    Science.gov (United States)

    Moore, R. C.; Fujimaru, S.

    2012-12-01

    Time-of-arrival (TOA) analysis is applied to observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska. In 2012, a variety of ELF/VLF wave generation techniques were employed to identify the dominant source altitude for each case. Observations were performed for beat-wave modulation, AM modulation, STF modulation, ICD modulation, and cubic frequency modulation, among others. For each of these cases, we identify the dominant ELF/VLF source altitude and compare the experimental results with theoretical HF heating predictions.

  8. Observational characteristics of ionospheric magnetic VLF wave in the solar minimum year%太阳活动低年电离层磁场VLF波的观测特性研究

    Institute of Scientific and Technical Information of China (English)

    路立; 杨俊英; 曹晋滨; 张学民; 陈化然

    2011-01-01

    Ionospheric VLF wave recorded by the Instrument Magnetometer Search-Coil (IMSC) onboard the DEMETER spacecraft during 2007. The solar minimum year, were investigated statistically. By excluding the influence of geomagnetic activity with geomagnetic active indexes Dst ≤-30 nT, Kp≥3 and AE≥200 nT, the quiet global distributions of power intensity spectrum of VLF wave, and the corresponding statistical error, were displayed for different seasons in both the dayside and the nightside. By using the power spectral global distribution background, the spectrum characteristics, seasonal variations and geomagnetic active responses of the VLF wave were analyzed statistically. The magnetic VLF wave observation in the solar synchronous orbit can also be sensitive to the magnetic anomalies produced from the Earth. At the frequency channel of 15 kHz and 17. 5 kHz, the south Atlantic magnetic anomaly contour was presented clearly with the power spectral enhancement under the global background. The Bermuda geomagnetic anomalies caused VLF wave power spectral increase in almost all spectral bands at the nighttime, and showed about similar geomagnetic active responses as observed at higher latitude. Especially in the frequency band 12. 5~17. 5 kHz, we found that the power spectral increase along the edge of geographical plates, which will enhance our search for ionospheric seismo-response caused by the plate motion, and accumulate experiential background references for such anomalous signal identification quantitatively.%本文利用搭载在DEMETER卫星上的感应式磁力仪(Instrument Magnetometer Search-Coil,IMSC)探测数据分析了磁场甚低频(Very Low Frequency,VLF)波功率谱的空间分布.在排除地磁扰动影响(Dst≤-30 nT,Kp≥3,AE≥200 nT)的前提下,我们给出2007年不同季节,日侧和夜侧,磁场VLF波功率谱的全球分布的背景场探测和对应的统计误差分布.利用太阳活动低年的背景场探测统计分析了磁场VLF

  9. Observing BVOC emissions from Space

    Science.gov (United States)

    Oetjen, Hilke; Hewson, William; Comyn-Platt, Edward M.; Barkley, Michael P.; Bösch, Hartmut

    2016-04-01

    Formaldehyde (HCHO) is formed in the atmosphere as an intermediate from the oxidation of methane and other hydrocarbons such as isoprene, but also from combustion processes. Further, global and accurate measurements of HCHO from space are important since they can be used to infer global isoprene emission (e.g. Barkley et al., 2013), the primary biogenic volatile organic compound (BVOC) that cannot be monitored from space directly. However, isoprene is an important source of ozone and secondary organic aerosol, and a sink for the hydroxyl radical. HCHO absorbs in the ultraviolet wavelengths range and can therefore be detected by scattered sunlight absorption spectroscopy. Here we present measurements with the GOME-2 instrument. The first of the 3 GOME-2 instruments has been flying on MetOp-A since 2006 and MetOp-B has been launched in 2012. MetOp-C is expected to be launched in 2018. The University of Leicester retrieval (Hewson et al., 2015) is a well characterised state-of-the-art algorithm which has been used to infer HCHO vertical columns from MetOp-A, and more recently from MetOp-B. The results have been employed for creating a global, multi-year time series. This dataset has been exploited to analyse regional year-to-year variations in HCHO abundances and also to test emission models via comparisons to GEOS-Chem simulations. Barkley, M. P., et al. (2013), J. Geophys. Res. Atmos., 118, 6849-6868, doi:10.1002/jgrd.50552 Hewson, W., et al. (2015), Atmos. Meas. Tech., 8, 4055-4074, doi:10.5194/amt-8-4055-2015

  10. VLF wave injections from the ground

    Science.gov (United States)

    Helliwell, R. A.

    1983-01-01

    Experiments on wave-particle interactions using VLF whistler-mode waves injected into the magnetosphere from Antartica are described. The injected signals are single-frequency coherent waves whose amplitudes and frequencies may be changed slowly with time, or else two or more coherent wave trains transmitted simultaneously to determine the nature of the response to multifrequency excitation. The waves may be amplified 30 dB or more and may trigger intense emissions having bandwidths that vary from a few to several hundred Hertz. In most cases significant growth and triggering occur only when the driving signal is essentially monochromatic (bandwidth 10 Hz). If two frequencies are transmitted simultaneously the signal at the lower frequency tends to be suppressed by 20 dB or more. These results are interpreted in terms of a feedback interaction between the waves and counter-streaming cyclotron resonant electrons in a region several hundred wavelengths long, centered on the magnetic equator.

  11. Observation of very low frequency emissions at Indian Antarctic station, Maitri

    Indian Academy of Sciences (India)

    R P Patel; R P Singh; Ashok K Singh; A K Gwal; D Hamar

    2003-10-01

    Recently, we have succeeded in recording VLF emissions at the Indian Antarctic station, Maitri (geom. lat. 62° S, geom. long. 57.23°E, =4.5) using a T-type antenna, pre/main amplifiers and digital audio tape recorder. VLF hiss in the frequency ranges 11–13 kHz and 13–14.5 kHz and some riser-type emissions in the frequency range 3–5 kHz and magnetospheric lines at about 6.2, 8.0 and 9.2 kHz are reported for the first time. The generation and propagation mechanism of these emissions are discussed briefly.

  12. More evidence for a one-to-one correlation between Sprites and Early VLF perturbations

    DEFF Research Database (Denmark)

    Haldoupis, C.; Amvrosiadi, N.; Cotts, B. R. T.;

    2010-01-01

    Past studies have shown a correlation between sprites and early VLF perturbations, but the reported correlation varies widely from ∼50% to 100%. The present study resolves these large discrepancies by analyzing several case studies of sprite and narrowband VLF observations, in which multiple...... for this option to be resolved we need more studies using highly sensitive optical systems capable of detecting weaker sprites, sprite halos and elves....

  13. Constraining CO emission estimates using atmospheric observations

    Science.gov (United States)

    Hooghiemstra, P. B.

    2012-06-01

    We apply a four-dimensional variational (4D-Var) data assimilation system to optimize carbon monoxide (CO) emissions and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. In the first study only a limited amount of surface network observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) is used to test the 4D-Var system. Uncertainty reduction up to 60% in yearly emissions is observed over well-constrained regions and the inferred emissions compare well with recent studies for 2004. However, since the observations only constrain total CO emissions, the 4D-Var system has difficulties separating anthropogenic and biogenic sources in particular. The inferred emissions are validated with NOAA aircraft data over North America and the agreement is significantly improved from the prior to posterior simulation. Validation with the Measurements Of Pollution In The Troposphere (MOPITT) instrument shows a slight improved agreement over the well-constrained Northern Hemisphere and in the tropics (except for the African continent). However, the model simulation with posterior emissions underestimates MOPITT CO total columns on the remote Southern Hemisphere (SH) by about 10%. This is caused by a reduction in SH CO sources mainly due to surface stations on the high southern latitudes. In the second study, we compare two global inversions to estimate carbon monoxide (CO) emissions for 2004. Either surface flask observations from NOAA or CO total columns from the MOPITT instrument are assimilated in a 4D-Var framework. In the Southern Hemisphere (SH) three important findings are reported. First, due to their different vertical sensitivity, the stations-only inversion increases SH biomass burning emissions by 108 Tg CO/yr more than the MOPITT-only inversion. Conversely, the MOPITT-only inversion results in SH natural emissions

  14. Multi-spacecraft observations of quasiperiodic emissions

    Science.gov (United States)

    Nemec, Frantisek; Pickett, Jolene S.; Hospodarsky, George; Santolik, Ondrej; Bezdekova, Barbora; Hayosh, Mykhaylo; Parrot, Michel; Kurth, William; Kletzing, Craig

    2016-04-01

    Whistler mode electromagnetic waves observed in the inner magnetosphere at frequencies of a few kilohertz sometimes exhibit a nearly periodic modulation of the wave intensity. The modulation periods may range from several tens of seconds up to a few minutes, and such emissions are usually called quasiperiodic (QP) emissions. The origin of these events is still unclear, but it seems that their generation might be related to compressional ULF magnetic field pulsations which periodically modulate resonance conditions in the source region. From an observational point of view, single-point measurements are quite insufficient, as they do not allow us to distinguish between spatial and temporal variations of the emissions. Multipoint observations of these events are, on the other hand, rather rare. We present several QP wave events observed simultaneously by several different spacecraft (Cluster, Van Allen Probes, THEMIS, DEMETER). We demonstrate that although the quasiperiodic modulation is observed over a huge spatial region, individual spacecraft do not see the QP elements at exactly the same times. Moreover, when an event is observed simultaneously on the dawnside and on the duskside, the modulation period observed on the duskside is about twice larger than the modulation period observed on the dawnside. We present a qualitative explanation of these phenomena.

  15. Terrestrial VLF transmitter injection into the magnetosphere

    OpenAIRE

    İnan, Umran Savaş; Cohen, M. B.

    2012-01-01

    Terrestrial VLF transmitter injection into the magnetosphere M. B. Cohen1 and U. S. Inan1,2 Received 1 June 2012; revised 15 June 2012; accepted 18 June 2012; published 9 August 2012. [1] Very Low Frequency (VLF, 3–30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly impact the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributing to the formation of the slot region. However, calculations of the...

  16. Unexpected Very Low Frequency (VLF) Radio Events Recorded by the Ionospheric Satellite DEMETER

    Science.gov (United States)

    Parrot, M.; Berthelier, J. J.; Blecki, J.; Brochot, J. Y.; Hobara, Y.; Lagoutte, D.; Lebreton, J. P.; Němec, F.; Onishi, T.; Pinçon, J. L.; Píša, D.; Santolík, O.; Sauvaud, J. A.; Slominska, E.

    2015-05-01

    DEMETER was a low Earth orbiting microsatellite in operation between July 2004 and December 2010. Its scientific objective was the study of ionospheric perturbations in relation to seismic activity and man-made activities. Its payload was designed to measure electromagnetic waves over a large frequency range as well as ionospheric plasma parameters (electron and ion densities, fluxes of energetic charged particles). This paper will show both expected and unusual events recorded by the satellite when it was in operation. These latter events have been selected from the DEMETER database because they are rare or even have never been observed before, because they have a very high intensity, or because they are related to abnormalities of the experiments under particular plasma conditions. Some events are related to man-made radio waves emitted by VLF ground-based transmitters or power line harmonic radiation. Natural waves, such as atypical quasi-periodic emissions or uncommon whistlers, are also shown.

  17. Whistler propagation in ionospheric density ducts: Simulations and DEMETER observations

    Science.gov (United States)

    Woodroffe, J. R.; Streltsov, A. V.; Vartanyan, A.; Milikh, G. M.

    2013-11-01

    On 16 October 2009, the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite observed VLF whistler wave activity coincident with an ionospheric heating experiment conducted at HAARP. At the same time, density measurements by DEMETER indicate the presence of multiple field-aligned enhancements. Using an electron MHD model, we show that the distribution of VLF power observed by DEMETER is consistent with the propagation of whistlers from the heating region inside the observed density enhancements. We also discuss other interesting features of this event, including coupling of the lower hybrid and whistler modes, whistler trapping in artificial density ducts, and the interference of whistlers waves from two adjacent ducts.

  18. The stopping time of the ULF/VLF wave and energetic (

    Science.gov (United States)

    Anagnostopoulos, George; Athanasiou, Michael; Vassiliadis, Basil; Karli, Anna; Fotinopoulos, Stavros

    2014-05-01

    An elaboration of the Demeter observations made in the topside ionosphere above Greece reveals the following constrains with the great (M≥6.4) earthquakes (EQs) occurred in the Greek territory: (1) ULF/VLF wave and electron precipitation (EP) activity was recorded by DEMETER for some days before the earthquake occurrence time, (2) all three phenomena (ULF/VLF/EP) ceased a few hours before all the Greek earthquakes. Therefore, we infer that the satellite observations above Greece during the period 2005-2010 are consistent with the stopping time of ULF/VLF/EP activity as a short time (few hours) earthquake predictor. These results for Greek EQs are in agreement with statistical results from an examination of the ULF/VLF/EP variations observed by DEMETER before the majority of the great (M≥7) earthquakes occurred worldwide, during the same period (2005-2010). Precise statistical results of the ULF/VLF/EP beginning and stopping times before the M≥7 before EQs are also presented in this work.

  19. Magion 5 observations of chorus-like emissions and their propagation features as inferred from ray-tracing simulation

    Directory of Open Access Journals (Sweden)

    J. Chum

    Full Text Available After reviewing briefly the present state of knowledge about chorus-like emissions, we present an overview of Magion 5 satellite observations of these emissions in the inner magnetosphere of the Earth. From the extensive VLF data recorded on board the Magion 5 satellite, we show examples of different types of discrete elements, representing rising and falling tones, and discuss their spectral properties, such as the bandwidth and the characteristic frequency as compared to the equatorial electron gyrofrequency. We analyse the possibility of satellite observation of discrete elements, assuming nonducted wave propagation from the source. As for the characteristic dimension of the generation region, we apply the figures obtained from the recently published correlation analysis of chorus emission recorded by four satellites in the Cluster experiment. We conclude that different frequencies in the chorus element should be emitted in a certain span of wave normal angles, so that the whole element could be observed far from the generation region.

    Key words. Magnetospheric physics (plasmasphere; plasma waves and instabilities – Space plasma physics (wave-particle interactions – Ionosphere (wave propagation

  20. Thermal emission spectrometer experiment - Mars Observer mission

    Science.gov (United States)

    Christensen, Philip R.; Anderson, Donald L.; Chase, Stillman C.; Clark, Roger N.; Kieffer, Hugh H.; Malin, Michael C.; Pearl, John C.; Carpenter, James; Bandiera, Nuno; Brown, F. G.

    1992-01-01

    The paper describes the thermal emission spectrometer (TES) designed for the Mars Observer mission. The TES measurements of the surface and the atmosphere of Mars will be used to determine and map the composition of the surface rocks, minerals, and the condensates. Examples of information that will be obtained from TES data include mineral abundance maps, condensate properties and their distribution in time and space, aerosol properties and their distribution in time and space, the rock abundance, the polar energy balance, and properties of gaseous species. Where appropriate, these derived parameters will be distributed in the form of gridded map, to allow direct comparison with other derived data sets.

  1. Satellite observation of plasma-wave disturbances induced by high-power radio emission from the NWC transmitter

    International Nuclear Information System (INIS)

    In this work, we present the results of in-situ measurements of the characteristics of electromagnetic and plasma disturbances in the ionospheric region modified by high-power emission from the NWC transmitter, which were obtained using the onboard equipment of the French microsatellite DEMETER. It is shown that under the influence of VLF emissions from the ground-based transmitters, artificial plasma-wave channels with typical transverse scales of about 1000 km can be formed in the ionospheric plasma.

  2. Analysis of observations backing up the existence of VLF and ionospheric TEC anomalies before the Mw6.1 earthquake in Greece, January 26, 2014

    Science.gov (United States)

    Sanchez-Dulcet, F.; Rodríguez-Bouza, M.; Silva, H. G.; Herraiz, M.; Bezzeghoud, M.; Biagi, P. F.

    The present work integrates ground-based ionosphere measurements using very-low-frequency radio transmissions with satellite measurements of the total electron content to draw common conclusions about the possible impact that the Mw6.1 earthquake that took place in Greece on January 26, 2014, had on the ionosphere. Very-low-frequency radio signals reveal the existence of an ∼4-day anomaly in the wavelet spectra of the signals received inside the earthquake preparation zone and a significant increase in the normalized variance of the signals prior to the earthquake (approximately 1 day before). Through total electron content analysis, it was possible to identify a clear anomaly from 15:00 until 20:00 UT on the day before the earthquake that appears again on the day of the earthquake between 07:00 UT and 08:00 UT. The anomalous values reach TEC∗Sigma ∼4.36 and 3.11, respectively. Their spatial and temporal distributions give grounds to assume a possible link with the earthquake preparation. The geomagnetic, solar and weather conditions during the considered period are presented and taken into account. This work is an initial and original step towards a multi-parameter approach to the problem of the possible earthquake-related effects on the ionosphere joining observations made from both ground stations and satellites. A well-founded knowledge of these phenomena is clearly necessary before dealing with their application to earthquake prediction purposes.

  3. 100 Days of ELF/VLF Generation via HF Heating with HAARP (Invited)

    Science.gov (United States)

    Cohen, M.; Golkowski, M.

    2013-12-01

    ELF/VLF radio waves are difficult to generate with conventional antennas. Ionospheric HF heating facilities generate ELF/VLF waves via modulated heating of the lower ionosphere. HF heating of the ionosphere changes the lower ionospheric conductivity, which in the presence of natural currents such as the auroral electrojet, creates an antenna in the sky when heating is modulated at ELF/VLF frequencies. We present a summary of nearly 100 days of ELF/VLF wave generation experiments at the 3.6 MW HAARP facility near Gakona, Alaska, and provide a baseline reference of ELF/VLF generation capabilities with HF heating. Between February 2007 and August 2008, HAARP was operated on close to 100 days for ELF/VLF wave generation experiments, at a variety of ELF/VLF frequencies, seasons and times of day. We present comprehensive statistics of generated ELF/VLF magnetic fields observed at a nearby site, in the 500-3500 Hz band. Transmissions with a specific HF beam configuration (3.25 MHz, vertical beam, amplitude modulation) are isolated so the data comparison is self-consistent, across nearly 5 million individual measurements of either a tone or a piece of a frequency-time ramp. There is a minimum in the average generation close to local midnight. It is found that generation during local nighttime is on average weaker, but more highly variable, with a small number of very strong generation periods. Signal amplitudes from day to day may vary by as much as 20-30 dB. Generation strengthens by ~5 dB during the first ~30 minutes of transmission, which may be a signature of slow electron density changes from sustained HF heating. Theoretical calculations are made to relate the amplitude observed to the power injected into the waveguide and reaching 250 km. The median power generated by HAARP and injected into the waveguide is ~0.05-0.1 W in this base-line configuration (vertical beam, 3.25 MHz, amplitude modulation), but may have generated hundreds of Watts for brief durations

  4. Comparative statistical and spectral studies of seismic and non-seismic sub-ionospheric VLF anomalies

    Science.gov (United States)

    Wolbang, Daniel; Biernat, Helfried; Schwingenschuh, Konrad; Eichelberger, Hans; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed Y.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Friedrich, Martin

    2013-04-01

    measured and derived VLF parameters are compared with VLF observations several weeks before an earthquake (e.g. L'Aquila, Italy, April 6, 2009) and with co- and post-seismic phenomena. It is shown that this comparative study will improve the one parameter seismo-electromagnetic VLF methods. References: [1] A. Molchanov, M. Hayakawa: Seismo-Electromagnetics and related Phenomena: History and latest results, Terrapub, 2008. [2] S. Pulinets, K. Boyarchuk: Ionospheric Precursors of Earthquakes, Springer, 2004 [3] A. Rozhnoi et al.: Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra, National Hazards and Earth System Sciences, 7, 625-628, 2007.

  5. ELF/VLF wave disturbances detected by the DEMETER satellite over the HAARP transmitter

    Science.gov (United States)

    Titova, Elena; Demekhov, Andrei; Parrot, Michel; Mogilevsky, Mikhail; Mochalov, Alexey; Pashin, Anatoly

    We report observations of electromagnetic the ELF/VLF wave disturbances by the DEMETER satellite (670 km altitude) overflying the HAARP heating facility (62.39(°) N, 145.15(°) W, L = 4.9). The HAARP HF transmitter operated at the maximum available power of 3.6 MW, O-mode polarization, and the beam directed towards the magnetic zenith. ELF/VLF waves caused by the HAARP heating are detected by the DEMETER satellite when the HF radio wave frequency was close to the critical frequency (foF2) of the ionospheric F2 layer but below it. ELF/VLF wave disturbances observed above the HAARP transmitter were detected by electrical antennas in an area with characteristic size 10 (2) km. We analyze amplitude and polarization spectra of the ELF disturbances and compare them with the characteristics of natural ELF hiss above HAARP. The VLF wave disturbances in the topside ionosphere above the HAARP transmitter were detected in the frequency ranges 8-17 kHz and 15-18 kHz which are close to the lower hybrid resonance frequency f _LHR in the heating region and its second harmonic (2f _LHR), respectively. In the case where the HAARP HF power was modulated, the detected VLF waves were also modulated with the same frequency whereas in the ELF frequency range the modulation period of the HAARP power was not observed. Possible mechanisms of generation of the ELF/VLF disturbances produced by the HAARP transmitter in the topside ionosphere are discussed.

  6. Constraining CO emission estimates using atmospheric observations

    NARCIS (Netherlands)

    Hooghiemstra, P.B.

    2012-01-01

    We apply a four-dimensional variational (4D-Var) data assimilation system to optimize carbon monoxide (CO) emissions and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. In the first study only a limited amount of surface network obs

  7. ULF/ELF emissions observed in Japan, possibly associated with the Chi-Chi earthquake in Taiwan

    Directory of Open Access Journals (Sweden)

    K. Ohta

    2001-01-01

    Full Text Available ULF/ELF emission observation has been performed at Nakatsugawa observatory (geographic coordinates; 35.4° N, 137.5° E, Gifu prefecture since January 1999. The equipment consists of three-orthogonal magnetic sensors (induction coils, amplifiers, A/D converters and the data logger with a computer. The frequency range of observation is from 0.001 Hz to 50 Hz. The serious changes in ELF magnetic field intensity were detected on 20 September 1999, in such a way that the ELF noise level is found to increase by more than 5 dB from the normal level for about 1.5 h during 21:30–23:00 Japanese Standard Time on 20 September and also the upper limit extends up to 50 Hz. A careful comparison with the nearby lightning as detected by VLF, enables us to confirm that this abnormal ELF noise level increase is not due to the nearby lightning. The phase difference of these ELF emissions (BX , BY was measured, and indicates that these ELF emissions are linearly polarized, suggesting that they have propagated in the subionospheric waveguide over long distances. This polarization result enables us to perform goniometric direction finding and the result shows that the main direction of these ULF/ELF emissions is toward Taiwan. Hence, it is likely that such ULF/ELF emissions are associated with the Chi-Chi earth-quake in Taiwan at 02:27 Japanese Standard Time on 21 September 1999 (M = 7.6; depth 11 km.

  8. Excitation of VLF quasi-electrostatic oscillations in the ionospheric plasma

    Directory of Open Access Journals (Sweden)

    B. Lundin

    Full Text Available A numerical solution of the dispersion equation for electromagnetic waves in a hot magnetized collisionless plasma has shown that, in a current-free ionospheric plasma, the distortion of the electron distribution function reproducing the downward flow of a thermal electron component and the compensating upward flow of the suprathermal electrons, which are responsible for the resulting heat flux, can destabilize quasi-electrostatic ion sound waves. The numerical analysis, performed with ion densities and electron temperature taken from the data recorded by the Interkosmos-24 (IK-24, Aktivny satellite, is compared with a VLF spectrum registered at the same time on board. This spectrum shows a wide frequency band emission below the local ion plasma frequency. The direction of the electron heat flux inherent to the assumed model of VLF emission generation is discussed

  9. Study of the effect of solar flares on VLF signals during D-layer preparation or disappearance time

    Science.gov (United States)

    Ray, Suman; Chakrabarti, Sandip Kumar; Palit, Sourav

    2016-07-01

    "Very Low Frequency" (VLF) is one of the bands of the Radio waves having frequency 3-30 KHz, which propagates through the Earth-ionosphere wave-guide. In relation to propagation of radio waves through ionosphere, low mass and high mobility cause electrons to play a vital role. Electrons are not distributed uniformly in the ionosphere and depending on this factor, ionosphere has different layers namely D, E and F. Different ionospheric layers generally exist during day and night time. During day-time when the main source of the ionization of the ionosphere is Sun, the lower most layer of ionosphere is D-layer. But during the night-time when Sun is absent and cosmic ray is the main source of the ionization of the ionosphere, this D-layer disappears and E-layer becomes the lower most region of the ionosphere. Normally, patterns of VLF signal depend on regular solar flux variations. However, during solar flares extra energetic particles are released from Sun, which makes the changes in the ionization of the ionosphere and these changes can perturb VLF signal amplitude. Usually if a solar flare occurs during any time of day, it only affects the amplitude and phase of the VLF signals. But in the present work, we found the if the flare occurs during D-layer preparation / disappearance time, then it will not only affect to amplitude and phase of the VLF signals but also to terminator times of VLF signals. We have observed that the sun set terminator time of the VLF signals shifted towards night time due to the effect of a M-class solar flare which occurred during the D-layer disappearance time. The shift is so high that it crossed 5σ level. We are now trying to a make model using the ion-chemistry and LWPC code to explain this observed effect.

  10. Cosmic rays from multiwavelength observations of the Galactic diffuse emission

    CERN Document Server

    Orlando, Elena

    2016-01-01

    Cosmic rays (CRs) generate diffuse emission while interacting with the Galactic magnetic field (B-field), the interstellar gas and the radiation field. This diffuse emission extends from radio, microwaves, through X-rays, to high-energy gamma rays. Diffuse emission has considerably increased the interest of the astrophysical community due to recent detailed observations by Planck, Fermi-LAT, and by very-high-energy Cherenkov telescopes. Observations of this emission and comparison with detailed predictions are used to gain information on the properties of CRs, such as their density, spectra, distribution and propagation in the Galaxy. Unfortunately disentangling and characterizing this diffuse emission strongly depends on uncertainties in the knowledge of unresolved sources, gas, radiation fields, and B-fields, other than CRs throughout the Galaxy. We report here on recent multiwavelength observations of the Galactic diffuse emission, and discuss the diffuse emission produced by CRs and its model uncertaintie...

  11. Investigation of TEC and VLF space measurements associated to L'Aquila (Italy earthquakes

    Directory of Open Access Journals (Sweden)

    G. Stangl

    2011-04-01

    Full Text Available In this study, we report on Total Electron Content (TEC and Very Low Frequency (VLF space measurements derived from Global Positioning System (GPS and DEMETER satellites, respectively. These measurements are associated with the earthquake (EQ of a magnitude of 6.3, which occurred on 6 April 2009, in L'Aquila (Italy. Anomaly features are derived from the analysis of TEC and VLF observations recorded two weeks before and after the seismic event occurrence. A TEC map with an interpolated regional pixel resolution of 1° × 1° × 15 min in latitude, longitude and time was generated, allowing for the checking of a possible presence of disturbances over the L'Aquila region. This analysis is combined with the study of the time profile associated to the VLF flux density variations recorded by the Instrument Champ Electrique (ICE experiment on-board DEMETER satellite. We discuss, on the one hand, the combination efficiency of the electronic density and the VLF electromagnetic measurements and, on the other hand, the difficulty to distinguish between global effects and regional ones related to the earthquake.

  12. Study of latitudinal effects on VLF transmitter signals recorded by DEMETER/ICE experiment

    Science.gov (United States)

    Boudjada, M. Y.; Schwingenschuh, K.; Berthelier, J. J.; Döller, R.; Galopeau, P. H. M.; Parrot, M.; Stangl, G.; Biernat, H.; Voller, W.; Besser, B.

    2010-05-01

    We report on VLF transmitter signals observed by the ‘Instrument Capteur Electrique' (ICE) experiment onboard the DEMETER micro-satellite. The DEMETER polar and circular sun-synchronous orbits lead to cover an invariant latitude range between -65° and +65° where up- and down-going half-orbits correspond to night-time (22:00 LT) and day-time (10:00 LT), respectively. The DEMETER orbit features permit to record signals emitted by some VLF ground-stations and detected by ICE experiment. We consider three transmitter signals emitted by stations in Europe (Germany, DFY, 16.58 kHz), in Asia (Japan, JP, 17.8 kHz) and in Australia (Australia, NWC, 19.8 kHz). We study the variation of these VLF signals taking into consideration the DEMETER satellite latitudes .We emphasis on latitudes where the satellite is close to the Earth's sub-auroral regions. We discuss particularly the presence, or not, of auroral magnetic activity effect on the VLF transmitter signals.

  13. Resonant scattering of energetic electrons in the outer radiation belt by HAARP-induced ELF/VLF waves

    Science.gov (United States)

    Chang, Shanshan; Zhu, Zhengping; Ni, Binbin; Cao, Xing; Luo, Weihua

    2016-10-01

    Several extremely low-frequency (ELF)/very low-frequency (VLF) wave generation experiments have been performed successfully at High-Frequency Active Auroral Research Program (HAARP) heating facility and the artificial ELF/VLF signals can leak into the outer radiation belt and contribute to resonant interactions with energetic electrons. Based on the artificial wave properties revealed by many of in situ observations, we implement test particle simulations to evaluate the effects of energetic electron resonant scattering driven by the HAARP-induced ELF/VLF waves. The results indicate that for both single-frequency/monotonic wave and multi-frequency/broadband waves, the behavior of each electron is stochastic while the averaged diffusion effect exhibits temporal linearity in the wave-particle interaction process. The computed local diffusion coefficients show that, the local pitch-angle scattering due to HARRP-induced single-frequency ELF/VLF whistlers with an amplitude of ∼10 pT can be intense near the loss cone with a rate of ∼10-2 rad2 s-1, suggesting the feasibility of HAARP-induced ELF/VLF waves for removal of outer radiation belt energetic electrons. In contrast, the energy diffusion of energetic electrons is relatively weak, which confirms that pitch-angle scattering by artificial ELF/VLF waves can dominantly lead to the precipitation of energetic electrons. Moreover, diffusion rates of the discrete, broadband waves, with the same amplitude of each discrete frequency as the monotonic waves, can be much larger, which suggests that it is feasible to trigger a reasonable broadband wave instead of the monotonic wave to achieve better performance of controlled precipitation of energetic electrons. Moreover, our test particle scattering simulation show good agreement with the predictions of the quasi-linear theory, confirming that both methods are applied to evaluate the effects of resonant interactions between radiation belt electrons and artificially generated

  14. 100 days of ELF/VLF generation via HF heating with HAARP

    Science.gov (United States)

    Cohen, M. B.; Gołkowski, M.

    2013-10-01

    Extremely low frequency/very low frequency (ELF/VLF) radio waves are difficult to generate with conventional antennas. Ionospheric high frequency (HF) heating facilities generate ELF/VLF waves via modulated heating of the lower ionosphere. HF heating of the ionosphere changes the lower ionospheric conductivity, which in the presence of natural currents such as the auroral electrojet creates an antenna in the sky when heating is modulated at ELF/VLF frequencies. We present a summary of nearly 100 days of ELF/VLF wave generation experiments at the 3.6 MW High Frequency Active Auroral Research Program (HAARP) facility near Gakona, Alaska, at a variety of ELF/VLF frequencies, seasons, and times of day. We present comprehensive statistics of generated ELF/VLF magnetic fields observed at a nearby site, in the 500-3500 Hz band. Transmissions with a specific HF beam configuration (3.25 MHz, vertical beam, amplitude modulation) are isolated so the data comparison is self-consistent, across nearly 5 million individual measurements of either a tone or a piece of a frequency-time ramp. There is a minimum in the average generation close to local midnight. It is found that generation during local nighttime is on average weaker but more highly variable, with a small number of very strong generation periods. Signal amplitudes from day to day may vary by as much as 20-30 dB. Generation strengthens by ˜5 dB during the first ˜30 min of transmission, which may be a signature of slow electron density changes from sustained HF heating. Theoretical calculations are made to relate the amplitude observed to the power injected into the waveguide and reaching 250 km. The median power generated by HAARP and injected into the waveguide is ˜0.05-0.1 W in this baseline configuration (vertical beam, 3.25 MHz, amplitude modulation) but may have generated hundreds of watts for brief durations. Several efficiency improvements have improved the ELF/VLF wave generation efficiency further.

  15. Prompt Emission Observations of Swift BAT Bursts

    Science.gov (United States)

    Barthelmy, Scott

    2009-01-01

    We review the prompt emission properties of Swift BAT gamma-ray bursts (GRBs). We present the global properties of BAT GRBs based on their spectral and temporal characteristics. The BAT T90 and T50 durations peak at 80 and 20 s, respectively. The peak energy (Epeak) of about 60% of BAT GRBs is very likely to be less than 1.00 keV. We also present the BAT characteristics of GRBs with soft spectra, so called Xray flashes (XRFs). We will compare the BAT GRBs and XRFs parameter distribution to the other missions.

  16. Turbulent Plasmaspheric Boundary Layer: Observables and Consequences

    Science.gov (United States)

    Mishin, Evgeny

    2014-10-01

    In situ satellite observations reveal strong lower hybrid/fast magnetosonic turbulence and broadband hiss-like VLF waves in the substorm subauroral geospace at and earthward of the electron plasmasheet boundary. These coincide with subauroral ion drifts/polarization streams (SAID/SAPS) in the plasmasphere and topside ionosphere. SAID/SAPS appear in ~10 min after the substorm onset consistent with the fast propagation of substorm injection fronts. The SAID channel follows the dispersionless cutoff of the energetic electron flux at the plasmapause. This indicates that the cold plasma maintains charge neutrality within the channel, thereby short-circuiting the injected plasma jet (injection fronts over the plasmasphere. Plasma turbulence leads to the circuit resistivity and magnetic diffusion as well as significant electron heating and acceleration. As a result, a turbulent boundary layer forms between the inner edge of the electron plasmasheet and plasmasphere. The SAID/SAPS-related VLF emissions appear to constitute a distinctive subset of substorm/storm-related VLF activity in the region co-located with freshly injected energetic ions inside the plasmasphere. Significant pitch-angle diffusion coefficients suggest that substorm SAID/SAPS-related VLF waves could be responsible for the alteration of the outer radiation belt boundary during (sub)storms. Supported by the Air Force Office of Scientific Research.

  17. Tectonomagnetic and VLF electromagnetic signals in Central Italy

    Directory of Open Access Journals (Sweden)

    P. Palangio

    2004-06-01

    Full Text Available Tectonomagnetic field observations from absolute magnetic field level measurements were undertaken in Central Italy in an area extending between latitude 41°N and 43°N and between longitude 13°E and 15°E. Moreover,natural electromagnetic signals from a system of two VLF search coil wide-band antennas were collected at the geomagnetic observatory of L Aquila (42º23'N, 13º19'E. The analysis of these data allowed the investigation of the electromagnetic properties of the study area at different time and spatial lengthscales. Tectonomagnetic field observations were obtained comparing data simultaneously recorded at three magnetometer stations using L'Aquila Observatory as a reference for differentiation. We report on the time evolution of magnetic and electromagnetic indicators related to local and regional seismic activity.

  18. Fast Emission Estimates in China Constrained by Satellite Observations (Invited)

    Science.gov (United States)

    Mijling, B.; van der A, R.

    2013-12-01

    Emission inventories of air pollutants are crucial information for policy makers and form important input data for air quality models. Unfortunately, bottom-up emission inventories, compiled from large quantities of statistical data, are easily outdated for an emerging economy such as China, where rapid economic growth changes emissions accordingly. Alternatively, top-down emission estimates from satellite observations of air constituents have important advantages of being spatial consistent, having high temporal resolution, and enabling emission updates shortly after the satellite data become available. Constraining emissions from concentration measurements is, however, computationally challenging. Within the GlobEmission project of the European Space Agency (ESA) a new algorithm has been developed, specifically designed for fast daily emission estimates of short-lived atmospheric species on a mesoscopic scale (0.25 × 0.25 degree) from satellite observations of column concentrations. The algorithm needs only one forward model run from a chemical transport model to calculate the sensitivity of concentration to emission, using trajectory analysis to account for transport away from the source. By using a Kalman filter in the inverse step, optimal use of the a priori knowledge and the newly observed data is made. We apply the algorithm for NOx emission estimates in East China, using the CHIMERE model together with tropospheric NO2 column retrievals of the OMI and GOME-2 satellite instruments. The observations are used to construct a monthly emission time series, which reveal important emission trends such as the emission reduction measures during the Beijing Olympic Games, and the impact and recovery from the global economic crisis. The algorithm is also able to detect emerging sources (e.g. new power plants) and improve emission information for areas where proxy data are not or badly known (e.g. shipping emissions). The new emission estimates result in a better

  19. Egret observations of the extragalactic gamma-ray emission

    DEFF Research Database (Denmark)

    Sreekumar, P.; Bertsch, D.L.; Dingus, B.L.;

    1998-01-01

    The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions...... likely explanation for the origin of this extragalactic high-energy gamma-ray emission is that it arises primarily from unresolved gamma-ray-emitting blazars....

  20. MLR events and associated triggered emissions observed by DEMETER

    Science.gov (United States)

    Parrot, M.; Němec, F.

    2009-11-01

    This paper gives an overview of different sets of new Magnetospheric Line Radiation (MLR) observed by the satellite DEMETER. Different types of emissions have been observed: emissions called Power Line Harmonic Radiation (PLHR) with frequency lines exactly separated by 50/100 or 60/120 Hz, emissions with frequency lines not exactly separated by 50/100 or 60/120 Hz and drifting in frequency (MLR). By comparison with past observations one can say that some MLR events are due to man-made PLHR which may suffer a non-linear gyro-resonant interaction at the magnetic equator. It is also shown that periodic emissions are very often associated with the MLR. In this case the origin of these waves is natural. The lines are produced by the periodicity and the frequency band limits of the individual elements which causes the appearance of lines on the spectrograms. Finally the paper shows that MLR can trigger emissions.

  1. Suzaku Observations of Charge Exchange Emission from Solar System Objects

    Science.gov (United States)

    Ezoe, Y.; Fujimoto, R.; Yamasaki, N. Y.; Mitsuda, K.; Ohashi, T.; Ishikawa, K.; Oishi, S.; Miyoshi, Y; Terada, N.; Futaana, Y.; Porter, F. S.; Brown, G. V.

    2012-01-01

    Recent results of charge exchange emission from solar system objects observed with the Japanese Suzaku satellite are reviewed. Suzaku is of great importance to investigate diffuse X-ray emission like the charge exchange from planetary exospheres and comets. The Suzaku studies of Earth's exosphere, Martian exosphere, Jupiter's aurorae, and comets are overviewed.

  2. Observation of Polarised Microwave Emission from Cosmic Ray Air Showers

    CERN Document Server

    Smida, R; Engel, R; Arteaga-Velazquez, J C; Bekk, K; Bertaina, M; Bluemer, J; Bozdog, H; Brancus, I M; Chiavassa, A; Cossavella, F; Di Pierro, F; Doll, P; Fuchs, B; Fuhrmann, D; Grupen, C; Haungs, A; Heck, D; Hoerandel, J R; Huber, D; Huege, T; Kampert, K -H; Kang, D; Klages, H; Kleifges, M; Kroemer, O; Link, K; Luczak, P; Ludwig, M; Mathes, H J; Mayer, H J; Mathys, S; Melissas, M; Morello, C; Neunteufel, P; Oehlschlaeger, J; Palmieri, N; Pekala, J; Pierog, T; Rautenberg, J; Rebel, H; Riegel, M; Roth, M; Salamida, F; Schieler, H; Schoo, S; Schroeder, F G; Sima, O; Stasielak, J; Toma, G; Trinchero, G C; Unger, M; Weber, M; Weindl, A; Wilczynski, H; Will, M; Wochele, J; Zabierowski, J

    2013-01-01

    We report on the first direct measurement of the basic features of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the signals of the microwave antennas of the CROME (Cosmic-Ray Observation via Microwave Emission) experiment have been read out and searched for signatures of radio emission by high-energy air showers. Microwave signals have been detected for more than 30 showers with energies above $3\\times10^{16}$\\,eV. The observations presented in this Letter are consistent with a mainly forward-beamed, coherent and polarised emission process in the GHz frequency range. An isotropic, unpolarised radiation is disfavoured as the dominant emission model. The measurements show that microwave radiation offers a new means of studying air showers at very high energy.

  3. A tiered observational system for anthropogenic methane emissions

    Science.gov (United States)

    Duren, R. M.; Miller, C. E.; Hulley, G. C.; Hook, S. J.; Sander, S. P.

    2014-12-01

    Improved understanding of anthropogenic methane emissions is required for closing the global carbon budget and addressing priority challenges in climate policy. Several decades of top-down and bottom-up studies show that anthropogenic methane emissions are systematically underestimated in key regions and economic sectors. These uncertainties have been compounded by the dramatic rise of disruptive technologies (e.g., the transformation in the US energy system due to unconventional gas and oil production). Methane flux estimates derived from inverse analyses and aircraft-based mass balance approaches underscore the disagreement in nationally and regionally reported methane emissions as well as the possibility of a long-tail distribution in fugitive emissions spanning the US natural gas supply chain; i.e. a small number of super-emitters may be responsible for most of the observed anomalies. Other studies highlight the challenges of sectoral and spatial attribution of fugitive emissions - including the relative contributions of dairies vs oil and gas production or disentangling the contributions of natural gas transmission, distribution, and consumption or landfill emissions in complex urban environments. Limited observational data remains a foundational barrier to resolving these challenges. We present a tiered observing system strategy for persistent, high-frequency monitoring over large areas to provide remote detection, geolocation and quantification of significant anthropogenic methane emissions across cities, states, basins and continents. We describe how this would both improve confidence in methane emission estimates and expedite resolution of fugitive emissions and leaks. We summarize recent prototype field campaigns that employ multiple vantage points and measurement techniques (including NASA's CARVE and HyTES aircraft and PanFTS instrument on Mt Wilson). We share preliminary results of this tiered observational approach including examples of individual

  4. Prediction of the Nighttime VLF Subionospheric Signal Amplitude by Using Nonlinear Autoregressive with Exogenous Input Neural Network Model

    Science.gov (United States)

    Santosa, H.; Hobara, Y.; Balikhin, M. A.

    2015-12-01

    Very Low Frequency (VLF) waves have been proposed as an approach to study and monitor the lower ionospheric conditions. The ionospheric perturbations are identified in relation with thunderstorm activity, geomagnetic storm and other factors. The temporal dependence of VLF amplitude has a complicated and large daily variabilities in general due to combinations of both effects from above (space weather effect) and below (atmospheric and crustal processes) of the ionosphere. Quantitative contributions from different external sources are not known well yet. Thus the modelling and prediction of VLF wave amplitude are important issues to study the lower ionospheric responses from various external parameters and to also detect the anomalies of the ionosphere. The purpose of the study is to model and predict nighttime average amplitude of VLF wave propagation from the VLF transmitter in Hawaii (NPM) to receiver in Chofu (CHO) Tokyo, Japan path using NARX neural network. The constructed model was trained for the target parameter of nighttime average amplitude of NPM-CHO path. The NARX model, which was built based on daily input variables of various physical parameters such as stratosphere temperature, cosmic rays and total column ozone, possessed good accuracies. As a result, the constructed models are capable of performing accurate multistep ahead predictions, while maintaining acceptable one step ahead prediction accuracy. The results of the predicted daily VLF amplitude are in good agreement with observed (true) value for one step ahead prediction (r = 0.92, RMSE = 1.99), multi-step ahead 5 days prediction (r = 0.91, RMSE = 1.14) and multi-step ahead 10 days prediction (r = 0.75, RMSE = 1.74). The developed model indicates the feasibility and reliability of predicting lower ionospheric properties by the NARX neural network approach, and provides physical insights on the responses of lower ionosphere due to various external forcing.

  5. Models of ionospheric VLF absorption of powerful ground based transmitters

    OpenAIRE

    İnan, Umran Savaş; Cohen, M. B; Lehtinen, N. G

    2012-01-01

    Models of ionospheric VLF absorption of powerful ground based transmitters M. B. Cohen,1 N. G. Lehtinen,1 and U. S. Inan1,2 Received 5 November 2012; accepted 16 November 2012; published 29 December 2012. [1] Ground based Very Low Frequency (VLF, 3–30 kHz) radio transmitters play a role in precipitation of energetic Van Allen electrons. Initial analyses of the contribution of VLF transmitters to radiation belt losses were based on early models of trans-ionospheric prop...

  6. Upper Limits on O VI Emission from Voyager Observations

    Indian Academy of Sciences (India)

    Jayant Murthy

    2002-03-01

    We have examined 426 Voyager fields distributed across the sky for O VI ( 1032/1038 Å) emission from the Galactic diffuse interstellar medium. No such emission was detected in any of our observed fields. Our most constraining limit was a 90% confidence upper limit of 2600 photons cm-2 sr-1 s-1 on the doublet emission in the direction (l, b) = (117.3, 50.6). Combining this with an absorption line measurement in nearly the same direction allows us to place an upper limit of 0.01 cm-3 on the electron density of the hot gas in this direction. We have placed 90% confidence upper limits of less than or equal to 10,000 photons cm-2 sr-1 s-1 on the O VI emission in 16 of our 426 observations.

  7. Jupiter's Various Auroral Emission Enhancements Observed by Hisaki/EXCEED

    Science.gov (United States)

    Tao, Chihiro

    2016-07-01

    Onboard a JAXA Earth-orbiting platform, the planetary telescope Hisaki monitors extreme ultraviolet emissions from Jovian aurora and Io plasma torus continuously. Hisaki succeeded to detect sporadic, large auroral power enhancements displaying both short- (a few rotations) variations and their modulations by Io's volcanic activity over several weeks. The spectral information taken by Hisaki enables us to investigate (1) the time variation of the auroral electron precipitating fluxes during these emission enhancements, (2) the occurrence statistics of polar-dominant events, and (3) the associated magnetospheric dynamics for these emission enhancement events using Knight's aurora acceleration theory. Expected collaborative observations with Juno will be discussed.

  8. Observed impact of aerosols on Arctic cloud emissivity

    OpenAIRE

    2011-01-01

    IPCC results indicate that the main bulk of uncertainties on global warming is within aerosol-cloud interactions. Based on observations this thesis aims to measure how anthropogenic aerosol from mid-latitudes increase emissivity of clouds in the Arctic, thus increasing Arctic surface temperatures. Until recently this effect have been thought insignificant, but recent studies indicate that in the Arctic, many clouds may be susceptible to changes in emissivity. This is due to the few CCN an...

  9. Evidence for Nonlinear VLF Wave Physics from Van Allen Probe Data

    Science.gov (United States)

    Crabtree, C. E.; Tejero, E. M.; Ganguli, G.; Hospodarsky, G. B.; Kletzing, C.

    2015-12-01

    VLF waves in the whistler mode branch in the Earth's radiation belts play a critical role in both the acceleration and loss of energetic electrons. VLF waves are often observed with magnetic field amplitudes that are a significant fraction of the background magnetic field suggesting that nonlinear effects may be important. We develop new Bayesian time-series analysis tools to investigate magnetic and electric field data from the EMFISIS instrument on board the Van Allen Probes. We also validate the analysis techniques through laboratory experiments. We apply these tools to Chorus waves to show that the picture of a single coherent plane wave is insufficient to explain EMFISIS data and that nonlinear collective wave interactions play an important role in moderating Chorus wave growth. We also apply these techniques to show that nonlinear induced scattering by thermal electrons can play a significant role in controlling the propagation of large amplitude lightning generated whistlers inside the plasmasphere.

  10. Hydrogeological investigation in Santiago Island (Cabo Verde) using magnetotellurics and VLF methods

    Science.gov (United States)

    Monteiro Santos, Fernando A.; Almeida, Eugénio P.; Gomes, Mota; Pina, António

    2006-08-01

    A geoelectromagnetic research was carried out in the Santa Cruz region (Santiago Island, Cabo Verde) during June 2004. The survey comprised MT soundings and VLF profiles. The main purpose of the MT profile, carried out across three important valleys associated with freshwater aquifers, was to study the tectonic structures correlated to seawater infiltration. The VLF method was used inside of the valleys for investigating shallow structures related to the aquifer contamination by seawater. Numerical modelling shows that the ocean effect is not important for MT data collected at periods shorter than 1 s. The MT data were inverted using a two-dimensional approach, to obtain the sub-superficial electrical conductivity distribution. The VLF data were processed applying the Karous-Hjelt filters to obtain the equivalent current distribution and inverted using 2-D approach. The results obtained in one of the most important valleys show anomalous current concentration/low resistivity (<20 Ω m) areas at depths greater than 40 m that may correspond to an increase in seawater content. The MT data modelling show that the deep zones beneath the valley are strongly fractured representing good pathways for seawater circulation. The depth of the conductive zones increases from south to north, suggesting a northward decreasing of the seawater infiltration effect. This observation correlates very well with in situ geochemical observations.

  11. Observation of Broadband Ultraviolet Emission From Hg 3 *

    Science.gov (United States)

    Chen, Wenting; Glavin, Thomas; Eden, James; Laboratory for Optical Physics; Engineering Team

    2016-05-01

    A previously-unobserved emission continuum, peaking at ~ 380 nm, has been observed when Hg vapor is photoexcited at 248 nm (KrF laser). Attributed to the mercury trimer, Hg3, this emission continuum has a spectral breadth (FWHM) which increases from ~ 65 nm to ~ 90 nm when the Hg number density rises from ~1016 cm-3 to ~ 2 ×1019 cm-3. Over the same interval in [Hg], the emission decay rate increases only slightly (~ 6 ×103 s-1 to ~ 7 ×103 s-1). Comparisons of the observed spectrum with theory suggest that the observed continuum is the result of transitions between pairs of electronic states having a linear or equilateral triangular configuration.

  12. Optimal VLF Parameters for Pitch Angle Scattering of Trapped Electrons

    Science.gov (United States)

    Albert, J. M.; Inan, U. S.

    2001-12-01

    VLF waves are known to determine the lifetimes of energetic radiation belt electrons in the inner radiation belt and slot regions. Artificial injection of such waves from ground- or space-based transmitters may thus be used to affect the trapped electron population. In this paper, we seek to determine the optimal parameters (frequency and wave normal angle) of a quasi-monochromatic VLF wave using bounce-averaged quasi-linear theory. We consider the cumulative effects of all harmonic resonances and determine the diffusion rates of particles with selected energies on particular L-shells. We also compare the effects of the VLF wave to diffusion driven by other whistler-mode waves (plasmaspheric hiss, lightning, and VLF transmitters). With appropriate choice of the wave parameters, it may be possible to substantially reduce the lifetime of selected classes of particles.

  13. SCIAMACHY formaldehyde observations: constraint for isoprene emission estimates over Europe?

    Directory of Open Access Journals (Sweden)

    G. Dufour

    2009-03-01

    Full Text Available Formaldehyde (HCHO is an important intermediate compound in the degradation of volatile organic compounds (VOCs in the troposphere. Sources of HCHO are largely dominated by its secondary production from VOC oxidation, methane and isoprene being the main precursors in unpolluted areas. As a result of the moderate lifetime of HCHO, its spatial distribution is determined by reactive hydrocarbon emissions. We focus here on Europe and investigate the influence of the different emissions on HCHO tropospheric columns with the CHIMERE chemical transport model in order to interpret the comparisons between SCIAMACHY and simulated HCHO columns. Europe was never specifically studied before for these purposes using satellite observations. The bias between measurements and model is less than 20% on average. The differences are discussed according to the errors on the model and the observations and remaining discrepancies are attributed to a misrepresentation of biogenic emissions. This study requires the characterisation of: (1 the model errors and performances concerning formaldehyde. The errors on the HCHO columns, mainly related to chemistry and mixed emission types, are evaluated to 2×1015 molecule/cm2 and the model performances evaluated using surface measurements are satisfactory (~13%; (2 the observation errors that define the needs in spatial and temporal averaging for meaningful comparisons. Using SCIAMACHY observations as constraint for biogenic isoprene emissions in an inverse modelling scheme reduces their uncertainties by about a factor of two in region of intense emissions. The retrieved correction factors for the isoprene emissions range from a factor of 0.15 (North Africa to a factor of 2 (Poland, the United Kingdom depending on the regions.

  14. Application of differential analysis of VLF signals for seismic-ionospheric precursor detection from multiple receivers

    Science.gov (United States)

    Skeberis, Christos; Zaharis, Zaharias; Xenos, Thomas; Contadakis, Michael; Stratakis, Dimitrios; Tommaso, Maggipinto; Biagi, Pier Francesco

    2015-04-01

    This study investigates the application of differential analysis on VLF signals emitted from a single transmitter and received by multiple stations in order to filter and detect disturbances that can be attributed to seismic-ionospheric precursor phenomena. The cross-correlation analysis applied on multiple VLF signals provides a way of discerning the nature of a given disturbance and accounts for more widespread geomagnetic interferences compared to local precursor phenomena. For the purpose of this paper, data acquired in Thessaloniki (40.59N, 22,78E) and in Heraklion (35.31N, 25.10E) from the VLF station in Tavolara, Italy (ICV station Lat. 40.923, Lon. 9.731) for a period of four months (September 2014 - December 2014) are used. The receivers have been developed by Elettronika Srl and are part of the International Network for Frontier Research on Earthquake Precursors (INFREP). A normalization process and an improved variant of the Hilbert-Huang transform are initially applied to the received VLF signals. The signals derived from the first two Intrinsic Mode Functions (IMF1 and IMF2) undergo a cross-correlation analysis and, in this way, time series from the two receivers can be compared. The efficacy of the processing method and the results produced by the proposed process are then discussed. Finally, results are presented along with an evaluation of the discrimination and detection capabilities of the method on disturbances of the received signals. Based upon the results, the merits of such a processing method are discussed to further improve the current method by using differential analysis to better classify between different disturbances but, more importantly, discriminate between points of interest in the provided spectra. This could provide an improved method of detecting disturbances attributed to seismic-ionospheric precursor phenomena and also contribute to a real-time method for correlating seismic activity with the observed disturbances.

  15. Land Surface Microwave Emissivity Dynamics: Observations, Analysis and Modeling

    Science.gov (United States)

    Tian, Yudong; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Kumar, Sujay; Ringerud, Sarah

    2014-01-01

    Land surface microwave emissivity affects remote sensing of both the atmosphere and the land surface. The dynamical behavior of microwave emissivity over a very diverse sample of land surface types is studied. With seven years of satellite measurements from AMSR-E, we identified various dynamical regimes of the land surface emission. In addition, we used two radiative transfer models (RTMs), the Community Radiative Transfer Model (CRTM) and the Community Microwave Emission Modeling Platform (CMEM), to simulate land surface emissivity dynamics. With both CRTM and CMEM coupled to NASA's Land Information System, global-scale land surface microwave emissivities were simulated for five years, and evaluated against AMSR-E observations. It is found that both models have successes and failures over various types of land surfaces. Among them, the desert shows the most consistent underestimates (by approx. 70-80%), due to limitations of the physical models used, and requires a revision in both systems. Other snow-free surface types exhibit various degrees of success and it is expected that parameter tuning can improve their performances.

  16. Radio emission from magnetic exoplanets: GMRT observations and results

    Science.gov (United States)

    Majid, W.; Winterhalter, D.; Kuiper, T.; Lazio, J.

    2011-10-01

    Massive extrasolar planets are expected to emit, in analogy with Jupiter and Saturn, detectable radio emission at low frequencies. We have carried out a series of observations of known extrasolar planetary systems at 150 MHz with the Giant Meterwave Radio Telescope (GMRT) in both interferometric and phased array modes. We will describe our observing campaign, target list, and preliminary results from studies of dynamic spectra. As low frequency observations are plagued with RFI, we will focus on observing strategies and analysis techniques to minimize, identify and remove RFI effects from dynamic spectra. We will also briefly discuss prospects for similar searches with future instruments such as LOFAR, the LWA, and the SKA instruments.

  17. Semi-annual oscillation (SAO) of the nighttime ionospheric D-region as detected through ground-based VLF receivers

    Science.gov (United States)

    Silber, I.; Price, C. G.; Rodger, C. J.

    2015-11-01

    Earth's middle and upper atmosphere exhibits several dominant large scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower-thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequencies (VLF) narrow-band subionospheric measurements. As VLF signals are reflected off the ionospheric D-region (at altitudes of ~65 and ~85 km, during the day and night, respectively), this implies that the upper part of the D-region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D-region is due to NOx molecules transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D-region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D-region in general and VLF wave propagation in particular.

  18. Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

    Science.gov (United States)

    Silber, Israel; Price, Colin; Rodger, Craig J.

    2016-03-01

    Earth's middle and upper atmosphere exhibits several dominant large-scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequency (VLF) narrowband (NB) subionospheric measurements. As VLF signals are reflected off the ionospheric D region (at altitudes of ˜ 65 and ˜ 85 km, during the day and night, respectively), this implies that the upper part of the D region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D region is NOx molecule transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D region in general and VLF wave propagation in particular.

  19. Multi-Spacecraft Observations of Saturn Kilometric Radio Emission

    Science.gov (United States)

    MacDowall, R. J.; Hess, R. A.

    2011-01-01

    Saturn kilometric radiation (SKR) is the auroral radio emission of Saturn, which has been observed by Voyager 1 & 2, Cassini, and Ulysses. Ulysses is able to detect the intense intervals of SKR from distances up to 10 AU, because of its long antennas (72 m tip-to-tip) and sensitive radio receivers. Studies of SKR by A. Lecacheux gave the surprising result that the periodicity of SKR varied with time; it was not locked to a planetary rotation of Saturn. This result has been confirmed by Cassini radio observations. Here, we compare Ulysses and Cassini observations of SKR to constrain a mode! for the SKR emission geometry. SpecifIcally, we examine the question - are the brighter sources of 5KR fixed in Saturn longitude or local time? The results have significant consequences for our understanding of SKR and its varying periodicity

  20. Ground-Based Observations of Unusual Atmospheric Light Emissions

    Institute of Scientific and Technical Information of China (English)

    杨静; 陆高鹏; 杜艰; 潘蔚琳

    2014-01-01

    Unusual atmospheric light emissions were observed from a station located in Shandong Province of East China. The main morphology of these events includes a bright glowing spot, which differs distinctly from any type of transient luminous events (TLEs) well recognized in literature, such as sprites, halos, elves, gigantic jets, blue jets, and blue starters. A comparison between the observations of four such light emission events and the data from lightning detection networks reveals no correlation between these events and the intense lightning activity in the adjacent area. The events reported in this paper may imply the existence of a new phenomenon with a mechanism that remains to be investigated with further observation and complementary lightning measurement.

  1. Optical emission spectroscopy observations of fast pulsed capillary discharge plasmas

    Science.gov (United States)

    Avaria, G.; Ruiz, M.; Guzmán, F.; Favre, M.; Wyndham, E. S.; Chuaqui, H.; Bhuyan, H.

    2014-05-01

    We present time resolved optical emission spectroscopic (OES) observations of a low energy, pulsed capillary discharage (PCD). The optical emission from the capillary plasma and plasma jets emitted from the capillary volume was recorded with with a SpectraPro 275 spectrograph, fitted with a MCP gated OMA system, with 15 ns time resolution. The discharge was operated with different gases, including argon, nitrogen, hydrogen and methane, in a repetitive pulsed discharge mode at 10-50 Hz, with, 10-12 kV pulses applied at the cathode side. The time evolution of the electron density was measured using Stark broadening of the Hβ line. Several features of the capillary plasma dynamics, such as ionization growth, wall effects and plasma jet evolution, are inferred from the time evolution of the optical emission.

  2. Biogenic nonmethane hydrocarbon emissions estimated from tethered balloon observations

    Science.gov (United States)

    Davis, K. J.; Lenschow, D. H.; Zimmerman, P. R.

    1994-01-01

    A new technique for estimating surface fluxes of trace gases, the mixed-layer gradient technique, is used to calculate isoprene and terpene emissions from forests. The technique is applied to tethered balloon measurements made over the Amazon forest and a pine-oak forest in Alabama at altitudes up to 300 m. The observations were made during the dry season Amazon Boundary Layer Experiment (ABLE 2A) and the Rural Oxidants in the Southern Environment 1990 experiment (ROSE I). Results from large eddy simulations of scalar transport in the clear convective boundary layer are used to infer fluxes from the balloon profiles. Profiles from the Amazon give a mean daytime emission of 3630 +/- 1400 micrograms isoprene sq m/h, where the uncertainty represents the standard deviation of the mean of eight flux estimates. Twenty profiles from Alabama give emissions of 4470 +/- 3300 micrograms isoprene sq m/h, 1740 +/- 1060 micrograms alpha-pinene sq m/h, and 790 +/- 560 micrograms beta-pinene sq m/h, respectively. These results are in agreement with emissions derived from chemical budgets. The emissions may be overestimated because of uncertainty about how to incorporate the effects of the canopy on the mixed-layer gradients. The large variability in these emission estimates is probably due to the relatively short sampling times of the balloon profiles, though spatially heterogeneous emissions may also play a role. Fluxes derived using this technique are representative of an upwind footprint of several kilometers and are independent of hydrocarbon oxidation rate and mean advection.

  3. Observation of dispersive wave emission by temporal cavity solitons.

    Science.gov (United States)

    Jang, Jae K; Erkintalo, Miro; Murdoch, Stuart G; Coen, Stéphane

    2014-10-01

    We examine a coherently-driven, dispersion-managed, passive Kerr fiber ring resonator and report, to the best of our knowledge, the first direct experimental observation of dispersive wave emission by temporal cavity solitons (CSs). Our observations are in excellent agreement with analytical predictions and they are fully corroborated by numerical simulations. These results lead to a better understanding of the behavior of temporal CSs under conditions where higher-order dispersion plays a significant role. Significantly, since temporal CSs manifest themselves in monolithic microresonators, our results are likely to explain the origins of spectral features observed in broadband Kerr frequency combs. PMID:25360913

  4. Ground and space observations of medium frequency auroral radio emissions

    Science.gov (United States)

    Broughton, Matthew C.

    The auroral zone is a rich source of natural radio emissions that can be observed in space and at ground-level. By studying these waves, scientists can gain insight into the plasma processes that generate them and use the near-Earth space environment as a large-scale plasma physics laboratory. This thesis uses both ground-level and in situ observations to study two kinds of natural radio emissions. First, we report observations of a new kind of auroral radio emission. The waves have frequencies ranging from 1.3-2.2 MHz, bandwidths ranging from 90-272 kHz, and durations ranging from 16-355 s. Spectral analysis of the waveform data has revealed that the emission has a complex combination of at least three kinds of fine structures. For model auroral electron distributions, calculations indicate that Langmuir waves could be excited at frequencies consistent with observations. The remainder of the thesis discusses auroral medium frequency (MF) burst, an impulsive, broadband natural radio emission observed at ground-level within a few minutes of local substorm onset. LaBelle [2011] proposed that MF burst originates as Langmuir/Z-mode waves on the topside of the ionosphere that subsequently mode convert to L-mode waves and propagate to ground-level. Using continuous waveform measurements and combined observations with the Sondrestrom Incoherent Scatter Radar, we have performed two tests of this mechanism. The results of these tests are consistent with the mechanism described in LaBelle [2011]. A survey of 8,624 half-orbits of the DEMETER spacecraft has revealed 68 observations of bursty MF waves. We have compared the wave properties of these waves to those of MF burst and have found that although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground-level MF burst. Finally, we have used numerical simulations to model both the fine structure of MF burst and to estimate the attenuation the

  5. Broad Iron Emission from Gravitationally Lensed Quasars Observed by Chandra

    CERN Document Server

    Walton, D J; Miller, J M; Reis, R C; Stern, D; Harrison, F A

    2015-01-01

    Recent work has demonstrated the potential of gravitationally lensed quasars to extend measurements of black hole spin out to high-redshift with the current generation of X-ray observatories. Here we present an analysis of a large sample of 27 lensed quasars in the redshift range 1.0observed with Chandra, utilizing over 1.6 Ms of total observing time, focusing on the rest-frame iron K emission from these sources. Although the X-ray signal-to-noise (S/N) currently available does not permit the detection of iron emission from the inner accretion disk in individual cases in our sample, we find significant structure in the stacked residuals. In addition to the narrow core, seen almost ubiquitously in local AGN, we find evidence for an additional underlying broad component from the inner accretion disk, with a clear red wing to the emission profile. Based on simulations, we find the detection of this broader component to be significant at greater than the 3-sigma level. This implies that iron emission...

  6. Deep 1.4-GHz observations of diffuse polarized emission

    CERN Document Server

    Carretti, E; Reich, W; Reich, P; Fürst, E; Bernardi, G; Cortiglioni, S; Sbarra, C

    2006-01-01

    Polarized diffuse emission observations at 1.4-GHz in a high Galactic latitude area of the northern Celestial hemisphere are presented. The 3.2 X 3.2 deg^2 field, centred at RA = 10h 58m, Dec = +42deg 18' (B1950), has Galactic coordinates l~172deg, b~+63deg and is located in the region selected as northern target of the BaR-SPOrt experiment. Observations have been performed with the Effelsberg 100-m telescope. We find that the angular power spectra of the E- and B-modes have slopes of beta_E = -1.79 +/- 0.13 and beta_B = -1.74 +/- 0.12, respectively. Because of the very high Galactic latitude and the smooth emission, a weak Faraday rotation action is expected, which allows both a fair extrapolation to Cosmic Microwave Background Polarization (CMBP) frequencies and an estimate of the contamination by Galactic synchrotron emission. We extrapolate the E-mode spectrum up to 32-GHz and confirm the possibility to safely detect the CMBP E-mode signal in the Ka band found in another low emission region (Carretti et a...

  7. VLF propagation measurements in the Canadian Arctic

    Science.gov (United States)

    Lauber, Wilfred R.; Bertrand, Jean M.

    1993-05-01

    For the past three years, during a period of high sun spot numbers, propagation measurements were made on the reception of VLF signals in the Canadian Arctic. Between Aug. and Dec. 1989, the received signal strengths were measured on the Canadian Coast Guard icebreaker, John A. MacDonald in the Eastern Canadian Arctic. Between Jul. 1991 and Jun. 1992, the received signal strengths were measured at Nanisivik, Baffin Island. The purposes of this work were to check the accuracy and estimate variances of the Naval Ocean Systems Center's (NOSC) Long Wave Propagation Capability (LWPC) predictions in the Canadian Arctic and to gather ionospheric storm data. In addition, the NOSC data taken at Fort Smith and our data at Nanisivik were used to test the newly developed Longwave Noise Prediction (LNP) program and the CCIR noise predictions, at 21.4 and 24.0 kHz. The results of the work presented and discussed in this paper show that in general the LWPC predicts accurate values of received signal strength in the Canadian Arctic with standard deviations of 1 to 2 dB over several months. Ionospheric storms can gauge the received signal strengths to decrease some 10 dB for a period of several hours or days. However, the effects of these storms are highly dependent on the propagation path. Finally the new LNP atmospheric noise model predicts lower values of noise in the Arctic than the CCIR model and our limited measurements tend to support these lower values.

  8. VLF Science at Indian Centre for Space Physics

    Science.gov (United States)

    Chakrabarti, Sandip Kumar

    2016-07-01

    Indian Centre for Space Physics has been monitoring VLF signals from stations around the world at its laboratories at Kolkata and Sitapur (Ionospheric and Earthquake Research Centre) as well as at several places throughout India when in a campaign mode. We have been interested to study high energy events from space, such as solar flares and gamma ray bursts. We have made studies during multiple solar eclipses and most importantly made substantial progress in the problem of lithosphere-ionosphere coupling while understanding various types of anomalies prior to major earthquakes. Other effects such as AGWs and LEPs are being studied. We have experience of two antarctic expedition and obtained VLF data from both Maitri and Bharati stations of India, which revealed, among other things, how the signal attenuation can indicate the extent of ice mass in Antarctica. We have been able to reproduce various VLF perturbation events using Atmospheric Chemical evolution model coupled with LWPC code. For instance we have reproduced solar flare induced VLF amplitude perturbation pattern by completely ab initio calculation. We also targeted the inverse problem, namely, deduction of the injected radiation spectra from space from the VLF signal alone, thereby establishing that the Earth can be used as a gigantic detector. These interesting results would be presented in my review talk.

  9. Coherent whistler emissions in the magnetosphere – Cluster observations

    Directory of Open Access Journals (Sweden)

    I. Dandouras

    2007-02-01

    Full Text Available The STAFF-SC observations complemented by the data from other instruments on Cluster spacecraft were used to study the main properties of magnetospheric lion roars: sporadic bursts of whistler emissions at f~0.1–0.2fe where fe is the electron gyrofrequency. Magnetospheric lion roars are shown to be similar to the emissions in the magnetosheath while the conditions for their generation are much less favorable: the growth rate of the cyclotron temperature anisotropy instability is much smaller due to a smaller number of the resonant electrons. This implies a nonlinear mechanism of generation of the observed wave emissions. It is shown that the observed whistler turbulence, in reality, consists of many nearly monochromatic wave packets. It is suggested that these structures are nonlinear Gendrin's whistler solitary waves. Properties of these waves are widely discussed. Since the group velocity of Gendrin's waves is aligned with the magnetic field, these well guided wave packets can propagate through many magnetic "bottles" associated with mirror structures, without being trapped.

  10. Observations of O VI Emission from the Diffuse Interstellar Medium

    CERN Document Server

    Shelton, R L; Murphy, E M; Andersson, B G; Blair, W P; Dixon, W V; Edelstein, J D; Fullerton, A W; Gry, C; Howk, J C; Jenkins, E B; Linsky, J L; Moos, H W; Oegerle, W R; Oey, M S; Roth, K C; Sahnow, D J; Sankrit, R; Savage, B D; Sembach, K R; Shull, J M; Siegmund, O H W; Vidal-Madjar, A; Welsh, B Y; York, D G

    2001-01-01

    We report the first Far Ultraviolet Spectroscopic Explorer (FUSE) measurements of diffuse O VI (lambda,lambda 1032,1038) emission from the general diffuse interstellar medium outside of supernova remnants or superbubbles. We observed a 30arcsec x 30arcsec region of the sky centered at l = 315 and b = -41. From the observed intensities (2930+/-290(random)+/-410(systematic) and 1790+/-260(random)+/-250(systematic) photons/cm/cm/s/sr in the 1032 and 1038 Angstrom emission lines, respectively), derived equations, and assumptions about the source location, we calculate the intrinsic intensity, electron density, thermal pressure, and emitting depth. The intensities are too large for the emission to originate solely in the Local Bubble. Thus, we conclude that the Galactic thick disk and lower halo also contribute. High velocity clouds are ruled out because there are none near the pointing direction. The calculated emitting depth is small, indicating that the O VI-bearing gas fills a small volume. The observations ca...

  11. Observation of Field-Emission Dependence on Stored Energy

    Science.gov (United States)

    Shao, Jiahang; Antipov, Sergey P.; Baryshev, Sergey V.; Chen, Huaibi; Conde, Manoel; Doran, Darrell S.; Gai, Wei; Jing, Chunguang; Liu, Wanming; Power, John; Qiu, Jiaqi; Shi, Jiaru; Wang, Dan; Wang, Faya; Whiteford, Charles E.; Wisniewski, Eric; Xiao, Liling

    2015-12-01

    Field emission from a solid metal surface has been continuously studied for a century over macroscopic to atomic scales. It is general knowledge that, other than the surface properties, the emitted current is governed solely by the applied electric field. A pin cathode has been used to study the dependence of field emission on stored energy in an L -band rf gun. The stored energy was changed by adjusting the axial position (distance between the cathode base and the gun back surface) of the cathode while the applied electric field on the cathode tip is kept constant. A very strong correlation of the field-emission current with the stored energy has been observed. While eliminating all possible interfering sources, an enhancement of the current by a factor of 5 was obtained as the stored energy was increased by a factor of 3. It implies that under certain circumstances a localized field emission may be significantly altered by the global parameters in a system.

  12. Observations of the spectrum of the interplanetary dust emission

    Science.gov (United States)

    Salama, A.; de Bernardis, P.; Masi, S.; Moreno, G.

    Published data from satellite (IRAS), rocket-borne (ZIP), and balloon-borne (ARGO) spectroscopic observations of interplanetary dust emission in the FIR are compiled and analyzed, extending the spatial-distribution results of Salama et al. (1986) to evaluate the possible role of silicate and graphite grains in determining the FIR spectrum. The zodiacal dust spectra in the ecliptic plane at solar elongations epsilon = 45 and 90 deg are calculated on the basis of theoretical models and compared with the observations. A model based on a flat distribution of 10-micron-diameter silicate grains is shown to reproduce the observed spectrum at epsilon = 45 deg but not at epsilon = 90 deg, where a model with a mixture of silicate and graphite grains gives a better, but still unsatisfactory fit to the observations.

  13. On the numerical modelling of VLF chorus dynamical spectra

    Directory of Open Access Journals (Sweden)

    D. Nunn

    2009-06-01

    Full Text Available This paper presents a study of the use of a one-dimensional Vlasov Hybrid Simulation (VHS computer code to simulate the dynamical spectra (i.e. frequency versus time spectrograms of ELF/VLF chorus signals (from ~a fraction to ~10 kHz. Recently excellent measurements of chorus have been made in the source region close to the geomagnetic equator aboard the four spacecraft Cluster mission. Using Cluster data for wave amplitude, which is up to 300 pT, local gyrofrequency, cold plasma density, and L-shell, observed chorus signals are reproduced with remarkable fidelity and, in particular, sweep rates in the range 1–10 kHz result as observed. Further, we find that the sweep rate is a falling function of increasing cold plasma density, again in accord with observations. Finally, we have satisfactorily simulated the rather rare falling frequency elements of chorus which are sometimes observed aboard Cluster in the generation region. For both rising and falling chorus we have presented detailed structural analyses of the generation regions. The main contributor to the frequency sweep rate is primarily the establishment of wave number/frequency gradients across the generation region by the out of phase component of the resonant particle current. The secondary contributor is the shortening of the wavelength of resonant particle current relative to that of the wave field. In view of the close agreement between observation and simulation, we conclude that nonlinear electron cyclotron resonance is indeed the mechanism underlying the generation of chorus signals just outside the plasmasphere.

  14. Adjoint inversion modeling of Asian dust emission using lidar observations

    Directory of Open Access Journals (Sweden)

    K. Yumimoto

    2008-06-01

    Full Text Available A four-dimensional variational (4D-Var data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4 is applied to an adjoint inversion of a heavy dust event over eastern Asia during 20 March–4 April 2007. The vertical profiles of the dust extinction coefficients derived from NIES Lidar network are directly assimilated, with validation using observation data. Two experiments assess impacts of observation site selection: Experiment A uses five Japanese observation sites located downwind of dust source regions; Experiment B uses these and two other sites near source regions. Assimilation improves the modeled dust extinction coefficients. Experiment A and Experiment B assimilation results are mutually consistent, indicating that observations of Experiment A distributed over Japan can provide comprehensive information related to dust emission inversion. Time series data of dust AOT calculated using modeled and Lidar dust extinction coefficients improve the model results. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square differences of dust AOT by 35–40%. However, at Beijing and Tsukuba, the RMS differences degrade because of fewer observations during the heavy dust event. Vertical profiles of the dust layer observed by CALIPSO are compared with assimilation results. The dense dust layer was trapped at potential temperatures (θ of 280–300 K and was higher toward the north; the model reproduces those characteristics well. Latitudinal distributions of modeled dust AOT along the CALIPSO orbit paths agree well with those of CALIPSO dust AOT, OMI AI, and MODIS coarse-mode AOT, capturing the latitude at which AOTs and AI have high values. Assimilation results show increased dust emissions over the Gobi Desert and Mongolia; especially for 29–30 March, emission flux is about 10 times greater. Strong dust uplift fluxes over the Gobi Desert and Mongolia cause the heavy dust event. Total optimized dust emissions are 57

  15. Seismo-electromagnetic VLF link calibration in Europe

    Science.gov (United States)

    Eichelberger, Hans; Schwingenschuh, Konrad; Wolbang, Daniel; Besser, Bruno P.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Stachel, Manfred; Prattes, Gustav; Boudjada, Mohammed Y.; Aydogar, Özer; Zehetleitner, Sigrid; Grill, Claudia; Jernej, Irmgard

    2015-04-01

    The general background is the investigation of seismic activity with electromagnetic signals, i.e. to disentangle amplitude and phase modifications from a variety of sources. This work focus on characterisation of very low frequency (VLF) radio links between several transmitters and the Graz receiver in the current active solar cycle. Particular emphasis is on solar flares related disturbances in the Earth-ionosphere waveguide, an important dayside non-seismic influence on the VLF paths. These variations can serve as a calibration tool of the facility even for nighttime periods when different seismo-electromagnetic (SEM) methods are applied, e.g. terminator time or nighttime amplitude. Supporting data are the GOES X-ray flux measurements. As immediate objective we study individual C/M/X-class solar flare events in the sub-ionospheric VLF waveguide (amplitude fluctuations) and calculate statistical parameters with the C-class population. The used system, which is part of a broader network of receiving stations, is primarily dedicated to investigate earthquake related phenomena and associated lithospheric atmospheric ionospheric coupling mechanisms. We receive simultaneously 12 VLF transmitters (amplitude and phase measurements) from the northern hemisphere with a selected temporal resolution of 20 seconds. We conclude that the numerous C/M/X-class solar flare events, together with the the high signal-to-noise ratio of the facility, are a valuable combination for short-term VLF path characterisation in a robust manner. As outlook, due to the steady VLF measurements, a monitoring service for certain lower atmospheric variations can be envisaged.

  16. FERMI Observations of Gamma -Ray Emission From the Moon

    Science.gov (United States)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwoo, W. B.; Baldini, I.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Gehrels, N.; Hays, E.; Thompson, D. J.; McEnery, J. E.; Troja, E.

    2012-01-01

    We report on the detection of high-energy ? -ray emission from the Moon during the first 24 months of observations by the Fermi Large Area Telescope (LAT). This emission comes from particle cascades produced by cosmicray (CR) nuclei and electrons interacting with the lunar surface. The differential spectrum of the Moon is soft and can be described as a log-parabolic function with an effective cutoff at 2-3 GeV, while the average integral flux measured with the LAT from the beginning of observations in 2008 August to the end of 2010 August is F(greater than100 MeV) = (1.04 plus or minus 0.01 [statistical error] plus or minus 0.1 [systematic error]) × 10(sup -6) cm(sup -2) s(sup -1). This flux is about a factor 2-3 higher than that observed between 1991 and 1994 by the EGRET experiment on board the Compton Gamma Ray Observatory, F(greater than100 MeV)˜5×10(sup -7) cm(sup -2) s(sup -1), when solar activity was relatively high. The higher gamma -ray flux measured by Fermi is consistent with the deep solar minimum conditions during the first 24 months of the mission, which reduced effects of heliospheric modulation, and thus increased the heliospheric flux of Galactic CRs. A detailed comparison of the light curve with McMurdo Neutron Monitor rates suggests a correlation of the trends. The Moon and the Sun are so far the only known bright emitters of gamma-rays with fast celestial motion. Their paths across the sky are projected onto the Galactic center and high Galactic latitudes as well as onto other areas crowded with high-energy gamma-ray sources. Analysis of the lunar and solar emission may thus be important for studies of weak and transient sources near the ecliptic.

  17. Modeling of the lower ionospheric response and VLF signal modulation during a total solar eclipse using ionospheric chemistry and LWPC

    Science.gov (United States)

    Chakraborty, Suman; Palit, Sourav; Ray, Suman; Chakrabarti, Sandip K.

    2016-02-01

    The variation in the solar Extreme Ultraviolet (EUV) radiation flux by any measure is the most dominant natural source to produce perturbations or modulations in the ionospheric chemical and plasma properties. A solar eclipse, though a very rare phenomenon, is similarly bound to produce a significant short time effect on the local ionospheric properties. The influence of the ionizing solar flux reduction during a solar eclipse on the lower ionosphere or, more precisely, the D-region, can be studied with the observation of Very Low Frequency (VLF) radio wave signal modulation. The interpretation of such an effect on VLF signals requires a knowledge of the D-region ion chemistry, which is not well studied till date. Dominant parameters which govern the ion chemistry, such as the recombination coefficients, are poorly known. The occurrence of events such as a solar eclipse provides us with an excellent opportunity to investigate the accuracy of our knowledge of the chemical condition in this part of Earth's atmosphere and the properties which control the ionospheric stability under such disturbances. In this paper, using existing knowledge of the lower ionospheric chemical and physical properties we carry out an interpretation of the effects obtained during the total solar eclipse of 22 of July 2009 on the VLF signal. Data obtained from a week long campaign conducted by the Indian Centre for Space Physics (ICSP) over the Indian subcontinent has been used for this purpose. Both positive and negative amplitude changes during the eclipse were observed along various receiver locations. In this paper, data for a propagation path between a Indian Navy VLF transmitter named VTX3 and a pair of receivers in India are used. We start from the observed solar flux during the eclipse and calculate the ionization during the whole time span over most of the influenced region in a range of height. We incorporate a D-region ion-chemistry model to find the equilibrium ion density over

  18. VLF effects in the outer ionosphere from the underground nuclear explosion of 24 October 1990 on the New Land island (Interkosmos-24 satellite data)

    International Nuclear Information System (INIS)

    Results on numerical treatment of the VLF auroral hiss and whistling atmospherics, registered at the height approximately 900 km on board of the Interkosmos-24 satellite over the New Land island 17 minutes after the underground nuclear explosion are presented. As the result of powerful acoustic effect there took place sharp increase (∼ 20 db) in the VLF hiss within the narrow range of invariant latitudes including the excitation source. Simultaneously decrease in the low frequency of the noise spectrum cut-off, coinciding with the frequency of the low hybrid resonance was observed

  19. Airborne observations of vegetation and implications for biogenic emission characterization.

    Science.gov (United States)

    Hawes, Amy K; Solomon, Susan; Portmann, Robert W; Daniel, John S; Langford, Andrew O; Miller, H LeRoy; Eubank, Charles S; Goldan, Paul; Wiedinmyer, Christine; Atlas, Elliot; Hansel, Armin; Wisthaler, Armin

    2003-12-01

    Measuring hydrocarbons from aircraft represents one way to infer biogenic emissions at the surface. The focus of this paper is to show that complementary remote sensing information can be provided by optical measurements of a vegetation index, which is readily measured with high temporal coverage using reflectance data. We examine the similarities between the vegetation index and in situ measurements of the chemicals isoprene, methacrolein, and alpha-pinene to estimate whether the temporal behavior of the in situ measurements of these chemicals could be better understood by the addition of the vegetation index. Data were compared for flights conducted around Houston in August and September 2000. The three independent sets of chemical measurements examined correspond reasonably well with the vegetation index curves for the majority of flight days. While low values of the vegetation index always correspond to low values of the in situ chemical measurements, high values of the index correspond to both high and low values of the chemical measurements. In this sense it represents an upper limit when compared with in situ data (assuming the calibration constant is adequately chosen). This result suggests that while the vegetation index cannot represent a purely predictive quantity for the in situ measurements, it represents a complementary measurement that can be useful in understanding comparisons of various in situ observations, particularly when these observations occur with relatively low temporal frequency. In situ isoprene measurements and the vegetation index were also compared to an isoprene emission inventory to provide additional insight on broad issues relating to the use of vegetation indices in emission database development.

  20. An aerostat-supported ELF/VLF transmitter

    Science.gov (United States)

    Field, E. C., Jr.; Kies, L. R.; Bannister, P. R.; Ingram, R. F.; Hopkins, W. D.; Roberts, M. A.

    1989-03-01

    A demonstration of an aerostat-supported extremely low frequency/very low frequency (ELF/VLF) transmitting antenna was performed. At ELF the vertical electric dipole (VED) antenna radiated at least 100,000 times more power than would a horizontal electric dipole having the same moment. That efficiency was achieved with an altitude of 12,500 feet (3810 m). Calculations show that the radiated power will increase as the fourth power of aerostat altitude. The tether antenna exhibited a corona onset voltage of 180 kV and was resistant to the degrading effects of ELF corona. Prolonged in-corona operation is therefore possible. The antenna was continuously tuned, despite changes in height and capacitance caused by the aerostat flight dynamics. The huge 300-H ELF tuning inductor posed no problem. Enhanced VED moments were achieved at ELF by operation at voltages up to 260 kV, 40% above the corona onset voltage. At VLF the antenna emulated a monopole that had a radiation efficiency greater than 90%. The measured bandwidths were large: 1.5 kHz at 23 kHz and 3.5 kHz at 34 kHz. The antenna height exceeded one-quarter wavelength at VLF, so the antenna could be tuned capacitively and required relatively low base voltages. At both VLF and ELF the measured fields agreed closely with predictions.

  1. The European VLF/LF radio network: current status

    Science.gov (United States)

    Biagi, Pier Francesco; Maggipinto, Tommaso; Ermini, A.

    2014-11-01

    For several years researches about correlation between seismicity and disturbances in radio broadcasting are being carried out: in particular, the Japanese Pacific VLF radio network and the European VLF-LF radio network have been developed during the last years. The European network has been developed starting from two LF receivers located in central Italy in 1996. Up to now, 11 receivers of a new type, able to sample the VLF and LF intensity of ten radio signals, are being into operation in different European countries. The daily updating of data is effective and the data bank is located at the Department of Physics of the University of Bari (Italy) which is the central node of the network. In order to discover anomalies, the software able to carry out automatically a daily data analysis by the Wavelet spectra method has been planned and realized. At the moment, the software operates on four signals (two LF and two VLF) collected by one of the receiver located in Italy. If the anomaly is particularly strong a warning system gives an advise on the work station into operation in the central node of the Network. In any case, before assuming an anomaly as a seismic anomaly, geomagnetic and meteorological data must be checked as well as any possible instrumental malfunction. At present these controls are carried out only discontinuously by the researchers of the Bari Team.

  2. Airborne VLF measurements and mapping of ground conductivity in Sweden

    Science.gov (United States)

    Pedersen, Laust B.; Persson, Lena; Bastani, Mehrdad; Byström, Sören

    2009-03-01

    Airborne VLF data are routinely collected by The Geological Survey of Sweden (SGU) as part of its bedrock mapping programme. In this paper we demonstrate that the novel Tensor VLF technique developed at Uppsala University and SGU can provide useful qualitative and quantitative information about the electrical conductivity distribution in the upper few hundred meters. Single transmitter scalar VLF maps emphasize those conductive structures that have dominant strikes in the direction of the transmitter. The tensor tipper (essentially the vertical magnetic field from currents along the strike direction) calculated from multiple transmitters is dependent only upon the underlying conductivity structure. Transformation of the tipper into the peaker (the horizontal divergence) has proven to enhance the lateral resolution while the transformation to the apparent resistivity can be used to discriminate different rock types. Two case histories from the application of VLF data are presented in this study. Two dimensional structures can be quantitatively modelled by modern inversion methods developed originally for deep electromagnetic MT soundings. Direct inversion of the real and imaginary parts of the tipper provides more quantitative information about the subsurface resistivity distribution.

  3. Investigations of natural and artificial disturbances in the Earth-ionosphere cavity via VLF radio links for the time span 2009-2015 (sunspot cycle 24)

    Science.gov (United States)

    Eichelberger, Hans; Schwingenschuh, Konrad; Besser, B. P.; Prattes, Gustav; Aydogar; Wolbang, Daniel; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Boudjada, Mohammed

    2016-07-01

    We focus on natural disturbances of the sub-ionospheric VLF waveguide in the time span 2009 to 2015 (sunspot cycle 24), i.e. variations in amplitude and phase measurements of the radio paths are considered. In particular we're investigating numerous solar flares (up to X-class), geomagnetic storms and substorms, therefore discuss how to discriminate natural from artificial variations between different transmitters and receivers. Meteorological effects could be important [1] and we estimate the possibility to detect the influence of lithospheric sources in the VLF radio links. As part of the VLF multistation network we're using the single receiver mid-latitude station in Graz, Austria. This facility receives up to 12 transmitter simultaneously (frequency range 10-50 kHz), has 20 sec temporal resolution, and is running continuously since 2009 [2]. We obtain the statistics relating VLF amplitude and phase fluctuations with C/M/X-class solar flares, and characterise night time fluctuations in connection with enhanced particle precipitation in the northern latitude path (Iceland transmitter). The statistics is important to improve the quality of seismo-electromagnetic studies. We conclude that for ionospheric perturbations (D-layer), e.g. solar flares, a reliable real time monitoring service can be established. Atmospheric and lithospheric variations are generally difficult to characterise, it's harder to distinguish between natural and man made signals, therefore - as a future outlook - complementary ground and satellite based measurements can deliver valuable additional information for environmental monitoring. References: [1] A. Rozhnoi et al.: Meteorological effects in the lower ionosphere as based on VLF/LF signal observations, Nat. Hazards Earth Syst. Sci., 14, 2671-2679, 2014. [2] K. Schwingenschuh et al.: The Graz seismo-electromagnetic VLF facility, Nat. Hazards Earth Syst. Sci., 11, 1121-1127, 2011.

  4. Electric fields, electron precipitation, and VLF radiation during a simultaneous magnetospheric substorm and atmospheric thunderstorm

    International Nuclear Information System (INIS)

    A balloon payload instrumented with a double-probe electric field detector and an X ray scintillation counter was launched from Roberval, Quebec, Canada (L=4.1) at 0828 UT (0328 LT) on July 9, 1975. A magnetospheric substorm was observed locally between 0815 and 1100 UT, which produced a maximum ΔB of approx.500 nT at approx.0930 UT. A single-cell atmospheric thunderstorm developed northeast of Roberval beginning around 0925 UT which was most intense from approx.1000 to 1035 UT. Detailed study of the electrical properties of the thunderstorm, the X ray precipitation data, and VLF spheric data leads to three conclusions. First, the electrical coupling from the thunderstorm to the magnetosphere increases with frequency from dc to the VLF; for the observed storm the amplitude at the ionosphere of thunderstorm produced electric fields was not significant at frequencies below 0.1 Hz. Second, the atmospheric conductivity above the thunderstorm was observed to be about one-half the fair weather value prior to 1000 UT; decreased to about one-quarter the fair weather value at about 1000 UT; and remained depressed after the end of the thunderstorm. This result was contrary to that expected on the basis of previous work and is one which merits considerably more investigation. Third, the data show a high probability that half-hop whistlers initiated by sferics from the thunderstorm triggered energetic electron precipitation from the magnetosphere

  5. Observations of Microwave Continuum Emission from Air Shower Plasmas

    CERN Document Server

    Gorham, P W; Varner, G S; Beatty, J J; Connolly, A; Chen, P; Conde, M E; Gai, W; Hast, C; Hebert, C L; Miki, C; Konecny, R; Kowalski, J; Ng, J; Power, J G; Reil, K; Saltzberg, D; Stokes, B T; Walz, D

    2007-01-01

    We investigate a possible new technique for microwave measurements of ultra-high energy cosmic ray (UHECR) extensive air showers which relies on detection of expected continuum radiation in the microwave range, caused by free-electron collisions with neutrals in the tenuous plasma left after the passage of the shower. We performed an initial experiment at the AWA (Argonne Wakefield Accelerator) laboratory in 2003 and measured broadband microwave emission from air ionized via high energy electrons and photons. A follow-up experiment at SLAC (Stanford Linear Accelerator Center) in summer of 2004 confirmed the major features of the previous AWA observations with better precision and made additional measurements relevant to the calorimetric capabilities of the method. Prompted by these results we built a prototype detector using satellite television technology, and have made measurements indicating possible detection of cosmic ray extensive air showers. The method, if confirmed by experiments now in progress, cou...

  6. Space shuttle observation of an unusual transient atmospheric emission

    Science.gov (United States)

    Yair, Yoav; Price, Colin; Ziv, Baruch; Israelevich, Peter L.; Sentman, Davis D.; São-Sabbas, Fernanda T.; Devir, Adam D.; Sato, Mitsuteru; Rodger, Craig J.; Moalem, Meir; Greenberg, Eran; Yaron, Ofer

    2005-01-01

    We report an observation of an unusual transient luminous event (TLE) detected in the near IR, south of Madagascar above the Indian Ocean. The event was imaged from the space shuttle Columbia during the MEIDEX sprite campaign [Yair et al., 2004]. It was delayed 0.23 seconds from a preceding visual lightning flash which was horizontally displaced >1000 km from the event. The calculated brightness in the 860 (+/-50) nm filter was ~310 +/- 30 kR, and the morphology of the emitting volume did not resemble any known class of TLE (i.e., sprites, ELVES or halos). This TIGER event (Transient Ionospheric Glow Emission in Red) may constitute a new class of TLE, not necessarily induced by a near-by thunderstorm. We discuss possible generation mechanisms, including the conjugate sprite hypothesis caused by lightning at the magnetic mirror point, lightning-induced electron precipitation and an extraterrestrial source, meteoric or cometary.

  7. Numerical modelling of VLF radio wave propagation through earth-ionosphere waveguide and its application to sudden ionospheric disturbances

    CERN Document Server

    Pal, Sujay

    2015-01-01

    In this thesis, we theoretically predict the normal characteristics of Very Low Frequency (3~30 kHz) radio wave propagation through Earth-ionosphere waveguide corresponding to normal behavior of the D-region ionosphere. We took the VLF narrow band data from the receivers of Indian Centre for Space Physics (ICSP) to validate our models. Detection of sudden ionospheric disturbances (SIDs) are common to all the measurements. We apply our theoretical models to infer the D-region characteristics and to reproduce the observed VLF signal behavior corresponding to such SIDs. We develop a code based on ray theory to simulate the diurnal behavior of VLF signals over short propagation paths (2000~3000 km). The diurnal variation from this code are comparable to the variation obtained from a more general Long Wave Propagation Capability (LWPC) code which is based on mode theory approach. We simulate the observational results obtained during the Total Solar Eclipse of July 22, 2009 in India. We also report and simulate a h...

  8. Study of Ionospheric Perturbations in D-Layer Using VLF Receiver at Tashkent IHY Station

    Science.gov (United States)

    Ahmedov, Bobomurat

    2016-07-01

    Tashkent International Heliophysical Year (IHY) station is a member of Atmospheric Weather Electromagnetic System for Observation, Modeling and Education (AWESOME) network being operated globally to study the ionosphere and the magnetosphere with the help of electromagnetic waves in Very Low Frequency (VLF) band. Regular monitoring of the D- and F-layers of ionosphere over Central Asia territory is being performed on the permanent basis starting year 2008 when one VLF receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University. The results obtained at Tashkent IHY station are applied to earthquake electromagnetic precursors, lightning, and Solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters connected with evolution of strongly magnetized neutron stars believed as magnetars. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Several Solar events are observed and the analysis has shown that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is examined.

  9. Analysis and Modeling of Jovian Radio Emissions Observed by Galileo

    Science.gov (United States)

    Menietti, J. D.

    2003-01-01

    Our studies of Jovian radio emission have resulted in the publication of five papers in refereed journals, with three additional papers in progress. The topics of these papers include the study of narrow-band kilometric radio emission; the apparent control of radio emission by Callisto; quasi-periodic radio emission; hectometric attenuation lanes and their relationship to Io volcanic activity; and modeling of HOM attenuation lanes using ray tracing. A further study of the control of radio emission by Jovian satellites is currently in progress. Abstracts of each of these papers are contained in the Appendix. A list of the publication titles are also included.

  10. Source location of chorus emissions observed by Cluster

    Directory of Open Access Journals (Sweden)

    M. Parrot

    Full Text Available One of the objectives of the Cluster mission is to study sources of various electromagnetic waves using the four satellites. This paper describes the methods we have applied to data recorded from the STAFF spectrum analyser. This instrument provides the cross spectral matrix of three magnetic and two electric field components. This spectral matrix is analysed to determine, for each satellite, the direction of the wave normal relative to the Earth’s magnetic field as a function of frequency and of time. Due to the Cluster orbit, chorus emissions are often observed close to perigee, and the data analysis determines the direction of these waves. Three events observed during different levels of magnetic activity are reported. It is shown that the component of the Poynting vector parallel to the magnetic field changes its sense when the satellites cross the magnetic equator, which indicates that the chorus waves propagate away from the equator. Detailed analysis indicates that the source is located in close vicinity of the plane of the geomagnetic equator.

    Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms; Space plasma physics (waves and instabilities

  11. Observations of Coastal IO Emissions on the Southern Hemisphere and Emission Potential of Different Seaweed Species

    Science.gov (United States)

    Horbanski, Martin; Schmitt, Stefan; Frieß, Udo; Pöhler, Denis; Johnston, Paul; Kreher, Karin; Robinson, Andrew D.; Thomas, Alan; Harris, Neil R. P.; Platt, Ulrich

    2014-05-01

    At coastal sites reactive iodine species emitted by seaweed in the intertidal zone during low tide are known to have an important influence on the atmospheric chemistry. However, many underlying mechanisms are presently not understood. Also coastal studies were focused on a few locations on the northern hemisphere and their predominant seaweed species laminaria digitata and ascophyllum nodosum. Therefore the spatial emission and extent of the areas where halogen chemistry is of importance needs to be much better quantified. Especially in the mid latitudes of the southern hemisphere RHS measurements are very sparse. Here we report the first observations of coastal iodine monoxide (IO) in the southern hemisphere during the HALMA/MAORI campaign which was carried out in February to March 2013 on the east coast of New Zealand's South Island at Shag Point located north of Dunedin. To detect IO we used a mobile Open Light Path Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) instrument and a stationary Long Path (LP)-DOAS Instrument, which was furthermore used to measure BrO, O3 and I2. The measurement path was positioned over the water and mainly measured air masses that only passes over submerged seaweed forests. With the CE-DOAS placed close to exposed seaweed patches (mainly Macrocystis Pyrifera) we were able to observe high IO mixing ratios of up to 50 ppt (2ppt detection limit). However, the LP-DOAS did not detect IO above the detection limit of 0.7 ppt. This is consistent with previous observations which found that seaweed only emits halogens when exposed to air. To further investigate the emission potential of the seaweed species we setup a Teflon chamber around the CE-DOAS and measured the emissions of five different species for several hours. Additionally the air in the chamber was probed by a compact gas chromatograph (μDIRAC) for measurements of halocarbons and a TEI Ozone monitor. We found very high IO mixing ratios of up to 500 ppt for

  12. Aperture synthesis observations of solar and stellar radio emission

    International Nuclear Information System (INIS)

    The work presented in this thesis relied upon the radio astronomical instrument, The Very Large Array. The thesis is divided into three major sections. In the first the author applied maximum entropy-type image reconstruction techniques, using both single dish and iterferometer data, to generate full disk images of the Sun at a wavelength λ ∼ 21 cm. Using a set of six such images obtained during the Sun's decline from sunspot maximum to minimum, he has noted a number of previously unreported phenomena. Among these: (1) a systematic decrease in quiet Sun's brightness temperature as it declined to minimum; (2) a systematic decrease in the Sun's radius at 21 cm; (3) evidence for the evolution of polar coronal holes during the course of the solar cycle. The observed variation, though not noted previously at radio wavelengths, is entirely consistent with white light K coronagraph data. The results reported here explain the conflicting nature of a number of past observations. In the second section of the thesis, he presents the results of a long term survey of magnetic cataclysmic variables (CVs). Cataclysmic variables are close binary systems which contain a white dwarf accreting mass from a late-type secondary, typically a dwarf of spectral type, G, K, or M. The survey resulted in the detection of two out of the eighteen systems observed. In the third section of the thesis, he presents new results on flare stars in the solar neighborhood and in the Pleiades. He has successfully employed the technique of dynamic spectroscopy to constrain the mechanisms(s) for radio flaring on other stars. The second part of section three is devoted to a search for radio emission from flare stars in the Pleiades which was motivated by the evolutionary questions raised by flare stars and the Pleiades lower main sequence

  13. Amplitude and phase perturbations on VLF/LF signals at Belgrade due to X-ray flare intensity

    Science.gov (United States)

    Sulic, Desanka

    2016-07-01

    Narrowband very low frequency (VLF, 3-30 kHz) and low frequency (LF, 30-300 kHz) radio signals are powerful tool for long-range remote sensing of the ionospheric D-region electron density. Propagation of VLF/LF signals emitted by man-made transmitters takes place in the Earth-ionosphere waveguide and strongly depends on the electrical properties of the ionosphere. Changes in the D-region electron density cause changes in the received amplitude and phase on VLF/LF signals. Comparing the measured VLF/LF perturbations with LWPC simulations based on the predicted changes to the D-region, so as to infer the average D-region electron density profiles along the waveguide. The data were recorded at a Belgrade (44.85 ^{0} N, 20.38 ^{0} E) Serbia by AbsPAL and AWESOME receivers since 2003 and 2008 up to 2015, respectively. The first purpose of this paper is to give an account on the dropping amplitude phenomena on one long and three short VLF paths. The NAA-BEL path is sufficiently long, D = 6540 km and oriented west-east to show well-developed sunrise and sunset effects on amplitude and phase. Measured NAA/24.00 kHz signal at Belgrade shows three amplitude minima in time interval when sunrise reaches Belgrade and Maine, USA. Similar but less evident changes occur in time interval defined by sunsets at receiver and transmitter sites. The results show that at the times of amplitude minima the rate of change of phase becomes quite large. GQD/22.10 kHz, DHO/23.40 kHz and NSC/45.90 kHz signals propagate over short paths, D flare. During occurrence of solar flare the altitude profile of ionospheric conductivity changes, a VLF/LF signal reflects from lower height and these changes result that VLF/LF propagation is performed with more discrete modes than in normal ionospheric condition. Amplitude and phase perturbations on different VLF/LF signals observed at Belgrade have sensitive dependence on: X-ray flare intensity, solar zenith angle, occurrence of solar flare under solar

  14. The South America VLF Network - SAVNET: Achievements, Latest Results and Future Directions

    Science.gov (United States)

    Raulin, J.

    2013-05-01

    In this paper we present recent results obtained by the South America VLF Network (SAVNET). The use of the VLF technique by tracking subionospheric propagation anomalies appears as a very promising tool to study various aspects of Space Weather disturbances. On long timescales it is possible to indirectly monitor the solar Lyman-alpha radiation along the solar cycles. Short time phenomena like solar explosive events can be observed with 100% probability, even for the small intensity events. The effect of high-energy precipitating solar particles can be tracked in the low ionosphere. The same technique is also relevant to study the ionospheric perturbations caused by geomagnetic storms on typical timescales of a day to few days. Extra solar and terrestrial high-energy phenomena are naturally detected in the very sensitive low ionospheric plasma, as Gamma-ray bursts and Soft Gamma-ray repeaters. Finally, the remote sensing of the low ionosphere is also used to search for seismic-electromagnetic effects prior to Earthquakes. At the present time, SAVNET is composed of nine (9) tracking receiver stations in Brazil, Peru, Argentina and Mexico. In this presentation we will describe our future plans for expanding the array. Eastern Europe, Ecuador and Asia are good host candidates to participate in these forthcoming activities. The array expansion is necessary to improve the probability detection of very high-energy remote phenomena, and to demonstrate that these processes of great astrophysical importance can be easily detected using a cheap and simple technique.

  15. Observations of exoelectron emission associated with heterogeneous catalysis

    Science.gov (United States)

    Hoenig, S. A.; Utter, M. G.

    1977-01-01

    It is suggested that the exoelectron emission from the catalyst may be used to monitor the rate of oxidation of CO and CH4 over palladium catalysts. Indirect heating of the catalyst and atmospheric pressure have no effect upon this monitoring system. Although the mechanism relating catalysis to exoelectron emission is not clear, it is considered possible that electron emission is triggered by the adsorption-desorption cycle.

  16. Excitation of guided ELF-VLF waves through modification of the F{sub 2} ionospheric layer by high-power radio waves

    Energy Technology Data Exchange (ETDEWEB)

    Markov, G. A.; Belov, A. S.; Komrakov, G. P. [Lobachevsky State University (Russian Federation); Parrot, M. [Environmental Physics and Chemistry Laboratory (France)

    2012-03-15

    The possibility of controlled excitation of ELF-VLF electromagnetic waves through modification of the F{sub 2} ionospheric layer by high-power high-frequency emission is demonstrated in a natural experiment by using the Sura midlatitude heating facility. The excited low-frequency waves can be used to explore the near-Earth space and stimulate the excitation of a magnetospheric maser.

  17. Microprocessor implementation of an FFT for ionospheric VLF observations

    Science.gov (United States)

    Elvidge, J.; Kintner, P.; Holzworth, R.

    1984-01-01

    A fast Fourier transform algorithm is implemented on a CMOS microprocessor for application to very low-frequency electric fields (less than 10 kHz) sensed on high-altitude scientific balloons. Two FFT's are calculated simultaneously by associating them with conjugate symmetric and conjugate antisymmetric results. One goal of the system was to detect spectral signatures associated with fast time variations present in natural signals such as whistlers and chorus. Although a full evaluation of the system was not possible for operational reasons, a measure of the system's success has been defined and evaluated.

  18. Response of the low ionosphere to X-ray and Lyman-α solar flare emissions

    Science.gov (United States)

    Raulin, Jean-Pierre; Trottet, GéRard; Kretzschmar, Matthieu; Macotela, Edith L.; Pacini, Alessandra; Bertoni, Fernando C. P.; Dammasch, Ingolf E.

    2013-01-01

    Using soft X-ray measurements from detectors onboard the Geostationary Operational Environmental Satellite (GOES) and simultaneous high-cadence Lyman-α observations from the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy 2 (PROBA2) ESA spacecraft, we study the response of the lower part of the ionosphere, the D region, to seven moderate to medium-size solar flares that occurred in February and March of 2010. The ionospheric disturbances are analyzed by monitoring the resulting sub-ionospheric wave propagation anomalies detected by the South America Very Low Frequency (VLF) Network (SAVNET). We find that the ionospheric disturbances, which are characterized by changes of the VLF wave phase, do not depend on the presence of Lyman-α radiation excesses during the flares. Indeed, Lyman-α excesses associated with flares do not produce measurable phase changes. Our results are in agreement with what is expected in terms of forcing of the lower ionosphere by quiescent Lyman-α emission along the solar activity cycle. Therefore, while phase changes using the VLF technique may be a good indicator of quiescent Lyman-α variations along the solar cycle, they cannot be used to scale explosive Lyman-α emission during flares.

  19. Modeling of very low frequency (VLF radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

    Directory of Open Access Journals (Sweden)

    S. Palit

    2013-09-01

    Full Text Available X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~60 to 100 km in excess of what is expected to occur due to a quiet sun. Very low frequency (VLF radio wave signals reflected from the D-region of the ionosphere are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class flare and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the D-region of the ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the change in VLF signal. We did the modeling of the VLF signal along the NWC (Australia to IERC/ICSP (India propagation path and compared the results with observations. The agreement is found to be very satisfactory.

  20. Modeling of the Very Low Frequency (VLF radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

    Directory of Open Access Journals (Sweden)

    S. Palit

    2013-03-01

    Full Text Available X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~ 60 to 100 km in excess of what is expected from a quiet sun. Very Low Frequency (VLF radio wave signals reflected from the D region are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the lower ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the VLF signal change. We did the modeling of the VLF signal along the NWC (Australia to IERC/ICSP (India propagation path and compared the results with observations. The agreement is found to be very satisfactory.

  1. VLF Perturbations Associated with Solar Eclipses of November 2012 and may 2013 IN the South Pacific Region

    Science.gov (United States)

    Kumar, S.; Kumar, A.

    2015-12-01

    Sub-ionospheric VLF signals from the NWC (19.8 kHz), NPM (21.4 kHz) and NLK (24.8 kHz) MSK VLF transmitters are monitored at Suva, Fiji, with a time resolution of 0.1s using GPS based timing and SoftPAL VLF system. Here one minute averaged amplitude and phase data have been used for analysis. We present perturbations in VLF propagation and D-region changes associated with 13 November 2012 total solar eclipse (SE) and 9-10 May 2013 annular SE using VLF observations at Suva, Fiji. During 13-14 November 2012 total SE, the totality shadow intercepted NWC-Suva path and NWC signal amplitude and phase decreased by about 0.70 dB and 23°, respectively. NPM signal amplitude during 9-10 May 2013 SE decreased by about 2.0 dB. The amplitude perturbation of ~1.8 dB on NLK signal was measured from the unperturbed level associated with 9-10 May 2013 SE. The decrease in the amplitude at the site can be understood in terms of destructive interference of modes converted at the discontinuity created by the eclipse intercepting the different Transmitter-receiver great circle paths (TRGCPs) and changes in the propagation conditions along TRGCPs. The decrease in the amplitude and phase of NWC signal for 13-14 November 2012 SE has been modeled using Long Wave Propagation Capability code to estimate the changes in D-region reflection height (H') and sharpness factor (β) which shows that H' and β were increased by 0.95 km and 0.01 km-1, respectively. The phase changes on NWC signal associated with 9-10 May 2013 SE have been used to estimate the recombination coefficient value, for 75 km height where electron density reduction due to SE was about 40%. The changes in the D-region parameters and the electron density are due to sudden decrease of the photo-ionization creating nighttime like conditions in the D-region ionosphere.

  2. Motorcycles, mopeds: polluting emissions and energy consumption. Initial observations

    Energy Technology Data Exchange (ETDEWEB)

    Barbusse, St.

    2001-05-01

    The present French fleet of two-wheel vehicles is very heterogeneous (2- and 4-stroke engines with cubic capacity from 50 cm{sup 3} to 1300 cm{sup 3} and automatic or manual transmissions) and generally lacking in any anti-pollution system, which leads to high emission levels of carbon monoxide and unburned hydrocarbons. Mopeds have high emission levels compared to those of 4-wheel vehicles, which have decreased markedly since 1970. The following chart of limit values confirms that the gap between these two vehicle categories in polluting emissions has increased in just a few years. The implementation of more restrictive regulations about pollution emissions was delayed for a long time because of cumulative technological delays in comparison to private vehicles. But in the end a European directive differentiating two kinds of two-wheel vehicles: mopeds and motorcycles was voted in 1997 (no. 97/24). There are two stages (in 1999 and 2002 respectively) for lowering emissions levels for mopeds (engine size smaller than 50 cm{sup 3}). For motorcycles a single stage was set for 1999, with a second stage still under consideration. Given the high stakes in terms of decreased pollution emission rom the necessary technological leap for the shift from outmoded carburetor engines to more refined technology (injection + post-treatment) under ADEME's guidance, the issue of exhaust-pollution reduction of two-wheel vehicles was included in both the PRIMEQUAL programme, 'Automobile Pollution Emissions' and the PREDIT call for proposals, 'Cycle Fuel Engine Pollution Reduction' in 1999. Several projects of varying technical natures (evaluations of existing engines and technological studies of new solutions in engines and exhaust pollution reduction) have been implemented in partnership with specialist research laboratories (such as the IFP) and manufacturers and outfitters in the sector (Sagem, Arvin Exhaust, Peugeot Motorcycles). Moreover, as the principle

  3. Mapping man-made CO2 emissions using satellite-observed nighttime lights

    Science.gov (United States)

    Oda, T.; Maksyutov, S. S.; Andres, R. J.; Elvidge, C.; Baugh, K.; Hsu, F. C.; Roman, M. O.

    2015-12-01

    The Open-Data Inventory for Anthropogenic Carbon dioxide (ODIAC) is a global high spatial resolution (1x1km) emission dataset for CO2 emissions from fossil fuel combustion. The original version of ODIAC was developed at the Japanese Greenhouse Gas Observing Satellite (GOSAT) project to prescribe their inverse model. ODIAC first introduced the combined use of satellite-observed nighttime light data and individual power plant emission/geolocation information to estimate the spatial extent of fossil fuel CO2. The ODIAC emission data has been widely used by the international carbon cycle research community and appeared in a number of publications in the literature. Since its original publication in 2011, we have made numerous modifications to the ODIAC emission model and the emission data have been updated on annual basis. We are switching from BP statistical data based emission estimates to estimates made by Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory. In recent versions of ODIAC data, the emission seasonality has been adopted from the CDIAC monthly emission dataset. The emissions from international bunkers, which are not included in the CDIAC gridded emission data, are estimated using the UN Energy Database and included with the spatial distributions. In the next version of ODIAC emission model, we will explore the use of satellite data collected by the NASA's Suomi National Polar-orbiting Partnership (NPP) satellite. We will estimate emission spatial distributions using global 500x500m nighttime lights data created from VIIRS data. We will also utilize a combustion detection algorithm Nightfire developed at NOAA National Geophysical Data Center to map gas flaring emissions. We also plan to expand our two emission sector emission distributing approach (power plant emission and non-point source emissions) by introducing a transportation emission sector which should improve emission distributions in urban and rural areas.

  4. A generation mechanism of chorus emissions using BWO theory

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ashutosh K; Singh, K K; Singh, A K; Patel, R P [Department of Physics, M. M. H. P. G. College, Ghaziabad (India); Singh, R, E-mail: abhay_s@rediffmail.co [Indian Institute of Geomagnetism, Navi Mumbai (India)

    2010-02-01

    In this paper, discrete VLF chorus emissions recorded at low latitude ground station Jammu (geomag. Lat. = 22{sup 0} 26{sup /} N, L = 1.17) are reported and their characteristics based on complete spectral analysis have been carried out. These discrete chorus emissions are generated during a strong geomagnetic storm period of 2-7 May, 1998. We have computed the sweep rate, repetition period, source region, and drift rate of the individual chorus elements. It is observed that the sweep rate increases with time. To explain the various temporal and spectral features of these emissions, a possible generation mechanism has been presented based on the backward wave oscillator (BWO) regime in the magnetospheric cyclotron maser. On the basis of this model, we have computed some discrete chorus emission parameters as well as magnetospheric parameters relevant to the generation process. A comparison of the computed and observed magnetospheric parameters has been presented. These results show a good agreement with the BWO model.

  5. Estimation of NOx Emissions from megacities using mobile MAX-DOAS and satellite observations

    OpenAIRE

    Shaiganfar, Reza

    2012-01-01

    The focus of this study is on the quantification of NOx emissions. We characterized and quantfified vertically integrated NO2 concentrations (VCDs) and NOx emissions by using mobile MAX-DOAS and satellite observations. The mobile MAX-DOAS observations are conducted on different circles around megacities. From the combination of MAX-DOAS observations with meteorological data, total NOx emissions from different megacities were estimated. In this thesis, several correction methods were develo...

  6. Optimization of NOx emissions in Yangtze Delta Region using in-situ observations

    Science.gov (United States)

    Wang, Hengmao; Jiang, Fei; Jiang, Ziqiang; Liu, Jane; Chen, Jing Ming; Ju, Weimin

    2016-04-01

    Well quantified NOx emissions are essential for air quality forecasting and air pollution mitigation. The traditional "bottom-up" estimates of NOx emissions, using activity data and emission factors, are subject to large uncertainties, especially in China. Inverse modelling, often referred to as "top-down" approach, using atmospheric observations made from satellites and ground stations, provides an effective means to optimize bottom-up NOx emission inventory. The rapid expansion of air quality monitoring network in China offers an opportunity to constrain NOx emissions using in-situ ground measurements. We explore the potential of using NO2 observations from the air quality monitoring network to improve NOx emissions estimates in China. The four dimensional variational data assimilation (4DVAR) scheme in the Community Multi-scale Air Quality (CMAQ) adjoint model is implemented to infer NOx emissions in Yangtze Delta Region at 12 km resolution. The optimized NOx emissions are presented. The uncertainly reduction of estimates is analyzed and discussed.

  7. Extended emission sources observed via two-proton correlations

    International Nuclear Information System (INIS)

    Two-proton correlations were measured as a function of the total energy and relative momentum of the proton. The correlation is analyzed for different orientations of the relative momentum, which allows information on the size and lifetime of the emission source to be extracted. The most energetic particles are emitted from a short- lived source of compound nucleus dimensions while the lower energy protons appear to be emitted from a source considerably larger than the compound nucleus. 9 refs., 3 figs

  8. On the numerical modelling of VLF chorus dynamical spectra

    OpenAIRE

    Nunn, D; O. Santolik; Rycroft, M.; Trakhtengerts, V.

    2009-01-01

    This paper presents a study of the use of a one-dimensional Vlasov Hybrid Simulation (VHS) computer code to simulate the dynamical spectra (i.e. frequency versus time spectrograms) of ELF/VLF chorus signals (from ~a fraction to ~10 kHz). Recently excellent measurements of chorus have been made in the source region close to the geomagnetic equator aboard the four spacecraft Cluster mission. Using Cluster data for wave amplitude, which is up to 300 pT, local gyrofrequency, cold plasma density, ...

  9. VLF study of low magnitude Earthquakes (4.5

    Science.gov (United States)

    Wolbang, Daniel; Biernat, Helfried; Schwingenschuh, Konrad; Eichelberger, Hans; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Friedrich, Martin

    2014-05-01

    In the course of the European VLF/LF radio receiver network (International Network for Frontier Research on Earthquake Precursors, INFREP), radio signals in the frequency range from 10-50 kilohertz are received, continuously recorded (temporal resolution 20 seconds) and analyzed in the Graz/Austria knot. The radio signals are generated by dedicated distributed transmitters and detected by INFREP receivers in Europe. In case the signal is crossing an earthquake preparation zone, we are in principle able to detect seismic activity if the signal to noise ratio is high enough. The requirements to detect a seismic event with the radio link methods are given by the magnitude M of the Earthquake (EQ), the EQ preparation zone and the Fresnel zone. As pointed out by Rozhnoi et al. (2009), the VLF methods are suitable for earthquakes M>5.0. Furthermore, the VLF/LF radio link gets only disturbed if it is crossing the EQ preparation zone which is described by Molchanov et al. (2008). In the frame of this project I analyze low seismicity EQs (M≤5.6) in south/eastern Europe in the time period 2011-2013. My emphasis is on two seismic events with magnitudes 5.6 and 4.8 which we are not able to adequately characterize using our single parameter VLF method. I perform a fine structure analysis of the residua of various radio links crossing the area around the particular 2 EQs. Depending on the individual paths not all radio links are crossing the EQ preparation zone directly, so a comparative study is possible. As a comparison I analyze with the same method the already good described EQ of L'Aquila/Italy in 2009 with M=6.3 and radio links which are crossing directly the EQ preparation zone. In the course of this project we try to understand in more detail why it is so difficult to detect EQs with 4.5Hazards and Earth System Sciences, 9, 1727-1732, 2009. [2] A. Molchanov, M. Hayakawa: Seismo-Electromagnetics and related Phenomena: History and latest results, Terrapub, 2008.

  10. Satellite observations indicate substantial spatiotemporal variability in biomass burning NOx emission factors for South America

    Directory of Open Access Journals (Sweden)

    P. Castellanos

    2013-08-01

    Full Text Available Biomass burning is an important contributor to global total emissions of NOx (NO + NO2. Generally bottom-up fire emissions models calculate NOx emissions by multiplying fuel consumption estimates with static biome specific emission factors, defined in units of grams of NO per kilogram of dry matter consumed. Emission factors are a significant source of uncertainty in bottom-up fire emissions modeling because relatively few observations are available to characterize the large spatial and temporal variability of burning conditions. In this paper we use NO2 tropospheric column observations from the Ozone Monitoring Instrument (OMI from the year 2005 over South America to calculate monthly NOx emission factors for four fire types: deforestation, savanna/grassland, woodland, and agricultural waste burning. In general, the spatial trends in NOx emission factors calculated in this work are consistent with emission factors derived from in situ measurements from the region, but are more variable than published biome specific global average emission factors widely used in bottom up fire emissions inventories such as the Global Fire Emissions Database (GFED v3. Satellite based NOx emission factors also indicate substantial temporal variability in burning conditions. Overall, we found that deforestation fires have the lowest NOx emission factors, on average 30 % lower than the emission factors used in GFED v3. Agricultural fire NOx emission factors were the highest, on average a factor of 2 higher than GFED v3 values. For savanna, woodland, and deforestation fires early dry season NOx emission factors were a factor of ~1.5–2.0 higher than late dry season emission factors. A minimum in the NOx emission factor seasonal cycle for deforestation fires occurred in August, the time period of severe drought in South America in 2005. Our results support the hypothesis that prolonged dry spells may lead to an increase in the contribution of smoldering combustion

  11. Detection efficiency of the VLF World-Wide Lightning Location Network (WWLLN: initial case study

    Directory of Open Access Journals (Sweden)

    C. J. Rodger

    2006-12-01

    Full Text Available An experimental Very Low Frequency (VLF World-Wide Lightning Location Network (WWLLN has been developed through collaborations with research institutions across the world, providing global real-time locations of lightning discharges. As of April 2006, the network included 25 stations providing coverage for much of the Earth. In this paper we examine the detection efficiency of the WWLLN by comparing the locations from this network with lightning location data purchased from a commercial lightning location network operating in New Zealand. Our analysis confirms that WWLLN favours high peak current return stroke lightning discharges, and that discharges with larger currents are observed by more stations across the global network. We then construct a first principles detection efficiency model to describe the WWLLN, combining calibration information for each station with theoretical modelling to describe the expected amplitudes of the VLF sferics observed by the network. This detection efficiency model allows the prediction of the global variation in WWLLN lightning detection, and an estimate of the minimum CG return stroke peak current required to trigger the network. There are strong spatial variations across the globe, primarily due to station density and sensitivity.

    The WWLLN is currently best suited to study the occurrence and impacts of high peak-current lightning. For example, in 2005 about 12% of the global elve-producing lightning will have been located by the network. Since the lightning-EMP which produce elves has a high mean rate (210 per minute it has the potential to significantly influence the ionosphere on regional scales.

  12. Emission of linalool from Valencia orange blossoms and its observation in ambient air

    Science.gov (United States)

    Arey, Janet; Corchnoy, Stephanie B.; Atkinson, Roger

    Emission measurements made over a 5-month period of a Valencia orange tree showed the significant emission of the terpenoid linalool (C 10H 18O) from Valencia orange blossoms. The average annual emission rate of this Olinda Valencia orange, derived from emission measurements which include the blossoming season, is a factor of ˜10 higher than the average annual emission rate derived from measurements taken outside of the blossom season. Ambient monoterpene and linalool concentrations were measured in Riverside, California, in the spring and supported the chamber plant emissions data, with linalool concentrations as high as 17 μg m -3 being observed in an orange grove. These results show that current biogenic emission inventories which are formulated from limited survey data, generally not including seasonal variations in the vegetative emissions, can be subject to large uncertainties.

  13. Analysis of auroral infrared emissions observed during the ELIAS experiment

    Directory of Open Access Journals (Sweden)

    G. E. Caledonia

    Full Text Available The ELIAS (Earth Limb Infrared Atmospheric Structure experiment was flown from the Poker Flat Research Range, Alaska in 1983 and successfully monitored visible and infrared emissions from an IBC III+ aurora. Measurements were performed in both staring and scanning modes over several hundred seconds. The data for short- and mid-wave infrared regions have been analyzed in terms of auroral excitation of the NO and NO+ vibrational bands. Auroral excitation efficiencies and kinetic implications are presented.

  14. Solution uniquity of an inverse VLF problem: A case-study of the polar, ground-based, VLF radio signal disturbances caused by the ultra-energetic relativistic electron precipitations and of their southern boundaries

    Science.gov (United States)

    Remenets, G. F.; Astafiev, A. M.

    2016-09-01

    Here we present the results of a case study of the rare, abnormal, qualitatively specific behavior of Aldra (northern Norway) and GBR (UK) VLF transmitter signals (10-16 kHz) received at Kola Peninsula. The abnormal amplitude and the phase disturbances of signals were used as a proxy for ultra-energetic relativistic (solar?) electron precipitation (URE, ∼100 MeV) into the middle polar atmosphere. The disturbances have been observed under quiet or moderately disturbed geomagnetic activity. Based on bearing results, it was established that the abnormal variations of the electric conductivity of ionized middle atmosphere (of a sporadic Ds layer under the regular ionosphere D layer) were characterized by the following: (i) the time function of height h(t) of an effective spherical waveguide between the Earth surface and the sporadic Ds layer shows a minimum value equal to ∼30 km and (ii) the reflection coefficient R(t) of radio wave with a grazing angle of incidence from a virtual boundary with height h(t) has a minimum value equal to ∼0.4. The southern boundaries of the ultra-energetic relativistic electron precipitations have been found as well. They turned out to be not southerly than 61 degree of magnetic latitude and similar to the ones obtained in our previous study of the events for other dates under the similar geophysical conditions although we do not know anything definite about the rigidity and density of the electron fluxes. A used calculation method of analysis is based on a necessary condition that a number n of input data should be greater than a number m of output parameter-functions. We have stated by numerical testing that a decrease of n from 6 to 4 generates a lack of uniqueness of an inverse VLF problem solution for m = 2. It is important for future VLF ground-based monitoring of the URE precipitation events.

  15. Regional nitrogen oxides emission trends in East Asia observed from space

    Directory of Open Access Journals (Sweden)

    B. Mijling

    2013-07-01

    Full Text Available Due to changing economic activity, emissions of air pollutants in East Asia change rapidly in space and time. Monthly emission estimates of nitrogen oxides derived from satellite observations provide valuable insight in the evolution of anthropogenic activity on a regional scale. We present the first results of a new emission estimation algorithm, specifically designed to use daily satellite observations of column concentrations for fast updates of emissions of short-lived atmospheric constituents on a~mesoscopic scale (~ 0.25° × 0.25°. The algorithm is used to construct a monthly NOx emission time series for 2007–2011 from tropospheric NO2 observations of GOME-2 for East Chinese provinces and surrounding countries. The new emission estimates correspond well with the bottom-up inventory of EDGAR v4.2, but are smaller than the inventories of INTEX-B and MEIC. They reveal a strong positive trend during 2007–2011 for almost all Chinese provinces, related to the country's economic development. We find a 41% increment of NOx emissions in East China during this period, which shows the need to update emission inventories in this region on a regular basis. Negative emission trends are found in Japan and South Korea, which can be attributed to a combined effect of local environmental policy and global economic crises. Analysis of seasonal variation distinguishes between regions with dominant anthropogenic or biogenic emissions. For regions with a mixed anthropogenic and biogenic signature, the opposite seasonality can be used for an estimation of the separate emission contributions. Finally, the non-local concentration/emission relationships calculated by the algorithm are used to quantify the direct effect of regional NOx emissions on tropospheric NO2 concentrations outside the region. For regions such as North Korea and Beijing province, a substantial part of the tropospheric NO2 originates from emissions elsewhere.

  16. Regional nitrogen oxides emission trends in East Asia observed from space

    Science.gov (United States)

    Mijling, B.; van der A, R. J.; Zhang, Q.

    2013-12-01

    Due to changing economic activity, emissions of air pollutants in East Asia are changing rapidly in space and time. Monthly emission estimates of nitrogen oxides derived from satellite observations provide valuable insight into the evolution of anthropogenic activity on a regional scale. We present the first results of a new emission estimation algorithm, specifically designed to use daily satellite observations of column concentrations for fast updates of emissions of short-lived atmospheric constituents on a mesoscopic scale (~ 0.25° × 0.25°). The algorithm is used to construct a monthly NOx emission time series for the period 2007-2011 from tropospheric NO2 observations of GOME-2 for East Chinese provinces and surrounding countries. The new emission estimates correspond well with the bottom-up inventory of EDGAR v4.2, but are smaller than the inventories of INTEX-B and MEIC. They reveal a strong positive trend during 2007-2011 for almost all Chinese provinces, related to the country's economic development. We find a 41% increment of NOx emissions in East China during this period, which shows the need to update emission inventories in this region on a regular basis. Negative emission trends are found in Japan and South Korea, which can be attributed to a combined effect of local environmental policy and global economic crises. Analysis of seasonal variation distinguishes between regions with dominant anthropogenic or biogenic emissions. For regions with a mixed anthropogenic and biogenic signature, the opposite seasonality can be used for an estimation of the separate emission contributions. Finally, the non-local concentration/emission relationships calculated by the algorithm are used to quantify the direct effect of regional NOx emissions on tropospheric NO2 concentrations outside the region. For regions such as North Korea and the Beijing municipality, a substantial part of the tropospheric NO2 originates from emissions elsewhere.

  17. Recent Observations of Venus' OI and O2 Emission from

    Science.gov (United States)

    Gray, C. L.; Chanover, N. J.; Slanger, T. G.

    2011-10-01

    Past observations of the Venusian night glow features O(1S -1 D) at 5577.3 Å (atomic oxygen green line) and O2 (a - X) 0 - 0 at 1.27 μm were found to be temporally and spatially variable. We report on the analysis of recent observations of these two features, obtained using optical and infrared spectrographs on the 3.5-meter Astrophysical Research Consortium Telescope at Apache Point Observatory (APO) in December 2010.

  18. Electric and VLF-MT survey of Tegatayama tunnel; Tegatayama tunnel no denki tansa oyobi VLF tansa

    Energy Technology Data Exchange (ETDEWEB)

    Nishitani, T. [Akita University, Akita (Japan). Mining College

    1997-05-27

    To survey the structure at the depth between 20 and 30 m, field tests were conducted by means of vertical electric and VFL-MT (magnetotelluric) survey. Tegatayama tunnel has a total length of 276 m, width of 7.5 m, and height of 4.7 m, and the depth from the surface is about 28 m near the top of mountain. Near the tunnel, the thickness of surface soil is about 60 cm, which consists of clay soil including soft mudstone gravel. It was found that terrace deposit is distributed up to the depth of 8 m, and that mudstone is distributed below the depth of 8 m. Weighted four-electrode method was adopted for the vertical electrical survey. Measurements were conducted at the immediately above the tunnel, 10 m apart from the center of tunnel in the right and left, and 20 m apart from the center in the east. For the VLF-MT method, component of frequency 22.2 kHz was used. As a result of the tests, it was difficult to illustrate the existence of tunnel from the vertical electrical survey only at one point. Feature of the tunnel could be well illustrated by means of the VLF-MT method. 3 refs., 9 figs.

  19. Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City

    OpenAIRE

    M. Zavala; Lei, W.; M. J. Molina; L. T. Molina

    2008-01-01

    The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on...

  20. Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes

    Science.gov (United States)

    Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; Liu, Si; He, Yihua; Wygant, J. R.; Baker, D. N.; Spence, H. E.; Reeves, G. D.; Funsten, H. O.

    2016-05-01

    The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. Here we report simultaneous observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ˜300-1500 Hz with the peak wave power density about 10-5 nT2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhile, hiss emissions are confined inside the plasmasphere, with a higher intensity and a broader area at a lower frequency. A sum of bi-Maxwellian distribution is used to model the observed anisotropic electron distributions and to evaluate the instability of waves. A three-dimensional ray tracing simulation shows that a portion of chorus emission outside the plasmasphere can propagate into the plasmasphere and evolve into plasmaspheric hiss. Moreover, hiss waves below 1 kHz are more intense and propagate over a broader area than those above 1 kHz, consistent with the observation. The current results can explain distributions of the observed hiss emission and provide a further support for the mechanism of evolution of chorus into hiss emissions.

  1. Gamma Ray and Very Low Frequency Radio Observations from a Balloon-Borne Platform

    Science.gov (United States)

    Quinn, C.; Sheldon, A.; Cully, C. M.; Davalos, A.; Osakwe, C.; Galts, D.; Delfin, J.; Duffin, C.; Mansell, J.; Russel, M.; Bootsma, M.; Williams, R.; Patrick, M.; Mazzino, M. L.; Knudsen, D. J.

    2015-12-01

    The University of Calgary's Student Organization for Aerospace Research (SOAR) built an instrument to participate in the High Altitude Student Platform (HASP) initiative organized by Louisiana State University and supported by the NASA Balloon Program Office (BPO) and the Louisiana Space Consortium (LaSPACE). The HASP platform will be launched in early September 2015 from Fort Sumner, New Mexico and will reach heights of 36 kilometers with a flight duration of 15 to 20 hours. The instrument, Atmospheric Phenomenon Observer Gamma/VLF Emissions Experiment (APOGEE), measures Terrestrial Gamma-Ray Flashes (TGF) and sferics from lightning strikes with the use of Geiger tubes and a VLF detector. TGFs, which are quick bursts of high energy radiation that can occur alongside lightning, are believed to be the result of Relativistic Runaway Electron Avalanche (RREA). RREA occurs when a large number of relativistic electrons overcome atmospheric frictional forces and accelerate to relativistic velocities which excite secondary electrons that collide with the atmosphere causing bremsstrahlung radiation. Lightning strikes also produce sferics within the Extremely Low Frequency (ELF) and Very Low Frequency (VLF) bands which can be detected and used to locate the strikes. The goal of APOGEE is to further investigate the link between TGFs and RREA. These phenomena are very difficult to measure together as Bremsstrahlung radiation is easily detected from space but ionospheric reflection facilitates surface detection of sferics. A high altitude balloon provides a unique opportunity to study both phenomena using one instrument because both phenomena can easily be detected from its altitude. APOGEE has been designed and built by undergraduate students at the University of Calgary with faculty assistance and funding, and is equipped with three devices for data collection: a camera to have visual conformation of events, a series of Geiger Tubes to obtain directional gamma readings, and

  2. Observation of optical emission from high refractive index waveguide excited by traveling electron beam

    OpenAIRE

    Kuwamura, Yuji; Yamada, Minoru; Okamoto, Ryuichi; Kanai, Takeshi; Fares, Hesham

    2008-01-01

    A new scheme for optical emission using a high refractive index waveguide and the traveling electron beam in vacuum was demonstrated. Optical emission around wavelength of 1.5 pm was observed for electron acceleration voltage of 40KV. © 2008 Optical Society of America.

  3. The INFREP European VLF/LF Radio Monitoring Network - Present Status and Preliminary Results of the Romanian Monitoring System

    Science.gov (United States)

    Moldovan, I. A.; Moldovan, A.; Biagi, P. F.; Placinta, A. O.; Maggipinto, T.

    2012-01-01

    The paper presents the Romanian VLF / LF monitoring system consisting in a radio receiver - made by Elettronika S.R.L. (Italy) and provided by the Bari University - and the infrastructure that is necessary to record and transmit the collected data. This system is a part of the international initiative INFREP. Through this initiative, originated in Italy, VLF / LF radio receivers are deployed in different locations in Europe. Each one is monitoring up to ten different transmissions of radio stations across the continent. Information on electromagnetic fields' intensities created by transmitters at each receiving site and gathered from this network are indicating the quality of the propagation along the paths between the receivers and transmitters. Studying the ionosphere influences on the electromagnetic waves' propagation along a certain path is a method to put into evidence possible modifications of ionosphere lower structure and composition as earthquakes' precursor. The VLF / LF receiver installed in Romania was put into operation in February 2009 and has proved its utility in the case of Abruzzo earthquake that occurred on 6th of April 2009 (Mw = 6.3). Since then, the receiver was relocated from Bucharest to the Black-Sea shore (Dobrogea Seismologic Observatory). Changing the receiving site produced unsatisfactory monitoring data, characterized by large fluctuations of the received signals' intensities. Trying to understand this behavior has led to the conclusion that the electric component of the electromagnetic field was possibly influenced by the local atmospheric conditions (as aerosols' concentrations could be). Starting from this observation we have run some tests which have indicated that a loop-type antenna is more appropriate than a vertical antenna, especially for highly electric-field polluted environments. Very good results were obtained with this new configuration, even in the site located at the Black-Sea shore. Future improvements of the receiver

  4. What would dense atmospheric observation networks bring to the quantification of city CO2 emissions?

    Science.gov (United States)

    Wu, Lin; Broquet, Grégoire; Ciais, Philippe; Bellassen, Valentin; Vogel, Felix; Chevallier, Frédéric; Xueref-Remy, Irène; Wang, Yilong

    2016-06-01

    Cities currently covering only a very small portion ( road transport, by 18 % for the production of energy by power plants, and by 31 % for total emissions. These results indicate that such a high number of stations would be likely required for the monitoring of sectoral emissions in Paris using this observation-model framework. They demonstrate some high potential that atmospheric inversions can contribute to the monitoring and/or the verification of city CO2 emissions (baseline) and CO2 emission reductions (commitments) and the advantage that could be brought by the current developments of lower-cost medium precision (LCMP) sensors.

  5. Directly observing continuum emission from self-gravitating spiral waves

    CERN Document Server

    Hall, Cassandra; Rice, Ken; Harries, Tim J; Klaassen, Pamela D; Biller, Beth

    2016-01-01

    We use a simple, self-consistent, self-gravitating semi-analytic disc model to conduct an examination of the parameter space in which self-gravitating discs may exist. We then use Monte-Carlo radiative transfer to generate synthetic ALMA images of these self-gravitating discs to determine the subset of this parameter space in which they generate non-axisymmetric structure that is potentially detectable by ALMA. Recently, several transition discs have been observed to have non-axisymmetric structure that extends out to large radii. It has been suggested that one possible origin of these asymmetries could be spiral density waves induced by disc self-gravity. We use our simple model to see if these discs exist in the region of parameter space where self-gravity could feasibly explain these spiral features. We find that for self-gravity to play a role in these systems typically requires a disc mass around an order of magnitude higher than the observed disc masses for the systems. The spiral amplitudes produced by...

  6. The properties of ULF/VLF signals generated by the SURA facility without ionospheric currents modulation

    Science.gov (United States)

    Kotik, D. S.; Raybov, A. V.; Ermakova, E. N.

    2012-12-01

    During the last three years the comprehensive study of ionospheric generation of the artificial signals in ULF/VLF band was carried out at SURA facility. This research was stimulated by successive HAARP experiments on detection the low frequency signals genreated due the action of the ponderomotive forces. Two experimental campaigns under different ionospheric, geomagnetic and facility operation mode conditions was undertaken every year from 2010 to 2012. Here we are summarizing the main features of the artificial ULF/VLF signals observed in vicinity the SURA site. The signals in the 2-20 Hz band were observed in the small area around the facility with the radius approximately 15 km. It was not signal detection at the 30 km distance. The maximum of the amplitude was detected in the nearest receiving point about 3 km away from the transmitting array. The amplitude increased about 3 times when the beam was inclined on16 degrees to the south so the footprint of the geomagnetic field line comes close to the point of observation. The ULF signals increased slightly when the SURA operating frequency overlaps the critical foF2 frequency. As a rule the daytime signals are smaller then nighttime one. No any correlation was observed with geomagnetic disturbances. The time delay of the ionospheric ULF signals measured by phase method was estimated as 300-400 ms. Polarization of the ULF signals has a pronounced elliptical character. Sometimes it was linear. The part of measurements in June 2012 was coincide with magnetic storm (June 16-18, Kp=6). It was observed broadening of the signal line at frequencies of 11 and 17 Hz up to 0.2 Hz at the recovery stage of the storm at June 18 (see the figure). This fact can be interpreted as the result of the signal interaction with the radiation belt protons appeared over there during the storm time. In 2012 campaigns it was firstly observed at SURA signals on frequencies of several kilohertz at nightime which could not be explained by

  7. Observation of valence band electron emission from n-type silicon field emitter arrays

    Science.gov (United States)

    Ding, Meng; Kim, Han; Akinwande, Akintunde I.

    1999-08-01

    Electron emission from the valence band of n-type Si field emitter arrays is reported. High electrostatic field at the surface of Si was achieved by reducing the radius of the emitter tip. Using oxidation sharpening, 1 μm aperture polycrystalline Si gate, n-type Si field emitter arrays with small tip radius (˜10 nm) were fabricated. Three distinct emission regions were observed: conduction band emission at low gate voltages, saturated current emission from the conduction band at intermediate voltages, and valence band plus conduction band emission at high gate voltages. Emission currents at low and high voltages obey the Fowler-Nordheim theory. The ratio of the slopes of the corresponding Fowler-Nordheim fits for these two regions is 1.495 which is in close agreement with the theoretical value of 1.445.

  8. The impact of PMSE and NLC particles on VLF propagation

    Directory of Open Access Journals (Sweden)

    D. Nunn

    2004-04-01

    Full Text Available PMSE or Polar Mesosphere Summer Echoes are a well-known phenomenon in the summer northern polar regions, in which anomalous VHF/UHF radar echoes are returned from heights ~85km. Noctilucent clouds and electron density biteouts are two phenomena that sometimes occur together with PMSE. Electron density biteouts are electron density depletion layers of up to 90%, which may be several kms thick. Using the NOSC Modefndr code based on Wait's modal theory for subionospheric propagation, we calculate the shifts in received VLF amplitude and phase that occur as a result of electron density biteouts. The code assumes a homogeneous background ionosphere and a homogeneous biteout layer along the Great Circle Path (GCP corridor, for transmitter receiver path lengths in the range of 500–6000km.

    For profiles during the 10h about midnight and under quiet geomagnetic conditions, where the electron density at 85km would normally be less than 500el/cc, it was found that received signal perturbations were significant, of the order of 1–4dB and 5–40° of phase. Perturbation amplitudes increase roughly as the square root of frequency. At short range perturbations are rather erratic, but more consistent at large ranges, readily interpretable in terms of the shifts in excitation factor, attenuation factor and v/c ratios for Wait's modes. Under these conditions such shifts should be detectable by a well constituted experiment involving multiple paths and multiple frequencies in the north polar region in summer. It is anticipated that VLF propagation could be a valuable diagnostic for biteout/PMSE when electron density at 85km is under 500el/cc, under which circumstances PMSE are not directly detectable by VHF/UHF radars.

    Key words. Electromagnetism (wave propagation – Ionosphere (polar ionosphere – Radioscience (ionospheric propagation

  9. Factorization of air pollutant emissions: projections versus observed trends in Europe.

    Science.gov (United States)

    Rafaj, Peter; Amann, Markus; Siri, José G

    2014-10-01

    This paper revisits the emission scenarios of the European Commission's 2005 Thematic Strategy on Air Pollution (TSAP) in light of today's knowledge. We review assumptions made in the past on the main drivers of emission changes, i.e., demographic trends, economic growth, changes in the energy intensity of GDP, fuel-switching, and application of dedicated emission control measures. Our analysis shows that for most of these drivers, actual trends have not matched initial expectations. Observed ammonia and sulfur emissions in European Union in 2010 were 10% to 20% lower than projected, while emissions of nitrogen oxides and particulate matter exceeded estimates by 8% to 15%. In general, a higher efficiency of dedicated emission controls compensated for a lower-than-expected decline in total energy consumption as well as a delay in the phase-out of coal. For 2020, updated projections anticipate lower sulfur and nitrogen oxide emissions than those under the 2005 baseline, whereby the degree to which these emissions are lower depends on what assumptions are made for emission controls and new vehicle standards. Projected levels of particulates are about 10% higher, while smaller differences emerge for other pollutants. New emission projections suggest that environmental targets established by the TSAP for the protection of human health, eutrophication and forest acidification will not be met without additional measures.

  10. Chorus, ECH, and Z mode emissions observed at Jupiter and Saturn and possible electron acceleration

    OpenAIRE

    Menietti, J.D.; Y. Y. Shprits; Horne, R. B.; E. E. Woodfield; Hospodarsky, G. B.; Gurnett, D. A.

    2012-01-01

    In this paper we compare and contrast chorus, electron cyclotron harmonics (ECH), and Z mode emissions observed at Jupiter and Saturn and relate them to recent work on electron acceleration at Earth. Intense chorus emissions are observed near the magnetic equator, the likely source region, but the strongest intensities are on either side of the magnetic equator. Chorus intensities at Jupiter are generally about an order of magnitude larger than at Saturn, and the bandwidth of chorus at Jupite...

  11. Spitzer observations of the thermal emission from WASP-43b

    CERN Document Server

    Blecic, Jasmina; Madhusudhan, Nikku; Stevenson, Kevin B; Hardy, Ryan A; Cubillos, Patricio E; Hardin, Matthew; Nymeyer, Sarah; Anderson, David R; Hellier, Coel; Smith, Alexis M S; Cameron, Andrew Collier

    2013-01-01

    WASP-43b (Hellier et al.; Gillon et al.) is one of the closest-orbiting hot Jupiters, with a semimajor axis a = 0.01526 +/- 0.00018 AU and a period of only 0.81 days. However, it orbits one of the coolest stars with a hot Jupiter (K7V, Tstar = 4520 +/- 120 K), giving the planet a modest equilibrium temperature of Teq = 1440 +/- 40 K, assuming zero Bond albedo and uniform planetary energy redistribution. This has resulted in strong signal-to-noise-ratio (S/N) observations and deep eclipses in both Warm Spitzer channels (3.6 and 4.5 microns). The eclipse depths and brightness temperatures from our jointly fit model are 0.346 +/- 0.013% and 1684 +/- 24 K at 3.6 microns and 0.382 +/- 0.015% and 1485 +/- 24 K at 4.5 microns. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347459 +/- 2.1x10-7 days) compared to Gillon et al. and put an upper limit on the eccentricity (e = 0.007+0.013-0.004). We use our Spitzer eclipse depths with two previously reported ground-based ...

  12. Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City

    Science.gov (United States)

    Zavala, M.; Lei, W.; Molina, M. J.; Molina, L. T.

    2009-01-01

    The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using observational and modeling approaches. The observed historical trends of ozone (O3), carbon monoxide (CO) and nitrogen oxides (NOx) suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-source emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio. This study presents the results of model analyses on the sensitivity of the observed ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM) and the standard Brute Force Method (BFM) in the 3-D CAMx chemical transport model. The model reproduces adequately the observed historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the

  13. Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City

    Directory of Open Access Journals (Sweden)

    M. Zavala

    2009-01-01

    Full Text Available The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using observational and modeling approaches. The observed historical trends of ozone (O3, carbon monoxide (CO and nitrogen oxides (NOx suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-source emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio.

    This study presents the results of model analyses on the sensitivity of the observed ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM and the standard Brute Force Method (BFM in the 3-D CAMx chemical transport model. The model reproduces adequately the observed historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with

  14. Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City

    Directory of Open Access Journals (Sweden)

    M. Zavala

    2008-08-01

    Full Text Available The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using observational and modeling approaches. The observed historical trends of ozone (O3, carbon monoxide (CO and nitrogen oxides (NOx suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-source emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio.

    This study presents the results of model analyses on the sensitivity of the observed ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM and the standard Brute Force Method (BFM in the 3-D CAMx chemical transport model. The model reproduces adequately the observed historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with

  15. Phenomenology of Neptune's radio emissions observed by the Voyager planetary radio astronomy experiment

    Science.gov (United States)

    Pedersen, B. M.; Lecacheux, A.; Zarka, P.; Aubier, M. G.; Kaiser, M. L.; Desch, M. D.

    1992-01-01

    The Neptune flyby in 1989 added a new planet to the known number of magnetized planets generating nonthermal radio emissions. We review the Neptunian radio emission morphology as observed by the planetary radio astronomy experiment on board Voyager 2 during a few weeks before and after closest approach. We present the characteristics of the two observed recurrent main components of the Neptunian kilometric radiation, i.e., the 'smooth' and the 'bursty' emissions, and we describe the many specific features of the radio spectrum during closest approach.

  16. Dark matter line emission constraints from NuSTAR observations of the Bullet Cluster

    DEFF Research Database (Denmark)

    Riemer-Sørensen, S.; Wik, D.; Madejski, G.;

    2015-01-01

    Some dark matter candidates, e.g., sterile neutrinos, provide observable signatures in the form of mono-energetic line emission. We present the first search for dark matter line emission in the range in a pointed observation of the Bullet Cluster with NuSTAR. We do not detect any significant line...... emission and instead we derive upper limits (95% CL) on the flux, and interpret these constraints in the context of sterile neutrinos and more generic dark matter candidates. NuSTAR does not have the sensitivity to constrain the recently claimed line detection at , but improves on the constraints...... for energies of 10–25 keV....

  17. Chandra Observations and Modeling of Geocoronal Charge Exchange X-Ray Emission During Solar Wind Gusts

    Science.gov (United States)

    Kornbleuth, Marc; Wargelin, Bradford J.; Juda, Michael

    2014-06-01

    Solar wind charge exchange (SWCX) X-rays are emitted when highly charged solar wind ions such as O7+ collide with neutral gas. The best known examples of this occur around comets, but SWCX emission also arises in the Earth's tenuous outer atmosphere and throughout the heliosphere as neutral H and He from the interstellar medium flows into the solar system. This geocoronal and heliospheric emission comprises much of the soft X-ray background and is seen in every X-ray observation. Geocoronal emission, although usually weaker than heliospheric emission, arises within a few tens of Earth radii and therefore responds much more quickly (on time scales of less than an hour) to changes in solar wind intensity than the widely distributed heliospheric emission.We have studied a dozen Chandra observations when the flux of solar wind protons and O7+ ions was at its highest. These gusts of wind cause correspondingly abrupt changes in geocoronal SWCX X-ray emission,which may or may not be apparent in Chandra data depending on a given observation's line of sight through the magnetosphere. We compare observed changes in the X-ray background with predictions from a fully 3D analysis of SWCX emission based on magnetospheric simulations using the BATS-R-US model.

  18. Spitzer observations of the thermal emission from WASP-43b

    Energy Technology Data Exchange (ETDEWEB)

    Blecic, Jasmina; Harrington, Joseph; Stevenson, Kevin B.; Hardy, Ryan A.; Cubillos, Patricio E.; Hardin, Matthew; Bowman, Oliver; Nymeyer, Sarah [Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States); Madhusudhan, Nikku [Department of Physics and Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Anderson, David R.; Hellier, Coel; Smith, Alexis M. S. [Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom); Cameron, Andrew Collier, E-mail: jasmina@physics.ucf.edu [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom)

    2014-02-01

    WASP-43b is one of the closest-orbiting hot Jupiters, with a semimajor axis of a = 0.01526 ± 0.00018 AU and a period of only 0.81 days. However, it orbits one of the coolest stars with a hot Jupiter (T {sub *} = 4520 ± 120 K), giving the planet a modest equilibrium temperature of T {sub eq} = 1440 ± 40 K, assuming zero Bond albedo and uniform planetary energy redistribution. The eclipse depths and brightness temperatures from our jointly fit model are 0.347% ± 0.013% and 1670 ± 23 K at 3.6 μm and 0.382% ± 0.015% and 1514 ± 25 K at 4.5 μm. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347436 ± 1.4 × 10{sup –7} days) and put an upper limit on the eccentricity (e=0.010{sub −0.007}{sup +0.010}). We use our Spitzer eclipse depths along with four previously reported ground-based photometric observations in the near-infrared to constrain the atmospheric properties of WASP-43b. The data rule out a strong thermal inversion in the dayside atmosphere of WASP-43b. Model atmospheres with no thermal inversions and fiducial oxygen-rich compositions are able to explain all the available data. However, a wide range of metallicities and C/O ratios can explain the data. The data suggest low day-night energy redistribution in the planet, consistent with previous studies, with a nominal upper limit of about 35% for the fraction of energy incident on the dayside that is redistributed to the nightside.

  19. Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions.

    Science.gov (United States)

    Zhang, Yanxu; Jacob, Daniel J; Horowitz, Hannah M; Chen, Long; Amos, Helen M; Krabbenhoft, David P; Slemr, Franz; St Louis, Vincent L; Sunderland, Elsie M

    2016-01-19

    Observations of elemental mercury (Hg(0)) at sites in North America and Europe show large decreases (∼ 1-2% y(-1)) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (flat or increasing emissions over that period. However, the inventories have three major flaws: (i) they do not account for the decline in atmospheric release of Hg from commercial products; (ii) they are biased in their estimate of artisanal and small-scale gold mining emissions; and (iii) they do not properly account for the change in Hg(0)/Hg(II) speciation of emissions from coal-fired utilities after implementation of emission controls targeted at SO2 and NOx. We construct an improved global emission inventory for the period 1990 to 2010 accounting for the above factors and find a 20% decrease in total Hg emissions and a 30% decrease in anthropogenic Hg(0) emissions, with much larger decreases in North America and Europe offsetting the effect of increasing emissions in Asia. Implementation of our inventory in a global 3D atmospheric Hg simulation [GEOS-Chem (Goddard Earth Observing System-Chemistry)] coupled to land and ocean reservoirs reproduces the observed large-scale trends in atmospheric Hg(0) concentrations and in Hg(II) wet deposition. The large trends observed in North America and Europe reflect the phase-out of Hg from commercial products as well as the cobenefit from SO2 and NOx emission controls on coal-fired utilities. PMID:26729866

  20. Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions

    Science.gov (United States)

    Yanxu Zhang,; Daniel J. Jacob,; Hannah M. Horowitz,; Long Chen,; Helen M. Amos,; Krabbenhoft, David P.; Franz Slemr,; Vincent L. St. Louis,; Elsie M. Sunderland,

    2015-01-01

    Observations of elemental mercury (Hg0) at sites in North America and Europe show large decreases (∼1–2% y−1) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (inventories indicating flat or increasing emissions over that period. However, the inventories have three major flaws: (i) they do not account for the decline in atmospheric release of Hg from commercial products; (ii) they are biased in their estimate of artisanal and small-scale gold mining emissions; and (iii) they do not properly account for the change in Hg0/HgII speciation of emissions from coal-fired utilities after implementation of emission controls targeted at SO2 and NOx. We construct an improved global emission inventory for the period 1990 to 2010 accounting for the above factors and find a 20% decrease in total Hg emissions and a 30% decrease in anthropogenic Hg0 emissions, with much larger decreases in North America and Europe offsetting the effect of increasing emissions in Asia. Implementation of our inventory in a global 3D atmospheric Hg simulation [GEOS-Chem (Goddard Earth Observing System-Chemistry)] coupled to land and ocean reservoirs reproduces the observed large-scale trends in atmospheric Hg0 concentrations and in HgII wet deposition. The large trends observed in North America and Europe reflect the phase-out of Hg from commercial products as well as the cobenefit from SO2 and NOx emission controls on coal-fired utilities.

  1. A study of the behavior of the terminator time shifts using multiple VLF propagation paths during the Pakistan earthquake (M = 7.2) of 18 January 2011

    Science.gov (United States)

    Ray, Suman; Chakrabarti, Sandip Kumar

    On 18 January 2011, at 20:23 UTC, an earthquake of magnitude 7.2 occurred in south-western Pakistan (latitude 28.73(°) N, longitude 63.93(°) E) at a depth of 68 km. We present the results of the analysis of very low frequency (VLF) radio signals, received at three stations located in India. We analyze the VLF signals around this earthquake day and look for possible precursory effects of this earthquake. For our analysis, we use four different VLF propagation paths. These propagation paths are DHO-IERC (Sitapur), VTX-Pune, VTX-ICSP (Indian Centre for Space Physics, Kolkata) and NWC-IERC. We observed significant shifts of the “sunrise terminator time” (SRT) for DHO-IERC and VTX-Pune paths. For DHO-IERC path, the SRT of the VLF signals shifted towards night time three days before the earthquake day, and in the case of VTX-Pune path it shifted towards night time just one day before the earthquake day. For VTX-Kolkata path, the shift of SRT is four days before the earthquake day, but here the shift is not so strong, somewhere between 2sigma and 3sigma lines. For the other two paths, namely, DHO-IERC and VTX-Pune, the terminator time shifts crossed the 3sigma line. We found no significant shifts of SRT for NWC-IERC propagation path. Higher deviation in the VTX-Pune path as compared to VTX-ICSP path could be due to the proximity of the former to the epicenter. Similarly, DHO-IERC path is over the epicenter while NWC-IERC path is totally away from the epicenter. This could be the reason why the effect in DHO-IERC path is stronger than that in NWC-IERC path.

  2. Substorm-related VLF chorus events: local-time dependence and relationship to newly-injected clouds of drifting energetic electrons

    International Nuclear Information System (INIS)

    VLF chorus is a naturally occurring, electromagnetic wave phenomenon that is generated in the earth's magnetosphere during interactions between VLF waves and energetic electrons. The macrostructure of a 9-day period of VLF ground station data, recorded at two Antarctic stations, Halley Bay and Siple, has been studied using compressed time-scale spectrograms. A magnetically quiet period was chosen for analysis, within which isolated substorms occurred. It has been found that chorus frequently occurs in events, the most characteristic feature of which is an initial rise in the upper cut-off frequency of the chorus band. The events are typically observed in the midnight to 16:00 MLT sector. They are correlated with disturbances of about 100 to 750 gammas in the AE magnetic activity index, or substorms, and with energetic electron flux enhancements measured by ATS 6 at geosynchronous orbit. In addition, parameters scaled from the upper and lower cut-off frequency variations of the events have a local-time dependence. During substorms, satellites consistently encounter clouds of energetic electrons that have been injected into the nightside outer radiation zone. It is believed that the time-developing characteristics, and local-time dependencies of the chorus events are a reflection of the time-developing characteristics of clouds of energetic electrons that have recently been injected during substorms. Two interpretations of the chorus events have been investigated based on this theory

  3. Emissions of Biogenic Volatile Organic Compounds and Observations of VOC Oxidation at Harvard Forest

    Science.gov (United States)

    McKinney, K. A.; Pho, T.; Vasta, A.; Lee, B. H.

    2009-12-01

    The contribution of biogenic volatile organic compounds (BVOCs) to oxidant concentrations and secondary organic aerosol (SOA) production in forested environments depends on the emission rates of these compounds. Recent findings have suggested that the emission rates of BVOCs and the range of species emitted could be larger than previously thought. In this study, Proton Transfer Reaction Mass Spectrometry (PTR-MS) was used to obtain fast (terpene oxidation products were also measured. Isoprene is the dominant emitted species, with peak emission rates and midday mixing ratios of ca. 4 mg isoprene m-2 h-1 and ca. 5 ppbv, respectively. Isoprene emission rates are expected to vary with temperature and radiation (PAR) levels, and are compared to standard emission algorithms based on these parameters. Interannual variability in isoprene emission rates is also observed, and contributing factors are explored. In contrast to isoprene, maximum monoterpene concentrations typically were less than 1 ppbv and occurred in the early evening, with a local minimum at midday. Monoterpene fluxes are about an order of magnitude smaller than those of isoprene. The amplitude of the flux diurnal cycle suggests monoterpene emissions at Harvard Forest may exhibit light dependence as well as temperature dependence. Fluxes of oxygenated VOCs, including methanol, acetone, methyl ethyl ketone, and oxygenated terpenes that have rarely been observed previously, are also reported, and the dependence of their emission rates on factors such as time of year, temperature, radiation levels, and meteorological conditions are investigated.

  4. Diffuse radio emission in the Coma cluster and Abell 1367: observations at 430 and 1400 MHz

    International Nuclear Information System (INIS)

    Two rich clusters of galaxies, Abell 1656 (the Coma cluster) and Abell 1367, have been mapped at both 430 and 1400 MHz with the 305-m telescope at Arecibo. The contribution to the observed radio emission due to known discrete sources has been calculated by convolving interferometrically determined source lists with observed Arecibo beam patterns, and maps of the diffuse radio emission alone have been constructed. Both clusters contain regions of diffuse radio emission, although the source in Coma is larger and much more luminous than the source in Abell 1367. The linear extent of the diffuse emission and its dependence on frequency have been used to study particle propagation rates and modes of diffusion in the intracluster medium. The possible correlations between the diffuse radio emission and x-ray emission in these clusters have been investigated, and it has been found that the observed x-ray luminosities can be accounted for if the intracluster gas is heated through Coulomb interactions with the relativistic electrons responsible for the diffuse radio emission

  5. VSA Observations of the Anomalous Microwave Emission in the Perseus Region

    CERN Document Server

    Tibbs, Christopher T; Dickinson, Clive; Davies, Rodney D; Davis, Richard J; del Burgo, Carlos; Franzen, Thomas M O; Génova-Santos, Ricardo; Grainge, Keith; Hobson, Michael P; Padilla-Torres, Carmen P; Rebolo, Rafael; Rubiño-Martín, Jóse Alberto; Saunders, Richard D E; Scaife, Anna M M; Scott, Paul F

    2009-01-01

    The dust feature G159.6--18.5 in the Perseus region has previously been observed with the COSMOSOMAS experiment \\citep{Watson:05} on angular scales of $\\approx$ 1$^{\\circ}$, and was found to exhibit anomalous microwave emission. We present new observations of this dust feature, performed with the Very Small Array (VSA) at 33 GHz, to help increase the understanding of the nature of this anomalous emission. On the angular scales observed with the VSA ($\\approx$ 10 -- 40$^{\\prime}$), G159.6--18.5 consists of five distinct components, each of which have been individually analysed. All five of these components are found to exhibit an excess of emission at 33 GHz, and are found to be highly correlated with far-infrared emission. We provide evidence that each of these compact components have anomalous emission that is consistent with electric dipole emission from very small, rapidly rotating dust grains. These components contribute $\\approx$ 10 % to the flux density of the diffuse extended emission detected by COSMO...

  6. Patterns in atmospheric carbonaceous aerosols in China: emission estimates and observed concentrations

    Directory of Open Access Journals (Sweden)

    H. Cui

    2015-03-01

    Full Text Available China is experiencing severe carbonaceous aerosol pollution driven mainly by large emissions resulting from intensive use of solid fuels. To gain a better understanding of the levels and trends of carbonaceous aerosol emissions and the resulting ambient concentrations at the national scale, we update an emission inventory of anthropogenic organic carbon (OC and elemental carbon (EC and employ existing observational studies to analyze characteristics of these aerosols including temporal, spatial, and size distributions, and the levels and shares of secondary organic carbon (SOC in total OC. We further use ground observations to test the levels and inter-annual trends of the calculated national and provincial emissions of carbonaceous aerosols, and propose possible improvements in emission estimation for the future. The national OC emissions are estimated to have increased 29% from 2000 (2127 Gg to 2012 (2749 Gg and EC by 37% (from 1356 to 1857 Gg. The residential, industrial, and transportation sectors contributed an estimated 76 ± 2, 19 ± 2 and 5 ± 1% of the total emissions of OC, respectively, and 52 ± 3, 32 ± 2 and 16 ± 2% of EC. Updated emission factors based on the most recent local field measurements, particularly for biofuel stoves, lead to considerably lower emissions of OC compared to previous inventories. Compiling observational data across the country, higher concentrations of OC and EC are found in northern and inland cities, while larger OC/EC and SOC/OC ratios are found in southern cities, due to the joint effects of primary emissions and meteorology. Higher SOC/OC ratios are estimated at rural and remote sites compared to urban ones, attributed to more emissions of OC from biofuel use, more biogenic emissions of volatile organic compound (VOC precursors to SOC, and/or transport of aged aerosols. For most sites, higher concentrations of OC, EC, and SOC are observed in colder seasons, while SOC/OC is reduced, particularly at

  7. Relative changes in CO emissions over megacities based on observations from space

    Science.gov (United States)

    Pommier, Matthieu; McLinden, Chris A.; Deeter, Merritt

    2013-07-01

    Urban areas are large sources of several air pollutants, with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multichannel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary layer, is used to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo, and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction in CO emission between 2000-2003 and 2004-2008, reaching -43% over Tehran and -47% over Baghdad. There is a contrasted agreement between these results and the MACCity and Emission Database for Global Atmospheric Research v4.2 inventories.

  8. Biomass burning emissions estimated with a global fire assimilation system based on observed fire radiative power

    NARCIS (Netherlands)

    Kaiser, J.W.; Heil, A.; Andreae, M.O.; Benedetti, A.; Chubarova, N.; Jones, L.; Morcrette, J.J.; Razinger, M.; Schultz, M.G.; Suttie, M.; Werf, van der G.R.

    2012-01-01

    The Global Fire Assimilation System (GFASv1.0) calculates biomass burning emissions by assimilating Fire Radiative Power (FRP) observations from the MODIS instruments onboard the Terra and Aqua satellites. It corrects for gaps in the observations, which are mostly due to cloud cover, and filters spu

  9. SOFIA observations of CO(12-11) emission along the L1157 bipolar outflow

    OpenAIRE

    Eislöffel, Jochen; Nisini, Brunella; Güsten, Rolf; Wiesemeyer, Helmut; Gusdorf, Antoine

    2012-01-01

    Carbon monoxide is an excellent tracer of the physical conditions of gas in molecular outflows from young stars. To understand the outflow mechanism we need to investigate the origin of the molecular emission and the structure and interaction of the outflowing molecular gas. Deriving the physical parameters of the gas will help us to trace and understand the various gas components in the flow. We observed CO(12-11) line emission at various positions along the L1157 bipolar outflow with GREAT ...

  10. On the emissivity of wire-grid polarizers for astronomical observations at mm-wavelengths

    CERN Document Server

    Schillaci, Alessandro; Alessandro, Giuseppe D'; de Bernardis, Paolo; Masi, Silvia

    2012-01-01

    We have measured, using a custom setup, the emissivity of metallic wire-grids, suitable for polarimeters and interferometers at mm and far infrared wavelengths. We find that the effective emissivity of these devices is of the order of a few %, depending on fabrication technology and aging. We discuss their use in astronomical instruments, with special attention to Martin Puplett Interferometers in low-background applications, like astronomical observations of the Cosmic Microwave Background.

  11. VLF signal modulations during the total solar eclipse of 22nd July, 2009: model using D region ion chemistry and LWPC

    Science.gov (United States)

    Chakraborty, Suman; Chakrabarti, Sandip Kumar; Palit, Sourav; Ray, Suman

    2016-07-01

    One of the major sources of ionospheric perturbations is variations in solar Extreme Ultraviolet (EUV) radiation flux. Solar eclipse is a phenomenon which is capable of producing significant effects on the physical and chemical properties of the ionospheric plasma. During a solar eclipse, the solar radiation flux reduces considerably for a limited period of time over specific locations on the Earth. This induces certain changes within the ionosphere or more precisely, in the D-region which can be studied with the observation of Very Low Frequency (VLF) radio signal modulations. The parameters which mainly govern the ion-chemistry, such as the recombination coefficients are poorly known till date. Solar eclipse provides us with an excellent opportunity to study these parameters as its time of occurrence is known beforehand and thus we can equip ourselves accordingly. In the present study we considered the Total Solar Eclipse (TSE) that occurred on 22nd July, 2009 within the Indian subcontinent. Indian Centre for Space Physics (ICSP) conducted a week long campaign during the eclipse and data were recorded from dozens of places within India and abroad. Both positive and negative changes in VLF signal amplitude were observed. In this paper, data for a propagation path between Indian Navy VLF transmitter named VTX3 and a pair of receivers in India, namely Malda and Kolkata are used. We start with calculating the obscuration function for these two places to find the variations in ionization flux within the period of the eclipse. After this, we incorporated the D region ion chemistry model to find the equilibrium ion density over the region and employ the LWPC code to find the VLF signal amplitude. We varied the values of recombination coefficients to achieve desired accuracy in our results. In doing so, we achieved two goals: First, we have been able to reproduce the trend of variation in VLF signal amplitude (both positive and negative) at both the receiving locations

  12. FERMI LARGE AREA TELESCOPE OBSERVATIONS OF TWO GAMMA-RAY EMISSION COMPONENTS FROM THE QUIESCENT SUN

    International Nuclear Information System (INIS)

    We report the detection of high-energy γ-rays from the quiescent Sun with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays (CRs) is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to CR cascades in the solar atmosphere and extended emission from the inverse Compton (IC) scattering of CR electrons on solar photons in the heliosphere. The observed integral flux (≥100 MeV) from the solar disk is (4.6 ± 0.2[statistical error]+1.0-0.8[systematic error]) x 10-7 cm-2 s-1, which is ∼7 times higher than predicted by the 'nominal' model of Seckel et al. In contrast, the observed integral flux (≥100 MeV) of the extended emission from a region of 20 deg. radius centered on the Sun, but excluding the disk itself, (6.8 ± 0.7[stat.]+0.5-0.4[syst.]) x 10-7 cm-2 s-1, along with the observed spectrum and the angular profile, is in good agreement with the theoretical predictions for the IC emission.

  13. Estimating Sulfur hexafluoride (SF6) emissions in China using atmospheric observations and inverse modeling

    Science.gov (United States)

    Fang, X.; Thompson, R.; Saito, T.; Yokouchi, Y.; Li, S.; Kim, J.; Kim, K.; Park, S.; Graziosi, F.; Stohl, A.

    2013-12-01

    With a global warming potential of around 22800 over a 100-year time horizon, sulfur hexafluoride (SF6) is one of the greenhouse gases regulated under the Kyoto Protocol. Global SF6 emissions have been increasing since circa the year 2000. The reason for this increase has been inferred to be due to rapidly increasing emissions in developing countries that are not obligated to report their annual emissions to the United Nations Framework Convention on Climate Change, notably China. In this study, SF6 emissions during the period 2006-2012 for China and other East Asian countries were determined using in-situ atmospheric measurements and inverse modeling. We performed various inversion sensitivity tests, which show the largest uncertainties in the a posteriori Chinese emissions are associated with the a priori emissions used and their uncertainty, the station network, as well as the meteorological input data. The overall relative uncertainty of the a posteriori emissions in China is estimated to be 17% in 2008. Based on sensitivity tests, we employed the optimal parameters in our inversion setup and performed yearly inversions for the study period. Inversion results show that the total a posteriori SF6 emissions from China increased from 1420 × 245 Mg/yr in 2006 to 2741 × 472 Mg/yr in 2009 and stabilized thereafter. The rapid increase in emissions reflected a fast increase in SF6 consumption in China, a result also found in bottom-up estimates. The a posteriori emission map shows high emissions concentrated in populated parts of China. During the period 2006-2012, emissions in northwestern and northern China peaked around the year 2009, while emissions in eastern, central and northeastern China grew gradually during almost the whole period. Fluctuating emissions are observed for southwestern China. These regional differences should be caused by changes of provincial SF6 usage and by shifts of usage among different sectors. Fig. 1. Footprint emission sensitivity

  14. Earth observations for estimating greenhouse gas emissions from deforestation in developing countries

    International Nuclear Information System (INIS)

    In response to the United Nations Framework Convention on Climate Change (UNFCCC) process investigating the technical issues surrounding the ability to reduce greenhouse gas (GHG) emissions from deforestation in developing countries, this paper reviews technical capabilities for monitoring deforestation and estimating emissions. Implementation of policies to reduce emissions from deforestation require effective deforestation monitoring systems that are reproducible, provide consistent results, meet standards for mapping accuracy, and can be implemented at the national level. Remotely sensed data supported by ground observations are key to effective monitoring. Capacity in developing countries for deforestation monitoring is well-advanced in a few countries and is a feasible goal in most others. Data sources exist to determine base periods in the 1990s as historical reference points. Forest degradation (e.g. from high impact logging and fragmentation) also contribute to greenhouse gas emissions but it is more technically challenging to measure than deforestation. Data on carbon stocks, which are needed to estimate emissions, cannot currently be observed directly over large areas with remote sensing. Guidelines for carbon accounting from deforestation exist and are available in approved Intergovernmental Panel on Climate Change (IPCC) reports and can be applied at national scales in the absence of forest inventory or other data. Key constraints for implementing programs to monitor greenhouse gas emissions from deforestation are international commitment of resources to increase capacity, coordination of observations to ensure pan-tropical coverage, access to free or low-cost data, and standard and consensual protocols for data interpretation and analysis

  15. Multiwavelength Observations of GRB 110731A: GeV Emission from Onset to Afterglow

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Asano, K.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bellazzini, R.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chaves, R. C. G.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Greiner, J.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Romoli, C.; Roth, M.; Ryde, F.; Sanchez, D. A.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spinelli, P.; Stamatikos, M.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Gruber, D.; Bhat, P. N.; Bissaldi, E.; Briggs, M. S.; Burgess, J. M.; Connaughton, V.; Foley, S.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; McGlynn, S.; Paciesas, W. S.; Pelassa, V.; Preece, R.; Rau, A.; van der Horst, A. J.; von Kienlin, A.; Kann, D. A.; Filgas, R.; Klose, S.; Krühler, T.; Fukui, A.; Sako, T.; Tristram, P. J.; Oates, S. R.; Ukwatta, T. N.; Littlejohns, O.

    2013-02-01

    We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Γ ~ 500-550.

  16. Earth observations for estimating greenhouse gas emissions from deforestation in developing countries

    Energy Technology Data Exchange (ETDEWEB)

    DeFries, R. [Department of Geography and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742 (United States); Achard, F. [Institute for Environment and Sustainability, Joint Research Centre of the European Commission 21020 Ispra, VA (Italy); Brown, S. [Winrock International, Ecosystem Services Unit 1621 N. Kent Street, Suite 1200, Arlington, VA 22207 (United States); Herold, M. [Department of Geography, Friedrich Schiller University Jena, Loebdergraben 32, 07743 Jena (Germany); Murdiyarso, D. [Center for International Forestry Research, P.O. Box 6596, JKPWB, Jakarta 10065 (Indonesia); Schlamadinger, B. [Joanneum Research, Elisabethstrasse 5, 8010 Graz (Austria); De Souza, C. Jr [Instituto Homem e Meio Ambiente da Amazonia, Imazon, Caixa Postal 5101, Belem, PA 66613-397 (Brazil)

    2007-06-15

    In response to the United Nations Framework Convention on Climate Change (UNFCCC) process investigating the technical issues surrounding the ability to reduce greenhouse gas (GHG) emissions from deforestation in developing countries, this paper reviews technical capabilities for monitoring deforestation and estimating emissions. Implementation of policies to reduce emissions from deforestation require effective deforestation monitoring systems that are reproducible, provide consistent results, meet standards for mapping accuracy, and can be implemented at the national level. Remotely sensed data supported by ground observations are key to effective monitoring. Capacity in developing countries for deforestation monitoring is well-advanced in a few countries and is a feasible goal in most others. Data sources exist to determine base periods in the 1990s as historical reference points. Forest degradation (e.g. from high impact logging and fragmentation) also contribute to greenhouse gas emissions but it is more technically challenging to measure than deforestation. Data on carbon stocks, which are needed to estimate emissions, cannot currently be observed directly over large areas with remote sensing. Guidelines for carbon accounting from deforestation exist and are available in approved Intergovernmental Panel on Climate Change (IPCC) reports and can be applied at national scales in the absence of forest inventory or other data. Key constraints for implementing programs to monitor greenhouse gas emissions from deforestation are international commitment of resources to increase capacity, coordination of observations to ensure pan-tropical coverage, access to free or low-cost data, and standard and consensual protocols for data interpretation and analysis.

  17. Simultaneous ground- and satellite-based observation of MF/HF auroral radio emissions

    Science.gov (United States)

    Sato, Yuka; Kumamoto, Atsushi; Katoh, Yuto; Shinbori, Atsuki; Kadokura, Akira; Ogawa, Yasunobu

    2016-05-01

    We report on the first simultaneous measurements of medium-high frequency (MF/HF) auroral radio emissions (above 1 MHz) by ground- and satellite-based instruments. Observational data were obtained by the ground-based passive receivers in Iceland and Svalbard, and by the Plasma Waves and Sounder experiment (PWS) mounted on the Akebono satellite. We observed two simultaneous appearance events, during which the frequencies of the auroral roar and MF bursts detected at ground level were different from those of the terrestrial hectometric radiation (THR) observed by the Akebono satellite passing over the ground-based stations. This frequency difference confirms that auroral roar and THR are generated at different altitudes across the F peak. We did not observe any simultaneous observations that indicated an identical generation region of auroral roar and THR. In most cases, MF/HF auroral radio emissions were observed only by the ground-based detector, or by the satellite-based detector, even when the satellite was passing directly over the ground-based stations. A higher detection rate was observed from space than from ground level. This can primarily be explained in terms of the idea that the Akebono satellite can detect THR emissions coming from a wider region, and because a considerable portion of auroral radio emissions generated in the bottomside F region are masked by ionospheric absorption and screening in the D/E regions associated with ionization which results from auroral electrons and solar UV radiation.

  18. Constraining Methane Emissions from Natural Gas Production in Northeastern Pennsylvania Using Aircraft Observations and Mesoscale Modeling

    Science.gov (United States)

    Barkley, Z.; Davis, K.; Lauvaux, T.; Miles, N.; Richardson, S.; Martins, D. K.; Deng, A.; Cao, Y.; Sweeney, C.; Karion, A.; Smith, M. L.; Kort, E. A.; Schwietzke, S.

    2015-12-01

    Leaks in natural gas infrastructure release methane (CH4), a potent greenhouse gas, into the atmosphere. The estimated fugitive emission rate associated with the production phase varies greatly between studies, hindering our understanding of the natural gas energy efficiency. This study presents a new application of inverse methodology for estimating regional fugitive emission rates from natural gas production. Methane observations across the Marcellus region in northeastern Pennsylvania were obtained during a three week flight campaign in May 2015 performed by a team from the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division and the University of Michigan. In addition to these data, CH4 observations were obtained from automobile campaigns during various periods from 2013-2015. An inventory of CH4 emissions was then created for various sources in Pennsylvania, including coalmines, enteric fermentation, industry, waste management, and unconventional and conventional wells. As a first-guess emission rate for natural gas activity, a leakage rate equal to 2% of the natural gas production was emitted at the locations of unconventional wells across PA. These emission rates were coupled to the Weather Research and Forecasting model with the chemistry module (WRF-Chem) and atmospheric CH4 concentration fields at 1km resolution were generated. Projected atmospheric enhancements from WRF-Chem were compared to observations, and the emission rate from unconventional wells was adjusted to minimize errors between observations and simulation. We show that the modeled CH4 plume structures match observed plumes downwind of unconventional wells, providing confidence in the methodology. In all cases, the fugitive emission rate was found to be lower than our first guess. In this initial emission configuration, each well has been assigned the same fugitive emission rate, which can potentially impair our ability to match the observed spatial variability

  19. Coronal O VI emission observed with UVCS/SOHO during solar flares: Comparison with soft X-ray observations

    Science.gov (United States)

    Mancuso, S.; Giordano, S.; Raymond, J. C.

    2016-06-01

    In this work, we derive the O VI 1032 Å luminosity profiles of 58 flares, during their impulsive phase, based on off-limb measurements by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the SOlar and Heliospheric Observatory (SOHO). The O VI luminosities from the transition region plasma (here defined as the region with temperatures 5.0 ≤ log T (K) ≤ 6.0) were inferred from the analysis of the resonantly scattered radiation of the O VI coronal ions. The temperature of maximum ionization for O VI is log Tmax (K) = 5.47. By comparison with simultaneous soft X-ray measurements, we investigate the likely source (chromospheric evaporation, footpoint emission, or heated prominence ejecta) for the transition region emission observed during the impulsive phase. In our study, we find evidence of the main characteristics predicted by the evaporation scenario. Specifically, most O VI flares precede the X-ray peaks typically by several minutes with a mean of 3.2 ± 0.1 min, and clear correlations are found between the soft X-ray and transition region luminosities following power laws with indices ~ 0.7 ± 0.3. Overall, the results are consistent with transition region emission originating from chromospheric evaporation; the thermal X-ray emission peaks after the emission from the evaporation flow as the loops fill with hot plasma. Finally, we were able to infer flow speeds in the range ~20-100 km s-1 for one-third of the events, 14 of which showed speeds between 60 and 80 km s-1. These values are compatible with those found through direct spectroscopic observations at transition region temperatures by the EUV Imaging Spectrometer (EIS) on board Hinode.

  20. Partial Effects on VLF Data due to a Solar Flare During 2010 Annular Solar Eclipse

    Science.gov (United States)

    Maji, Surya K.; Chakrabarti, Sandip K.; Mondal, Sushanta K.

    2010-10-01

    The VLF radio waves propagate through the Earth-ionosphere waveguide. Irregularities caused by excesses or deficient soft X-rays which sustain the ionosphere changes the waveguide properties and hence the signals are modified. We report the results of our monitoring of the NWC transmitter from Khukurdaha (~80 km away from Kolkata) during the partial solar eclipse (75%) of 15th January, 2010. The receiving station and the transmitter were on two opposite sides of the annular eclipse belt. We got clear depression in the data during the period of partial eclipse. There was also a solar flare (spot no. 1040) on that day during the time the eclipse was near maximum. The flare started from B, reaching maximum to C1.3 (as observed by GOES 14 satellite). We saw the partial effect of this flare since a part of the active region was blocked by the moon. To our knowledge this is the first such incident where the solar flare was observed through lunar occultation.

  1. OBSERVATIONS OF FAR-ULTRAVIOLET DIFFUSE EMISSION FROM THE SMALL MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    We report the first observations of far-ultraviolet (FUV: 1000-1150 Å) diffuse radiation from the Small Magellanic Cloud (SMC) using observations from the Far-Ultraviolet Spectroscopic Explorer. The strength of FUV diffuse surface brightness in the SMC ranges from the detection limit of 2000 photons cm–2 s–1 sr–1 Å–1 to a maximum of 3 × 105 photons cm–2 s–1 sr–1 Å–1 at 1004 Å. The contribution of diffuse emission to the total radiation field was found to be 34% at 1004 Å to 44% at 1117 Å with a maximum observed uncertainty of 30%. There is a striking difference between the FUV diffuse fraction from the SMC and the Large Magellanic Cloud with the SMC fraction being higher probably because of the higher dust albedo. The FUV diffuse emission correlates with Hα emission in the H II regions of the SMC.

  2. Observation of solar high energy gamma and X-ray emission and solar energetic particles

    CERN Document Server

    Struminsky, Alexei

    2015-01-01

    We considered 18 solar flares observed between June 2010 and July 2012, in which high energy >100 MeV {\\gamma}-emission was registered by the Large Area Telescope (LAT) aboard FermiGRO. We examined for these {\\gamma}-events soft X-ray observations by GOES, hard X-ray observations by the Anti-Coincidence Shield of the SPectrometer aboard INTEGRAL (ACS SPI) and the Gamma-Ray burst Monitor (GBM) aboard FermiGRO. Hard X-ray and {\\pi}0-decay {\\gamma}-ray emissions are used as tracers of electron and proton acceleration, respectively. Bursts of hard X-ray were observed by ACS SPI during impulsive phase of 13 events. Bursts of hard X-ray >100 keV were not found during time intervals, when prolonged hard {\\gamma}-emission was registered by LAT/FermiGRO. Those events showing prolonged high-energy gamma-ray emission not accompanied by >100 keV hard X-ray emission are interpreted as an indication of either different acceleration processes for protons and electrons or as the presence of a proton population accelerated du...

  3. Inverse modeling of carbon monoxide surface emissions using Climate Monitoring and Diagnostics Laboratory network observations

    Science.gov (United States)

    PéTron, Gabrielle; Granier, Claire; Khattatov, Boris; Lamarque, Jean-Francois; Yudin, Valery; Müller, Jean-Francois; Gille, John

    2002-12-01

    A three-dimensional (3-D) inverse modeling scheme is used to constrain the direct surface emissions of carbon monoxide CO. A priori estimates of CO emissions are taken from various inventories and are included in the IMAGES model to compute the distribution of CO. The modeled CO mixing ratios are compared with observations at 39 CMDL stations, averaged over the years 1990-1996. The interannual variability of CO sources is therefore ignored. We show that the method used (time-dependent synthesis inversion) is able to adjust the surface fluxes on a monthly basis in order to improve the agreement between the observed and the modeled CO mixing ratios at the stations. The Earth surface is divided into regions. The spatial distribution of CO sources is fixed inside each of these regions. The inversion scheme optimizes the intensities of the emissions fluxes for the following processes: technological activities, forest and savanna burning, agricultural waste burning and fuelwood use, soil/vegetation emissions, and oceanic emissions. The inversion significantly reduces the uncertainties on the surface sources over Europe, North America and Asia. The most striking result is the increase (almost by a factor of 2) of CO flux from Asia in all a posteriori scenarios. The uncertainties on the Southern Hemisphere emissions remain large after the inversion, because the current observational surface network is too sparse at these latitudes. The inversion, moreover, shifts the peak in biomass burning emissions in the Southern Hemisphere by one month. This temporal shift ensures a better match of the observed and modeled CO seasonal cycle at the Ascension Island station. We also attempted to optimize the annual and global productions of CO due to methane and NMHC. With the current set of data, the scheme was not able to differentiate between these two sources, and hence only the total chemical production of CO can be optimized.

  4. Observation of the O I ultraviolet intercombination emissions in the terrestrial dayglow

    International Nuclear Information System (INIS)

    Spectroscopic observations have been made of the terrestrial ultraviolet dayglow (850-1,850 angstrom) using newly developed instrumentation in a sounding rocket payload. The atmospheric conditions and viewing geometry were such as to suppress nitrogen emissions relative to those from atomic oxygen. This permitted the identification and measurement of the weak O I 1,173-angstrom (3s' 3D0 - 2p41D) intercombination multiplet and the 1,641-angstrom (3s 3S0 - 2p41D) line as well as the strong 989-angstrom and 1,304-angstrom emissions. The 1,173-angstrom emission rate increase at lower altitudes, while the 989-angstrom emission, from the same upper level, decreased at lower altitudes. This behavior is consistent with the radiative entrapment model of Meier (1982) and the laboratory value of the 1,173-angstrom/989-angstrom branching ratio of 1.5 x 10-4 (Morrison, 1985). The 1,641-angstrom/1,304-angstrom emission ratio is also consistent with a radiative entrapment model and a branching ratio near 5.0 x 10-6. Lack of detection of the 1,484-angstrom (3s' 3D10 - 2p41S0) intercombination line allows an upper limit to be placed on the 1,484-angstrom branching ratio, confirming that emission in this line is less significant in depleting the 3s' 3D0 term than is 1,173-angstrom emission

  5. The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum

    CERN Document Server

    Peér, A; Rees, Martin J; Pe'er, Asaf; M\\'esz\\'aros, Peter; Rees, Martin J.

    2005-01-01

    A thermal radiative component is likely to accompany the first stages of the prompt emission of Gamma-ray bursts (GRB's) and X-ray flashes (XRF's). We analyze the effect of such a component on the observable spectrum, assuming that the observable effects are due to a dissipation process occurring below or near the thermal photosphere. We consider both the internal shock model and a 'slow heating' model as possible dissipation mechanisms. For comparable energy densities in the thermal and the leptonic component, the dominant emission mechanism is Compton scattering. This leads to a nearly flat energy spectrum (\

  6. First MERLIN Observations of Line Emission from the OH Megamaser toward IRAS 10173+0828

    Institute of Scientific and Technical Information of China (English)

    Zhi-Yao Yu

    2005-01-01

    Many galaxies are thought to contain massive black holes, with masses in excess of ten million solar masses, at their centres and warped circumnuclear toruses. The best evidence comes from observing gas or masers rotating rapidly within a circumnuclear torus surrounding a central body. Here we report on the first MERLIN observations of line emission from the OH megamaser toward IRAS 10173+0828. The position of peak flux contours of the OH megamaser is consistent with that of the continuum in IRAS 10173+0828. This means that the OH megamaser is a diffuse unsaturated maser which could amplify the diffuse 18 cm continuum emission with an amplification factor of order unity.

  7. A multi-scale comparison of modeled and observed seasonal methane emissions in northern wetlands

    Science.gov (United States)

    Xu, Xiyan; Riley, William J.; Koven, Charles D.; Billesbach, Dave P.; Chang, Rachel Y.-W.; Commane, Róisín; Euskirchen, Eugénie S.; Hartery, Sean; Harazono, Yoshinobu; Iwata, Hiroki; McDonald, Kyle C.; Miller, Charles E.; Oechel, Walter C.; Poulter, Benjamin; Raz-Yaseef, Naama; Sweeney, Colm; Torn, Margaret; Wofsy, Steven C.; Zhang, Zhen; Zona, Donatella

    2016-09-01

    Wetlands are the largest global natural methane (CH4) source, and emissions between 50 and 70° N latitude contribute 10-30 % to this source. Predictive capability of land models for northern wetland CH4 emissions is still low due to limited site measurements, strong spatial and temporal variability in emissions, and complex hydrological and biogeochemical dynamics. To explore this issue, we compare wetland CH4 emission predictions from the Community Land Model 4.5 (CLM4.5-BGC) with site- to regional-scale observations. A comparison of the CH4 fluxes with eddy flux data highlighted needed changes to the model's estimate of aerenchyma area, which we implemented and tested. The model modification substantially reduced biases in CH4 emissions when compared with CarbonTracker CH4 predictions. CLM4.5 CH4 emission predictions agree well with growing season (May-September) CarbonTracker Alaskan regional-level CH4 predictions and site-level observations. However, CLM4.5 underestimated CH4 emissions in the cold season (October-April). The monthly atmospheric CH4 mole fraction enhancements due to wetland emissions are also assessed using the Weather Research and Forecasting-Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) model coupled with daily emissions from CLM4.5 and compared with aircraft CH4 mole fraction measurements from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) campaign. Both the tower and aircraft analyses confirm the underestimate of cold-season CH4 emissions by CLM4.5. The greatest uncertainties in predicting the seasonal CH4 cycle are from the wetland extent, cold-season CH4 production and CH4 transport processes. We recommend more cold-season experimental studies in high-latitude systems, which could improve the understanding and parameterization of ecosystem structure and function during this period. Predicted CH4 emissions remain uncertain, but we show here that benchmarking against observations across spatial scales can

  8. The European VLF/LF Radio Network: the current status

    Science.gov (United States)

    Biagi, Pier Francesco; Maggipinto, Tommaso; Schiavulli, Luigi; Ligonzo, Teresa; Colella, Roberto; Ermini, Anita; Martinelli, Giovanni; Palangio, Paolo; Moldovan, Iren; Silva, Hugo; Contadakis, Michael; Frantzis, Xenophon; Katzis, Konstantinos; Buyuksarac, Aydin; D'Amico, Sebastiano

    2014-05-01

    Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers has been put into operation in Europe in order to study earthquakes precursors. At the moment the network consists of eleven receivers four of which are located in Italy, two in Greece and one in Portugal, Romania, Malta, Cyprus and Turkey. The data (sampling rate of 1min) are downloaded automatically at the end of each day and they are stored in the server located at the Department of Physics of the University of Bari (Italy), that is the central node of the network. Still, in some case, problems of connection exist. The different trends are open and visible on the web site: http://beta.fisica.uniba.it/infrep/Hom.aspx. The data files can be downloaded by the same web site but they are protected by username and password. Among the different methods of data analysis the Wavelet spectra appear to be the most sensitive ones. The software able to apply this technique on the radio data automatically at the end of each day has been planned and realized. At the moment it operates on four signals collected by one of the Italian receivers; if an anomaly stands up and it is over a fixed threshold a warning advise appears. In the web site, this activity is protected by a specific username and password.

  9. Observed effects of soil organic matter content on the microwave emissivity of soils

    Science.gov (United States)

    O'Neill, P. E.; Jackson, T. J.

    1990-01-01

    In order to determine the significance of organic matter content on the microwave emissivity of soils when estimating soil moisture, field experiments were conducted in which 1.4 GHz microwave emissivity data were collected over test plots of sandy loam soil with different organic matter levels (1.8, 4.0, and 6.1 percent) for a range of soil moisture values. Analyses of the observed data show only minor variation in microwave emissivity due to a change in organic matter content at a given moisture level for soils with similar texture and structure. Predictions of microwave emissivity made using a dielectric model for aggregated soils exhibit the same trends and type of response as the measured data when appropriate values for the input parameters were utilized.

  10. In Situ Observation of Dark Current Emission in a High Gradient rf Photocathode Gun

    Science.gov (United States)

    Shao, Jiahang; Shi, Jiaru; Antipov, Sergey P.; Baryshev, Sergey V.; Chen, Huaibi; Conde, Manoel; Gai, Wei; Ha, Gwanghui; Jing, Chunguang; Wang, Faya; Wisniewski, Eric

    2016-08-01

    Undesirable electron field emission (also known as dark current) in high gradient rf photocathode guns deteriorates the quality of the photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (˜100 μ m ) dark current imaging experiment has been performed in an L -band photocathode gun operating at ˜100 MV /m of surface gradient. Scattered strong emission areas with high current have been observed on the cathode. The field enhancement factor β of selected regions on the cathode has been measured. The postexaminations with scanning electron microscopy and white light interferometry reveal the origins of ˜75 % strong emission areas overlap with the spots where rf breakdown has occurred.

  11. Observed effects of soil organic matter content on the microwave emissivity of soils

    International Nuclear Information System (INIS)

    In order to determine the significance of organic matter content on the microwave emissivity of soils when estimating soil moisture, a series of field experiments were conducted in which 1.4 GHz microwave emissivity data were collected over test plots of sandy loam soil with different organic matter levels (1.8%, 4.0%, and 6.1%) for a range of soil moisture values. Analyses of the observed data showed only minor variation in microwave emissivity due to a change in organic matter content at a given moisture level for soils with similar texture and structure. Predictions of microwave emissivity made using a dielectric model for aggregated soils exhibited the same trends and type of response as the measured data when adjusted values for the input parameters were utilized

  12. Estimation of Swiss methane emissions by near surface observations and inverse modeling

    Science.gov (United States)

    Henne, Stephan; Brian, Oney; Leuenberger, Markus; Bamberger, Ines; Eugster, Werner; Steinbacher, Martin; Meinhardt, Frank; Brunner, Dominik

    2015-04-01

    On a global scale methane (CH4) is the second most important long-lived greenhouse gas. It is released from both natural and anthropogenic processes and its atmospheric burden has more than doubled since preindustrial times. Current CH4 emission estimates are associated with comparatively large uncertainties both globally and regionally. For example, the Swiss national greenhouse gas inventory assigns an uncertainty of 18% to the country total anthropogenic CH4 emissions as compared to only 3% for anthropogenic CO2 emissions. In Switzerland, CH4 is thought to be mainly released by agricultural activities (ruminants and manure management >80%), while natural emissions from wetlands and wild animals represent a minor source (~3 %). The country total and especially the spatial distribution of CH4 emission within Switzerland strongly differs between the national and different European scale inventories. To validate the 'bottom-up' Swiss CH4 emission estimate and to reduce its uncertainty both in total and spatially, 'top-down' methods combining atmospheric CH4 observations and regional scale transport simulations can be used. Here, we analyse continuous, near surface observations of CH4 concentrations as collected within the newly established CarboCountCH measurement network (http://www.carbocount.ch). The network consists of 4 sites situated on the Swiss Plateau, comprising a tall tower site (217 m), two elevated (mountaintop) sites and a small tower site (32 m) in flat terrain. In addition, continuous CH4 observations from the nearby high-altitude site Jungfraujoch (Alps) and the mountaintop site Schauinsland (Germany) were used. Two inversion frameworks were applied to the CH4 observations in combination with source sensitivities (footprints) calculated with the regional scale version of the Lagrangian Particle Dispersion Model FLEXPART. One inversion system was based on a Bayesian framework, while the other utilized an extended Kalman filter approach. The transport

  13. How do Biomass Burning Carbon Monixide Emissions from South America influence Satellite Observed Columns over Africa?

    Science.gov (United States)

    Krol, M. C.; van Leeuwen, T. T.; Aouizerats, B.; van der Werf, G.

    2015-12-01

    Large amounts of Carbon Monoxide (CO) are emitted during biomass burning events. These emissions severely perturb the atmospheric composition. For this reason, satellite observations of CO can help to constrain emissions from biomass burning. Other sources of CO, such as the production of CO from naturally emitted non-methane hydrocarbons, may interfere with CO from biomass burning and inverse modeling efforts to estimate biomass burning emissions have to account for these CO sources. The atmospheric lifetime of CO varies from weeks to months, depending on the availability of atmospheric OH for atmospheric oxidation of CO to carbon dioxide. This means that CO can be transported over relatively long distances. It also implies that satellite-observed CO does not necessarily originate from the underlying continent, but may be caused by distant emissions transported to the observation location. In this presentation we focus on biomass burning emissions from South America and Southern Africa during 2010. This year was particularly dry over South America with a large positive anomaly in biomass burning in the 2010 burning season (July-October). We will adress the question how CO plumes from South America biomass burning influence satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI) instrument over Southern Africa. For this we employ the TM5 atmospheric chemistry model, with 1x1 degree zoom resolutions over Africa and South America. Also, we use the TM5-4DVAR code to estimate CO biomass burning emissions using IASI CO observations. The accompanying image shows IASI CO oberservations over Africa on August 27, 2010, compared to the columns simulated with TM5. Clear signs of intercontinental transport from South America are visible over the Southermost region.

  14. Tropospheric methanol observations from space: constraints on the seasonality of biogenic emissions

    Science.gov (United States)

    Wells, K. C.; Millet, D. B.; Cady-Pereira, K. E.; Shephard, M. W.; Xiao, Y.; Razavi, A.; Clerbaux, C.

    2011-12-01

    Methanol is the most abundant non-methane organic compound in the atmosphere, and is an important precursor of atmospheric pollutants such as CO and formaldehyde. The recent development of methanol retrievals from nadir-viewing satellite-based platforms offers powerful new information for quantifying methanol emissions on a global scale. This study uses methanol observations from the Tropospheric Emission Spectrometer (TES) on the Aura satellite and the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A satellite, in conjunction with aircraft data, to investigate methanol emissions from major plant functional types in the GEOS-Chem global chemical transport model (driven with MEGAN biogenic emissions). We first evaluate the TES methanol retrievals by comparing to simulation results and flight observations from several North American field campaigns. Results show that the retrieval performs well when the degrees of freedom for signal are above 0.5. We analyze one full year of TES and IASI observations and find a persistent model underestimate in springtime, and make recommendations for an improved seasonal distribution of biogenic methanol emissions over temperate regions of the globe.

  15. Observation of Fluorescence Emissions from Single-Bubble Sonoluminescence in Water doped with Quinine

    CERN Document Server

    Lu, J Q; Lin, F K; Liu, Y H

    2005-01-01

    Sonoluminescence is a phenomenon involving the transduction of sound into light. The detailed mechanism as well as the energy-focusing potentials are not yet fully explored and understood. So far only optical photons are observed, while emissions in the ultra-violet range are only inferred. By doping the fluorescent dye quinine into water with dilute sulphuric acid, the high energy photons can be converted into the optical photons with slower decay constants. These sonoluminescence and fluorescent emissions were observed in coincidence, and the emitted energy of the two modes can be differentiated by their respective timing profiles. Plans for using this technique as a diagnostic tool to quantitatively study ultra-violet and other high energy emissions in sonoluminescence are discussed.

  16. Observation of the Emission Spectra of an Atmospheric Pressure Radio-frequency Plasma Jet

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    An atmospheric pressure plasma jet (APPJ) using radio-frequency (13.56 MHz)power has been developed to produce homogeneous glow discharge at low temperature. With optical emission spectroscopy, we observed the excited species (atomic helium, atomic oxygen and metastable oxygen) generated in this APPJ and their dependence on gas composition ratio and RF power. O and O2(b1∑g+) are found in the effluent outside the jet by measuring the emission spectra of effluent perpendicular to the jet. An interesting phenomenon is found that there is an abnormal increase of O emission intensity (777.4 nm) between 10 mm and 40 mm away from the nozzle. This observation result is very helpful in practical operation.

  17. Probing 67P/Churyumov-Gerasimenko's Electron Environment Through Ultraviolet Emission by Rosetta Alice Observations

    Science.gov (United States)

    Schindhelm, Eric; Noonan, John; Keeney, Brian A.; Broiles, Thomas; Bieler, Andre; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Parker, Joel Wm.; Steffl, Andrew Joseph; Stern, S. Alan; Weaver, Harold A.

    2016-10-01

    The Alice Far-Ultraviolet (FUV) Spectrograph onboard ESA's Rosetta spacecraft has observed the coma of comet 67P/Churyumov-Gerasimenko from far approach in summer 2014 until the end of mission in September 2016. We present an overall perspective of the bright FUV emission lines (HI 1026 Å, OI 1302/1305/1306 Å multiplet, OI] 1356 Å, CO 1510 (1-0) Å, and CI 1657 Å) above the sunward hemisphere, detailing their spatial extent and brightness as a function of time and the heliocentric distance of the comet. We compare our observed gas column densities derived using electron temperatures and densities from the Ion Electron Sensor (IES) with those derived using the Inner Coma Environment Simulator (ICES) models in periods when electron-impact excited emission dominates over solar fluorescence emission. The electron population is characterized with 2 three-dimensional kappa functions, one dense and warm, one rarefied and hot.

  18. Biomass burning emissions estimated with a global fire assimilation system based on observed fire radiative power

    Directory of Open Access Journals (Sweden)

    J. W. Kaiser

    2011-07-01

    Full Text Available The Global Fire Assimilation System (GFASv1.0 calculates biomass burning emissions by assimilating Fire Radiative Power (FRP observations from the MODIS instruments onboard the Terra and Aqua satellites. It corrects for gaps in the observations, which are mostly due to cloud cover, and filters spurious FRP observations of volcanoes, gas flares and other industrial activity. The combustion rate is subsequently calculated with land cover-specific conversion factors. Emission factors for 40 gas-phase and aerosol trace species have been compiled from a literature survey. The corresponding daily emissions have been calculated on a global 0.5° × 0.5° grid from 2003 to the present. General consistency with the Global Fire Emission Database version 3.1 (GFED3.1 within its accuracy is achieved while maintaining the advantages of an FRP-based approach: GFASv1.0 makes use of the quantitative information on the combustion rate that is contained in the observations, and it detects fires in real time at high spatial and temporal resolution. GFASv1.0 indicates omission errors in GFED3.1 due to undetected small fires. It also exhibits slightly longer fire seasons in South America and North Africa and a slightly shorter fire season in Southeast Asia. GFASv1.0 has already been used for atmospheric reactive gas simulations in an independent study, which found good agreement with atmospheric observations. We have performed simulations of the atmospheric aerosol distribution with and without the assimilation of MODIS aerosol optical depth (AOD. They indicate that the emissions of particulate matter need to be boosted with a factor of 2–4 to reproduce the global distribution of organic matter and black carbon. This discrepancy is also evident in the comparison of previously published top-down and bottom-up estimates. For the time being, a global enhancement of the particulate matter emissions by 3.4 is recommended. Validation with independent AOD and PM10

  19. The efficiency and sensitivity analysis of observations for atmospheric transport model with emissions

    Science.gov (United States)

    Wu, Xueran; Elbern, Hendrik; Jacob, Birgit

    2015-04-01

    Air quality and climate change are influenced by the fluxes of green house gases, reactive emissions and aerosols in the atmosphere. But observations of the chemical states in the atmosphere typically have low temporal and spatial density. Therefore, many works are introduced to spatio-temporal data assimilation methods in atmospheric chemistry in recent years. There is no doubt that the optimization of the initial state is always of great importance for the improvement of predictive skill. However, specified to the chemistry transport model with high dependence on the emissions in the troposphere, the optimization of the initial state is no longer the only issue. The lack of the ability to observe and estimate surface emission fluxes and important inner atmospheric fluxes with necessary accuracy is a major roadblock of hampering the progress in predictive skills of the atmospheric transport model. However, in many cases, the better estimations for both the initial state and emission rates are not always obtained with certain observational network configurations via various popular data assimilation methods, such as the ensemble Kalman filter and smoother and 4D-variation. It leads to the waste of resource by optimizing the improper parameters or brings the inaccuracy of the optimization by unsuitable weight between the initial state and emission rates. Hence, in order to make a scientific and quantitative decision about which parameters to be optimized and how to balance them before any data assimilation procedure, we establish the dynamic model for emission rates with the constraint of diurnal profile shape and extend the state vector of atmospheric transport model so that the emission rates are included. Then, a theoretical approach, based on Kalman filter and smoother and their ensemble cases, to evaluate the potential improvement is introduced. By singular value decomposition, the efficiency of observations to optimize initial state and emission rates of the

  20. Constraining atmospheric ammonia emissions through new observations with an open-path, laser-based sensor

    Science.gov (United States)

    Sun, Kang

    As the third most abundant nitrogen species in the atmosphere, ammonia (NH3) is a key component of the global nitrogen cycle. Since the industrial revolution, humans have more than doubled the emissions of NH3 to the atmosphere by industrial nitrogen fixation, revolutionizing agricultural practices, and burning fossil fuels. NH3 is a major precursor to fine particulate matter (PM2.5), which has adverse impacts on air quality and human health. The direct and indirect aerosol radiative forcings currently constitute the largest uncertainties for future climate change predictions. Gas and particle phase NH3 eventually deposits back to the Earth's surface as reactive nitrogen, leading to the exceedance of ecosystem critical loads and perturbation of ecosystem productivity. Large uncertainties still remain in estimating the magnitude and spatiotemporal patterns of NH3 emissions from all sources and over a range of scales. These uncertainties in emissions also propagate to the deposition of reactive nitrogen. To improve our understanding of NH3 emissions, observational constraints are needed from local to global scales. The first part of this thesis is to provide quality-controlled, reliable NH3 measurements in the field using an open-path, quantum cascade laser-based NH3 sensor. As the second and third part of my research, NH3 emissions were quantified from a cattle feedlot using eddy covariance (EC) flux measurements, and the similarities between NH3 turbulent fluxes and those of other scalars (temperature, water vapor, and CO2) were investigated. The fourth part involves applying a mobile laboratory equipped with the open-path NH3 sensor and other important chemical/meteorological measurements to quantify fleet-integrated NH3 emissions from on-road vehicles. In the fifth part, the on-road measurements were extended to multiple major urban areas in both the US and China in the context of five observation campaigns. The results significantly improved current urban NH3

  1. Topographic Effects on the Surface Emissivity of a Mountainous Area Observed by a Spaceborne Microwave Radiometer

    Science.gov (United States)

    Pulvirenti, Luca; Pierdicca, Nazzareno; Marzano, Frank S.

    2008-01-01

    A simulation study to understand the influence of topography on the surface emissivity observed by a satellite microwave radiometer is carried out. We analyze the effects due to changes in observation angle, including the rotation of the polarization plane. A mountainous area in the Alps (Northern Italy) is considered and the information on the relief extracted from a digital elevation model is exploited. The numerical simulation refers to a radiometric image, acquired by a conically-scanning radiometer similar to AMSR-E, i.e., flying at 705 km of altitude with an observation angle of 55°. To single out the impact on surface emissivity, scattering of the radiation due to the atmosphere or neighboring elevated surfaces is not considered. C and X bands, for which atmospheric effects are negligible, and Ka band are analyzed. The results indicate that the changes in the local observation angle tend to lower the apparent emissivity of a radiometric pixel with respect to the corresponding flat surface characteristics. The effect of the rotation of the polarization plane enlarges (vertical polarization), or attenuates (horizontal polarization) this decrease. By doing some simplifying assumptions for the radiometer antenna, the conclusion is that the microwave emissivity at vertical polarization is underestimated, whilst the opposite occurs for horizontal polarization, except for Ka band, for which both under- and overprediction may occur. A quantification of the differences with respect to a flat soil and an approximate evaluation of their impact on soil moisture retrieval are yielded.

  2. Observations of the auroral hectometric radio emission onboard the INTERBALL-1 satellite

    Science.gov (United States)

    Kuril'Chik, V. N.

    2007-06-01

    The results of five-year (1995 2000) continuous observations of the auroral radio emission (ARE) in the hectometric wavelength range on the high-apogee INTERBALL-1 satellite are presented. Short intense bursts of the auroral hectometric radio emission (AHR) were observed at frequencies of 1463 and 1501 kHz. The bursts were observed predominantly at times when the terrestrial magnetosphere was undisturbed (in the quiet Sun period), and their number decreased rapidly with increasing solar activity. The bursts demonstrated seasonal dependence in the Northern and Southern hemispheres (dominating in the autumn-winter period). Their appearance probably depends on the observation time (UT). A qualitative explanation of the AHR peculiarities is given.

  3. Results of VLF campaigns in Summer, Winter and during Solar Eclipse in Indian Subcontinent and Beyond

    International Nuclear Information System (INIS)

    VLF propagation effects are generally understood in terms of the earth-ionosphere waveguide. However, details of the theory are still incomplete. Particularly important are the newly emerging fields of VLF Astronomy where the ionosphere is treated as a giant detector for extraterrestrial energetic phenomena and the subject of lithosphere-ionosphere coupling where the the disturbances of this giant detector is influenced by terrestrial events, especially earthquakes and other seismic activities. We review the activities of our group in these fields. In particular, we concentrate on the results of the VLF campaigns we conducted using over a dozen receiving stations in Summer, in Winter and during the Total Solar eclipse in July, 2009. We also discuss briefly the results we obtained in Antarctica and their implications.

  4. The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum

    OpenAIRE

    Pe'er, Asaf; Mészáros, Peter; Rees, Martin J.

    2005-01-01

    A thermal radiative component is likely to accompany the first stages of the prompt emission of Gamma-ray bursts (GRB's) and X-ray flashes (XRF's). We analyze the effect of such a component on the observable spectrum, assuming that the observable effects are due to a dissipation process occurring below or near the thermal photosphere. We consider both the internal shock model and a 'slow heating' model as possible dissipation mechanisms. For comparable energy densities in the thermal and the ...

  5. Observational constraints on the external shock prior emission hypothesis of GRBs

    CERN Document Server

    Birnbaum, Tesla; Zhang, Bin-Bin; Liang, En-Wei

    2011-01-01

    An intriguing hypothesis, i.e. there exists a decaying X-ray emission component before the GRB trigger, has been suggested to interpret the shallow decay phase of the X-ray afterglow detected in many {\\em Swift} GRBs. If this "prior emission" is from an external shock, one would expect a corresponding optical emission component during the GRB prompt emission phase. In this paper we apply the available prompt optical emission data (both detections and upper limits) to constrain such a scenario. We fit the shallow and normal decay segments of the XRT light curves with a $T_0$-shifted single power law, and extrapolate the X-ray flux back to the time of the early optical observations. We then use the synchrotron spectrum predicted by the standard external shock model to extrapolate from the X-ray flux to the optical band, and obtain the possible range of the predicted optical flux. Finally, we compare the predictions with the observations. In the cases where later optical data are available, we also compare the s...

  6. Space-based observations of fire NOx emission coefficients: a global biome-scale comparison

    Directory of Open Access Journals (Sweden)

    A. K. Mebust

    2013-08-01

    Full Text Available Biomass burning represents both a significant and highly variable source of NOx to the atmosphere. This variability stems from both the episodic nature of fires, and from fire conditions such as the modified combustion efficiency of the fire, the nitrogen content of the fuel and possibly other factors that have not been identified or evaluated by comparison with observations. Satellite instruments offer an opportunity to observe emissions from wildfires, providing a large suite of measurements which allow us to study mean behavior and variability on the regional scale in a statistically rigorous manner. Here we use space-based measurements of fire radiative power from the Moderate Resolution Imaging Spectroradiometer in combination with NO2 tropospheric column densities from the Ozone Monitoring Instrument to measure mean emission coefficients (ECs in g NO MJ−1 from fires for global biomes, and across a wide range of smaller-scale ecoregions, defined as spatially-distinct clusters of fires with similar fuel type. Mean ECs for all biomes fall between 0.250–0.362 g NO MJ−1, a range that is smaller than found in previous studies of biome-scale emission factors. The majority of ecoregion ECs fall within or near this range, implying that under most conditions, mean fire emissions per unit energy are similar between different regions regardless of fuel type or spatial variability. In contrast to these similarities, we find that about 24% of individual ecoregion ECs deviate significantly (p x emissions.

  7. Diffuse X-ray Emission from the Carina Nebula Observed with Suzaku

    CERN Document Server

    Hamaguchi, Kenji

    2007-01-01

    A number of giant HII regions are associated with soft diffuse X-ray emission. Among these, the Carina nebula possesses the brightest soft diffuse emission. The required plasma temperature and thermal energy can be produced by collisions or termination of fast winds from main-sequence or embedded young O stars, but the extended emission is often observed from regions apart from massive stellar clusters. The origin of the X-ray emission is unknown. The XIS CCD camera onboard Suzaku has the best spectral resolution for extended soft sources so far, and is therefore capable of measuring key emission lines in the soft band. Suzaku observed the core and the eastern side of the Carina nebula (Car-D1) in 2005 Aug and 2006 June, respectively. Spectra of the south part of the core and Car-D1 similarly showed strong L-shell lines of iron ions and K-shell lines of silicon ions, while in the north of the core these lines were much weaker. Fitting the spectra with an absorbed thin-thermal plasma model showed kT~0.2, 0.6 k...

  8. Hard X-ray emissions from Cassiopeia A observed by INTEGRAL

    CERN Document Server

    Wang, Wei

    2016-01-01

    Cassiopeia A (Cas A) as the nearby young remnant of a core-collapse supernova is the best candidate for astrophysical studies in supernova explosion and its environment. We studied hard X-ray emissions from Cas A using the ten-year data of INTEGRAL observations, and first detected non-thermal continuum emission from the source up to 220 keV. The $^{44}$Ti line emissions at 68 and 78 keV are confirmed by our observations with a mean flux of $\\sim (2.2\\pm 0.4)\\times 10^{-5}$ ph cm$^{-2}$ s$^{-1}$, corresponding to a $^{44}$Ti yield in Cas A of $(1.3\\pm 0.4)\\times 10^{-4}$ \\ms. The continuum emission from 3 -- 500 keV can be fitted with a thermal bremsstrahlung of $kT\\sim 0.79\\pm 0.08$ keV plus a power-law model of $\\Gamma \\sim 3.13\\pm 0.03$. The non-thermal emission from Cas A is well fitted with a power-law model without a cutoff up to 220 keV. This radiation characteristic is inconsistent with the diffusive shock acceleration models with the remnant shock velocity of only 5000km s$^{-1}$. The central compact ...

  9. The long-wavelength thermal emission of the Pluto-Charon system from Herschel observations. Evidence for emissivity effects

    Science.gov (United States)

    Lellouch, E.; Santos-Sanz, P.; Fornasier, S.; Lim, T.; Stansberry, J.; Vilenius, E.; Kiss, Cs.; Müller, T.; Marton, G.; Protopapa, S.; Panuzzo, P.; Moreno, R.

    2016-04-01

    Thermal observations of the Pluto-Charon system acquired by the Herschel Space Observatory in February 2012 are presented. They consist of photometric measurements with the PACS and SPIRE instruments (nine visits to the Pluto system each), covering six wavelengths from 70 to 500 μm altogether. The thermal light curve of Pluto-Charon is observed in all filters, albeit more marginally at 160 and especially 500 μm. Putting these data into the context of older ISO, Spitzer and ground-based observations indicates that the brightness temperature (TB) of the system (rescaled to a common heliocentric distance) drastically decreases with increasing wavelength, from ~53 K at 20 μm to ~35 K at 500 μm, and perhaps ever less at longer wavelengths. Considering a variety of diurnal and/or seasonal thermophysical models, we show that TB values of 35 K are lower than any expected temperature for the dayside surface or subsurface of Pluto and Charon, implying a low surface emissivity. Based on multiterrain modeling, we infer a spectral emissivity that decreases steadily from 1 at 20-25 μm to ~0.7 at 500 μm. This kind of behavior is usually not observed in asteroids (when proper allowance is made for subsurface sounding), but is found in several icy surfaces of the solar system. We tentatively identify that a combination of a strong dielectric constant and a considerable surface material transparency (typical penetration depth ~1 cm) is responsible for the effect. Our results have implications for the interpretation of the temperature measurements by REX/New Horizons at 4.2 cm wavelength. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  10. Evolution of magnetotelluric, total magnetic field, and VLF field parameters in Central Italy: relations to local seismic activity

    Directory of Open Access Journals (Sweden)

    T. Ernst

    2001-06-01

    Full Text Available Magnetotelluric data were collected at Collemeluccio (41.72°N, 14.37°E in Central Italy from summer 1991 to spring 1998. Analyzed by means of tensor decomposition on the geoelectric potential and robust estimation on the geomagnetic field, this set of data allowed the investigation of the electric properties at different time-periods. The variation of some indicators, related to the phenomenon of electromagnetic induction, is presented here in its time evolution and compared to local and regional seismic activity. Tectonomagnetic field observations from absolute magnetic field level in Central Italy were also made on data simultaneously recorded at four magnetometer stations, using L'Aquila Geomagnetic Observatory as a reference for differentiation. Recent results gathered from a system of two VLF search coil wide-band antennas, installed in the L'Aquila Observatory, are also discussed in relation to local seismic activity.

  11. Observation of delayed electron emission in a two-phase liquid xenon detector

    International Nuclear Information System (INIS)

    Results of the experimental study of electron emission from liquid xenon via electroluminescence of the gas phase are presented. We report on observation of a peculiar kind of delayed electroluminescent signal following initial electroluminescence caused by ionizing particles. We also present the results of a study of spontaneous single electron emission following cosmic muon signals. It was found that the rate of spontaneous single electron signals strongly depends on the time passed since the initial electroluminescence happened. The analysis of experimental data showed that both spontaneous single electron signals and delayed electroluminescent signals are associated with ionization electrons which are trapped by the potential barrier at the interface

  12. Helium Emissions Observed in Ground-Based Spectra of Solar Prominences

    OpenAIRE

    Ramelli, Renzo; Stellmacher, Goetz; Wiehr, Eberhard; Bianda, Michele

    2012-01-01

    The only prominent line of singly ionized helium in the visible spectral range, helium-II 4686 A, is observed together with the helium-I 5015 A singlet and the helium-I 4471 A triplet line in solar prominences. The sodium emission, NaD2, is used as a tracer for helium-II emissions which are sufficiently bright to exceed the noise level near 10^-6 of the disk-center intensity. The so selected prominences are characterized by small non-thermal line broadening and almost absent velocity shifts, ...

  13. Dust emissivity in the Submm/Mm: SCUBA and SIMBA observations of Barnard 68

    OpenAIRE

    Bianchi, S.; Goncalves, J; Albrecht, M.; Caselli, P.; Chini, R.; Galli, D.; Walmsley, M

    2003-01-01

    We have observed the dark cloud Barnard 68 with SCUBA at 850 um and with SIMBA at 1.2 mm. The submillimetre and millimetre dust emission correlate well with the extinction map of Alves, Lada and Lada (2001).The A_V/850um correlation is clearly not linear and suggests lower temperatures for the dust in the inner core of the cloud. Assuming a model for the temperature gradient, we derive the cloud-averaged dust emissivities (normalised to the V-Band extinction efficiency) at 850 um and 1.2 mm. ...

  14. HF beam parameters in ELF/VLF wave generation via modulated heating of the ionosphere

    OpenAIRE

    İnan, Umran Savaş; Cohen, M. B. ; Golkowski, M. ; Lehtinen, N. G. ; McCarrick, M. J.

    2012-01-01

    ELF/VLF (0.3–30 kHz) wave generation is achievable via modulated HF (3–30 MHz) heating of the lower ionosphere in the presence of natural currents such as the auroral electrojet. Using the 3.6 MW High Frequency Active Auroral Research Program (HAARP) facility near Gakona, AK, we investigate the effect of HF frequency and beam size on the generated ELF/VLF amplitudes, as a function of modulation frequency, and find that generation in the Earth-ionosphere waveguide generally decr...

  15. Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters

    OpenAIRE

    İnan, Umran Savaş; Graf, K. L.; Spasojevic, M.; Marshall, R. A.; Lehtinen, N. G.; Foust, F. R.

    2013-01-01

    JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 7783–7797, doi:10.1002/2013JA019337, 2013 Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters K. L. Graf,1 M. Spasojevic,1 R. A. Marshall,2 N. G. Lehtinen,1 F. R. Foust,1 and U. S. Inan1,3 Received 16 August 2013; revised 9 October 2013; accepted 11 November 2013; published 3 December 2013. [1] The effects of ground-based very low frequency (VLF) transmitters on the lower ionospher...

  16. Direct observation of aqueous secondary organic aerosol from biomass-burning emissions

    Science.gov (United States)

    Gilardoni, Stefania; Massoli, Paola; Paglione, Marco; Giulianelli, Lara; Carbone, Claudio; Rinaldi, Matteo; Decesari, Stefano; Sandrini, Silvia; Costabile, Francesca; Gobbi, Gian Paolo; Chiara Pietrogrande, Maria; Visentin, Marco; Scotto, Fabiana; Fuzzi, Sandro; Facchini, Maria Cristina

    2016-09-01

    The mechanisms leading to the formation of secondary organic aerosol (SOA) are an important subject of ongoing research for both air quality and climate. Recent laboratory experiments suggest that reactions taking place in the atmospheric liquid phase represent a potentially significant source of SOA mass. Here, we report direct ambient observations of SOA mass formation from processing of biomass-burning emissions in the aqueous phase. Aqueous SOA (aqSOA) formation is observed both in fog water and in wet aerosol. The aqSOA from biomass burning contributes to the “brown” carbon (BrC) budget and exhibits light absorption wavelength dependence close to the upper bound of the values observed in laboratory experiments for fresh and processed biomass-burning emissions. We estimate that the aqSOA from residential wood combustion can account for up to 0.1-0.5 Tg of organic aerosol (OA) per y in Europe, equivalent to 4-20% of the total OA emissions. Our findings highlight the importance of aqSOA from anthropogenic emissions on air quality and climate.

  17. Direct observation of aqueous secondary organic aerosol from biomass-burning emissions.

    Science.gov (United States)

    Gilardoni, Stefania; Massoli, Paola; Paglione, Marco; Giulianelli, Lara; Carbone, Claudio; Rinaldi, Matteo; Decesari, Stefano; Sandrini, Silvia; Costabile, Francesca; Gobbi, Gian Paolo; Pietrogrande, Maria Chiara; Visentin, Marco; Scotto, Fabiana; Fuzzi, Sandro; Facchini, Maria Cristina

    2016-09-01

    The mechanisms leading to the formation of secondary organic aerosol (SOA) are an important subject of ongoing research for both air quality and climate. Recent laboratory experiments suggest that reactions taking place in the atmospheric liquid phase represent a potentially significant source of SOA mass. Here, we report direct ambient observations of SOA mass formation from processing of biomass-burning emissions in the aqueous phase. Aqueous SOA (aqSOA) formation is observed both in fog water and in wet aerosol. The aqSOA from biomass burning contributes to the "brown" carbon (BrC) budget and exhibits light absorption wavelength dependence close to the upper bound of the values observed in laboratory experiments for fresh and processed biomass-burning emissions. We estimate that the aqSOA from residential wood combustion can account for up to 0.1-0.5 Tg of organic aerosol (OA) per y in Europe, equivalent to 4-20% of the total OA emissions. Our findings highlight the importance of aqSOA from anthropogenic emissions on air quality and climate. PMID:27551086

  18. P-MaNGA Galaxies: Emission Lines Properties - Gas Ionisation and Chemical Abundances from Prototype Observations

    CERN Document Server

    Belfiore, F; Bundy, K; Thomas, D; Maraston, C; Wilkinson, D; Sánchez, S F; Bershady, M; Blanc, G A; Bothwell, M; Cales, S L; Coccato, L; Drory, N; Emsellem, E; Fu, H; Gelfand, J; Law, D; Masters, K; Parejko, J; Tremonti, C; Wake, D; Weijmans, A; Yan, R; Xiao, T; Zhang, K; Zheng, T; Bizyaev, D; Kinemuchi, K; Oravetz, D; Simmons, A

    2014-01-01

    MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) is a SDSS-IV survey that will obtain spatially resolved spectroscopy from 3600 \\AA\\ to 10300 \\AA\\ for a representative sample of over 10000 nearby galaxies. In this paper we present the analysis of nebular emission line properties using observations of 14 galaxies obtained with P-MaNGA, a prototype of the MaNGA instrument. By using spatially resolved diagnostic diagrams we find extended star formation in galaxies that are centrally dominated by Seyfert/LINER-like emission, illustrating that galaxy characterisations based on single fibre spectra are necessarily incomplete. We observe extended (up to $\\rm 1 R_{e}$) LINER-like emission in the central regions of three galaxies. We make use of the $\\rm EW(H \\alpha)$ to argue that the observed emission is consistent with ionisation from hot evolved stars. Using stellar population indices we conclude that galactic regions which are ionised by a Seyfert/LINER-like radiation field are also devoid of recent st...

  19. Efficiency and Sensitivity Analysis of Observation Networks for Atmospheric Inverse Modelling with Emissions

    CERN Document Server

    Wu, Xueran; Jacob, Birgit

    2015-01-01

    The controllability of advection-diffusion systems, subject to uncertain initial values and emission rates, is estimated, given sparse and error affected observations of prognostic state variables. In predictive geophysical model systems, like atmospheric chemistry simulations, different parameter families influence the temporal evolution of the system.This renders initial-value-only optimisation by traditional data assimilation methods as insufficient. In this paper, a quantitative assessment method on validation of measurement configurations to optimize initial values and emission rates, and how to balance them, is introduced. In this theoretical approach, Kalman filter and smoother and their ensemble based versions are combined with a singular value decomposition, to evaluate the potential improvement associated with specific observational network configurations. Further, with the same singular vector analysis for the efficiency of observations, their sensitivity to model control can be identified by deter...

  20. Non-thermal emission from high-energy binaries through interferometric radio observations

    CERN Document Server

    Marcote, B

    2016-01-01

    High-mass binary systems involve extreme environments that produce non-thermal emission from radio to gamma rays. Only three types of these systems are known to emit persistent gamma-ray emission: colliding-wind binaries, high-mass X-ray binaries and gamma-ray binaries. This thesis is focused on the radio emission of high-mass binary systems through interferometric observations, and we have explored several of these sources with low- and high-frequency radio observations, and very high-resolution VLBI ones. We have studied two gamma-ray binaries, LS 5039 and LS I +61 303, at low frequencies. We have obtained their light-curves and spectra, and we have determined the physical properties of their radio emitting regions. We have also studied the gamma-ray binary HESS J0632+057 through VLBI observations. A new colliding wind binary, HD 93129A, has been discovered through VLBI and optical observations. Finally, we have conducted radio observations of two sources that were candidates to be gamma-ray binaries.

  1. Observational Characteristics of Radio Emission Related to Multi-polar Magnetic Configuration

    Institute of Scientific and Technical Information of China (English)

    Min Wang; Rui-Xiang Xie; Chun Xu; Shuo-Biao Shi; Yi-Hua Yan

    2005-01-01

    We present a large complex radio burst and its associated fast time structures observed on 2001 April 10 in the frequency range of 0.65-7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a biposuggests that the radio burst is generated from a very complicated loop structure.According to the spectral and image observations, we assume that the beginning connection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type Ⅲ bursts, and slowly drifting and no-drift structures.ture, which is an important source of the various types of fast time structures.The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively.Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the lar).

  2. Observations of volatile organic compounds during ARCTAS – Part 1: Biomass burning emissions and plume enhancements

    Directory of Open Access Journals (Sweden)

    A. Hills

    2011-05-01

    Full Text Available Mixing ratios of a large number of volatile organic compounds (VOCs were observed by the Trace Organic Gas Analyzer (TOGA on board the NASA DC-8 as part of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS field campaign. Many of these VOCs were observed concurrently by one or both of two other VOC measurement techniques on board the DC-8: proton-transfer-reaction mass spectrometry (PTR-MS and whole air canister sampling (WAS. A comparison of these measurements to the data from TOGA indicates good agreement for the majority of co-measured VOCs. The ARCTAS study, which included both spring and summer deployments, provided opportunities to sample a large number of biomass burning (BB plumes with origins in Asia, California and Central Canada, ranging from very recent emissions to plumes aged one week or more. For this analysis, identified BB plumes were grouped by flight, source region and, in some cases, time of day, generating 40 individual plume groups, each consisting of one or more BB plume interceptions. Normalized excess mixing ratios (EMRs to CO were determined for each of the 40 plume groups for up to 19 different VOCs or VOC groups, many of which show significant variability, even within relatively fresh plumes. This variability demonstrates the importance of assessing BB plumes both regionally and temporally, as emissions can vary from region to region, and even within a fire over time. Comparisons with literature confirm that variability of EMRs to CO over an order of magnitude for many VOCs is consistent with previous observations. However, this variability is often diluted in the literature when individual observations are averaged to generate an overall regional EMR from a particular study. Previous studies give the impression that emission ratios are generally consistent within a given region, and this is not necessarily the case, as our results show. For some VOCs, earlier assumptions

  3. Nine years of global hydrocarbon emissions based on source inversion of OMI formaldehyde observations

    Science.gov (United States)

    Bauwens, Maite; Stavrakou, Trissevgeni; Müller, Jean-François; De Smedt, Isabelle; Van Roozendael, Michel; van der Werf, Guido R.; Wiedinmyer, Christine; Kaiser, Johannes W.; Sindelarova, Katerina; Guenther, Alex

    2016-08-01

    As formaldehyde (HCHO) is a high-yield product in the oxidation of most volatile organic compounds (VOCs) emitted by fires, vegetation, and anthropogenic activities, satellite observations of HCHO are well-suited to inform us on the spatial and temporal variability of the underlying VOC sources. The long record of space-based HCHO column observations from the Ozone Monitoring Instrument (OMI) is used to infer emission flux estimates from pyrogenic and biogenic volatile organic compounds (VOCs) on the global scale over 2005-2013. This is realized through the method of source inverse modeling, which consists in the optimization of emissions in a chemistry-transport model (CTM) in order to minimize the discrepancy between the observed and modeled HCHO columns. The top-down fluxes are derived in the global CTM IMAGESv2 by an iterative minimization algorithm based on the full adjoint of IMAGESv2, starting from a priori emission estimates provided by the newly released GFED4s (Global Fire Emission Database, version 4s) inventory for fires, and by the MEGAN-MOHYCAN inventory for isoprene emissions. The top-down fluxes are compared to two independent inventories for fire (GFAS and FINNv1.5) and isoprene emissions (MEGAN-MACC and GUESS-ES). The inversion indicates a moderate decrease (ca. 20 %) in the average annual global fire and isoprene emissions, from 2028 Tg C in the a priori to 1653 Tg C for burned biomass, and from 343 to 272 Tg for isoprene fluxes. Those estimates are acknowledged to depend on the accuracy of formaldehyde data, as well as on the assumed fire emission factors and the oxidation mechanisms leading to HCHO production. Strongly decreased top-down fire fluxes (30-50 %) are inferred in the peak fire season in Africa and during years with strong a priori fluxes associated with forest fires in Amazonia (in 2005, 2007, and 2010), bushfires in Australia (in 2006 and 2011), and peat burning in Indonesia (in 2006 and 2009), whereas generally increased fluxes

  4. Constraints on ship NOx emissions in Europe using OMI NO2 observations

    Science.gov (United States)

    Vinken, G. C. M.; Boersma, K. F.

    2012-04-01

    About 90% of world trade is transported by oceangoing ships, and seaborne trade has been shown to have increased by about 5% per year in the past decade. Global ship traffic is currently not regulated under international treaties (e.g. Kyoto protocol) and ships are still allowed to burn low-grade bunker fuel. As a result, ships emit large quantities of nitrogen oxides (NOx = NO + NO2), important precursors for ozone (O3) and particulate matter formation. Previous studies indicated that the global NOx emissions from shipping are in the range 3.0-10.4 Tg N per year (15-30% of total global NOx emissions). Because most ships sail within 400 km of the coast, it is important to understand the contribution of ship emissions to atmospheric composition in the densely populated coastal regions. Chemistry Transport Models (CTMs), in combination with emission inventories, are used to simulate atmospheric concentrations of air pollutants to assess the impact of ship emissions. However, these bottom-up inventories, based on extrapolation of a few engine measurements and strong assumptions, suffer from large uncertainties. In this study we provide top-down constraints on ship NOx emissions in Europe using satellite observations of NO2 columns. We use the nested version of the GEOS-Chem model (0.5°-0.667°) to simulate tropospheric NO2 columns over Europe for the years 2005-2006, using our plume-in-grid treatment of ship NOx emissions. We improve the NO2 retrievals from the Ozone Monitoring Instrument (OMI v2.0) by replacing the coarse a priori (TM4) vertical NO2 profiles (2°-3°) with the high-resolution GEOS-Chem profiles. This ensures consistency between the retrievals and model simulations. GEOS-Chem simulations of tropospheric NO2 columns show remarkable quantitative agreement with the observed OMI columns over Europe (R2=0.89, RMS difference < 0.2-1015 molec. cm-2), providing confidence in the ability of the model to simulate NO2 pollution over the European mainland. We

  5. Ten years of satellite observations reveal highly variable sulphur dioxide emissions at Anatahan Volcano, Mariana Islands

    Science.gov (United States)

    McCormick, Brendan; Popp, Christoph; Andrews, Benjamin; Cottrell, Elizabeth

    2015-07-01

    Satellite remote sensing enables continuous multiyear observations of volcanic activity in remote settings. Anatahan (Mariana Islands) is a remote volcano in the western North Pacific. Available ground-based measurements of sulphur dioxide (SO2) gas emissions at Anatahan place it among thelargest volcanic SO2 sources worldwide. These ground-based measurements, however, are restricted to eruptive intervals. Anatahan's activity since 2003 has been dominated temporally by prolonged periods of quiescence. Using 10 years of satellite observations from OMI, AIRS, SCIAMACHY, and GOME-2, we report highly variable SO2 emissions within and between eruptive and quiescent intervals at Anatahan. We find close correspondence between levels of activity reported at the volcano and levels of SO2 emissions detected from space. Eruptive SO2 emission rates have a mean value of ˜6400 t d-1, but frequently are in excess of 20,000 t d-1. Conversely, SO2 emissions during quiescent intervals are below the detection limit of space-based sensors and therefore are not likely to exceed ˜300 t d-1. We show that while Anatahan occupies a quiescent state for 85% of the past 10 years, only ˜15% of total SO2 emissions over this interval occur during quiescence, with the remaining ˜85% released in short duration but intense syn-eruptive degassing. We propose that the integration of multiyear satellite data sets and activity histories are a powerful complement to targeted ground-based campaign measurements in better describing the long-term degassing behavior of remote volcanoes.

  6. Panchromatic observations of the textbook GRB 110205A: constraining physical mechanisms of prompt emission and afterglow

    CERN Document Server

    Zheng, W; Sakamoto, T; Beardmore, A P; Pasquale, M; Wu, X F; Gorosabel, J; Urata, Y; Sugita, S; Zhang, B; Pozanenko, A; Nissinen, M; Sahu, D K; Im, M; Ukwatta, T N; Andreev, M; Klunko, E; Volnova, A; Akerlof, C W; Anto, P; Barthelmy, S D; Breeveld, A; Carsenty, U; Castillo-Carri'on, S; Castro-Tirado, A J; Chester, M M; Chuang, C J; Cunniffe, R; Postigo, A; Duffard, R; Flewelling, H; Gehrels, N; Guver, T; Guziy, S; Hentunen, V P; Huang, K Y; Jelínek, M; Koch, T S; Kub'anek, P; Kuin, P; McKay, T A; Mottola, S; Oates, S R; O'Brien, P; Page, M J; Pandey, S B; Pulgar, C; Rujopakarn, W; Rykoff, E; Salmi, T; S'anchez-Ramírez, R; Schaefer, B E; Sergeev, A; Sonbas, E; Sota, A; Tello, J C; Yamaoka, K; Yost, S A; Yuan, F

    2011-01-01

    We present a comprehensive analysis of a bright, long duration (T90 ~ 257 s) GRB 110205A at redshift z= 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the GRB was still radiating in the gamma-ray band. Nearly 200 s of observations were obtained simultaneously from optical, X-ray to gamma-ray, which makes it one of the exceptional cases to study the broadband spectral energy distribution across 6 orders of magnitude in energy during the prompt emission phase. By fitting the time resolved prompt spectra, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard GRB synchrotron emission model in the fast cooling regime. Although the prompt optical emission is brighter than the extrapolation of the best fit X/gamma-ray spectra, it traces the gamma-ray light curve shape, suggesting a relation to the prompt high energy emission. The synchrotron + SSC scenario is disfavored by the data, but the models i...

  7. Observations of artificial and natural optical emissions at the HAARP facility

    Directory of Open Access Journals (Sweden)

    T. Pedersen

    2008-05-01

    Full Text Available Extensive optical observations have been carried out at the High Frequency Active Auroral Research Program (HAARP ionospheric heating facility since it began operations in 1999. A number of modern optical diagnostic instruments are hosted at remote sites as well as the main transmitter facility, which has recently been expanded from the initial 960 kW prototype configuration to its full 3.6 MW design capability. Upgrades to optical diagnostics have allowed a number of interesting new observations to be made at the 960 kW power level since 2004. Systematic beam-swinging experiments generating quantifiable levels of optical emission at various regions in the sky for the first time clearly show that emission intensity is very sensitive to distance from the magnetic zenith, and drops off rapidly at about 15° zenith angle in directions other than magnetic south. High temporal resolution measurements of emissions in the 557.7 nm green line at start-up and in short transmitter pulses demonstrate that localized irregularities are preferentially excited in the initial seconds of heating, with evolution into a more homogenous spot occurring over a period of about 1 min. High-quality emission altitude profiles at both 630.0 and 557.7 nm have recently been isolated from side-looking data, spanning an altitude extent of over 200 km, which has allowed determination of the effective lifetime of O (1D over an unprecedented altitude range. An innovative automated remote imager network utilizing low-cost mirror optics has been designed and deployed to make such measurements routinely. Observations of natural optical emissions at the site have revealed the common presence of highly structured but faint co-rotating subauroral precipitation that acts to suppress excitation of artificial F region optical emissions in areas of active precipitation. The observed spatial modulation of artificial optical emissions by structured precipitation is consistent

  8. Herschel HIFI observations of O{sub 2} toward Orion: special conditions for shock enhanced emission

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jo-Hsin; Goldsmith, Paul F. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Viti, Serena [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Snell, Ronald [Department of Astronomy, University of Massachusetts, LGRT-B 619E, 710 North Pleasant Street, Amherst, MA 01003 (United States); Lis, Dariusz C. [California Institute of Technology, Cahill Center for Astronomy and Astrophysics 301-17, Pasadena, CA 91125 (United States); Benz, Arnold [Institute of Astronomy, ETH Zurich, Zurich (Switzerland); Bergin, Edwin [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Black, John; Hjalmarson, Åke [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Caselli, Paola [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching (Germany); Encrenaz, Pierre; Falgarone, Edith [LRA/LERMA, CNRS, UMR8112, Observatoire de Paris and École Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex 05 (France); Goicoechea, Javier R. [Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), E-28049, Cantoblanco, Madrid (Spain); Hollenbach, David [SETI Institute, Mountain View, CA 94043 (United States); Kaufman, Michael [Department of Physics and Astronomy, San José State University, San Jose, CA 95192 (United States); Melnick, Gary [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 66, Cambridge, MA 02138 (United States); Neufeld, David [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Pagani, Laurent [LERMA and UMR8112 du CNRS, Observatoire de Paris, 61 Av. de l' Observatoire, F-75014, Paris (France); and others

    2014-10-01

    We report observations of molecular oxygen (O{sub 2}) rotational transitions at 487 GHz, 774 GHz, and 1121 GHz toward Orion Peak A. The O{sub 2} lines at 487 GHz and 774 GHz are detected at velocities of 10-12 km s{sup –1} with line widths ∼3 km s{sup –1}; however, the transition at 1121 GHz is not detected. The observed line characteristics, combined with the results of earlier observations, suggest that the region responsible for the O{sub 2} emission is ≅9'' (6 × 10{sup 16} cm) in size, and is located close to the H {sub 2} Peak 1 position (where vibrationally excited H{sub 2} emission peaks), and not at Peak A, 23'' away. The peak O{sub 2} column density is ≅1.1 × 10{sup 18} cm{sup –2}. The line velocity is close to that of the 621 GHz water maser emission found in this portion of the Orion Molecular Cloud, and having a shock with velocity vector lying nearly in the plane of the sky is consistent with producing maximum maser gain along the line of sight. The enhanced O{sub 2} abundance compared to that generally found in dense interstellar clouds can be explained by passage of a low-velocity C shock through a clump with preshock density 2 × 10{sup 4} cm{sup –3}, if a reasonable flux of UV radiation is present. The postshock O{sub 2} can explain the emission from the source if its line-of-sight dimension is ≅10 times larger than its size on the plane of the sky. The special geometry and conditions required may explain why O{sub 2} emission has not been detected in the cores of other massive star-forming molecular clouds.

  9. Observations of Ellerman bomb emission features in He I D3 and He I 10830 {\\AA}

    CERN Document Server

    Libbrecht, Tine; Rodríguez, Jaime de la Cruz; Leenaarts, Jorrit; Ramos, Andrés Asensio

    2016-01-01

    Context. Ellerman bombs (EBs) are short-lived emission features, characterized by extended wing emission in hydrogen Balmer lines. Until now, no distinct signature of EBs has been found in the He I 10830 {\\AA} line, and conclusive observations of EBs in He I D 3 have never been reported. Aims. We aim to study the signature of EBs in neutral helium triplet lines. Methods. The observations consist of 10 consecutive SST/TRIPPEL raster scans close to the limb, featuring the H$\\beta$, He I D3 and He I 10830 {\\AA} spectral regions. We also obtained raster scans with IRIS and make use of the SDO/AIA 1700 {\\AA} channel. We use Hazel to invert the neutral helium triplet lines. Results. Three EBs in our data show distinct emission signatures in neutral helium triplet lines, most prominently visible in the He I D3 line. The helium lines have two components: a broad and blue-shifted emission component associated with the EB, and a narrower absorption component formed in the overlying chromosphere. One of the EBs in our d...

  10. HST/ACS Observations of Europa's Atmospheric UV Emission at Eastern Elongation

    CERN Document Server

    Saur, Joachim; Roth, Lorenz; Nimmo, Francis; Strobel, Darrell F; Retherford, Kurt D; McGrath, Melissa A; Schilling, Nico; Gérard, Jean-Claude; Grodent, Denis

    2011-01-01

    We report results of a Hubble Space Telescope (HST) campaign with the Advanced Camera for Surveys to observe Europa at eastern elongation, i.e. Europa's leading side, on 2008 June 29. With five consecutive HST orbits, we constrain Europa's atmospheric \\ion{O}{1} 1304 \\A and \\ion{O}{1} 1356 \\A emissions using the prism PR130L. The total emissions of both oxygen multiplets range between 132 $\\pm$ 14 and 226 $\\pm$ 14 Rayleigh. An additional systematic error with values on the same order as the statistical errors may be due to uncertainties in modelling the reflected light from Europa's surface. The total emission also shows a clear dependence of Europa's position with respect to Jupiter's magnetospheric plasma sheet. We derive a lower limit for the O$_2$ column density of 6 $\\times$ 10$^{18}$ m$^{-2}$. Previous observations of Europa's atmosphere with STIS in 1999 of Europa's trailing side show an enigmatic surplus of radiation on the anti-Jovian side within the disk of Europa. With emission from a radially symm...

  11. Simultaneous optical/gamma-ray observations of GRB 121217's prompt emission

    CERN Document Server

    Elliott, J; Schmidl, S; Greiner, J; Gruber, D; Oates, S; Kobayashi, S; Zhang, B; Cummings, J R; Filgas, R; Gehrels, N; Grupe, D; Kann, D A; Klose, S; Krühler, T; Guelbenzu, A Nicuesa; Rau, A; Rossi, A; Siegel, M; Schady, P; Sudilovsky, V; Tanga, M; Varela, K

    2013-01-01

    Since the advent of the Swift satellite it has been possible to obtain precise localisations of GRB positions of sub-arcsec accuracy within seconds, facilitating ground-based robotic telescopes to automatically slew to the target within seconds. This has yielded a plethora of observational data for the afterglow phase of the GRB, but the quantity of data (<2 keV) covering the initial prompt emission still remains small. Only in a handful of cases has it been possible obtain simultaneous coverage of the prompt emission in a multi-wavelength regime (gamma-ray to optical), as a result of: observing the field by chance prior to the GRB (e.g. 080319B/naked-eye burst), long-prompt emission (e.g., 080928, 110205A) or triggered on a pre-cursor (e.g., 041219A, 050820A, 061121). This small selection of bursts have shown both correlated and uncorrelated gamma-ray and optical light curve behaviour, and the multi-wavelength emission mechanism remains far from resolved (i.e. single population synchrotron self-Component,...

  12. The long-wavelength thermal emission of the Pluto-Charon system from Herschel observations. Evidence for emissivity effects

    CERN Document Server

    Lellouch, E; Fornasier, S; Lim, T; Stansberry, J; Vilenius, E; Kiss, Cs; Müller, T; Marton, G; Protopapa, S; Panuzzo, P; Moreno, R

    2016-01-01

    Thermal observations of the Pluto-Charon system acquired by the Herschel Space Observatory in February 2012 are presented. They consist of photometric measurements with the PACS and SPIRE instruments (nine visits to the Pluto system each), covering six wavelengths from 70 to 500 $\\mu$m altogether. The thermal light curve of Pluto-Charon is observed in all filters, albeit more marginally at 160 and especially 500 $\\mu$m. Putting these data into the context of older ISO, Spitzer and ground-based observations indicates that the brightness temperature (T$_B$) of the system (rescaled to a common heliocentric distance) drastically decreases with increasing wavelength, from $\\sim$53 K at 20 $\\mu$m to $\\sim$35 K at 500 $\\mu$m, and perhaps ever less at longer wavelengths. Considering a variety of diurnal and/or seasonal thermophysical models, we show that T$_B$ values of 35 K are lower than any expected temperature for the dayside surface or subsurface of Pluto and Charon, implying a low surface emissivity. Based on m...

  13. Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations

    Directory of Open Access Journals (Sweden)

    L. Meng

    2012-07-01

    Full Text Available Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011 into the Community Land Model 4.0 (CLM4CN in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr−1 (including the soil sink and rice paddy emissions in the year 2000 were 42 Tg CH4 yr−1. Tropical wetlands contributed 201 Tg CH4 yr−1, or 78% of the global wetland flux. Northern latitude (>50 N systems contributed 12 Tg CH4 yr−1. However, sensitivity studies show a large range (150–346 Tg CH4 yr−1 in predicted global methane emissions (excluding emissions from rice paddies. The large range is

  14. Synchrotron emission in GRBs observed by Fermi: Its limitations and the role of the photosphere

    CERN Document Server

    Iyyani, S; Burgess, J M; Pe'er, A; egué, D B\\'

    2015-01-01

    It has been suggested that the prompt emission in gamma-ray bursts consists of several components giving rise to the observed spectral shape. Here we examine a sample of the 8 brightest, single pulsed {\\it Fermi} bursts whose spectra are modelled by using synchrotron emission as one of the components. Five of these bursts require an additional photospheric component (blackbody). In particular, we investigate the inferred properties of the jet and the physical requirements set by the observed components for these five bursts, in the context of a baryonic dominated outflow, motivated by the strong photospheric component. We find similar jet properties for all five bursts: the bulk Lorentz factor decreases monotonously over the pulses and lies between 1000 and 100. This evolution is robust and can neither be explained by a varying radiative efficiency nor a varying magnetisation of the jet assuming the photosphere radius is above the coasting radius. Such a behaviour challenges several dissipation mechanisms, e....

  15. Estimates of surface methane emissions over Europe using observed surface concentrations and the FLEXPART trajectory model

    Science.gov (United States)

    Weaver, C. J.; Kiemle, C.; Kawa, S. R.; Aalto, T.; Necki, J.; Steinbacher, M.; Arduini, J.; Apadula, F.; Berkhout, H.; Hatakka, J.; O'Doherty, S.

    2013-12-01

    We use surface methane observations from nine European ground stations, and the FLEXPART Lagrangian transport model to obtain surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands and the coal mines in Upper Silesia Poland. This is qualitatively consistent with the EDGAR surface flux inventory. We also report significant surface fluxes from wetlands in southern Finland during July and August and reduced wetland fluxes later in the year. Our simulated methane surface concentration captures at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. We also use our trajectory model to determine whether future space-based remote sensing instruments (MERLIN) will be able to detect both natural and anthropogenic changes in the surface flux strengths.

  16. Observations of the Prompt Gamma-Ray Emission of GRB 070125

    CERN Document Server

    Bellm, Eric C; Pal'shin, Valentin; Yamaoka, Kazutaka; Bandstra, Mark E; Boggs, Steven E; Hong, Soojing; Kodaka, Natsuki; Kozyrev, A S; Litvak, M L; Mitrofanov, I G; Nakagawa, Yujin E; Ohno, Masanori; Onda, Kaori; Sanin, A B; Sugita, Satoshi; Tashiro, Makoto; Tretyakov, V I; Urata, Yuji; Wigger, Claudia

    2007-01-01

    The long, bright gamma-ray burst GRB 070125 was localized by the Interplanetary Network. We present light curves of the prompt gamma-ray emission as observed by Konus-WIND, RHESSI, Suzaku-WAM, and Swift-BAT. We detail the results of joint spectral fits with Konus and RHESSI data. The burst shows moderate hard-to-soft evolution in its multi-peaked emission over a period of about one minute. The total burst fluence as observed by Konus is $1.75 \\times 10^{-4}$ erg/cm$^2$ (20 keV-10 MeV). Using the spectroscopic redshift z = 1.547, we find that the burst is consistent with the Amati $E_{peak,i}-E_{iso}$ and the Ghirlanda $E_{peak,i}-E_\\gamma$ correlations.

  17. Investigation of VLF and HF waves showing seismo-ionospheric anomalies induced by the 29 September 2009 Samoa earthquake (Mw=8.1

    Directory of Open Access Journals (Sweden)

    M. Parrot

    2010-05-01

    Full Text Available In Samoa Islands, a powerful earthquake took place at 17:48:10.99 UTC (06:48:10.99 LT on 29 September 2009 with a magnitude Mw=8.1. Using ICE (Instrument Champ Electrique and IMSC (Instrument Magnetic Search Coil experiments onboard the DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions satellite we have surveyed possible variations in electromagnetic signals transmitted by the ground-based VLF transmitter NPM in Hawaii and in HF plasma waves close to the Samoa earthquake during the seismic activity. The indices Dst and Kp were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic activities. In a previous study we have shown that anomalies in IAP (plasma analyzer and ISL (Langmuir probe experiments onboard the DEMETER and also TEC (Total Electron Content data appear 1 to 5 days before the Samoa earthquake. In this paper we show that the anomalies in the VLF transmitter signal and in the HF range appear with the same time scale. The lack of significant geomagnetic activities indicates that these anomalous behaviors could be regarded as seismo-ionospheric precursors. It is also shown that comparative analysis is more effective in seismo-ionospheric studies.

  18. Low-dimensional models for the estimation of anthropogenic CO2 emissions from atmospheric observations

    Science.gov (United States)

    van Bloemen Waanders, B.; Ray, J.; McKenna, S. A.; Yadav, V.; Michalak, A. M.

    2011-12-01

    The estimation of anthropogenic fossil fuel emissions using atmospheric observations of CO2 has recently attracted increasing interest due to its relevance to monitoring of CO2 mitigation treaties and programs. To date, techniques to perform large-scale inversions had primarily been developed within the context of understanding biospheric and oceanic fluxes. Such fluxes tend to vary relatively smoothly in space and time, making it possible to use multiGaussian models to parameterize and regularize such inversions, predicated on limited measurements of CO2 concentrations. However, the spatial distribution of anthropogenic emissions is non-stationary and multiscale, and therefore makes the use of multiGaussians models less suitable. Thus, a need exists to identify how anthropogenic emissions may be represented in a low-dimensional manner (i.e., with few parameters), for use in top-down estimation. Certain aspects of the spatial extent of anthropogenic emissions can be represented using easily measurable proxies such as nightlights, population density and GDP; in fact, fossil fuel inventories regularly use them to disaggregate regional emission budgets to finer spatial resolutions. However, such proxies can also be used to construct a priori models for anthropogenic emissions, which can then be updated, with data, through inverse modeling. In this presentation, we compare 3 low-dimensional parameterizations to characterize anthropogenic sources. The models are derived from images of nightlights over the continental USA, but adopt different arguments to achieve their dimensionality reduction. In the first model, we threshold nightlights and fit bivariate Gaussian kernels over clusters to represent emission sources; the emission field is modeled as a weighted sum of the kernels. The second approach models emissions as a weighted superposition of a filtered nightlight-distribution and a multiresolution defect, modeled with Haar wavelet. The nightlight-based methods

  19. Dust emission mechanisms in the central Sahara: new insights from remote field observations

    Science.gov (United States)

    Allen, C.; Washington, R.; Engelstaedter, S.

    2013-12-01

    North Africa is the world's largest source of mineral aerosol (dust). The Fennec Project, an international consortium led by the University of Oxford, is the first project to systematically instrument the remote central Sahara Desert. These observations have, among others, provided new insights into the atmospheric mechanisms of dust emission. Bordj Badji Mokhtar, in south-west Algeria, is within kilometres of the centre of the global mean summer dust maximum. The site, operated by Fennec partners ONM Algerie, has been heavily instrumented since summer 2011. During the Intensive Observation Period (IOP) in June 2011, four main emission mechanisms were observed and documented: cold pool outflows, low level jets (LLJs), monsoon surges and dry convective plumes. Establishing the relative importance of dust emission mechanisms has been a long-standing research goal. A detailed partitioning exercise of dust events during the IOP shows that 45% of the dust over BBM was generated by local emission in cold pool outflows, 14% by LLJs and only 2% by dry convective plumes. 27% of the dust was advected to the site rather than locally emitted and 12% of the dust was residual or ';background' dust. The work shows the primacy of cold pool outflows for dust emission in the region and also the important contribution of dust advection. In accordance with long-held ideas, the cube of wind speed is strongly correlated with dust emission. Surprisingly however, particles in long-range advection (>500km) were found to be larger than locally emitted dust. Although a clear LLJ wind structure is evident in the mean diurnal cycle during the IOP (12m/s peak winds at 935hPa between 04-05h), LLJs are only responsible for a relatively small amount of dust emission. There is significant daily variability in LLJ strength; the strongest winds are produced by a relatively small number of events. The position and strength of the Saharan Heat Low is strongly associated with the development (or

  20. The "APEC Blue" phenomenon: Regional emission control effects observed from space

    Science.gov (United States)

    Huang, Kan; Zhang, Xingying; Lin, Yanfen

    2015-10-01

    Observations from space were used to evaluate the effect of emission control measures on the changes of air pollutants in Beijing and its surroundings during the 2014 Asia-Pacific Economic Cooperation (APEC) Summit held in Beijing. Compared to the past three years (2011-2013), NO2 tropospheric vertical column densities in 2014 were found to exhibit almost across-the-board significant reductions over the North China Plain, suggesting the effectiveness of the national policy on NOx emission reduction during China's 12th "Five-Year-Plan". During the APEC period (Nov. 3-11), AOD and AAOD were found reduced the most in Beijing, followed by Hebei province. Stringent emission control measures implemented in Beijing and the regional joint control over the surroundings especially in Hebei were responsible for the good air quality and so-called "APEC Blue". However, air quality plummeted during the post-APEC period (Nov. 12-30), which was largely related to the lifting of local and regional joint emission control measures. By applying a spatial correlation analysis method, the potential emission source regions impacting air quality of Beijing included widespread areas in Hebei, Shandong, Shanxi, and Tianjin in the past three years (2011-2013). While during the study period in 2014, areas impacting Beijing evidently shrank and were limited within Hebei, suggesting evident effects of intense emission perturbations on lowering the extent of regional transport. This study indicates short-term measures did fix the air pollution problems in China but a permanent solution is still a tremendous challenge.

  1. Study of the NWC electrons belt observed on DEMETER Satellite

    CERN Document Server

    Li, Xinqiao; Wang, Ping; Wang, Huanyu; Lu, Hong; Zhang, Xuemin; Huang, Jianping; Shi, Feng; Yu, Xiaoxia; Xu, Yanbing; Meng, Xiangcheng; Wang, Hui; Zhao, Xiaoyun; Parrot, M

    2010-01-01

    We analyzed the data from 2007 to 2008, which is observed by IDP onboard DEMETER satellite, during ten months of NWC working and seven months of NWC shutdown. The characteristic of the space instantaneous electron belts, which come from the influence of the VLF transmitted by NWC, is studied comprehensively. The main distribution region of the NWC electron belts and the flux change are given. We also studied the distribution characteristic of the average energy spectrum in different magnetic shell at the height of DEMETER orbit and the difference of the average energy spectrum of the electrons in the drift loss-cone between day and night. As a result, the powerful power of NWC transmitter and the 19.8 kHz narrow bandwidth VLF emission not only created a momentary electrons enhancement region, which strides 180 degree in them longitude direction and from 1.6 to 1.9 in L value, with the rise of the electrons flux reaching to 3 orders of magnitude mostly, but also induced the enhancement or loss of electrons in ...

  2. Topographic Effects on the Surface Emissivity of a Mountainous Area Observed by a Spaceborne Microwave Radiometer

    Directory of Open Access Journals (Sweden)

    Frank S. Marzano

    2008-03-01

    Full Text Available A simulation study to understand the influence of topography on the surfaceemissivity observed by a satellite microwave radiometer is carried out. We analyze theeffects due to changes in observation angle, including the rotation of the polarization plane.A mountainous area in the Alps (Northern Italy is considered and the information on therelief extracted from a digital elevation model is exploited. The numerical simulation refersto a radiometric image, acquired by a conically-scanning radiometer similar to AMSR-E,i.e., flying at 705 km of altitude with an observation angle of 55°. To single out the impacton surface emissivity, scattering of the radiation due to the atmosphere or neighboringelevated surfaces is not considered. C and X bands, for which atmospheric effects arenegligible, and Ka band are analyzed. The results indicate that the changes in the localobservation angle tend to lower the apparent emissivity of a radiometric pixel with respectto the corresponding flat surface characteristics. The effect of the rotation of thepolarization plane enlarges (vertical polarization, or attenuates (horizontal polarizationthis decrease. By doing some simplifying assumptions for the radiometer antenna, theconclusion is that the microwave emissivity at vertical polarization is underestimated,whilst the opposite occurs for horizontal polarization, except for Ka band, for which bothunder- and overprediction may occur. A quantification of the differences with respect to aflat soil and an approximate evaluation of their impact on soil moisture retrieval areyielded.

  3. Training School Pupils in the Scientific Method: Student Participation in an International VLF Radio Experiment

    Science.gov (United States)

    Denton, J. J.; Denton, M. H.; Kavanagh, A. J.; Harron, H.; Ulich, T.; Denton, J. S.

    2012-01-01

    We report on a school-university collaboration to involve students in the deployment, testing, and operation of a very low frequency (VLF) radio receiver as part of an international network of such experiments. A background to the collaboration is presented, along with a summary of planning and development, and the ultimate deployment of the…

  4. Comparative Analysis of VLF Signal Variation along Trajectory Induced by X-ray Solar Flares

    Science.gov (United States)

    Kolarski, A.; Grubor, D.

    2015-12-01

    Comparative qualitative analysis of amplitude and phase delay variations was carried out along the trajectory of GQD/22.1 kHz and NAA/24.0 kHz VLF signal traces, propagating from Skelton (UK) and Maine (USA) toward Belgrade, induced by four isolated solar X-ray flare events occurred during the period from September 2005 to December 2006. For monitoring, recording and for storage of VLF data at the Institute of Physics in Belgrade, Serbia, the AbsPAL system was used. For modeling purposes of propagating conditions along GQD and NAA signal propagation paths, LWPCv21 program code was used. Occurred solar flare events induced lower ionosphere electron density height profile changes, causing perturbations in VLF wave propagation within Earth-ionosphere waveguides. As analyzed VLF signals characterize by different propagation parameters along trajectories from their transmitters to the Belgrade receiver site, their propagation is affected in different ways for different solar flare events and also for the same solar flare events.

  5. Development of ground-based ELF/VLF receiver system in Wuhan and its first results

    Science.gov (United States)

    Chen, Yanping; Yang, Guobin; Ni, Binbin; Zhao, Zhengyu; Gu, Xudong; Zhou, Chen; Wang, Feng

    2016-05-01

    A new digital low-frequency receiver system has been developed at Wuhan University for sensitive reception of low-latitude broadband Extremely Low Frequency (ELF) and Very Low Frequency (VLF) radio waves originating from either natural or artificial sources. These low-frequency radio waves are useful for ionospheric remote sensing, geospace environment monitoring, and submarine communications. This paper presents the principle and architecture of the system framework, including magnetic loop antenna design, low-noise analog front-end and digital receiver with data sampling and transmission. A new structure is adopted in the analog front end to provide high common-mode rejection and to reduce interference. On basis of field programmable gate array (FPGA) device and Universal Serial Bus (USB) architecture, the digital receiver is developed along with time keeping and synchronization module. The validity and feasibility of the self-developed ground-based ELF/VLF receiver system is evaluated by first results of experimental data that show the temporal variation of broadband ELF/VLF wave spectral intensity in Wuhan (30.54 °N, 114.37 °E). In addition to the acquisition of VLF transmitter signals at various frequencies, tweek atmospherics are also clearly captured to occur at multiple modes up to n = 6.

  6. Observation of enhanced field emission properties of Au/TiO2 nanocomposite

    Science.gov (United States)

    Patil, Girish P.; Bagal, Vivekanand S.; Suryawanshi, Sachin R.; Late, Dattatray J.; More, Mahendra A.; Chavan, Padmakar G.

    2016-05-01

    Simple and low-cost method of thermal annealing was used to decorate Gold (Au) nanoparticles on aligned TiO2 nanotubes. The aligned TiO2 nanotubes were decorated by Au nanoparticles with an average diameter of 9, 18 and 28 nm (aligned TiO2 nanotubes referred as specimen A and TiO2 nanotubes decorated by Au nanoparticles with average diameter of 9, 18 and 28 nm are referred as specimen B, C and D, respectively). The detailed characterization such as structural, morphological and elemental analysis of TiO2 and Au/TiO2 nanocomposite have been carried out using X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and Raman spectroscopy. Furthermore, the meticulous comparative field emission characteristics of the aligned TiO2 nanotubes and Au/TiO2 nanocomposite have been performed. The turn-on field defined for the current density of 10 μA/cm2 has been found to be 3.9, 2.8, 3.2 and 3.7 V/μm for specimen A, B, C and D, respectively. The observed low turn-on field of specimen B has been found to be superior than the other semiconducting nanocomposites reported in the literature. The emission current stability over a period of 3 h is found to be better for all the specimens. To the best of our knowledge, a systematic field emission study of Au/TiO2 nanocomposite has not been explored. The observed superior field emission study of Au/TiO2 nanocomposite indicates their possible use in micro/nanoelectronic devices.

  7. The benefits of China's efforts on gaseous pollutant control indicated by the bottom-up emissions and satellite observation

    Science.gov (United States)

    Xia, Y.; Zhao, Y.

    2015-12-01

    To evaluate the effectiveness of national policies of air pollution control, the emissions of SO2, NOX, CO and CO2 in China are estimated with a bottom-up method from 2000 to 2014, and vertical column densities (VCD) from satellite observation are used to evaluate the inter-annual trends and spatial distribution of emissions and the temporal and spatial patterns of ambient levels of gaseous pollutants across the country. In particular, an additional emission case named STD case, which combines the most recent issued emission standards for specific industrial sources, is developed for 2012-2014. The inter-annual trends in emissions and VCDs match well except for SO2, and the revised emissions in STD case improve the comparison, implying the benefits of emission control for most recent years. Satellite retrieval error, underestimation of emission reduction and improved atmospheric oxidization caused the differences between emissions and VCDs trend of SO2. Coal-fired power plants play key roles in SO2 and NOX emission reduction. As suggested by VCD and emission inventory, the control of CO in 11th five year plan (FYP) period was more effective than that in the 12th FYP period, while the SO2 appeared opposite. As the new control target added in 12th FYP, NOX emissions have been clearly decreased 4.3 Mt from 2011 to 2014, in contrast to the fast growth before 2011. The inter-annual trends in NO2 VCDs has the poorest correlation with vehicle ownership (R=0.796), due to the staged emission standard of vehicles. In developed regions, transportation has become the main pollutants emission source and we prove this by comparing VCDs of NO2 to VCDs of SO2. Moreover, air quality in mega cities has been evaluated based on satellite observation and emissions, and results indicate that Beijing suffered heavily from the emissions from Hebei and Tianjin, while the local emissions tend to dominate in Shanghai.

  8. First Observation of Planet-Induced X-ray Emission: The System HD 179949

    OpenAIRE

    Saar, S. H.; Cuntz, M.; Kashyap, V. L.; Hall, J. C.

    2007-01-01

    We present the first observation of planet-induced stellar X-ray activity, identified for the HD 179949 system, using Chandra / ACIS-S. The HD 179949 system consists of a close-in giant planet orbiting an F9V star. Previous ground-based observations already showed enhancements in Ca II K in phase with the planetary orbit. We find an ~30% increase in the X-ray flux over quiescent levels coincident with the phase of the Ca II enhancements. There is also a trend for the emission to be hotter at ...

  9. A climatology of dust emission events from northern Africa using long-term surface observations

    Science.gov (United States)

    Cowie, S. M.; Knippertz, P.; Marsham, J. H.

    2014-08-01

    Long-term (1984-2012) surface observations from 70 stations in the Sahara and Sahel are used to explore the diurnal, seasonal and geographical variations in dust emission events and thresholds. The frequency of dust emission (FDE) is calculated using the present weather codes of SYNOP reports. Thresholds are estimated as the wind speed for which there is a 50% probability of dust emission and are then used to calculate strong wind frequency (SWF) and dust uplift potential (DUP), where the latter is an estimate of the dust-generating power of winds. Stations are grouped into six coherent geographical areas for more in-depth analysis. FDE is highest at stations in Sudan and overall peaks in spring north of 23° N. South of this, where stations are directly influenced by the summer monsoon, the annual cycle in FDE is more variable. Thresholds are highest in northern Algeria, lowest in the latitude band 16-21° N and have greatest seasonal variations in the Sahel. Spatial variability in thresholds partly explain spatial variability in frequency of dust emission events on an annual basis. However, seasonal variations in thresholds for the six grouped areas are not the main control on seasonal variations in FDE. This is demonstrated by highly correlated seasonal cycles of FDE and SWF which are not significantly changed by using a fixed, or seasonally varying, threshold. The likely meteorological mechanisms generating these patterns such as low-level jets and haboobs are discussed.

  10. Electromagnetic emissions and fine structures observed near main ionospheric trough during geomagnetic storms and their interactions

    Science.gov (United States)

    Przepiórka, Dorota; Marek, Michał; Matyjasiak, Barbara; Rothkaehl, Hanna

    2016-04-01

    Geomagnetic conditions triggered by the solar activity affect the ionosphere, its fine and global structures. Very intense magnetic storms substantially change the plasma density, concentration and circulation. Especially sensitive region is located near auroral oval, where most energy is deposited during geomagnetic storms. In this region and just below it, where the main ionospheric trough is located, we observe enhanced electromagnetic emissions in different frequency ranges. In particular the AKR-like (Auroral Kilometric Radiation) emissions are seen at frequencies of the order of hundreds of kHz in the ionosphere, just below the auroral oval. Analyzing spectrograms from DEMETER mission and comparing them with electron density measurements from DEMETER, we found that AKR-like emissions are seen near poleward wall of the main ionospheric trough, during geomagnetic storms. Main ionospheric trough is known as a turbulent region which properties change as the geomagnetic storm evolves. This work is an attempt to determine how the presence of the different emissions affect main ionospheric trough parameters such as location, width and depth. Data used in this study come from DEMETER and RELEC missions. This work was partly supported by NCN grant Rezonans 2012/07/B/ST9/04414.

  11. Observations and numerical studies of gamma-ray emission in colliding-wind binaries

    International Nuclear Information System (INIS)

    Massive stars in binary systems have long been regarded as potential sources of high-energy gamma rays. The emission is thought to arise in the region where the stellar winds collide, thereby producing accelerated particles which subsequently emit gamma rays.This scenario is supported by observations with the Fermi Large Area Telescope presented in this thesis. To address the underlying emission mechanisms in a quantitative way, numerical simulations that incorporate hydrodynamics, the acceleration of charged particles as well as the subsequent gamma-ray emission were found to be needed.This thesis presents the analysis of a high-energy gamma-ray source and its identification with the particle-accelerating colliding-wind binary system Eta Carinae. In order to go beyond the present understanding of such objects, this work provides detailed description of a new 3D-hydrodynamical model, which incorporates the line-driven acceleration of the winds, gravity, orbital motion and the radiative cooling of the shocked plasma, as well as the diffusive shock acceleration of charged particles in the wind collision region. In a subsequent step we simulate and study the resulting gamma-ray emission via relativistic bremsstrahlung, anisotropic inverse Compton radiation and neutral pion decay. (author)

  12. Using Swift observations of prompt and afterglow emission to classify GRBs

    CERN Document Server

    O'Brien, P T

    2007-01-01

    We present an analysis of early BAT and XRT data for 107 gamma--ray bursts (GRBs) observed by the Swift satellite. We use these data to examine the behaviour of the X-ray light curve and propose a classification scheme for GRBs based on this behaviour. As found for previous smaller samples, the earliest X-ray light curve can be well described by an exponential which relaxes into a power law, often with flares superimposed. The later emission is well fit using a similar functional form and we find that these two functions provide a good description of the entire X-ray light curve. For the prompt emission, the transition time between the exponential and the power law gives a well-defined timescale, T_p, for the burst duration. We use T_p, the spectral index of the prompt emission, beta_p, and the prompt power law decay index, alpha_p to define four classes of burst: short, slow, fast and soft. Bursts with slowly declining emission have spectral and temporal properties similar to the short bursts despite having ...

  13. Modeling infrared thermal emissions on Mars during dust storm of MY28: PFS/MEX observation

    Science.gov (United States)

    Haider, Syed A.; Kasaba, Yasumasa; Giuranna, Marco; Kuroda, Takeshi; Jethwa, Masoom P.

    2016-07-01

    We have analysed thermal emission spectra obtained from Planetary Fourier Spectrometer (PFS) onboard Mars Express (MEX) for Martian Year (MY) 28 in presence and absence of dust storm at low latitude. A radiative transfer model for dusty atmosphere of Mars is developed to estimate the thermal emission spectra at latitude range 0-10oS, 10-20oS and 20-30oS. These calculations are made at Ls=240o, 280o, 300o, and 320o between wave numbers 250-1400 cm-1. We have also retrieved brightness temperatures from thermal emission spectra by inverting the Planck function. The model reproduces the observed features at wave numbers 600-750 cm-1 and 900-1200 cm-1 due to absorptions by CO2 and dust respectively. In presence of dust storm thermal emission spectra and brightness temperature are reduced by a factor of ~ 2 between wave numbers 900-1200 cm-1. The altitude profiles of dust concentration are also estimated for different aerosol particles of sizes 0.2 to 3 micron. The best fit to the PFS measurements is obtained in presence of aerosol particle of size 0.2 micron.

  14. FERMI OBSERVATIONS OF HIGH-ENERGY GAMMA-RAY EMISSION FROM GRB 090217A

    International Nuclear Information System (INIS)

    The Fermi observatory is advancing our knowledge of gamma-ray bursts (GRBs) through pioneering observations at high energies, covering more than seven decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here, we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9σ. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to ∼1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.

  15. Fluorescent H_2 Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

    CERN Document Server

    Le, Huynh Anh N; Kaplan, Kyle F; Mace, Gregory N; Lee, Sungho; Pavel, Michael D; Jeong, Ueejeong; Oh, Heeyoung; Lee, Hye-In; Chun, Moo-Young; Yuk, In-Soo; Pyo, Tae-Soo; Hwang, Narae; Kim, Kang-Min; Park, Chan; Oh, Jae Sok; Yu, Young S; Park, Byeong-Gon; Minh, Young Chol; Jaffe, Daniel T

    2016-01-01

    We have analyzed the temperature, velocity and density of H_2 gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ~ 45,000 with the Immersion GRating INfrared Spectrograph (IGRINS), we detected 70 H_2 emission lines within the 1" x 15" slit. The diagnostic ratios of 2-1 S(1)/1-0 S(1) are 0.39-0.54. In addition, the estimated ortho-to-para ratios (OPR) are 1.57-1.62, indicating that the H_2 transitions in the observed regions are mostly from UV fluorescence. Gradients in the temperature, velocity, and OPR of the observed areas imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H_2 from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rota...

  16. An Observational Method for Verifying Trends in Urban CO2 Emissions Using Continuous Measurements and High Resolution Meteorology (Invited)

    Science.gov (United States)

    Wofsy, S. C.; McKain, K.; Eluszkiewicz, J.; Nehrkorn, T.; Pataki, D. E.; Ehleringer, J.

    2010-12-01

    Nations of the world are attempting to reach international and domestic agreements to limit greenhouse gas emissions. Participants will demonstrate their compliance to such commitments with self-reported emissions estimates based largely on measurements of behavior and generalized conversion factors. Atmospheric observations are the only source of information that will allow reported emissions to be independently and directly verified. Testing of observation-based verification methods is required to establish current capabilities, identify and prioritize areas for improvement, and ensure that policy goals are verifiable. In particular, observations made in major source regions, such as cities, could provide a great deal of information about trends and patterns in anthropogenic emissions with relatively modest investment. This study presents an inaugural effort to estimate carbon dioxide (CO2) emissions from a city using atmospheric measurements. We have developed an observation-modeling framework to track changes in urban emissions, which, in addition to the observations, utilizes an atmospheric transport model and a prior emissions estimates. We have conducted a pilot study of the method using an existing longterm dataset of CO2 observations from Salt Lake City, Utah. Model-simulated CO2 concentrations track diurnal and synoptic patterns in observations reasonably well, although areas for improvement are evident. The modeling framework tends to underestimate observed CO2 enhancements, especially at night, which could be due to underestimated emissions and/or to excessive ventilation in the modeled meteorology. Despite some deficiencies, modeled and observed CO2 values are quantitatively and systematically related and application of a scaling factor to previously estimated emissions improves the match between modeled and observed values. This pilot-study presents a generalized, albeit provisional, method for using urban atmospheric greenhouse gas observations to

  17. DEMETER observations of bursty MF emissions and their relation to ground-level auroral MF burst

    Science.gov (United States)

    Broughton, M. C.; LaBelle, J.; Parrot, M.

    2014-12-01

    A survey of medium frequency (MF) electric field data from selected orbits of the Detection of Electro-Magnetic Emissions Transmitted from Earthquakes (DEMETER) spacecraft reveals 68 examples of a new type of bursty MF emissions occurring at high latitudes associated with auroral phenomena. These resemble auroral MF burst, a natural radio emission observed at ground level near local substorm onsets. Similar to MF burst, the bursty MF waves observed by DEMETER have broadband, impulsive frequency structure covering 1.5-3.0 MHz, amplitudes of 50-100 μV/m, an overall occurrence rate of ˜0.76% with higher occurrence during active times, and strong correlation with auroral hiss. The magnetic local time distribution of the MF waves observed by DEMETER shows peak occurrence rate near 18 MLT, somewhat earlier than the equivalent peak in the occurrence rate of ground level MF burst, though propagation effects and differences in the latitudes sampled by the two techniques may explain this discrepancy. Analysis of solar wind and SuperMAG data suggests that while the bursty MF waves observed by DEMETER are associated with enhanced auroral activity, their coincidence with substorm onset may not be as exact as that of ground level MF burst. One conjunction occurs in which MF burst is observed at Churchill, Manitoba, within 8 min of MF emissions detected by DEMETER on field lines approximately 1000 km southeast of Churchill. These observations may plausibly be associated with the same auroral event detected by ground level magnetometers at several Canadian observatories. Although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground level MF burst. Hence, theories of MF burst generation in the ionosphere, such as beam-generated Langmuir waves excited over a range of altitudes or strong Langmuir turbulence generating a range of frequencies within a narrow altitude range, need to be revisited to

  18. Time-monitoring Observations of Br$\\gamma$ Emission from Young Stars

    CERN Document Server

    Eisner, J A; Rieke, M J; Flaherty, K M; Stone, Jordan M; Arnold, T J; Cortes, S R; Cox, E; Hawkins, C; Cole, A; Zajac, S; Rudolph, A L

    2014-01-01

    We present multiple epochs of near-IR spectroscopy for a sample of 25 young stars, including T Tauri, Herbig Ae/Be, and FU Ori objects. Using the FSPEC instrument on the Bok 90-inch telescope, we obtained K-band spectra of the BrGamma transition of hydrogen, with a resolution of ~3500. Epochs were taken over a span of >1 year, sampling time-spacings of roughly one day, one month, and one year. The majority of our targets show BrGamma emission, and in some cases these are the first published detections. Time-variability is seen in approximately half of the targets showing BrGamma emission. We compare the observed variability with expectations for rotationally-modulated accretion onto the central stars and time-variable continuum emission or extinction from matter in the inner disk. Our observations are not entirely consistent with models of rotationally-modulated magnetospheric accretion. Further monitoring, over a larger number of epochs, will facilitate more quantitative constraints on variability timescales...

  19. Observation of phase transitions in hydrogenated Yttrium films via normalized infrared emissivity

    Energy Technology Data Exchange (ETDEWEB)

    Hattrick-Simpers, Jason R., E-mail: jhsimper@nist.go [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Wang Ke [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Cao Lei [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742 (United States); Chiu Chun [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Heilweil, Edwin [Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Downing, Robert Gregory [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Bendersky, Leonid A. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)

    2010-02-04

    The direct observation of a sequence of phase transitions during hydrogenation of Y thin films has been realized through the use of in situ isothermal infrared emissivity measurements. The formation of different phases, alpha-Y(H), YH{sub 2} and YH{sub 3}, has been identified based on the observation of changes in the slope of the normalized IR emissivity vs. time curve during hydrogen loading. The presence of alpha-Y(H), YH{sub 2} and YH{sub 3} was confirmed by ex situ X-ray diffraction, transmission electron microscopy, and prompt gamma activation analysis. Transmission electron microscopy further demonstrated epitaxial orientation relationships between the Al{sub 2}O{sub 3} substrate, Ti buffer layer, the as-deposited Y film, as well as its hydrides. These results clearly demonstrate the power of IR emissivity imaging to monitor, in real time, the formation of hydride phases of both metallic and insulating character near the surface of a thin-film sample.

  20. UV and EUV Emissions at the Flare Foot-points Observed by AIA

    CERN Document Server

    Qiu, Jiong; Longcope, Dana W; James,; Klimchuk, A; Wen-Juan,; Liu,

    2013-01-01

    A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a two-phase evolution pattern of UV 1600\\AA\\ emission at the feet of these loops: a rapid pulse lasting for a few seconds to a few minutes, followed by a gradual decay on timescales of a few tens of minutes. Multiple band EUV observations by AIA further reveal very similar signatures. These two phases represent different but related signatures of an impulsive energy release in the corona. The rapid pulse is an immediate response of the lower atmosphere to an intense thermal conduction flux resulting from the sudden heating of the corona to high temperatures (we rule out energetic particles due to a lack of significant hard X-ray emission). The gradual phase is associated with the cooling of hot plasma that has been evaporated into the corona. The observed footpoint emission is again powered by thermal conduction (and enthalpy), but now during a period when appr...

  1. Imaging Observations of Quasi-Periodic Pulsatory Non-Thermal Emission in Ribbon Solar Flares

    CERN Document Server

    Zimovets, I V

    2008-01-01

    Using RHESSI and some auxiliary observations we examine possible connections between spatial and temporal morphology of the sources of non-thermal hard X-ray (HXR) emission which revealed minute quasi-periodic pulsations (QPPs) during the two-ribbon flares on 2003 May 29 and 2005 January 19. Microwave emission also reveals the same quasi-periodicity. The sources of non-thermal HXR emission are situated mainly inside the footpoints of the flare arcade loops observed by the TRACE and SOHO instruments. At least one of the sources moves systematically both during the QPP-phase and after it in each flare that allows to examine the sources velocities and the energy release rate via the process of magnetic reconnection. The sources move predominantly parallel to the magnetic inversion line or the appropriate flare ribbon during the QPP-phase whereas the movement slightly changes to more perpendicular regime after the QPPs. Each QPP is emitted from its own position. It is also seen that the velocity and the energy re...

  2. OT1_rpaladin_1: PACS and SPIRE observations of Galactic anomalous emission sources.

    Science.gov (United States)

    Paladini, R.

    2010-07-01

    Despite the increasing evidence that the anomalous emission is a new physical mechanism acting in the diffuse interstellar medium, the nature and distribution of this component remains elusive. The currently most favored models attribute the observed microwave excess to rotating very small dust grains (PAHs and VSGs). Nonetheless, the infrared properties of the sources which, to date, are known to exhibit this type of emission are very poorly known mostly due to the limited angular resolution and frequency coverage of DIRBE and IRAS data. We propose HERSCHEL PACS and SPIRE mapping of three Galactic anomalous emission sources (LDN 1780, LDN 675 and LDN 1111). This data, when combined with ancillary NIR and mid-IR data of comparable angular resolution (mainly from Spitzer), and coupled with available dust models, will allow to set tight constraints on the radiation field in the emitting sources as well as in their immediate surroundings. Such constraints, in turn, will allow to estimate the abundances of PAHs, VSGs and BGs, hence to shed light on the potential link between these dust populations and the observed microwave excess.

  3. Volcanic carbon dioxide emissions: observation strategies using GOSAT FTS SWIR data

    Science.gov (United States)

    Schwandner, F. M.; Carn, S. A.; Head, E. M.; Newhall, C. G.

    2010-12-01

    About one tenth of the Earth’s human population lives under direct threat of volcanic hazards. Being able to provide sufficiently early and scientifically sound warning is a key to volcanic hazard mitigation. Forecasting volcanic eruptions is based on epidemiological and probabilistic analyses of monitoring data. In times of crisis, the extremely short time for decisions, validation and response leads to a quest for the earliest possible indicators of unrest. Among the first potential signals of ascending magma is the exsolution of volatiles contained in magma induced by dynamic depressurization, crystallization, and temperature variations. The three most abundant gas species in these emissions are usually water (H2O), Carbon Dioxide (CO2), and Sulfur Dioxide (SO2). SO2 monitoring methods are widespread, using COSPEC, mini-DOAS, SO2 cameras, and space-borne SO2 data. However, since H2O and SO2 are frequently scrubbed out by near-surface processes, they may be obscured unless the magma is already near the surface. SO2 is most useful for volcanoes that erupt frequently and have a dry chimney for easy gas escape. CO2 is more difficult to measure remotely than SO2} because the atmospheric background concentration of CO2 is so much higher than for SO2. Nevertheless, CO2 is important because it is the first gas to exsolve from magma (together with helium), and it is minimally affected by scrubbing and other near-surface processes. CO2 monitoring has been attempted by ground-based CO2 flux monitoring and by crater plume CO2 measurements using ground-based open-path FTIR and airborne closed-path IR measurements. In this study, we assess data acquired by JAXA’s GOSAT satellite for detection and eventually quantification of volcanic CO2 emissions. Two strategies are being investigated: (1) standard scheduled observation points, (2) repeat targeted observation requests of known centers of strong volcanic emissions. With a field of view of 10 km, GOSAT has the potential to

  4. Location accuracy of VLF World-Wide Lightning Location (WWLL network: Post-algorithm upgrade

    Directory of Open Access Journals (Sweden)

    C. J. Rodger

    2005-02-01

    Full Text Available An experimental VLF World-Wide Lightning Location (WWLL network has been developed through collaborations with research institutions across the globe. The aim of the WWLL is to provide global real-time locations of lightning discharges, with >50% CG flash detection efficiency and mean location accuracy of <10km. While these goals are essentially arbitrary, they do define a point where the WWLL network development can be judged a success, providing a breakpoint for a more stable operational mode. The current network includes 18 stations which cover much of the globe. As part of the initial testing phase of the WWLL the network operated in a simple mode, sending the station trigger times into a central processing point rather than making use of the sferic Time of Group Arrival (TOGA. In this paper the location accuracy of the post-TOGA algorithm WWLL network (after 1 August 2003 is characterised, providing estimates of the globally varying location accuracy for this network configuration which range over 1.9-19km, with the global median being 2.9km, and the global mean 3.4km. The introduction of the TOGA algorithm has significantly improved the location accuracies.

    The detection efficiency of the WWLL is also considered. In the selected region the WWLL detected ~13% of the total lightning, suggesting a ~26% CG detection efficiency and a ~10% IC detection efficiency. Based on a comparison between all WWLL good lightning locations in February-April 2004, and the activity levels expected from satellite observations we estimate that the WWLL is currently detecting ~2% of the global total lightning, providing good locations for ~5% of global CG activity. The existing WWLL network is capable of providing real-time positions of global thunderstorm locations in its current form.

  5. Searching the Nearest Stars for Exoplanetary Radio Emission: VLA and LOFAR Observations

    Science.gov (United States)

    Knapp, Mary; Winterhalter, Daniel; Lazio, Joseph

    2016-10-01

    Six of the eight solar system planets and one moon (Ganymede) exhibit present-day dynamo magnetic fields. To date, however, there are no conclusive detections of exoplanetary magnetic fields. Low frequency radio emission via the cyclotron maser instability (CMI) from interactions between a planet and the solar/stellar wind is the most direct means of detecting and characterizing planetary/exoplanetary magnetic fields. We have undertaken a survey of the very nearest stars in low frequency radio (30 MHz - 4 GHz) in order to search for yet-undiscovered planets. The closest stars are chosen in order to reduce the attenuation of the magnetospheric radio signal by distance dilution, thereby increasing the chances of making a detection if a planet with a strong magnetic field is present. The VLA telescope (P-band: 230-470 MHz, L-band: 1-2 GHz, S-band: 2-4 GHz) and LOFAR telescope (LBA: 30-75 MHz) have been used to conduct this survey.This work focuses on VLA and LOFAR observations of an M-dwarf binary system: GJ 725. We present upper limits on radio flux as a function of frequency. Since the peak emission frequency of CMI-type emission is the local plasma frequency in the emission region, the peak frequency of planetary radio emission is a direct proxy for the magnetic field strength of the planet. Our spectral irradiance upper limits therefore represent upper limits on the magnetic field strengths of any planets in the GJ 725 system.Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  6. Search for extended gamma ray emission in Markarian 421 using VERITAS observations

    CERN Document Server

    ,

    2014-01-01

    Very high energy (VHE: >100 GeV) gamma rays coming from AGN can pair-produce on the intergalactic background light generating an electromagnetic cascade. If the Intergalactic Magnetic Field (IGMF) is sufficiently strong, this cascade may result in an extended isotropic emission of photons around the source, or halo. Using VERITAS observations of the blazar Markarian 421, we search for extended emission by comparing the source angular distribution (${\\theta}^2$) from a quiescent period with one coming from a flare period, which can be considered as halo-free. ${\\chi}^2$ test showed no significant statistical differences between the samples, suggesting that the effect is either non-existent or too weak to be detected. We calculated upper limits for the extended flux considering different angle ranges, the most stringent being <8% of the Crab Nebulae flux (C.U), in the range $0\\deg \\leq {\\theta} \\leq 0.1\\deg$ .

  7. Observation of Nonthermal Emission from the Supernova Remnant IC443 with RXTE

    Science.gov (United States)

    Sturner, S. J.; Keohane, J. W.; Reimer, O.

    2002-01-01

    In this paper we present analysis of X-ray spectra from the supernova remnant IC443 obtained using the PCA on RXTE. The spectra in the 3 - 20 keV band are well fit by a two-component model consisting of thermal and nonthermal components. We compare these results with recent results of other X-ray missions and discuss the need for a cut-off in the nonthermal spectrum. Recent Chandra and XMM-Newton observations suggest that much of the nonthermal emission from IC443 can be attributed to a pulsar wind nebula. We present the results of our search for periodic emission in the RXTE PCA data. We then discuss the origin o f the nonthermal component and its possible association with the unidentified EGRET source.

  8. Energetic Neutral Atom Emissions From Venus: VEX Observations and Theoretical Modeling

    Science.gov (United States)

    Fok, M.-C.; Galli, A.; Tanaka, T.; Moore, T. E.; Wurz, P.; Holmstrom, M.

    2007-01-01

    Venus has almost no intrinsic magnetic field to shield itself from its surrounding environment. The solar wind thus directly interacts with the planetary ionosphere and atmosphere. One of the by-products of this close encounter is the production of energetic neutral atom (ENA) emissions. Theoretical studies have shown that significant amount of ENAs are emanated from the planet. The launch of the Venus Express (VEX) in 2005 provided the first light ever of the Venus ENA emissions. The observed ENA flux level and structure are in pretty good agreement with the theoretical studies. In this paper, we present VEX ENA data and the comparison with numerical simulations. We seek to understand the solar wind interaction with the planet and the impacts on its atmospheres.

  9. In situ Observation of Dark Current Emission in a High Gradient RF Photocathode Gun

    CERN Document Server

    Shao, Jiahang; Baryshev, Sergey V; Chen, Huaibi; Conde, Manoel; Gai, Wei; Ha, Gwanghui; Jing, Chunguang; Shi, Jiaru; Wang, Faya; Wisniewski, Eric

    2016-01-01

    Undesirable electron field emission (a.k.a. dark current) in high gradient RF photocathode guns deteriorates the quality of photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (~100 um) dark current imaging experiment has been performed in an L-band photocathode gun operating at ~100 MV/m of surface gradient. Dark current from the cathode has been observed to be dominated by several separated strong emitters. The field enhancement factor, beta, of selected regions on the cathode has been measured. The post scanning electron microscopy (SEM) and white light interferometer (WLI) surface examinations reveal the origins of ~75% strong emitters overlap with the spots where rf breakdown have occurred.

  10. Submillimetre continuum emission from Class 0 sources: Theory, Observations, and Modelling

    CERN Document Server

    Rengel, M; Fröbrich, D; Wolf, S; Eislöffel, J; Rengel, Miriam; Hodapp, Klaus; Froebrich, Dirk; Wolf, Sebastian; Eisloeffel, Jochen

    2004-01-01

    We report on a study of the thermal dust emission of the circumstellar envelopes of a sample of Class 0 sources. The physical structure (geometry, radial intensity profile, spatial temperature and spectral energy distribution) and properties (mass, size, bolometric luminosity (L_bol) and temperature (T_ bol), and age) of Class 0 sources are derived here in an evolutionary context. This is done by combining SCUBA imaging at 450 and 850 microm of the thermal dust emission of envelopes of Class 0 sources in the Perseus and Orion molecular cloud complexes with a model of the envelope, with the implementation of techniques like the blackbody fitting and radiative transfer calculations of dusty envelopes, and with the Smith evolutionary model for protostars. The modelling results obtained here confirm the validity of a simple spherical symmetric model envelope, and the assumptions about density and dust distributions following the standard envelope model. The spherically model reproduces reasonably well the observe...

  11. In-situ stressing of rock: Observation of infrared emission prior to failure

    Science.gov (United States)

    Dahlgren, R.; Freund, F. T.; Momayez, M.; Bleier, T. E.; Dunson, C.; Joggerst, P.; Jones, K.; Wang, S.

    2009-12-01

    non-thermal IR emission is observed within minutes of the rock failure.

  12. Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations

    Directory of Open Access Journals (Sweden)

    L. Meng

    2011-06-01

    Full Text Available Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources is still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011 into the Community Land Model 4.0 (CLM4CN in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model because there are large differences between simulated fractional inundation and satellite observations. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr−1, and rice paddy emissions in the year 2000 were 42 Tg CH4 yr−1. Tropical wetlands contributed 201 Tg CH4 yr−1, or 78 % of the global wetland flux. Northern latitude (>50 N systems contributed 12 Tg CH4 yr−1. We expect this latter number may be an underestimate due to the low high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4. Sensitivity analysis showed a large range (150–346 Tg CH4 yr−1 in

  13. HST WFC3 Early Release Science: Emission-Line Galaxies from IR Grism Observations

    Science.gov (United States)

    Straughn, A. N.; Kuntschner, H.; Kuemmel, M.; Walsh, J. R.; Cohen, S. H.; Gardner, J. P.; Windhorst, R. A.; O'Connell, R. W.; Pirzkal, N.; Meurer, G.; McCarthy, P. J.; Hathi, N. P.; Malhotra, S.; Rhoads, J.; Balick, B.; Bond, H. E.; Calzetti, D.; Disney, M. J.; Dopita, M. A.; Frogel, J. A.; Hall, D. N. B.; Holtzman, J. A.; Kimlbe, R. A.; Trauger, J. T.; Young, E. T.

    2010-01-01

    We present grism spectra of emission line galaxies (ELGs) from 0.6-1.6 microns from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). These new infrared grism data augment previous optical Advanced Camera for Surveys G800L (0.6-0.95 micron) grism data in GOODS South, extending the wavelength coverage well past the G800L red cutoff. The ERS grism field was observed at a depth of 2 orbits per grism, yielding spectra of hundreds of faint objects, a subset of which are presented here. ELGs are studied via the Ha, [O III ], and [OII] emission lines detected in the redshift ranges 0.2 less than or equal to z less than or equal to 1.6, 1.2 less than or equal to z less than or equal to 2.4 and 2.0 less than or equal to z less than or equal to 3.6 respectively in the G102 (0.8-1.1 microns; R approximately 210) and C141 (1.1-1.6 microns; R approximately 130) grisms. The higher spectral resolution afforded by the WFC3 grisms also reveals emission lines not detectable with the G800L grism (e.g., [S II] and [S III] lines). From these relatively shallow observations, line luminosities, star formation rates, and grism spectroscopic redshifts are determined for a total of 25 ELGs to M(sub AB)(F098M) approximately 25 mag. The faintest source in our sample with a strong but unidentified emission line--is MAB(F098M)=26.9 mag. We also detect the expected trend of lower specific star formation rates for the highest mass galaxies in the sample, indicative of downsizing and discovered previously from large surveys. These results demonstrate the remarkable efficiency and capability of the WFC3 NIR grisms for measuring galaxy properties to faint magnitudes.

  14. The development of the International Network for Frontier Research on Earthquake Precursors (INFREP) by designing new analysing software and by setting up new recording locations of radio VLF/LF signals in Romania

    Science.gov (United States)

    Moldovan, Iren-Adelina; Petruta Constantin, Angela; Emilian Toader, Victorin; Toma-Danila, Dragos; Biagi, Pier Francesco; Maggipinto, Tommaso; Dolea, Paul; Septimiu Moldovan, Adrian

    2014-05-01

    Based on scientific evidences supporting the causality between earthquake preparatory stages, space weather and solar activity and different types of electromagnetic (EM) disturbances together with the benefit of having full access at ground and space based EM data, INFREP proposes a complex and cross correlated investigation of phenomena that occur in the coupled system Lithosphere-Atmosphere-Ionsophere in order to identify possible causes responsible for anomalous effects observed in the propagation characteristics of radio waves, especially at low (LF) and very low frequency (VLF). INFREP, a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers, was put into operation in Europe in 2009, having as principal goal, the study of disturbances produced by the earthquakes on the propagation properties of these signals. The Romanian NIEP VLF / LF monitoring system consisting in a radio receiver -made by Elettronika S.R.L. (Italy) and provided by the Bari University- and the infrastructure that is necessary to record and transmit the collected data, is a part of the international initiative INFREP. The NIEP VLF / LF receiver installed in Romania was put into operation in February 2009 in Bucharest and relocated to the Black-Sea shore (Dobruja Seismologic Observatory) in December 2009. The first development of the Romanian EM monitoring system was needed because after changing the receiving site from Bucharest to Eforie we obtained unsatisfactory monitoring data, characterized by large fluctuations of the received signals' intensities. Trying to understand this behavior has led to the conclusion that the electric component of the electromagnetic field was possibly influenced by the local conditions. Starting from this observation we have run some tests and changed the vertical antenna with a loop-type antenna that is more appropriate in highly electric-field polluted environments. Since the amount of recorded data is huge, for streamlining the research process

  15. Response of low latitude D-region ionosphere to the Total Solar Eclipse of 22 July 2009, deduced from ELF/VLF analysis

    Science.gov (United States)

    Singh, A. K.; Singh, R.; Singh, A. K.

    2011-12-01

    Response of the D-region of the ionosphere to the total solar eclipse of 22 July 2009 at low latitude, Varanasi (geomagnetic lat = 140 55'N, longitude = 1540 E, dip. angle = 37.30) was investigated using ELF/VLF radio signal. The solar eclipse started at 05:30:04.4 hrs IST and lasted up to 07:27 hrs IST with totally from 6.25 IST to 6.27 IST.The changes in D-region ionospheric VLF reflection heights and electron density during eclipse have been estimated from tweek analysis. The reflection height increased from ~90 km from the first occurrence of tweek to about 93-94 km at the totality and then decreased to ~89 km at the end of the eclipse. The reflection heights are lower by 2-3 km as compared to the usual nighttime tweek reflection heights. The electron density is found to vary between 25-27 cm-3 at the reflection heights. The significant increase in tweek reflection height of about 15 km during the eclipse as compared to the daytime (morning) reflection heights of ~ 78 km is observed. Observations suggest that about 30-40% obscuration of solar disc can lead to the tweeks occurrence which otherwise occur only in the nighttime. A significant increase of 3dB in the strength of the amplitude of VLF signal is observed around the time of TSE as compared to a control day. These low latitude ionospheric perturbations on the eclipse day are discussed and compared with other normal days. During a solar eclipse, the decrease in solar flux due to moon's shadow causes sudden change in the D-region physical and chemical processes. During the totality due to blocking of Lyman-α 1215Å (major D-region ionizing radiation) by moon's umbral shadow, the electron density decreases drastically towards the nighttime values [Smith, 1972]. During the TSE, there was no production of ionization in the ionosphere and the ions and electrons in the lowest part of it recombined at a rapid rate resulting a depletion in the electron density in the 'D' region of the Ionosphere and hence an

  16. Probing geomagnetic storm-driven magnetosphere-ionosphere dynamics in D-region ionosphere using VLF signal propagation characteristics

    Science.gov (United States)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar; Ogunmodimu, Olugbenga

    2016-07-01

    When propagating in the Earth-ionosphere waveguide, the amplitude and phase of VLF/LF radio signals are sensitive to changes in the electrical conductivity of the lower ionosphere. This characteristic makes it useful in studying sudden ionospheric disturbances, especially those related to prompt X-ray flux output from solar flares and gamma ray bursts (GRBs). However, strong geomagnetic disturbances and/or storm conditions are known to produce large and global ionospheric disturbances, which can significantly affect VLF radio propagation in the D region ionosphere. Diurnal VLF signature may also convey other important information, especially those related to geomagnetic disturbance/storm induced ionospheric changes. In this paper, using the data of three propagation paths (at latitudes 40-54º), we analyze in detail the trend of anomalies of VLF diurnal signal under varying solar and geomagnetic space environmental conditions to identify possible geomagnetic footprints on the D region ionosphere.

  17. Observations of nonmethane organic compounds during ARCTAS − Part 1: Biomass burning emissions and plume enhancements

    Directory of Open Access Journals (Sweden)

    A. Wisthaler

    2011-11-01

    Full Text Available Mixing ratios of a large number of nonmethane organic compounds (NMOCs were observed by the Trace Organic Gas Analyzer (TOGA on board the NASA DC-8 as part of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS field campaign. Many of these NMOCs were observed concurrently by one or both of two other NMOC measurement techniques on board the DC-8: proton-transfer-reaction mass spectrometry (PTR-MS and whole air canister sampling (WAS. A comparison of these measurements to the data from TOGA indicates good agreement for the majority of co-measured NMOCs. The ARCTAS study, which included both spring and summer deployments, provided opportunities to sample a large number of biomass burning (BB plumes with origins in Asia, California and central Canada, ranging from very recent emissions to plumes aged one week or more. For this analysis, BB smoke interceptions were grouped by flight, source region and, in some cases, time of day, generating 40 identified BB plumes for analysis. Normalized excess mixing ratios (NEMRs to CO were determined for each of the 40 plumes for up to 19 different NMOCs or NMOC groups. Although the majority of observed NEMRs for individual NMOCs or NMOC groups were in agreement with previously-reported values, the observed NEMRs to CO for ethanol, a rarely quantified gas-phase trace gas, ranged from values similar to those previously reported, to up to an order of magnitude greater. Notably, though variable between plumes, observed NEMRs of individual light alkanes are highly correlated within BB emissions, independent of estimated plume ages. BB emissions of oxygenated NMOC were also found to be often well-correlated. Using the NCAR Master Mechanism chemical box model initialized with concentrations based on two observed scenarios, fresh Canadian BB and fresh Californian BB, decreases are predicted for the low molecular weight carbonyls (i.e. formaldehyde, acetaldehyde, acetone and

  18. NuSTAR Observations of the Bullet Cluster: Constraints on Inverse Compton Emission

    CERN Document Server

    Wik, Daniel R; Molendi, Silvano; Madejski, Grzegorz; Harrison, Fiona A; Zoglauer, Andreas; Grefenstette, Brian W; Gastaldello, Fabio; Madsen, Kristin K; Westergaard, Niels J; Ferreira, Desiree D M; Kitaguchi, Takao; Pedersen, Kristian; Boggs, Steven E; Christensen, Finn E; Craig, William W; Hailey, Charles J; Stern, Daniel; Zhang, William W

    2014-01-01

    The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Background and contamination uncertainties present in the data of non-focusing observatories result in lower sensitivity to IC emission and a greater chance of false detection. We present 266ks NuSTAR observations of the Bullet cluster, detected from 3-30 keV. NuSTAR's unprecedented hard X-ray focusing capability largely eliminates confusion between diffuse IC and point sources; however, at the highest energies the background still dominates and must be well understood. To this end, we have developed a complete background model constructed of physically inspired components constrained by extragalactic survey field observations, the specific parameters of which are derived locally from data in non-source regions of target observations. Applying the background model to the Bullet cluster dat...

  19. BeppoSAX Observations of Synchrotron X-ray Emission from Radio Quasars

    CERN Document Server

    Padovani, P; Ghisellini, G; Giommi, P; Perlman, E

    2002-01-01

    We present new BeppoSAX LECS, MECS, and PDS observations of four flat-spectrum radio quasars (FSRQ) having effective spectral indices alpha_ro and alpha_ox typical of high-energy peaked BL Lacs. Our sources have X-ray-to-radio flux ratios on average ~ 70 times larger than ``classical'' FSRQ and lie at the extreme end of the FSRQ X-ray-to-radio flux ratio distribution. The collected data cover the energy range 0.1 - 10 keV (observer's frame), reaching ~ 100 keV for one object. The BeppoSAX band in one of our sources, RGB J1629+4008, is dominated by synchrotron emission peaking at ~ 2 x 10^16 Hz, as also shown by its steep (energy index alpha_x ~ 1.5) spectrum. This makes this object the FIRST known FSRQ whose X-ray emission is not due to inverse Compton radiation. Two other sources display a flat BeppoSAX spectrum (alpha_x ~ 0.7), with weak indications of steepening at low X-ray energies. The combination of BeppoSAX and ROSAT observations, (non-simultaneous) multifrequency data, and a synchrotron inverse Compt...

  20. The Binary Black Hole Model for Mrk 231 Cannot Explain the Observed Emission Lines

    CERN Document Server

    Leighly, Karen M; Gallagher, Sarah C; Lucy, Adrian B

    2016-01-01

    Mrk 231 is a nearby quasar with an unusually red continuum, generally explained as heavy reddening by dust (e.g., Leighly et al. 2014). Yan et al. 2015 proposed that Mrk 231 is a milli-parsec black-hole binary with little intrinsic reddening. The large-mass black hole experiences advection-dominated accretion, emitting little continuum, while the accretion disk of the small-mass black hole emits as an ordinary quasar, dominating the observed weak UV continuum and contributing all of the photoionizing flux. We demonstrate that this model is untenable for four reasons. (1) To produce the observed near-infrared emission lines, the equivalent widths would have to be ~100 times larger than typical values with respect to the photoionizing continuum, a situation that seems energetically unlikely. (2) We use the photoionization code Cloudy to demonstrate it is not possible to produce the HeI* emission line intensity for the observed HeI*/Pbeta flux ratios, even if the line-emitting gas intersects all of the photoioni...

  1. Correcting atmospheric effects in thermal ground observations for hyperspectral emissivity estimation

    Science.gov (United States)

    Timmermans, Joris; Buitrago, Maria

    2014-05-01

    Knowledge of Land surface temperature is of crucial importance in energy balance studies and environmental modeling. Accurate retrieval of land surface temperature (LST) demands detailed knowledge of the land surface emissivity. Measured radiation by remote sensing sensors to land surface temperature can only be performed using a-priori knowledge of the emissivity. Uncertainties in the retrieval of this emissivity can cause huge errors in LST estimations. The retrieval of emissivity (and LST) is per definition an underdetermined inversion, as only one observation is made while two variables are to be estimated. Several researches have therefore been performed on measuring emissivity, such as the normalized emissivity method, the temperature-emissivity separation (TES) using the minimum and maximum difference of emissivity and the use of vegetation indices. In each of these approaches atmospherically corrected radiance measurements by remote sensing sensors are correlated to ground measurements. Usually these ground measurements are performed with the ground equivalent of the remote sensing sensors; the CIMEL 312-2 has the same spectral bands as ASTER. This way parameterizations acquired this way are only usable for specific sensors and need to be redone for newer sensors. Recently hyperspectral thermal radiometers, such as the MIDAC, have been developed that can solve this problem. By using hyperspectral observations of emissivity, together with sensor simulators, ground measurements of different satellite sensor can be simulated. This facilitates the production of validation data for the different TES algorithms. However before such measurements can be performed extra steps of processing need to be performed. Atmospheric correction becomes more important in hyperspectral observations than for broadband observations, as energy levels measured per band is lower. As such the atmosphere has a relative larger contribution if bandwidths become smaller. The goal of this

  2. Evaluation of a plot-scale methane emission model using eddy covariance observations and footprint modelling

    Directory of Open Access Journals (Sweden)

    A. Budishchev

    2014-09-01

    Full Text Available Most plot-scale methane emission models – of which many have been developed in the recent past – are validated using data collected with the closed-chamber technique. This method, however, suffers from a low spatial representativeness and a poor temporal resolution. Also, during a chamber-flux measurement the air within a chamber is separated from the ambient atmosphere, which negates the influence of wind on emissions. Additionally, some methane models are validated by upscaling fluxes based on the area-weighted averages of modelled fluxes, and by comparing those to the eddy covariance (EC flux. This technique is rather inaccurate, as the area of upscaling might be different from the EC tower footprint, therefore introducing significant mismatch. In this study, we present an approach to validate plot-scale methane models with EC observations using the footprint-weighted average method. Our results show that the fluxes obtained by the footprint-weighted average method are of the same magnitude as the EC flux. More importantly, the temporal dynamics of the EC flux on a daily timescale are also captured (r2 = 0.7. In contrast, using the area-weighted average method yielded a low (r2 = 0.14 correlation with the EC measurements. This shows that the footprint-weighted average method is preferable when validating methane emission models with EC fluxes for areas with a heterogeneous and irregular vegetation pattern.

  3. SMA Observations of the Extended CO(6-5) Emission in the Starburst Galaxy NGC253

    CERN Document Server

    Krips, Melanie; Peck, Alison; Sakamoto, Kazushi; Neri, Roberto; Gurwell, Mark; Petitpas, Glen; Zhao, Jun-Hui

    2016-01-01

    We present observations of the $^{12}$CO(6-5) line and 686GHz continuum emission in NGC253 with the Submillimeter Array at an angular resolution of ~4arcsec. The $^{12}$CO(6-5) emission is clearly detected along the disk and follows the distribution of the lower $^{12}$CO line transitions with little variations of the line ratios in it. A large-velocity gradient analysis suggests a two-temperature model of the molecular gas in the disk, likely dominated by a combination of low-velocity shocks and the disk wide PDRs. Only marginal $^{12}$CO(6-5) emission is detected in the vicinity of the expanding shells at the eastern and western edges of the disk. While the eastern shell contains gas even warmer (T$_{\\rm kin}$>300~K) than the hot gas component (T$_{\\rm kin}$=300K) of the disk, the western shell is surrounded by gas much cooler (T$_{\\rm kin}$=60K) than the eastern shell but somewhat hotter than the cold gas component of the disk (for similar H$_2$ and CO column densities), indicative of different (or differe...

  4. Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA

    Science.gov (United States)

    Lewicki, Jennifer L.; Hilley, George E.

    2014-01-01

    One of the primary indicators of volcanic unrest at Mammoth Mountain is diffuse emission of magmatic CO2, which can effectively track this unrest if its variability in space and time and relationship to near-surface meteorological and hydrologic phenomena versus those occurring at depth beneath the mountain are understood. In June–October 2013, we conducted accumulation chamber soil CO2 flux surveys and made half-hourly CO2 flux measurements with automated eddy covariance and accumulation chamber (auto-chamber) instrumentation at the largest area of diffuse CO2 degassing on Mammoth Mountain (Horseshoe Lake tree kill; HLTK). Estimated CO2 emission rates for HLTK based on 20 June, 30 July, and 24–25 October soil CO2 flux surveys were 165, 172, and 231 t d− 1, respectively. The average (June–October) CO2 emission rate estimated for this area was 123 t d− 1 based on an inversion of 4527 eddy covariance CO2 flux measurements and corresponding modeled source weight functions. Average daily eddy covariance and auto-chamber CO2 fluxes consistently declined over the four-month observation time. Wavelet analysis of auto-chamber CO2 flux and environmental parameter time series was used to evaluate the periodicity of, and local correlation between these variables in time–frequency space. Overall, CO2 emissions at HLTK were highly dynamic, displaying short-term (hourly to weekly) temporal variability related to meteorological and hydrologic changes, as well as long-term (monthly to multi-year) variations related to migration of CO2-rich magmatic fluids beneath the volcano. Accumulation chamber soil CO2 flux surveys were also conducted in the four additional areas of diffuse CO2 degassing on Mammoth Mountain in July–August 2013. Summing CO2 emission rates for all five areas yielded a total for the mountain of 311 t d− 1, which may suggest that emissions returned to 1998–2009 levels, following an increase from 2009 to 2011.

  5. Observations and modeling of forward and reflected chorus waves captured by THEMIS

    Directory of Open Access Journals (Sweden)

    O. Agapitov

    2011-03-01

    Full Text Available Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms spacecraft Search Coil Magnetometer (SCM and Electric Field Instrument (EFI at ELF/VLF frequencies up to 4 kHz at L≥8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar, discrete structure and rising tones, reflected waves are attenuated by a factor of 10–30 and have 10% higher frequency than concurrently-observed forward waves. Modeling of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger.

  6. NuSTAR observations of the bullet cluster: constraints on inverse Compton emission

    Energy Technology Data Exchange (ETDEWEB)

    Wik, Daniel R.; Zhang, W. W. [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Hornstrup, A.; Westergaard, N. J.; Ferreira, D. D. M.; Pedersen, K.; Christensen, F. E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Molendi, S.; Gastaldello, F. [IASF-Milano, INAF, Via Bassini 15, I-20133 Milano (Italy); Madejski, G. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Harrison, F. A.; Grefenstette, B. W.; Madsen, K. K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Zoglauer, A.; Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Kitaguchi, T. [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Stern, D., E-mail: daniel.r.wik@nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2014-09-01

    The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Because all prior telescopes sensitive at E > 10 keV do not focus light and have degree-scale fields of view, their backgrounds are both high and difficult to characterize. The associated uncertainties result in lower sensitivity to IC emission and a greater chance of false detection. In this work, we present 266 ks NuSTAR observations of the Bullet cluster, which is detected in the energy range 3-30 keV. NuSTAR's unprecedented hard X-ray focusing capability largely eliminates confusion between diffuse IC and point sources; however, at the highest energies, the background still dominates and must be well understood. To this end, we have developed a complete background model constructed of physically inspired components constrained by extragalactic survey field observations, the specific parameters of which are derived locally from data in non-source regions of target observations. Applying the background model to the Bullet cluster data, we find that the spectrum is well—but not perfectly—described as an isothermal plasma with kT = 14.2 ± 0.2 keV. To slightly improve the fit, a second temperature component is added, which appears to account for lower temperature emission from the cool core, pushing the primary component to kT ∼ 15.3 keV. We see no convincing need to invoke an IC component to describe the spectrum of the Bullet cluster, and instead argue that it is dominated at all energies by emission from purely thermal gas. The conservatively derived 90% upper limit on the IC flux of 1.1 × 10{sup –12} erg s{sup –1} cm{sup –2} (50-100 keV), implying a lower limit on B ≳ 0.2 μG, is barely consistent with detected fluxes previously reported. In addition to discussing the possible origin of this discrepancy, we remark on the

  7. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    International Nuclear Information System (INIS)

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl62− dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl62− ⋅ thymine and PtCl62− ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)42− ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl62− ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN)42− ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to allow autodetachment

  8. Photoelectron Spectroscopy of Hexachloroplatinate-Nucleobase Complexes: Nucleobase Excited State Decay Observed via Delayed Electron Emission

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ananya; Matthews, Edward M.; Hou, Gao-Lei; Wang, Xue B.; Dessent, Caroline

    2015-11-14

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ~1.7 eV, values that are lower than the RCB of the uncomplexed PtCl6 2- dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl6 2-∙thymine and PtCl6 2-∙adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)4 2-∙nucleobase complexes [Sen et al, J. Phys. Chem. B, 119, 11626, 2015]. The observation of delayed electron emission bands in the PtCl6 2-∙nucleobase spectra obtained in this work, as for the previously studied Pt(CN)4 2-∙nucleobase complexes, is attributed to onephoton excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a timescale long enough to allow autodetachment.

  9. Virtual observatory tools and amateur radio observations supporting scientific analysis of Jupiter radio emissions

    Science.gov (United States)

    Cecconi, Baptiste; Hess, Sebastien; Le Sidaner, Pierre; Savalle, Renaud; Stéphane, Erard; Coffre, Andrée; Thétas, Emmanuel; André, Nicolas; Génot, Vincent; Thieman, Jim; Typinski, Dave; Sky, Jim; Higgins, Chuck; Imai, Masafumi

    2016-04-01

    In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol, as well as data from the Iitate Low Frquency Radio Antenna, in Japan. Amateur radio data from the RadioJOVE project is also available. The attached figure shows data from those three providers. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  10. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research

    Energy Technology Data Exchange (ETDEWEB)

    Lampert, M. [Wigner RCP, Euratom Association-HAS, Budapest (Hungary); BME NTI, Budapest (Hungary); Anda, G.; Réfy, D.; Zoletnik, S. [Wigner RCP, Euratom Association-HAS, Budapest (Hungary); Czopf, A.; Erdei, G. [Department of Atomic Physics, BME IOP, Budapest (Hungary); Guszejnov, D.; Kovácsik, Á.; Pokol, G. I. [BME NTI, Budapest (Hungary); Nam, Y. U. [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2015-07-15

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera’s measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  11. RESIK observations of He-like Ar X-ray line emission in solar flares

    CERN Document Server

    Sylwester, J; Phillips, K J H

    2008-01-01

    The Ar XVII X-ray line group principally due to transitions 1s2 - 1s2l (l=s, p) near 4 Anstroms was observed in numerous flares by the RESIK bent crystal spectrometer aboard CORONAS-F between 2001 and 2003. The three line features include the Ar XVII w (resonance line), a blend of x and y (intercombination lines), and z (forbidden line), all of which are blended with Ar XVI dielectronic satellites. The ratio G, equal to [I(x+y) + I(z)]/I(w), varies with electron temperature Te mostly because of unresolved dielectronic satellites. With temperatures estimated from GOES X-ray emission, the observed G ratios agree fairly well with those calculated from CHIANTI and other data. With a two-component emission measure, better agreement is achieved. Some S XV and S XVI lines blend with the Ar lines, the effect of which occurs at temperatures greater than 8MK, allowing the S/Ar abundance ratio to be determined. This is found to agree with coronal values. A nonthermal contribution is indicated for some spectra in the rep...

  12. Supermassive binary black holes - possible observational effects in the x-ray emission

    Directory of Open Access Journals (Sweden)

    Jovanović Predrag

    2014-01-01

    Full Text Available Here we discuss the possible observational effects in the X-ray emission from two relativistic accretion disks in a supermassive binary black hole system. For that purpose we developed a model and performed numerical simulations of the X-ray radiation from a relativistic accretion disk around a supermassive black hole, based on the ray-tracing method in the Kerr metric, and applied it to the case of the close binary supermassive black holes. Our results indicate that the broad Fe Kα line is a powerful tool for detecting such systems and studying their properties. The most favorable candidates for observational studies are the supermassive binary black holes in the galactic mergers during the phase when the orbital velocities of their components are very large and exceed several thousand kms -1. [Projekat Ministarstva nauke Republike Srbije, br. 176003: Gravitation and the Large Scale Structure of the Universe i br. 176001: Astrophysical Spectroscopy of Extragalactic Objects

  13. Soft X-ray Observation of the Prompt Emission of GRB100418A

    CERN Document Server

    Imatani, Ritsuko; Nakahira, Satoshi; Kimura, Masashi; Sakamoto, Takanori; Arimoto, Makoto; Morooka, Yoshitaka; Yonetoku, Daisuke; Kawai, Nobuyuki; Tsunemi, Hiroshi

    2015-01-01

    We have observed the prompt emission of GRB100418A, from its beginning by the MAXI/SSC (0.7-7 keV) on board the International Space Station followed by the Swift/XRT (0.3-10 keV) observation. The light curve can be fitted by a combination of a power law component and an exponential component (decay constant is $31.6\\pm 1.6$). The X-ray spectrum is well expressed by the Band function with $E_{\\rm p}\\leq$8.3 keV. This is the brightest GRB showing a very low value of $E_{\\rm p}$. It is also consistent with the Yonetoku-relation ($E_{\\rm p}$-$L_{\\rm p}$) while it is not clear with the Amati-relation ($E_{\\rm p}$-$E_{\\rm iso}$).

  14. Fermi Observations of high-energy gamma-ray emissions from GRB 080916C

    CERN Document Server

    Abdo, A A; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, Guido; Baring, Matthew G; Bastieri, Denis; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, Elliott D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, Thompson H; Burrows, David N; Busetto, Giovanni; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, Annalisa; Charles, E; Chekhtman, A; Cheung, C.C.Teddy; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, Johann; Cominsky, Lynn R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; DeKlotz, M; Dermer, C D; De Angelis, Alessandro; de Palma, F; Digel, S W; Dingus, B L; do Couto e Silva, Eduardo; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, Justin D; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, Thomas Lynn; Godfrey, Gary L; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M H; Grove, J.Eric; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, Alice K; Hayashida, M; Hays, Elizabeth A; Hernando Morata, J A; Hoover, A; Hughes, R E; Johannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, Tsuneyoshi; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knodlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, Frederick Gabriel Ivar; Kuss, Michael; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, Pasquale; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, Sheila; McEnery, J E; McGlynn, S; Meegan, C; Miszaros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, Igor Vladimirovich; Murgia, Simona; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, Takashi; Okumura, Akira; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, Vahe; Pinchera, M; Piron, F; Porter, Troy A; Preece, R; Rainr, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, Soebur; Rea, N; Reimer, A; Reimer, O; Reposeur, Thierry; Reyes, Luis C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F W; Sanchez, D; Sander, A; Parkinson, P.M.Saz; Scargle, J D; Schalk, T L; Segal, K N; Sgro, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, Jean-Luc; Stecker, Floyd William; Steinle, H; Stephens, T E; Strickman, M S; Suson, Daniel J; Tagliaferri, G.; Tajima, Hiroyasu; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, Diego F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M

    2009-01-01

    Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

  15. Soft X-ray observation of the prompt emission of GRB 100418A

    Science.gov (United States)

    Imatani, Ritsuko; Tomida, Hiroshi; Nakahira, Satoshi; Kimura, Masashi; Sakamoto, Takanori; Arimoto, Makoto; Morooka, Yoshitaka; Yonetoku, Daisuke; Kawai, Nobuyuki; Tsunemi, Hiroshi

    2016-06-01

    We have observed the prompt emission of GRB 100418A from its beginning captured by the MAXI SSC (0.7-7 keV) on board the International Space Station followed by the Swift XRT (0.3-10 keV) observation. The light curve can be fitted by a combination of a power-law component and an exponential component (the decay constant is 31.6 ± 1.6 s). The X-ray spectrum is well expressed by the Band function with Ep ≤ 8.3 keV. This is the brightest gamma-ray burst showing a very low value of Ep. It satisfies the Yonetoku relation (Ep-Lp). It is also consistent with the Amati relation (Ep-Eiso) within a 2.5σ level.

  16. LOW-FREQUENCY OBSERVATIONS OF TRANSIENT QUASI-PERIODIC RADIO EMISSION FROM THE SOLAR ATMOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    Sasikumar Raja, K.; Ramesh, R., E-mail: sasikumar@iiap.res.in [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034 (India)

    2013-09-20

    We report low-frequency observations of quasi-periodic, circularly polarized, harmonic type III radio bursts whose associated sunspot active regions were located close to the solar limb. The measured periodicity of the bursts at 80 MHz was ≈5.2 s, and their average degree of circular polarization (dcp) was ≈0.12. We calculated the associated magnetic field B (1) using the empirical relationship between the dcp and B for the harmonic type III emission, and (2) from the observed quasi-periodicity of the bursts. Both the methods result in B ≈ 4.2 G at the location of the 80 MHz plasma level (radial distance r ≈ 1.3 R{sub ☉}) in the active region corona.

  17. Satellite observations indicate substantial spatiotemporal variability in biomass burning NOx emission factors for South America

    NARCIS (Netherlands)

    Castellanos, P.; Boersma, K.F.; Werf, van de G.R.

    2014-01-01

    Biomass burning is an important contributor to global total emissions of NOx (NO+NO2). Generally bottom-up fire emissions models calculate NOx emissions by multiplying fuel consumption estimates with static biome-specific emission factors, defined in units of grams of NO per kilogram of dry matter c

  18. Location accuracy of VLF World-Wide Lightning Location (WWLL) network: Post-algorithm upgrade

    OpenAIRE

    Rodger, C. J.; Brundell, J. B.; Dowden, R. L.

    2005-01-01

    An experimental VLF World-Wide Lightning Location (WWLL) network has been developed through collaborations with research institutions across the globe. The aim of the WWLL is to provide global real-time locations of lightning discharges, with >50% CG flash detection efficiency and mean location accuracy of <10km. While these goals are essentially arbitrary, they do define a point where the WWLL network development can be judged a success, providing a breakpoint for a more stable...

  19. Observational constraints on the distribution, seasonality, and environmental predictors of North American boreal methane emissions

    Science.gov (United States)

    Miller, Scot M.; Worthy, Doug E. J.; Michalak, Anna M.; Wofsy, Steven C.; Kort, Eric A.; Havice, Talya C.; Andrews, Arlyn E.; Dlugokencky, Edward J.; Kaplan, Jed O.; Levi, Patricia J.; Tian, Hanqin; Zhang, Bowen

    2014-02-01

    Wetlands comprise the single largest global source of atmospheric methane, but current flux estimates disagree in both magnitude and distribution at the continental scale. This study uses atmospheric methane observations over North America from 2007 to 2008 and a geostatistical inverse model to improve understanding of Canadian methane fluxes and associated biogeochemical models. The results bridge an existing gap between traditional top-down, inversion studies, which typically emphasize total emission budgets, and biogeochemical models, which usually emphasize environmental processes. The conclusions of this study are threefold. First, the most complete process-based methane models do not always describe available atmospheric methane observations better than simple models. In this study, a relatively simple model of wetland distribution, soil moisture, and soil temperature outperformed more complex model formulations. Second, we find that wetland methane fluxes have a broader spatial distribution across western Canada and into the northern U.S. than represented in existing flux models. Finally, we calculate total methane budgets for Canada and for the Hudson Bay Lowlands, a large wetland region (50-60°N, 75-96°W). Over these lowlands, we find total methane fluxes of 1.8±0.24 Tg C yr-1, a number in the midrange of previous estimates. Our total Canadian methane budget of 16.0±1.2 Tg C yr-1 is larger than existing inventories, primarily due to high anthropogenic emissions in Alberta. However, methane observations are sparse in western Canada, and additional measurements over Alberta will constrain anthropogenic sources in that province with greater confidence.

  20. The Annual Cycle of Water Vapor on Mars as Observed by the Thermal Emission Spectrometer

    Science.gov (United States)

    Smith, Michael D.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Spectra taken by the Mars Global Surveyor Thermal Emission Spectrometer (TES) have been used to monitor the latitude, longitude, and seasonal dependence of water vapor for over one full Martian year (March 1999-March 2001). A maximum in water vapor abundance is observed at high latitudes during mid-summer in both hemispheres, reaching a maximum value of approximately 100 pr-micrometer in the north and approximately 50 pr-micrometer in the south. Low water vapor abundance (water vapor. The latitudinal and seasonal dependence of the decay of the northern summer water vapor maximum implies cross-equatorial transport of water to the southern hemisphere, while there is little or no corresponding transport during the decay of the southern hemisphere summer maximum. The latitude-longitude dependence of annually-averaged water vapor (corrected for topography) has a significant positive correlation with albedo and significant negative correlations with thermal inertia and surface pressure. Comparison of TES results with those retrieved from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) experiments shows some similar features, but also many significant differences. The southern hemisphere maximum observed by TES was not observed by MAWD and the large latitudinal gradient in annually-averaged water vapor observed by MAWD does not appear in the TES results.

  1. VHE gamma-ray emission from the FSRQs observed by the MAGIC telescopes

    CERN Document Server

    Lindfors, E; de Almeida, U Barres; Mazin, D; Paneque, D; Saito, K; Gonzalez, J Becerra; Berger, K; De Caneva, G; Schultz, C; Sitarek, J; Stamerra, A; Tavecchio, F; Buson, S; D'Ammando, F; Hayashida, M; Tornikoski, M; Hovatta, T

    2013-01-01

    Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs): PKS 1510-089, PKS 1222+216 and 3C 279. The detection of FSRQs in the VHE range is challenging, mainly because of their steep soft spectra in the GeV-TeV regime. MAGIC has observed and detected all FSRQs known to be VHE emitters up to now and found that they exhibit very different behavior. The 2010 discovery of PKS 1222+216 (z = 0.432) with the fast variability observed, challenges simple one-zone emission models and more complicated scenarios have been proposed. 3C 279 is the most distant VHE gamma-ray emitting AGN (z = 0.536), which was discovered by MAGIC in 2006 and detected again in 2007. In 2011 MAGIC observed 3C 279 two times: first during a monitoring campaign and later observations were triggered by a flare detected with Fermi-LAT. We present the MAGIC results and the multiwavelength behavior during this flaring epoch. Finally, we report the ...

  2. Quantifying the Seasonal and Interannual Variability of North American Isoprene Emissions Using Satellite Observations of the Formaldehyde Column

    Science.gov (United States)

    Palmer, Paul I.; Abbot, Dorian S.; Fu, Tzung-May; Jacob, Daniel J.; Chance, Kelly; Kurosu, Thomas P.; Guenther, Alex; Wiedinmyer, Christine; Stanton, Jenny C.; Pilling, Michael J.; Pressley, Shelley N.; Lamb, Brian; Sumner, Anne Louise

    2006-01-01

    Quantifying isoprene emissions using satellite observations of the formaldehyde (HCHO) columns is subject to errors involving the column retrieval and the assumed relationship between HCHO columns and isoprene emissions, taken here from the GEOS-CHEM chemical transport model. Here we use a 6-year (1996-2001) HCHO column data set from the Global Ozone Monitoring Experiment (GOME) satellite instrument to (1) quantify these errors, (2) evaluate GOME-derived isoprene emissions with in situ flux measurements and a process-based emission inventory (Model of Emissions of Gases and Aerosols from Nature, MEGAN), and (3) investigate the factors driving the seasonal and interannual variability of North American isoprene emissions. The error in the GOME HCHO column retrieval is estimated to be 40%. We use the Master Chemical Mechanism (MCM) to quantify the time-dependent HCHO production from isoprene, alpha- and beta-pinenes, and methylbutenol and show that only emissions of isoprene are detectable by GOME. The time-dependent HCHO yield from isoprene oxidation calculated by MCM is 20-30% larger than in GEOS-CHEM. GOME-derived isoprene fluxes track the observed seasonal variation of in situ measurements at a Michigan forest site with a -30% bias. The seasonal variation of North American isoprene emissions during 2001 inferred from GOME is similar to MEGAN, with GOME emissions typically 25% higher (lower) at the beginning (end) of the growing season. GOME and MEGAN both show a maximum over the southeastern United States, but they differ in the precise location. The observed interannual variability of this maximum is 20-30%, depending on month. The MEGAN isoprene emission dependence on surface air temperature explains 75% of the month-to-month variability in GOME-derived isoprene emissions over the southeastern United States during May-September 1996-2001.

  3. Field Observations of Methane Emissions from Unconventional and Conventional Fossil Fuel Exploration

    Science.gov (United States)

    Dubey, M.; Lindenmaier, R.; Arata, C.; Costigan, K. R.; Frankenberg, C.; Kort, E. A.; Rahn, T. A.; Henderson, B. G.; Love, S. P.; Aubrey, A. D.

    2013-12-01

    Energy from methane (CH4) has lower carbon dioxide and air pollutant emissions per unit energy produced than coal or oil making it a desirable fossil fuel. Hydraulic fracturing is allowing United States to harvest the nation's abundant domestic shale gas reservoirs to achieve energy independence. However, CH4 is a gas that is hard to contain during mining, processing, transport and end-use. Therefore fugitive CH4 leaks occur that are reported in bottom up inventories by the EPA. Recent targeted field observations at selected plays have provided top down CH4 leak estimates that are larger than the reported EPA inventories. Furthermore, no long-term regional baselines are available to delineate leaks from unconventional mining operations from historical conventional mining. We will report and compare observations of fugitive CH4 leaks from conventional and unconventional mining to understand changes from technology shifts. We will report in situ and regional column measurements of CH4, its isotopologue 13CH4 and ethane (C2H6) at our Four Corners site near Farmington, NM. The region has substantial coal bed methane, conventional oil and gas production, processing and distribution with minimal hydraulic fracturing activity. We observe large enhancements in in situ and regional column CH4 with distinct time dependence. Our in situ 13CH4 observations and remote C2H6/CH4 provide strong evidence of thermogenic sources. Comparisons of WRF-simulations with emissions inventory (Edgar) with our observations show that the fugitive CH4 leaks from conventional mining are 3 times greater than reported. We also compare in situ mobile surveys of fugitive CH4 and 13CH4 leak signals in basins with conventional (San Juan) mining and unconventional (Permian and Powder River) mining. A large number of active and closed wells were sampled in these regions. Furthermore, play scale surveys on public roads allowed us to gain a regional perspective. The composition of atmospheric 13CH4

  4. New Maser Emission from Nonmetastable Ammonia in NGC 7538. II. Green Bank Telescope Observations Including Water Masers

    CERN Document Server

    Hoffman, Ian M

    2011-01-01

    We present new maser emission from ^{14}NH_3 (9,6) in NGC 7538. Our observations include the known spectral features near v_LSR = -60 km/s and -57 km/s and several more features extending to -46 km/s. In three epochs of observation spanning two months we do not detect any variability in the ammonia masers, in contrast to the >10-fold variability observed in other ^{14}NH_3 (9,6) masers in the Galaxy over comparable timescales. We also present observations of water masers in all three epochs for which emission is observed over the velocity range -105 km/s < v_LSR < -4 km/s, including the highest velocity water emission yet observed from NGC 7538. Of the remarkable number of maser species in IRS 1, H_2O and, now, ^{14}NH_3 are the only masers known to exhibit emission outside of the velocity range -62 km/s < v_LSR < -51 km/s. However, we find no significant intensity or velocity correlations between the water emission and ammonia emission. We also present a non-detection in the most sensitive search...

  5. Modeling the thermal emission from asteroid 3 Juno using ALMA observations and the KRC thermal model

    Science.gov (United States)

    Titus, Timothy N.; Li, Jian-Yang; Moullet, Arielle; Sykes, Mark V.

    2015-11-01

    Asteroid 3 Juno (hereafter referred to as Juno), discovered 1 September 1804, is the 11th largest asteroid in the Main Asteroid Belt (MAB). Containing approximately 1% of the mass in the MAB [1], Juno is the second largest S-type [2].As part of the observations acquired from Atacama Large Millimeter/submillimeter Array (ALMA) [3], 10 reconstructed images at ~60km/pixel resolution were acquired of Juno [4] that showed significant deviations from the Standard Thermal Model (STM) [5]. These deviations could be a result of surface topography, albedo variations, emissivity variations, thermal inertia variations, or any combination.The KRC thermal model [6, 7], which has been extensively used for Mars [e.g. 8, 9] and has been applied to Vesta [10] and Ceres [11], will be used to compare model thermal emission to that observed by ALMA at a wavelength of 1.33 mm [4]. The 10 images, acquired over a four hour period, captured ~55% of Juno’s 7.21 hour rotation. Variations in temperature as a function of local time will be used to constrain the source of the thermal emission deviations from the STM.This work is supported by the NASA Solar System Observations Program.References:[1] Pitjeva, E. V. (2005) Solar System Research 39(3), 176. [2] Baer, J. and S. R. Chesley (2008) Celestial Mechanics and Dynamical Astronomy, 100, 27-42. [3] Wootten A. et al. (2015) IAU General Assembly, Meeting #29, #2237199 [4] arXiv:1503.02650 [astro-ph.EP] doi: 10.1088/2041-8205/808/1/L2 [5] Lebofsky, L.A. eta al. (1986) Icarus, 68, 239-251. [6] Kieffer, H. H., et al. (1977) J. Geophys. Res., 82, 4249-4291. [7] Kieffer, Hugh H., (2013) Journal of Geophysical Research: Planets, Volume 118, Issue 3, pp. 451-470 [8] Titus, T. N., H. H. Kieffer, and P. N. Christensen (2003) Science, 299, 1048-1051. [9] Fergason, R. L. et al. (2012) Space Sci. Rev, 170, 739-773, doi:10.1007/s11214-012-9891-3. [10] Titus, T. N. et al. (2012) 43rd LPSC, held March 19-23, 2012 at The Woodlands, Texas. LPI Contribution No

  6. Observation of a physical matrix effect during cold vapour generation measurement of mercury in emissions samples

    International Nuclear Information System (INIS)

    Highlights: • A matrix effect for CV-AFS measurement of mercury in emissions samples is reported. • This results from the different efficiencies of liberation of reduced mercury. • There is a good correlation between solution density and the size of the effect. • Several methods to overcome the bias are presented and discussed. - Abstract: The observation of a physical matrix effect during the cold vapour generation–atomic fluorescence measurement of mercury in emissions samples is reported. The effect is as a result of the different efficiencies of liberation of reduced mercury from solution as the matrix of the solution under test varies. The result of this is that peak area to peak height ratios decease as matrix concentration increases, passing through a minimum, before the ratio then increases as matrix concentration further increases. In the test matrices examined – acidified potassium dichromate and sodium chloride solutions – the possible biases caused by differences between the calibration standard matrix and the test sample matrix were as large as 2.8% (relative) representing peak area to peak height ratios for calibration standards and matrix samples of 45 and 43.75, respectively. For the system considered there is a good correlation between the density of the matrix and point of optimum liberation of dissolved mercury for both matrix types. Several methods employing matrix matching and mathematical correction to overcome the bias are presented and their relative merits discussed; the most promising being the use of peak area, rather than peak height, for quantification

  7. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission

    CERN Document Server

    Gold, B; Weiland, J L; Hill, R S; Kogut, A; Bennett, C L; Hinshaw, G; Dunkley, J; Halpern, M; Jarosik, N; Komatsu, E; Larson, D; Limon, M; Meyer, S S; Nolta, M R; Page, L; Smith, K M; Spergel, D N; Tucker, G S; Wollack, E; Wright, E L

    2010-01-01

    [Abridged] We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground contamination outside of the updated (KQ85y7) foreground mask. We place a 15 microKelvin upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. We find no indication in the polarization data of an extra "haze" of hard synchrotron emission from energetic electrons near the Galactic center. We provide an updated map of the cosmic microwave background (CMB) using the internal linear combination (ILC) method, updated foreground masks, and updates to point source catalogs with 62 newly detected sources. Also new are tests of the Markov chain Monte Carlo (MCMC) foreground fitting procedure against systematics in the time-stream data, and tests against the observed beam asymmetry. Within a few degrees of the Galactic plane, WMAP total intensity data show...

  8. Derivation of an observation-based map of North African dust emission

    Energy Technology Data Exchange (ETDEWEB)

    Evan, Amato T.; Fiedler, Stephanie; Zhao, Chun; Menut, Laurent; Schepanski, Kerstin; Flamant, C.; Doherty, Owen

    2015-03-01

    Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodélé depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Aïr and Hoggar Mountains, making this area the second most important region of emission within North Africa.

  9. observations of hot molecular gas emission from embedded low-mass protostars

    DEFF Research Database (Denmark)

    Visser, R.; Kristensen, L. E.; Bruderer, S.;

    2012-01-01

    the observations quantitatively, to investigate the origin of the emission, and to use the lines as probes of the various heating mechanisms. Methods. The model consists of a spherical envelope with a power-law density structure and a bipolar outflow cavity. Three heating mechanisms are considered: passive heating...... such as luminosity and envelope mass. Results. The bulk of the gas in the envelope, heated by the protostellar luminosity, accounts for 3–10% of the CO luminosity summed over all rotational lines up to J = 40–39; it is best probed by low-J CO isotopologue lines such as C18O 2–1 and 3–2. The UV-heated gas and the C......-type shocks, probed by 12CO 10–9 and higher-J lines, contribute 20–80% each. The model fits show a tentative evolutionary trend: the CO emission is dominated by shocks in the youngest source and by UV-heated gas in the oldest one. This trend is mainly driven by the lower envelope density in more evolved...

  10. SOFIA observations of CO(12-11) emission along the L1157 bipolar outflow

    CERN Document Server

    Eislöffel, Jochen; Güsten, Rolf; Wiesemeyer, Helmut; Gusdorf, Antoine

    2012-01-01

    Carbon monoxide is an excellent tracer of the physical conditions of gas in molecular outflows from young stars. To understand the outflow mechanism we need to investigate the origin of the molecular emission and the structure and interaction of the outflowing molecular gas. Deriving the physical parameters of the gas will help us to trace and understand the various gas components in the flow. We observed CO(12-11) line emission at various positions along the L1157 bipolar outflow with GREAT aboard SOFIA. Comparing these new data with CO(2-1), we find basically constant line ratios along the outflow and even at the position of the source. These line ratios lead us to estimates of 10^5 to 10^6 cm^-3 for the gas density and 60 to 100 K for the gas temperature of the outflowing gas. The constrained density and temperature values indicate that we are mostly tracing a low-velocity gas component everywhere along the outflow, which is intermediate between the already known cold gas component, which gets entrained in...

  11. Observed spectral energy distribution of the thermal emission from the dayside of WASP-46b

    CERN Document Server

    Chen, Guo; Wang, Hongchi; Nikolov, Nikolay; Seemann, Ulf; Henning, Thomas

    2014-01-01

    We aim to construct a spectral energy distribution (SED) for the emission from the dayside atmosphere of the hot Jupiter WASP-46b and to investigate its energy budget. We observed a secondary eclipse of WASP-46b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2m telescope. Eclipse depths of the acquired light curves were derived to infer the brightness temperatures at multibands that cover the SED peak. We report the first detection of the thermal emission from the dayside of WASP-46b in the K band at 4.2-sigma level and tentative detections in the H (2.5-sigma) and J (2.3-sigma) bands, with flux ratios of 0.253 +0.063/-0.060%, 0.194 +/- 0.078%, and 0.129 +/- 0.055%, respectively. The derived brightness temperatures (2306 +177/-187K, 2462 +245/-302K, and 2453 +198/-258K, respectively) are consistent with an isothermal temperature profile of 2386K, which is significantly higher than the dayside-averaged equilibrium temperature, indicative of very poor heat redistribution eff...

  12. Observations of the Quadrantid meteor shower from 2008 to 2012: Orbits and emission spectra

    Science.gov (United States)

    Madiedo, José M.; Espartero, Francisco; Trigo-Rodríguez, Josep M.; Castro-Tirado, Alberto J.; Pujols, Pep; Pastor, Sensi; de los Reyes, José A.; Rodríguez, Diego

    2016-09-01

    The activity of the Quadrantids in January during several years (2008, 2010, 2011 and 2012) has been investigated in the framework of the SPanish Meteor Network (SPMN). For this purpose, an array of high-sensitivity CCD video devices and CCD all-sky cameras have been used to obtain multi-station observations of these meteors. These allowed to obtain precise radiant and orbital information about this meteoroid stream. This paper presents a large set of orbital data (namely, 85 orbits) of Quadrantid meteoroids. Most meteors produced by these particles were recorded during the activity peak of this shower. Besides, we discuss four Quadrantid emission spectra. The tensile strength of Quadrantid meteoroids has been also obtained.

  13. Observing and modelling f-region ionospheric dynamics using the (OII) 7320a emission. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Carr, S.S.

    1992-01-01

    Limb-scan observations of Doppler line profiles from the (OII) lambda 7320A emission at F-Region altitudes, made with the Fabry-Perot interferometer (FPI) on the Dynamics Explorer-2 (DE-2) spacecraft, have been analyzed to provide measurements of the meridional component of the ion convection velocity along the instrument line-of-sight. The DE-2 results presented here demonstrate the first spaceborne use of the remote-sensing Doppler techniques for measurements of ionospheric convection. The FPI meridional ion drift measurements have been compared with nearly simultaneous in situ ion drift measurements from the Retarding Potential Analyzer (RPA) on DE 2. Once allowance is made for the temporal lag between the in situ and remote measurements, the results from the two techniques are found to be in good agreement, within specified experimental errors, giving confidence in the FPI measurements.

  14. Observations of the Quadrantid meteor shower from 2008 to 2012: orbits and emission spectra

    CERN Document Server

    Madiedo, José M; Trigo-Rodríguez, Josep M; Castro-Tirado, Alberto J; Pujols, Pep; Pastor, Sensi; Reyes, José A de los; Rodríguez, Diego

    2016-01-01

    The activity of the Quadrantids in January during several years (2008, 2010, 2011 and 2012) has been investigated in the framework of the SPanish Meteor Network (SPMN). For this purpose, an array of high-sensitivity CCD video devices and CCD all-sky cameras have been used to obtain multi-station observations of these meteors. These allowed us to obtain precise radiant and orbital information about this meteoroid stream. This paper presents a large set of orbital data (namely, 85 orbits) of Quadrantid meteoroids. Most meteors produced by these particles were recorded during the activity peak of this shower. Besides, we discuss four Quadrantid emission spectra. The tensile strength of Quadrantid meteoroids has been also obtained.

  15. Recent Large Reduction in Sulfur Dioxide Emissions from Chinese Power Plants Observed by the Ozone Monitoring Instrument

    Science.gov (United States)

    Li, Can; Zhang, Qiang; Krotkov, Nickolay A.; Streets, David G.; He, Kebin; Tsay, Si-Chee; Gleason, James F.

    2010-01-01

    The Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite observed substantial increases in total column SO2 and tropospheric column NO2 from 2005 to 2007, over several areas in northern China where large coal-fired power plants were built during this period. The OMI-observed SO2/NO2 ratio is consistent with the SO2/ NO2, emissions estimated from a bottom-up approach. In 2008 over the same areas, OMI detected little change in NO2, suggesting steady electricity output from the power plants. However, dramatic reductions of S0 2 emissions were observed by OMI at the same time. These reductions confirm the effectiveness of the flue-gas desulfurization (FGD) devices in reducing S02 emissions, which likely became operational between 2007 and 2008. This study further demonstrates that the satellite sensors can monitor and characterize anthropogenic emissions from large point sources.

  16. Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems

    Energy Technology Data Exchange (ETDEWEB)

    Grover, Samantha P.P., E-mail: samantha.grover@monash.edu [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Cohan, Amanda, E-mail: acoh5@student.monash.edu [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Chan, Hon Sen, E-mail: hon.sen.chan@gmail.com [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Livesley, Stephen J., E-mail: sjlive@unimelb.edu.au [Department of Resource Management and Geography, The University of Melbourne, Richmond, Victoria, 3121 (Australia); Beringer, Jason, E-mail: jason.beringer@monash.edu [School of Geography and Environmental Science, Monash University, Clayton, Victoria, 3800 (Australia); Monash Water for Liveability, Monash University, Clayton, Victoria, 3800 (Australia); Daly, Edoardo, E-mail: edoardo.daly@monash.edu [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Monash Water for Liveability, Monash University, Clayton, Victoria, 3800 (Australia)

    2013-11-01

    inflow events, which were not seen in other urban systems. CO{sub 2} fluxes increased with soil temperature in both cells, and in the cell without the saturated zone CO{sub 2} fluxes decreased as soil moisture increased. Other studies of CO{sub 2} fluxes from urban soils have found both similar and larger CO{sub 2} emissions than those measured in the biofilter. The results of this study suggest that the greenhouse gas footprint of stormwater treatment warrant consideration in the planning and implementation of engineered green infrastructures. - Highlights: ► First study of greenhouse gas fluxes from a stormwater biofilter. ► Observed occasional large emissions of nitrous oxide and methane. ► Biofilter designs with and without a saturated zone were net sinks for methane. ► Carbon dioxide emissions were four times less than those from lawns.

  17. Estimation of NOx emissions from Delhi using Car MAX-DOAS observations and comparison with OMI satellite data

    Directory of Open Access Journals (Sweden)

    R. P. Singh

    2011-11-01

    Full Text Available We present the first Multi-Axis-(MAX- DOAS observations in India performed during April 2010 and January 2011 in Delhi and nearby regions. The MAX-DOAS instrument was mounted on a car roof, which allowed us to perform measurements along individual driving routes. From car MAX-DOAS observations along closed circles around Delhi, together with information on wind speed and direction, the NOx emissions from the greater Delhi area were determined: our estimate of 4.4 × 1025 molecules s−1 is found to be slightly lower than the corresponding emission estimates using the EDGAR emission inventory and substantially smaller compared to a recent study by Gurjar et al. (2004. We also determined NOx emissions from Delhi using OMI satellite observations on the same days. These emissions are slightly smaller than those from the car MAX-DOAS measurements. Finally the car MAX-DOAS observations were also used for the validation of simultaneous OMI satellite measurements of the tropospheric NO2 VCD and found a good agreement of the spatial patterns. Concerning the absolute values, OMI data are, on average, higher than the car MAX-DOAS observations close to strong emission sources, and vice versa over less polluted regions. Our results indicate that OMI NO2 VCDs are biased low over strongly polluted regions, probably caused by inadequate a-priori profiles used in the OMI satellite retrieval.

  18. Estimate of carbonyl sulfide tropical oceanic surface fluxes using Aura Tropospheric Emission Spectrometer observations

    Science.gov (United States)

    Kuai, Le; Worden, John R.; Campbell, J. Elliott; Kulawik, Susan S.; Li, King-Fai; Lee, Meemong; Weidner, Richard J.; Montzka, Stephen A.; Moore, Fred L.; Berry, Joe A.; Baker, Ian; Denning, A. Scott; Bian, Huisheng; Bowman, Kevin W.; Liu, Junjie; Yung, Yuk L.

    2015-10-01

    Quantifying the carbonyl sulfide (OCS) land/ocean fluxes contributes to the understanding of both the sulfur and carbon cycles. The primary sources and sinks of OCS are very likely in a steady state because there is no significant observed trend or interannual variability in atmospheric OCS measurements. However, the magnitude and spatial distribution of the dominant ocean source are highly uncertain due to the lack of observations. In particular, estimates of the oceanic fluxes range from approximately 280 Gg S yr-1 to greater than 800 Gg S yr-1, with the larger flux needed to balance a similarly sized terrestrial sink that is inferred from NOAA continental sites. Here we estimate summer tropical oceanic fluxes of OCS in 2006 using a linear flux inversion algorithm and new OCS data acquired by the Aura Tropospheric Emissions Spectrometer (TES). Modeled OCS concentrations based on these updated fluxes are consistent with HIAPER Pole-to-Pole Observations during 4th airborne campaign and improve significantly over the a priori model concentrations. The TES tropical ocean estimate of 70 ± 16 Gg S in June, when extrapolated over the whole year (about 840 ± 192 Gg S yr-1 ), supports the hypothesis proposed by Berry et al. (2013) that the ocean flux is in the higher range of approximately 800 Gg S yr-1.

  19. Radio-wave emission due to hypervelocity impacts and its correlation with optical observations

    Science.gov (United States)

    Takano, T.; Maki, K.; Yamori, A.

    This paper describes the most interesting phenomena of radio-wave emission due to hypervelocity impacts. A projectile of polycarbonate with 1.1 g weight was accelerated by a rail gun to 3.8 km/sec, and hit two targets which are a 2 mm thick aluminum plate upstream and a 45 mm diameter aluminum column downstream, respectively. The projectile first breaks wires to give a triggering signal to a data recorder, then penetrates the aluminum plate, and finally hit the column, The emitted radio-waves propagate through the chamber window, and are received by antennas at each frequency band. The receivers in 22 GHz- and 2 GHz-bands consist of a low noise amplifier, a mixer, a local oscillator and an IF amplifier , respectively. The receiver in 1 MHz-band is a simple RF amplifier. The outputs of all receivers are fed to a data recorder which is actually a high-speed digital oscilloscope with a large amount of memory. The radio-waves were successfully recorded in 22 GHz-band with 500 MHz bandwidth, in 2 GHz-band with 300 MHz bandwidth, and in 1MHz-band. The waveforms in 22 GHz- and 2 GHz-bands coincide well each other, and are composed of two groups of sharp impulses with a separation of about 20 micro seconds. The width of an impulse is less than 2 n sec. which is the resolution limit of the data recorder. We carried out optical observations using an ultra-high speed camera simultaneously through another window of the chamber. The time interval between scenes is 2 micro sec. We can see a faint light of the projectile before the first impact to the plate, and then a brilliant gas exploding backward from the plate and forward to the column. After hitting the column target, the brilliant gas flows to the chamber wall and is reflected back to make a mixture with dark gas in the chamber. Excellent correlation between radio-wave emission and the observed optical phenomena was obtained in the experiment. It is easily conceived that the radio-waves consist of quite a wide frequency

  20. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ananya; Matthews, Edward M.; Dessent, Caroline E. H., E-mail: caroline.dessent@york.ac.uk, E-mail: xuebin.wang@pnnl.gov [Department of Chemistry, University of York, Heslington, York YO10 5DD (United Kingdom); Hou, Gao-Lei; Wang, Xue-Bin, E-mail: caroline.dessent@york.ac.uk, E-mail: xuebin.wang@pnnl.gov [Physical Sciences Division, Pacific Northwest National Laboratory, MS K8-88, P.O. Box 999, Richland, Washington 99352 (United States)

    2015-11-14

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl{sub 6}{sup 2−} dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl{sub 6}{sup 2−} ⋅ thymine and PtCl{sub 6}{sup 2−} ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN){sub 4}{sup 2−} ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl{sub 6}{sup 2−} ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN){sub 4}{sup 2−} ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to

  1. Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at HAARP and EISCAT

    Science.gov (United States)

    Scales, W.; Mahmoudian, A.; Fu, H.; Bordikar, M. R.; Samimi, A.; Bernhardt, P. A.; Briczinski, S. J., Jr.; Kosch, M. J.; Senior, A.; Isham, B.

    2014-12-01

    There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities and computational modeling will be provided. Possible applications of NSEE will be pointed out including triggering diagnostics for artificial ionization layer formation, proton precipitation event diagnostics, electron temperature measurements in the heated

  2. CO2 non-LTE limb emissions in Mars' atmosphere as observed by OMEGA/Mars Express

    Science.gov (United States)

    Piccialli, A.; López-Valverde, M. A.; Määttänen, A.; González-Galindo, F.; Audouard, J.; Altieri, F.; Forget, F.; Drossart, P.; Gondet, B.; Bibring, J. P.

    2016-06-01

    We report on daytime limb observations of Mars upper atmosphere acquired by the OMEGA instrument on board the European spacecraft Mars Express. The strong emission observed at 4.3 μm is interpreted as due to CO2 fluorescence of solar radiation and is detected at a tangent altitude in between 60 and 110 km. The main value of OMEGA observations is that they provide simultaneously spectral information and good spatial sampling of the CO2 emission. In this study we analyzed 98 dayside limb observations spanning over more than 3 Martian years, with a very good latitudinal and longitudinal coverage. Thanks to the precise altitude sounding capabilities of OMEGA, we extracted vertical profiles of the non-local thermodynamic equilibrium (non-LTE) emission at each wavelength and we studied their dependence on several geophysical parameters, such as the solar illumination and the tangent altitude. The dependence of the non-LTE emission on solar zenith angle and altitude follows a similar behavior to that predicted by the non-LTE model. According to our non-LTE model, the tangent altitude of the peak of the CO2 emission varies with the thermal structure, but the pressure level where the peak of the emission is found remains constant at ˜0.03 ± 0.01 Pa, . This non-LTE model prediction has been corroborated by comparing SPICAM and OMEGA observations. We have shown that the seasonal variations of the altitude of constant pressure levels in SPICAM stellar occultation retrievals correlate well with the variations of the OMEGA peak emission altitudes, although the exact pressure level cannot be defined with the spectroscopy for the investigation of the characteristics of the atmosphere of Venus (SPICAM) nighttime data. Thus, observed changes in the altitude of the peak emission provide us information on the altitude of the 0.03 Pa pressure level. Since the pressure at a given altitude is dictated by the thermal structure below, the tangent altitude of the peak emission represents

  3. Aging in autonomic control by multifractal studies of cardiac interbeat intervals in the VLF band

    International Nuclear Information System (INIS)

    The heart rate responds dynamically to various intrinsic and environmental stimuli. The autonomic nervous system is said to play a major role in this response. Multifractal analysis offers a novel method to assess the response of cardiac interbeat intervals. Twenty-four hour ECG recordings of RR interbeat intervals (of 48 elderly volunteers (age 65–94), 40 middle-aged persons (age 45–53) and 36 young adults (age 18–26)) were investigated to study the effect of aging on autonomic regulation during normal activity in healthy adults. Heart RR-interval variability in the very low frequency (VLF) band (32–420 RR intervals) was evaluated by multifractal tools. The nocturnal and diurnal signals of 6 h duration were studied separately. For each signal, the analysis was performed twice: for a given signal and for the integrated signal. A multifractal spectrum was quantified by the hmax value at which a multifractal spectrum attained its maximum, width of a spectrum, Hurst exponent, extreme events hleft and distance between the maxima of a signal and its integrated counterpart. The following seven characteristics are suggested as quantifying the age-related decrease in the autonomic function ('int' refers to the integrated signal): (a) hsleepmax − hmaxwake > 0.05 for a signal; (b) hintmax > 1.15 for wake; (c) hintmax − hmax > 0.85 for sleep; (d) Hurstwake − Hurstsleep < 0.01; (e) widthwake > 0.07; (f) widthint < 0.30 for sleep; (g) hintleft > 0.75. Eighty-one percent of elderly people had at least four of these properties, and ninety-two percent of young people had three or less. This shows that the multifractal approach offers a concise and reliable index of healthy aging for each individual. Additionally, the applied method yielded insights into dynamical changes in the autonomic regulation due to the circadian cycle and aging. Our observations support the hypothesis that imbalance in the autonomic control due to healthy aging could be related to

  4. Airborne Ethane Observations over the Barnett and Bakken Shale Formations: Quantification of Ethane Fluxes and Attribution of Methane Emissions

    Science.gov (United States)

    Smith, M. L.; Kort, E. A.; Karion, A.; Sweeney, C.; Peischl, J.; Ryerson, T. B.

    2014-12-01

    The largest emissions sources of methane, a potent greenhouse gas and the primary component of natural gas, are the fossil fuel sector and microbial processes that occur in agricultural settings, landfills, and wetlands. Attribution of methane to these different source sectors has proven difficult, as evidenced by persistent disagreement between the annual emissions estimated from atmospheric observations (top-down) and from inventories (bottom-up). Given the rapidly changing natural gas infrastructure in North America, and the implications of associated rapid changes in emissions of methane for climate, it is crucial we improve our ability to quantify and understand current and future methane emissions. Here, we present evidence that continuous in-situ airborne observations of ethane, which is a tracer for fossil fuel emissions, are a new and useful tool for attribution of methane emissions to specific source sectors. Additionally, with these new airborne observations we present the first tightly constrained ethane emissions estimates of oil and gas production fields using the well-known mass balance method. The ratios of ethane-to-methane (C2H6:CH4) of specific methane emissions sources were studied over regions of high oil and gas production from the Barnett, TX and Bakken, ND shale plays, using continuous (1Hz frequency) airborne ethane measurements paired with simultaneous methane measurements. Despite the complex mixture of sources in the Barnett region, the methane emissions were well-characterized by distinct C2H6:CH4 relationships indicative of a high-ethane fossil fuel source (e.g., "wet" gas), a low-ethane fossil fuel source (e.g., "dry" gas), and an ethane-free, or microbial source. The defined set of C2H6:CH4 that characterized the emissions input to the atmosphere was used in conjunction with the total ethane and methane fluxes to place bounds on the fraction of methane emissions attributable to each source. Additionally, substantial ethane fluxes

  5. Constraints on ship NOx emissions in Europe using GEOS-Chem and OMI satellite NO2 observations

    Directory of Open Access Journals (Sweden)

    G. C. M. Vinken

    2013-07-01

    Full Text Available We present a top-down ship NOx emission inventory for the Baltic Sea, North Sea, Bay of Biscay and Mediterranean Sea, based on satellite observed tropospheric NO2 columns of the Ozone Monitoring Instrument (OMI for 2005–2006. We improved the representation of ship emissions in the GEOS-Chem chemistry transport model, and compared simulated NO2 columns to consistent satellite observations. Relative differences between simulated and observed NO2 columns have been used to constrain ship emissions in four European seas (Baltic Sea, North Sea, Bay of Biscay and Mediterranean Sea. The constrained ship tracks account for 39% of total top-down European ship NOx emissions, which amounts to 0.96 Tg N for 2005, and 1.0 Tg N for 2006 (11–15% lower than the bottom-up EMEP ship emission inventory. Our results indicate that EMEP emissions in the Mediterranean Sea are too high (by 60% and misplaced by up to 150 km, which can have important consequences for local air quality simulations. In the North Sea, our top-down emissions amount to 0.05 Tg N for 2005 (35% lower than EMEP. Increased top-down emissions were found for the Baltic Sea and Bay of Biscay, with emission totals of 0.05 Tg N (131% higher than EMEP and 0.08 Tg N for 2005 (128% higher than EMEP, respectively. Our study explicitly accounts for the (non-linear sensitivity of satellite retrievals to changes in the a priori NO2 profiles. Although the effect of this sensitivity might be minor for small emission increments, our findings stress the need for consistent information in satellite retrieval and model, as satellite observations are never fully independent of model information (i.e. assumptions on vertical NO2 profiles. Our study provides for the first time a space-based top-down ship NOx emission inventory, and can serve as a framework for future studies to constrain ship emissions using satellite NO2 observations in other seas.

  6. Inhibition of type III radio emissions due to the interaction between two electron beams: Observations and simulations

    OpenAIRE

    Briand, C; Henri, P.; Hoang, S

    2014-01-01

    We report the peculiar interaction of two type III bursts observed in the solar wind. As electronbeams propagating on the same magnetic field lines cross, a spectacular depletion of the type III radioemission is observed. We combine observations from the WAVES experiment on board the STEREO missiontogether with kinetic plasma simulations to study the extinction of type III radio emission resulting fromthe interaction between two electron beams. The remote observations enable to follow the ele...

  7. Mars Global Surveyor Thermal Emission Spectrometer (TES) Observations of Dust Opacity During Aerobraking and Science Phasing

    Science.gov (United States)

    Smith, Michael D.; Pearl, John C.; Conrath, Barney J.; Christensen, Philip R.

    1999-01-01

    The Mars Global Surveyor (MGS) arrived at Mars in September 1997 near Mars southern spring equinox and has now provided monitoring of conditions in the Mars atmosphere for more than half a Mars year. The large majority of the spectra taken by the Thermal Emission Spectrometer (TES) are in a nadir geometry (downward looking mode) where Mars is observed through the atmosphere. Most of these contain the distinct spectral signature of atmospheric dust. For these nadir-geometry spectra we retrieve column-integrated infrared aerosol (dust) opacities. TES observations during the aerobraking and science-phasing portions of the MGS mission cover the seasonal range L(sub s)=184 deg - 28 deg. Excellent spatial coverage was obtained in the southern hemisphere. Northern hemisphere coverage is generally limited to narrow strips taken during the periapsis pass but is still very valuable. At the beginning of the mission the 9-(micron)meter dust opacity at midsouthern latitudes was low (0.15-0.25). As the season advanced through southern spring and into summer, TES observed several regional dust storms (including the Noachis dust storm of November 1997) where peak 9-(micron)meter dust opacities approached or exceeded unity, as well as numerous smaller local storms. Both large and small dust storms exhibited significant changes in both spatial coverage and intensity over a timescale of a day. Throughout southern spring and summer the region at the edge of the retreating southern seasonal polar ice cap was observed to be consistently more dusty than other latitudes.

  8. The Supernova Blast Wave and the Molecular Cloud: an Observational Study of Molecular Shock Emission.

    Science.gov (United States)

    Richter, Matthew Joseph

    1995-01-01

    Shock waves in molecular clouds heat, compress, accelerate, and chemically alter the gas they encounter. Despite their crucial role in determining the physical state of the dense interstellar medium and despite their making possible direct observations of H_2, molecular shocks are still poorly understood, as evidenced by the many discrepancies between theory and observations. In my dissertation, I use the supernova remnant IC 443 as a laboratory to test our understanding of shock -excited H_2 emission. By examining roughly 20 separate 2-4 μm Ha transitions, I find the non-uniform temperature structure essentially reproduces that found in Orion Peak 1, and so is consistent with the partially dissociating J-shock model presented by Brand and collaborators. Subsequent mid-infrared observations of the pure rotational S(2) transition at 12 mu m strengthens these conclusions. Velocity resolved line profiles of the strong 1-0 S(1) transition uncover a relationship between the remnant's large-scale geometry and the line profile's full-width at 10% intensity, centroid, and shape. The relationship contradicts any model requiring local bow geometries to explain broad H_2 line widths. Comparing the 1-0 S(1) data with similar observations of the 2-1 S(1) line, I demonstrate that the excitation temperature in the shocked gas depends primarily on position, not velocity. Taken together, the identical velocity extent of the 1-0 S(1) and the 2-1 S(1) lines and their upper state energy separation of E/k ~ 6000 K proves the H_2 -emitting gas reaches its full velocity dispersion prior to cooling below roughly 1500 K. Finally, I compare, with similar spatial and spectral resolution, H_2 and HCO^+ J = 1 - 0 and find evidence for temperature gradients as a result of both preshock density inhomogeneities and postshock cooling.

  9. Observations of 6-200 μm emission of the Ophiuchus cloud LDN 1688

    Science.gov (United States)

    Rawlings, M. G.; Juvela, M.; Lehtinen, K.; Mattila, K.; Lemke, D.

    2013-01-01

    We examine two positions, ON1 and ON2, within the Ophiuchus cloud LDN 1688 using observations made with the ISO photo-polarimeter (ISOPHOT) instrument aboard the Infrared Space Observatory (ISO) satellite. The data include mid-infrared spectra (˜6-12 μm) and several photometric bands up to 200 μm. The data probe the emission from molecular polycyclic aromatic hydrocarbon (PAH)-type species, transiently heated very small grains and large classical dust grains. We compare the observations to earlier studies, especially those carried out towards an isolated translucent cloud in Chamaeleon (Paper I). The spectra towards the two LDN 1688 positions are very similar to each other in spite of position ON1 having a larger column density and probably being subjected to a stronger radiation field. The ratios of the mid-infrared features are similar to those found in other diffuse and translucent clouds. Compared to Paper I, the 7.7/11.3 μm band ratios are lower, ˜2.0, at both LDN 1688 positions. A continuum is detected in the ˜10 μm region. This is stronger towards the position ON1 but still lower than on any of the sightlines in Paper I. The far-infrared opacities are higher than in diffuse medium. The value of the position ON2, τ200/N(H) = 3.9 × 10- 25 cm2/H, is twice the value found for ON1. The radiation field of LDN 1688 is dominated by the two embedded B-type double stars, ρ Oph AB and HD 147889, with an additional contribution from the Upper Sco OB association. The strong heating is reflected in the high colour temperature, ˜24 K, of the large grain emission. Radiative transfer modelling confirms a high level of the radiation field and points to an increased abundance of PAH grains. However, when the hardening of the radiation field caused by the local B stars is taken into account, the observations can be fitted with almost no change to the standard dust models. However, all the examined models underestimate the level of the mid-infrared continuum.

  10. New radio observations of anomalous microwave emission in the HII region RCW175

    CERN Document Server

    Battistelli, E S; Cruciani, A; de Bernardis, P; Genova-Santos, R; Masi, S; Naldi, A; Paladini, R; Piacentini, F; Tibbs, C T; Verstraete, L; Ysard, N

    2015-01-01

    We have observed the HII region RCW175 with the 64m Parkes telescope at 8.4GHz and 13.5GHz in total intensity, and at 21.5GHz in both total intensity and polarization. High angular resolution, high sensitivity, and polarization capability enable us to perform a detailed study of the different constituents of the HII region. For the first time, we resolve three distinct regions at microwave frequencies, two of which are part of the same annular diffuse structure. Our observations enable us to confirm the presence of anomalous microwave emission (AME) from RCW175. Fitting the integrated flux density across the entire region with the currently available spinning dust models, using physically motivated assumptions, indicates the presence of at least two spinning dust components: a warm component with a relatively large hydrogen number density n_H=26.3/cm^3 and a cold component with a hydrogen number density of n_H=150/cm^3. The present study is an example highlighting the potential of using high angular-resolutio...

  11. AN OBSERVED CORRELATION BETWEEN THERMAL AND NON-THERMAL EMISSION IN GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Michael Burgess, J.; Preece, Robert D. [Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Ryde, Felix; Axelsson, Magnus [Department of Physics, Royal Institute of Technology (KTH), AlbaNova, SE-106 91 Stockholm (Sweden); Veres, Peter; Mészáros, Peter [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Connaughton, Valerie; Briggs, Michael; Bhat, P. N.; Pelassa, Veronique [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Pe' er, Asaf [Physics Department, University College Cork, Cork (Ireland); Iyyani, Shabnam [The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm (Sweden); Goldstein, Adam [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Byrne, David; Fitzpatrick, Gerard; Foley, Suzanne [University College Dublin, Belfield, Dublin 4 (Ireland); Kocevski, Daniel; Omodei, Nicola [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Paciesas, William S., E-mail: jmichaelburgess@gmail.com, E-mail: rob.preece@nasa.gov, E-mail: felix@particle.kth.se, E-mail: veres@gwu.edu, E-mail: npp@astro.psu.edu [Universities Space Research Association, Huntsville, AL 35805 (United States); and others

    2014-04-01

    Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal γ-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, E {sub p} and kT, of these two components are correlated via the relation E {sub p}∝T {sup α} which varies from GRB to GRB. We present an interpretation in which the value of the index α indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.

  12. An Observed Correlation Between Thermal and Non-Thermal Emission in Gamma-Ray Bursts

    CERN Document Server

    Burgess, J Michael; Ryde, Felix; Veres, Peter; Meszaros, Peter; Connaughton, Valerie; Briggs, Michael; Pe'er, Asaf; Iyyani, Shabnam; Goldstein, Adam; Axelsson, Magnus; Baring, Matthew G; Bhat, P N; Byrne, David; Fitzpatrick, Gerard; Foley, Suzanne; Kocevski, Daniel; Omodei, Nicola; Paciesas, William S; Pelassa, Veronique; Kouveliotou, Chryssa; Xiong, Shaolin; Yu, Hoi-Fung; Zhang, Binbin; Zhu, Sylvia

    2014-01-01

    Recent observations by the $Fermi$ Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some Gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal $\\gamma$-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, $E_{\\rm p}$ and $kT$, of these two components are correlated via the relation $E_{\\rm p} \\propto T^{\\alpha}$ which varies from GRB to GRB. We present an interpretation in which the value of index $\\alpha$ indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.

  13. Observation of ion cyclotron emission owing to DD fusion product H ions in JT-60U

    International Nuclear Information System (INIS)

    High-frequency fluctuations in the ion cyclotron range of frequency (ICRF) are excited in magnetically confined plasmas because of the distortion of velocity distribution. In deuterium plasma experiments in JT-60U, ion cyclotron emission (ICE) detected as magnetic fluctuations is observed using ICRF antennas as pickup loops. The toroidal wave-numbers can be estimated using the phase differences between the signals from antenna elements arrayed in the toroidal direction. In this manuscript, ICE due to fusion product (FP) H ions, ICE(H), which is identified separately from the second-harmonic ICE caused by D ions, is newly reported. ICE is considered to result from spontaneous excitation of magnetosonic waves associated with FP high-energy ions. ICE caused by 3He ions and T ions has already been identified and confirmed to have finite toroidal wave-numbers. In contrast, ICE caused by ions originating in neutral beam injection has no toroidal wave-numbers. It is suggested that the appearance of ICE(H) depends strongly on the plasma density, and weak magnetic shear operation is one of the possible conditions for the observation of ICE(H). (author)

  14. DIRECT OBSERVATION OF SOLAR CORONAL MAGNETIC FIELDS BY VECTOR TOMOGRAPHY OF THE CORONAL EMISSION LINE POLARIZATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kramar, M. [Physics Department, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); Lin, H. [Institute for Astronomy, University of Hawaii at Manoa, 34 Ohia Ku Street, Pukalani, Maui, HI 96768 (United States); Tomczyk, S., E-mail: kramar@cua.edu, E-mail: lin@ifa.hawaii.edu, E-mail: tomczyk@ucar.edu [High Altitude Observatory, 3080 Center Green Drive, Boulder, CO 80301 (United States)

    2016-03-10

    We present the first direct “observation” of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The vector tomographic inversion uses measurements of the Fe xiii 10747 Å Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and 3D coronal density and temperature derived from scalar tomographic inversion of Solar Terrestrial Relations Observatory (STEREO)/Extreme Ultraviolet Imager (EUVI) coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, we compared the tomography inverted coronal magnetic fields with those constructed by magnetohydrodynamic (MHD) simulations based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for several regions. Particularly, for one of the most noticeable regions, we found that the MHD simulation for CR 2113 predicted a model that more closely resembles the vector tomography inverted magnetic fields. In another case, our tomographic reconstruction predicted an open magnetic field at a region where a coronal hole can be seen directly from a STEREO-B/EUVI image. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments.

  15. Observations of 6 - 200 {\\mu}m emission of the Ophiuchus cloud LDN 1688

    CERN Document Server

    Rawlings, M G; Lehtinen, K; Mattila, K; Lemke, D

    2012-01-01

    We examine two positions, ON1 and ON2, within the Ophiuchus cloud LDN 1688 using observations made with the ISOPHOT instrument aboard the ISO satellite. The data include mid-IR spectra (~6-12{\\mu}m) and several photometric bands up to 200{\\mu}m. The data probe the emission from molecular PAH-type species, transiently-heated Very Small Grains (VSGs), and large classical dust grains. We compare the observations to earlier studies, especially those carried out towards an isolated translucent cloud in Chamaeleon (Paper I). The spectra towards the two LDN 1688 positions are very similar to each other, in spite of position ON1 having a larger column density and probably being subjected to a stronger radiation field. The ratios of the mid-IR features are similar to those found in other diffuse and translucent clouds. Compared to paper I, the 7.7/11.3{\\mu}m band ratios are lower, ~2.0, at both LDN 1688 positions. A continuum is detected in the ~10{\\mu}m region. This is stronger towards the position ON1 but still lowe...

  16. A comparative study of measured amplitude and phase perturbations of VLF and LF radio signals induced by solar flares

    Directory of Open Access Journals (Sweden)

    Šulić D.M.

    2014-01-01

    Full Text Available Very Low Frequency (VLF and Low Frequency (LF signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares in order to understand processes involved in propagation of VLF/LF radio signals over short paths and to estimate specific characteristics of each short path. The receiver at the Belgrade station is constantly monitoring the amplitude and phase of a coherent and subionospherically propagating LF signal operated in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, respectively. A significant number of similarities between these short paths is a direct result of both transmitters and the receiver’s geographic location. The main difference is in transmitter frequencies. From July 2008 to February 2014 there were about 200 events that were chosen for further examination. All selected examples showed that the amplitude and phase of VLF and LF signals were perturbed by solar X-ray flares occurrence. This six-year period covers both minimum and maximum of solar activity. Simultaneous measurement of amplitude and phase of the VLF/LF signals during a solar flare occurrence was applied to evaluate the electron density profile versus altitude, to carry out the function of time over the middle Europe. [Projekat Ministarstva nauke Republike Srbije, br. 176002 i br. III4402

  17. Statistical correlation of low-altitude ENA emissions with geomagnetic activity from IMAGE/MENA observations

    Science.gov (United States)

    Mackler, D. A.; Jahn, J.-M.; Perez, J. D.; Pollock, C. J.; Valek, P. W.

    2016-03-01

    Plasma sheet particles transported Earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low-altitude (300-800 km) ion precipitation in the high-latitude atmosphere/ionosphere are termed low-altitude emissions (LAEs). Remotely observed LAEs are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90°. The Geomagnetic Emission Cone of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity. The LAE data are from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000-2005). The SYM-H, AE, and Kp indices are used to describe geomagnetic activity. The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM-H showing the greatest sensitivity. The magnetic local time distribution of LAEs is centered about midnight and spreads with increasing activity. The invariant latitude for all indices has a slightly negative correlation. The combined results indicate LAE behavior similar to that of ion precipitation.

  18. A flare observed in coronal, transition region, and helium I 10830 Å emissions

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Zhicheng; Cao, Wenda [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, Newark, NJ 07102 (United States); Qiu, Jiong [Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States); Judge, Philip G. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307-3000 (United States)

    2014-10-01

    On 2012 June 17, we observed the evolution of a C-class flare associated with the eruption of a filament near a large sunspot in the active region NOAA 11504. We obtained high spatial resolution filtergrams using the 1.6 m New Solar Telescope at the Big Bear Solar Observatory in broadband TiO at 706 nm (bandpass: 10 Å) and He I 10830 Å narrow band (bandpass: 0.5 Å, centered 0.25 Å to the blue). We analyze the spatio-temporal behavior of the He I 10830 Å data, which were obtained over a 90''×90'' field of view with a cadence of 10 s. We also analyze simultaneous data from the Atmospheric Imaging Assembly and Extreme Ultraviolet Variability Experiment instruments on board the Solar Dynamics Observatory spacecraft, and data from the Reuven Ramaty High Energy Solar Spectroscopic Imager and GOES spacecrafts. Non-thermal effects are ignored in this analysis. Several quantitative aspects of the data, as well as models derived using the '0D' enthalpy-based thermal evolution of loops model code, indicate that the triplet states of the 10830 Å multiplet are populated by photoionization of chromospheric plasma followed by radiative recombination. Surprisingly, the He II 304 Å line is reasonably well matched by standard emission measure calculations, along with the C IV emission which dominates the Atmosphere Imaging Assembly 1600 Å channel during flares. This work lends support to some of our previous work combining X-ray, EUV, and UV data of flares to build models of energy transport from corona to chromosphere.

  19. Assessment of Models of Galactic Thermal Dust Emission Using COBE/FIRAS and COBE/DIRBE Observations

    CERN Document Server

    Odegard, N; Chuss, D T; Miller, N J

    2016-01-01

    Accurate modeling of the spectrum of thermal dust emission at millimeter wavelengths is important for improving the accuracy of foreground subtraction for CMB measurements, for improving the accuracy with which the contributions of different foreground emission components can be determined, and for improving our understanding of dust composition and dust physics. We fit four models of dust emission to high Galactic latitude COBE/FIRAS and COBE/DIRBE observations from 3 millimeters to 100 microns and compare the quality of the fits. We consider the two-level systems model because it provides a physically motivated explanation for the observed long wavelength flattening of the dust spectrum and the anticorrelation between emissivity index and dust temperature. We consider the model of Finkbeiner, Davis, and Schlegel because it has been widely used for CMB studies, and the generalized version of this model recently applied to Planck data by Meisner and Finkbeiner. For comparison we have also fit a phenomenologic...

  20. Observation of CH4 and other Non-CO2 Green House Gas Emissions from California

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Marc L.; Zhao, Chuanfeng; Riley, William J.; Andrews, Arlyn C.

    2009-01-09

    In 2006, California passed the landmark assembly bill AB-32 to reduce California's emissions of greenhouse gases (GHGs) that contribute to global climate change. AB-32 commits California to reduce total GHG emissions to 1990 levels by 2020, a reduction of 25 percent from current levels. To verify that GHG emission reductions are actually taking place, it will be necessary to measure emissions. We describe atmospheric inverse model estimates of GHG emissions obtained from the California Greenhouse Gas Emissions Measurement (CALGEM) project. In collaboration with NOAA, we are measuring the dominant long-lived GHGs at two tall-towers in central California. Here, we present estimates of CH{sub 4} emissions obtained by statistical comparison of measured and predicted atmospheric mixing ratios. The predicted mixing ratios are calculated using spatially resolved a priori CH{sub 4} emissions and surface footprints, that provide a proportional relationship between the surface emissions and the mixing ratio signal at tower locations. The footprints are computed using the Weather Research and Forecast (WRF) coupled to the Stochastic Time-Inverted Lagrangian Transport (STILT) model. Integral to the inverse estimates, we perform a quantitative analysis of errors in atmospheric transport and other factors to provide quantitative uncertainties in estimated emissions. Regressions of modeled and measured mixing ratios suggest that total CH{sub 4} emissions are within 25% of the inventory estimates. A Bayesian source sector analysis obtains posterior scaling factors for CH{sub 4} emissions, indicating that emissions from several of the sources (e.g., landfills, natural gas use, petroleum production, crops, and wetlands) are roughly consistent with inventory estimates, but livestock emissions are significantly higher than the inventory. A Bayesian 'region' analysis is used to identify spatial variations in CH{sub 4} emissions from 13 sub-regions within California

  1. Estimating methane and nitrous oxide emissions in California using multi-tower observations and hierarchical Bayesian inversion

    Science.gov (United States)

    Jeong, S.; Hsu, Y.; Newman, S.; Zhang, J.; Andrews, A. E.; Bianco, L.; Bagley, J.; Cui, X.; Graven, H. D.; Kim, J.; Salameh, P.; LaFranchi, B. W.; Priest, C.; Campos-Pineda, M.; Novakovskaia, E.; Sloop, C.; Michelsen, H. A.; Bambha, R.; Weiss, R. F.; Keeling, R. F.; Fischer, M. L.

    2015-12-01

    We present an analysis of annual state total methane (CH4) and nitrous oxide (N2O) emissions from California using atmospheric observations from thirteen sites (six sites for N2O) in California during June 2013 - May 2014. A hierarchical Bayesian inversion (HBI) method is used to estimate CH4 and N2O emissions for spatial regions (0.3 degree pixels) by comparing measured mixing ratios with transport model (WRF-STILT) predictions. Using the multi-site measurements across California, the HBI analysis constrains a significant portion of expected emissions for both CH4 and N2O in the Central Valley and southern California. Based on the HBI analysis, we estimate a likely range of the state's annual CH4 emissions is 2.4 - 2.7 Tg CH4/yr (at 68% confidence), which is 1.4 - 1.6 times the total estimated by the California Air Resources Board (CARB). Similarly, we estimate the state's annual N2O emissions to be 77 - 95 Gg N2O/yr (at 68% confidence), which are 1.6 - 2.0 times CARB's state total. These results suggest that the combined total of CH4 and N2O emissions from the HBI analysis would comprise 18 - 21% of state total greenhouse gas (GHG) emissions, higher than 12% estimated in the current state inventory. Additionally, we expand previous evaluations of possible systematic bias in annual emission estimates due to transport model error by comparing measured and predicted carbon monoxide (CO) for four of the sites. These results highlight the need for multiple independent methods to estimate non-CO2 GHG emissions, and offer insight into opportunities for non-CO2 GHG emission mitigation efforts towards achieving California's GHG emission goals.

  2. Observation of modulated spontaneous emission of Rhodamine 6G in low refractive index contrast 1D-periodic gelatin film

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The modulation of the spontaneous emission of Rhodamine 6G has been observed in one-dimensional periodic dielectric structure of dichromated gelatin film with refractive index contrast as low as 0.01. The spontaneous emission is enhanced at the band edges and inhibits in the band gap, which agree well with the theoretical analysis on the redistribution of the fractional local density of optical states.

  3. Observation of the O I ultraviolet intercombination emissions in the terrestrial dayglow

    Science.gov (United States)

    Bowers, C. W.; Feldman, P. D.; Tennyson, P. D.; Kane, M.

    1987-01-01

    The first measurement of the 1173-A O I intercombination line in emission in the terrestrial dayglow was performed using the EUV-FUV spectrometer designed to be flown with the Astro-1 observatory. The atmospheric conditions and viewing geometry were such as to suppress nitrogen emission relative to those from atomic oxygen, permitting the identification and measurement of the weak O I 1173-A intercombination multiplet and the 1641-A line as well as the strong 989-A and 1304-A emissions. At lower altitudes, the 1173-A emission rate increased while the 989-A emission, from the same upper level, decreased. This behavior is consistent with the radiative entrapment model of Meier (1982) and the laboratory value of the 1173-A/989-A branching ratio measured by Morrison (1985). The 1641-A/1304-A emission ratio is also consistent with a radiative entrapment model.

  4. Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at the HAARP Facility

    Science.gov (United States)

    Scales, Wayne; Bernhardt, Paul; McCarrick, Michael; Briczinski, Stanley; Mahmoudian, Alireza; Fu, Haiyang; Ranade Bordikar, Maitrayee; Samimi, Alireza

    There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. There is also important parametric behavior on both classes of NSEE depending on the pump wave parameters including the field strength, antenna beam angle, and electron gyro-harmonic number. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities will be provided. Computer simulation model results will be presented

  5. NUV/Blue spectral observations of sprites in the 320-460 nm region: ${\\mathrm N_2}$ (2PG) Emissions

    CERN Document Server

    Heavner, M J; Siefring, C; Sentman, D D; Moudry, D R; Wescott, E M; Bucsela, E J

    2010-01-01

    A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98 aircraft sprite observation campaign during July 1998. In this wavelength range video rate (60 fields/sec) spectrographic observations found the NUV/blue emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG) present in the spectrum is confirmed by observations of a co-aligned, narrowly filtered 427.8 nm imager and is in agreement with previous ground-based filtered photometer observations. The synthetic spectral fit to the observations indicates a characteristic energy of ~1.8 eV, in agreement with our other NUV observations.

  6. Characteristic properties of Nu whistlers as inferred from observations and numerical modelling

    Directory of Open Access Journals (Sweden)

    D. R. Shklyar

    2004-11-01

    Full Text Available The properties of Nu whistlers are discussed in the light of observations by the MAGION 5 satellite, and of numerically simulated spectrograms of lightning-induced VLF emissions. The method of simulation is described in full. With the information from this numerical modelling, we distinguish the characteristics of the spectrograms that depend on the site of the lightning strokes from those that are determined mainly by the position of the satellite. Also, we identify the region in the magnetosphere where Nu whistlers are observed most often, and the geomagnetic conditions favouring their appearance. The relation between magnetospherically reflected (MR whistlers and Nu whistlers is demonstrated by the gradual transformation of MR whistlers into Nu whistlers as the satellite moves from the high-altitude equatorial region to lower altitudes and higher latitudes. The magnetospheric reflection of nonducted whistler-mode waves, which is of decisive importance in the formation of Nu whistlers, is discussed in detail.

  7. Vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma.

    Science.gov (United States)

    Wang, T. N. C.; Bell, T. F.

    1972-01-01

    With the use of a power integral formulation, a study is made of the vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma. Expressions for the ray patterns are initially developed that apply for arbitrary values of driving frequency, static magnetic-field strength, plasma density, and composition. These expressions are subsequently specialized to vlf/elf radiation in a plasma modeled on the magnetosphere. A series of representative pattern plots are presented for frequencies between the proton and electron gyrofrequencies. These patterns illustrate the fact that focusing effects that arise from the geometrical properties of the refractive index surface tend to dominate the radiation distribution over the entire range from the electron gyrofrequency to 4.6 times the proton gyrofrequency. It is concluded that focusing effects should be of significant importance in the design of a vlf/elf satellite transmitting system in the magnetosphere.

  8. Fermi Large Area Telescope observations of high-energy gamma-ray emission from behind-the-limb solar flares

    CERN Document Server

    Pesce-Rollins, Melissa; Petrosian, Vahe'; Liu, Wei; da Costa, Fatima Rubio; Allafort, Alice

    2015-01-01

    Fermi-LAT >30 MeV observations have increased the number of detected solar flares by almost a factor of 10 with respect to previous space observations. These sample both the impulsive and long duration phases of GOES M and X class flares. Of particular interest is the recent detections of three solar flares whose position behind the limb was confirmed by the STEREO-B spacecraft. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources and implications for the particle acceleration mechanisms.

  9. Estimating SO2 emissions from a large point source using 10 year OMI SO2 observations: Afsin Elbistan Power Plant

    Science.gov (United States)

    Kaynak Tezel, Burcak; Firatli, Ertug

    2016-04-01

    SO2 pollution has still been a problem for parts of Turkey, especially regions with large scale coal power plants. In this study, 10 year Ozone Monitoring Instrument (OMI) SO2 observations are used for estimating SO2 emissions from large point sources in Turkey. We aim to estimate SO2 emissions from coal power plants where no online monitoring is available and improve the emissions given in current emission inventories with these top-down estimates. High-resolution yearly averaged maps are created on a domain over large point sources by oversampling SO2 columns for each grid for the years 2005-2014. This method reduced the noise and resulted in a better signal from large point sources and it was used for coal power plants in U.S and India, previously. The SO2 signal over selected power plants are observed with this method, and the spatiotemporal changes of SO2 signal are analyzed. With the assumption that OMI SO2 observations are correlating with emissions, long-term OMI SO2 observation averages can be used to estimate emission levels of significant point sources. Two-dimensional Gaussian function is used for explaining the relationships between OMI SO2 observations and emissions. Afsin Elbistan Power Plant, which is the largest capacity coal power plant in Turkey, is investigated in detail as a case study. The satellite scans within 50 km of the power plant are selected and averaged over a 2 x 2 km2 gridded domain by smoothing method for 2005-2014. The yearly averages of OMI SO2 are calculated to investigate the magnitude and the impact area of the SO2 emissions of the power plant. A significant increase in OMI SO2 observations over Afsin Elbistan from 2005 to 2009 was observed (over 2 times) possibly due to the capacity increase from 1715 to 2795 MW in 2006. Comparison between the yearly gross electricity production of the plant and OMI SO2 observations indicated consistency until 2009, but OMI SO2 observations indicated a rapid increase while gross electricity

  10. Source attribution using FLEXPART and carbon monoxide emission inventories for the IAGOS In-situ Observation database

    Science.gov (United States)

    Fontaine, Alain; Sauvage, Bastien; Pétetin, Hervé; Auby, Antoine; Boulanger, Damien; Thouret, Valerie

    2016-04-01

    Since 1994, the IAGOS program (In-Service Aircraft for a Global Observing System http://www.iagos.org) and its predecessor MOZAIC has produced in-situ measurements of the atmospheric composition during more than 46000 commercial aircraft flights. In order to help analyzing these observations and further understanding the processes driving their evolution, we developed a modelling tool SOFT-IO quantifying their source/receptor link. We improved the methodology used by Stohl et al. (2003), based on the FLEXPART plume dispersion model, to simulate the contributions of anthropogenic and biomass burning emissions from the ECCAD database (http://eccad.aeris-data.fr) to the measured carbon monoxide mixing ratio along each IAGOS flight. Thanks to automated processes, contributions are simulated for the last 20 days before observation, separating individual contributions from the different source regions. The main goal is to supply add-value products to the IAGOS database showing pollutants geographical origin and emission type. Using this information, it may be possible to link trends in the atmospheric composition to changes in the transport pathways and to the evolution of emissions. This tool could be used for statistical validation as well as for inter-comparisons of emission inventories using large amounts of data, as Lagrangian models are able to bring the global scale emissions down to a smaller scale, where they can be directly compared to the in-situ observations from the IAGOS database.

  11. Airborne Observations of Mercury Emissions from the Chicago/Gary Urban/Industrial Area during the 2013 NOMADSS Campaign

    Science.gov (United States)

    Gratz, L.; Ambrose, J. L., II; Jaffe, D. A.; Knote, C. J.; Jaegle, L.; Selin, N. E.; Campos, T. L.; Flocke, F. M.; Reeves, J. M.; Stechman, D. M.; Stell, M. H.; Weinheimer, A. J.; Knapp, D. J.; Montzka, D.; Tyndall, G. S.; Mauldin, L.; Cantrell, C. A.; Apel, E. C.; Hornbrook, R. S.; Blake, N. J.

    2015-12-01

    Atmospheric emissions from the Chicago/Gary urban/industrial area significantly enhance ambient mercury (Hg) concentrations and lead to increased levels of atmospheric mercury deposition within the Lake Michigan Basin (Gratz et al., 2013a; Gratz et al., 2013b; Landis and Keeler, 2002; Landis et al., 2002; Vette et al., 2002). In this study we use airborne observations of total atmospheric Hg (THg) collected over Lake Michigan during summer 2013 as part of the Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) field campaign to quantify the outflow of total atmospheric Hg from the Chicago/Gary urban/industrial area. We use concurrent airborne measurements of THg, carbon monoxide (CO), nitrogen oxides (NOx), and sulfur dioxide (SO2) to calculate measured enhancement ratios (ER) and thus characterize Chicago/Gary emissions. We determine the observed THg/CO ER in outflow from Chicago/Gary to be 2.11x10-7 mol mol-1, which is comparable to values reported in the literature for other major U.S. urban/industrial areas (Radke et al., 2007; Talbot et al., 2008; Weiss-Penzias et al., 2013). We also employ the FLEXPART Lagrangian transport and dispersion model to simulate air mass transport during plume encounters. We convolve the emissions of each species from the 2011 U.S. EPA National Emissions Inventory (NEI) with the FLEXPART-modeled air mass transport to compare our observations to inventoried emission ratios (EmR). We find that the inventoried THg/CO EmRs are biased low by -63% to -67% compared to the observed ERs for the Chicago/Gary area. This suggests that there are many small emission sources that are not fully accounted for within the inventory, and/or that the re-emission of legacy Hg is a significant source of THg to the atmosphere in this region.

  12. Global Partitioning of NOx Sources Using Satellite Observations: Relative Roles of Fossil Fuel Combustion, Biomass Burning and Soil Emissions

    Science.gov (United States)

    Jaegle, Lyatt; Steinberger, Linda; Martin, Randall V.; Chance, Kelly

    2005-01-01

    This document contains the following abstract for the paper "Global partitioning of NOx sources using satellite observations: Relative roles of fossil fuel combustion, biomass burning and soil emissions." Satellite observations have been used to provide important new information about emissions of nitrogen oxides. Nitrogen oxides (NOx) are significant in atmospheric chemistry, having a role in ozone air pollution, acid deposition and climate change. We know that human activities have led to a three- to six-fold increase in NOx emissions since pre-industrial times, and that there are three main surface sources of NOx: fuel combustion, large-scale fires, and microbial soil processes. How each of these sources contributes to the total NOx emissions is subject to some doubt, however. The problem is that current NOx emission inventories rely on bottom-up approaches, compiling large quantities of statistical information from diverse sources such as fuel and land use, agricultural data, and estimates of burned areas. This results in inherently large uncertainties. To overcome this, Lyatt Jaegle and colleagues from the University of Washington, USA, used new satellite observations from the Global Ozone Monitoring Experiment (GOME) instrument. As the spatial and seasonal distribution of each of the sources of NOx can be clearly mapped from space, the team could provide independent topdown constraints on the individual strengths of NOx sources, and thus help resolve discrepancies in existing inventories. Jaegle's analysis of the satellite observations, presented at the recent Faraday Discussion on "Atmospheric Chemistry", shows that fuel combustion dominates emissions at northern mid-latitudes, while fires are a significant source in the Tropics. Additionally, she discovered a larger than expected role for soil emissions, especially over agricultural regions with heavy fertilizer use. Additional information is included in the original extended abstract.

  13. HST-COS Observations of Hydrogen, Helium, Carbon and Nitrogen Emission from the SN 1987A Reverse Shock

    CERN Document Server

    France, Kevin; Penton, Steven V; Kirshner, Robert P; Challis, Peter; Laming, J Martin; Bouchet, Patrice; Chevalier, Roger; Fransson, Claes; Garnavich, Peter M; Heng, Kevin; Larsson, Josefin; Lawrence, Stephen; Lundqvist, Peter; Panagia, Nino; Pun, Chun S J; Smith, Nathan; Sollerman, Jesper; Sonneborn, George; Sugerman, Ben; Wheeler, J Craig

    2011-01-01

    We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (dv \\sim 300 km/s) emission lines from the circumstellar ring, broad (dv \\sim 10 -- 20 x 10^3 km/s) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise (> 40 per resolution element) broad LyA emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at \\lambda > 1350A can be explained by HI 2-photon emission from the same region. We confirm our earlier, tentative detection of NV \\lambda 1240 emission from the reverse shock and we present the first detections of broad HeII \\lambda1640, CIV \\lambda1550, and NIV] \\lambda1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 +/- 0.06. The NV/H-alpha line ratio requires partial ion-electron e...

  14. Free-free and H42alpha emission from the dusty starburst within NGC 4945 as observed by ALMA

    CERN Document Server

    Bendo, G J; D'Cruze, M J; Dickinson, C; Fuller, G A; Karim, A

    2016-01-01

    We present observations of the 85.69 GHz continuum emission and H42alpha line emission from the central 30 arcsec within NGC 4945. Both sources of emission originate from nearly identical structures that can be modelled as exponential discs with a scale length of ~2.1 arcsec (or ~40 pc). An analysis of the spectral energy distribution based on combining these data with archival data imply that 84% +/- 10% of the 85.69 GHz continuum emission originates from free-free emission. The electron temperature is 5400 +/- 600 K, which is comparable to what has been measured near the centre of the Milky Way Galaxy. The star formation rate (SFR) based on the H42alpha and 85.69 GHz free-free emission (and using a distance of 3.8 Mpc) is 4.35 +/- 0.25 M/yr. This is consistent with the SFR from the total infrared flux and with previous measurements based on recombination line emission, and it is within a factor of ~2 of SFRs derived from radio data. The Spitzer Space Telescope 24 micron data and Wide-field Infrared Survey E...

  15. Observations of free-free and anomalous microwave emission from LDN 1622 with the 100 m Green Bank Telescope

    Science.gov (United States)

    Harper, S. E.; Dickinson, C.; Cleary, K.

    2015-11-01

    LDN 1622 has previously been identified as a possible strong source of dust-correlated anomalous microwave emission (AME). Previous observations were limited by resolution meaning that the radio emission could not be compared with current generation high-resolution infrared data from Herschel, Spitzer or Wide-field Infrared Sky Explorer. This paper presents arcminute resolution mapping observations of LDN 1622 at 4.85 and 13.7 GHz using the 100 m Robert C. Byrd Green Bank Telescope. The 4.85 GHz map reveals a corona of free-free emission enclosing LDN 1622 that traces the photodissociation region of the cloud. The brightest peaks of the 4.85 GHz map are found to be within ≈10 per cent agreement with the expected free-free predicted by Southern H-Alpha Sky Survey Atlas H α data of LDN 1622. At 13.7 GHz, the AME flux density was found to be 7.0 ± 1.4 mJy and evidence is presented for a rising spectrum between 13.7 and 31 GHz. The spinning dust model of AME is found to naturally account for the flux seen at 13.7 GHz. Correlations between the diffuse 13.7 GHz emission and the diffuse mid-infrared emission are used to further demonstrate that the emission originating from LDN 1622 at 13.7 GHz is described by the spinning dust model.

  16. Detecting leachate plumes and groundwater pollution at Ruseifa municipal landfill utilizing VLF-EM method

    Science.gov (United States)

    Al-Tarazi, E.; Abu Rajab, J.; Al-Naqa, A.; El-Waheidi, M.

    2008-09-01

    A Very Low Frequency-Electromagnetic (VLF-EM) survey was carried out in two sites of domestic waste of old and recent landfills. The landfill structures lie on a major highly fractured limestone aquifer of shallow groundwater less than 30 m, which is considered as the main source of fresh water in Amman-Zarqa region. A total of 18 VLF-EM profiles were conducted with length ranges between 250 and 1500 m. Hydrochemical and biochemical analysis of water samples, taken from wells in the region, has also been conducted. The integrated results of previous DC resistivity method of the same study area and the outcomes of the 2-D tipper inversion of VLF-EM data proved the efficiency of this method in locating shallow and deep leachate plume with resistivity less than 20 Ω m, and enabling the mapping of anomalous bodies and their extensions down to 40 m depth. The sign of groundwater contamination was noticed in many surrounding wells resulting in the high number of fecal coliform bacteria and total coliform bacteria and the increase in inorganic parameters such as chloride (Cl). The pollution of groundwater wells in the landfill area is attributed to the leachate bodies which flow through the upper part of Wadi Es Sir (A7) or Amman-Wadi Es Sir Aquifer (B2/A7). Furthermore, several structural features were detected and the direction of local groundwater movement has been determined. The structural features have been found to have critical effects on the flowing of leachate plume towards north-northeast and west-southwest of the potable aquifer in the area.

  17. Eddy covariance observations of methane and nitrous oxide emissions: Towards more accurate estimates from ecosystems

    NARCIS (Netherlands)

    Kroon-van Loon, P.S.

    2010-01-01

    About 30% of the increased greenhouse gas (GHG) emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are related to land use changes and agricultural activities. In order to select effective measures, knowledge is required about GHG emissions from these ecosystems and how these e

  18. Right-hand polarized 4fce auroral roar emissions: 1. Observations

    Science.gov (United States)

    LaBelle, J.; Chen, Y.

    2016-08-01

    A receiving system installed at Sondrestrom, Greenland, was used to monitor all detectable auroral radio emissions at the fourth harmonic of the electron cyclotron frequency (called 4fce roar emissions) between May 2015 and March 2016. Of 88 events detected, 86 occurred during daylit conditions and were left-hand polarized. Two occurred during darkness conditions and were right-hand polarized. The left-hand and right-hand polarized events had entirely different frequency distributions. One of the right-hand polarized 4fce emissions occurred at the same time as and at exactly twice the frequency of a second harmonic emission (2fce roar). The occurrence rate of 4fce emissions during premidnight hours under daylit conditions at Sondrestrom is 5%, comparable to previously reported occurrence rates of 2fce roar in darkness conditions at optimum latitudes of occurrence, but the occurrence rate of 4fce emissions during dark conditions is much lower, suggesting that if the right-hand polarized events arise from coalescence of 2fce waves, only for a small fraction of nighttime 2fce roar emissions does such a process yield 4fce emissions detectable at ground level.

  19. Features of amplitude and Doppler frequency variation of ELF/VLF waves generated by "beat-wave" HF heating at high latitudes

    Science.gov (United States)

    Tereshchenko, E. D.; Shumilov, O. I.; Kasatkina, E. A.; Gomonov, A. D.

    2014-07-01

    Observations of extremely low frequency (ELF, 3-3000 Hz) radio waves generated by a "beat-wave" (BW) high frequency (~ 4.04-4.9 MHz) ionospheric heating are presented. ELF waves were registered with the ELF receiver located at Lovozero (68°N, 35°E), 660 km east from the European Incoherent Scatter Tromso heating facility (69.6°N, 19.2°E). Frequency shifts between the generated beat-wave and received ELF waves were detected in all sessions. It is shown that the amplitudes of ELF waves depend on the auroral electrojet current strength. Our results showing a strong dependence of ELF signal intensities on the substorm development seem to support the conclusion that electrojet currents may affect the BW generation of ELF/VLF waves.

  20. Application of an Automated System for the Processing of VLF signals to Detect, Analyze and Classify Seismic-Ionospheric Precursor Phenomena

    Science.gov (United States)

    Skeberis, Christos; Xenos, Thomas; Contadakis, Michael; Arabelos, Dimitrios; Biagi, Pier Francesco; Maggipinto, Tommaso

    2013-04-01

    This paper studies the development and application of an automated system based on Predictive Modular Neural Networks (PREMONNs) and Self Organizing Maps (SOMs) along with the necessary backend development of database classification required to provide a fully integrated system for detecting disturbances that can be attributed to seismic-ionospheric precursor phenomena using VLF radio signals. The aforementioned system can analyze all the relevant data and bring forth and adaptively discriminate different characteristics in the received signals, in real time in order to provide data segments of interest that can be correlated to subsequent seismic phenomena and can be classified with respect to pre-recorded samples of previous points of interest (POIs). PREMONNs as it was demonstrated in previous studies can be used for time-series switching detection and can be applied to the detection of POIs , whereas SOMs have been extensively used in unsupervised pattern recognition and classification of datasets. For the purpose of this paper, data acquired in Thessaloniki (40.59N, 22,78E) from the VLF station in Tavolara, Italy (ICV station Lat 40.923, Lon. 9.731) for over two years (December 2010 - December 2012) are used. The receiver was developed by Elettronika Srl, and is part of the International Network for Frontier Research on Earthquake Precursors (INFREP). The received VLF signal is normalized and then processed using the Empirical Mode Decomposition Method (EMD). The resulting data are passed to an Artificial Neural Network (ANN) based on PREMONNs trained specifically for this purpose and the output from that stage is passed onto a classifier based on SOMs to compare and classify points of interest based on a current database of received signals and identifying and storing new ones for future reference. The efficacy of the detection and the results of the aforementioned process is then discussed and results are presented. Therefore, based on the results it may be

  1. Analysis of experimentally validated trans-ionospheric attenuation estimates of VLF signals

    OpenAIRE

    İnan, Umran Savaş; Graf, K. L.; Lehtinen, N. G.; Spasojevic, M.; Cohen,M.B; Marshall, R. A.

    2013-01-01

    JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 1–13, doi:10.1002/jgra.50228, 2013 Analysis of experimentally validated trans-ionospheric attenuation estimates of VLF signals K. L. Graf,1 N. G. Lehtinen,1 M. Spasojevic,1 M. B. Cohen,1 R. A. Marshall,1 and U. S. Inan1,2 Received 7 February 2013; revised 6 March 2013; accepted 12 March 2013. [1] Accurate models of trans-ionospheric propagation are needed to assess the role of Earth-originating very low frequency (...

  2. SNR changes of VLF radio signals detected onboard the DEMETER satellite and their possible relationship to the Wenchuan earthquake

    Institute of Scientific and Technical Information of China (English)

    HE YuFei; YANG DongMei; CHEN HuaRan; QIAN JiaDong; ZHU Rong; M.Parrot

    2009-01-01

    Here we used the VLF signal data received by the DEMETER satellite,transmitted from various ground VLF transmitters which are located around China,to study the changes in the signal to noise ratio (SNR) before and after the Wenchuan earthquake,which had a magnitude of 8.0.We also found that the SNRs of different frequency signals decreased significantly over the epicenter region before the earthquake,and reverted to their original levels after the earthquake.This phenomenon may be related to the earthquake.

  3. SNR changes of VLF radio signals detected onboard the DEMETER satellite and their possible relationship to the Wenchuan earthquake

    Institute of Scientific and Technical Information of China (English)

    M.; Parrot

    2009-01-01

    Here we used the VLF signal data received by the DEMETER satellite, transmitted from various ground VLF transmitters which are located around China, to study the changes in the signal to noise ratio (SNR) before and after the Wenchuan earthquake, which had a magnitude of 8.0. We also found that the SNRs of different frequency signals decreased significantly over the epicenter region before the earthquake, and reverted to their original levels after the earthquake. This phenomenon may be related to the earthquake.

  4. Correlation of VLF-EM Data with Radiometric Measurements: Implications for Uranium Exploration around Beldih, South Purulia Shear Zone, India

    OpenAIRE

    Saurabh Mittal; Sharma, S P; Arkoprovo Biswas; SenGupta, D

    2014-01-01

    This study is an attempt to correlate VLF-EM data with the radiometric measurements to decipher the subsurface structure and to locate uranium mineralization in the shear zone. The study area is around Beldih mine which is an open cast apatite mine located on the South Purulia Shear Zone. VLF method has been applied to map the structure and the presence of radioactive minerals has been delineated by the detection of high α and γ counts with respect to the background radiations. High radiation...

  5. Development of a United States-Mexico Emissions Inventory for the Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study.

    Science.gov (United States)

    Kuhns, Hampden; Knipping, Eladio M; Vukovich, Jeffrey M

    2005-05-01

    The Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study was commissioned to investigate the sources of haze at Big Bend National Park in southwest Texas. The modeling domain of the BRAVO Study includes most of the continental United States and Mexico. The BRAVO emissions inventory was constructed from the 1999 National Emission Inventory for the United States, modified to include finer-resolution data for Texas and 13 U.S. states in close proximity. The first regional-scale Mexican emissions inventory designed for air-quality modeling applications was developed for 10 northern Mexican states, the Tula Industrial Park in the state of Hidalgo, and the Popocatépetl volcano in the state of Puebla. Emissions data were compiled from numerous sources, including the U.S. Environmental Protection Agency (EPA), the Texas Natural Resources Conservation Commission (now Texas Commission on Environmental Quality), the Eastern Research Group, the Minerals Management Service, the Instituto Nacional de Ecología, and the Instituto Nacional de Estadistica Geografía y Informática. The inventory includes emissions for CO, nitrogen oxides, sulfur dioxide, volatile organic compounds (VOCs), ammonia, particulate matter (PM) < 10 microm in aerodynamic diameter, and PM < 2.5 microm in aerodynamic diameter. Wind-blown dust and biomass burning were not included in the inventory, although high concentrations of dust and organic PM attributed to biomass burning have been observed at Big Bend National Park. The SMOKE modeling system was used to generate gridded emissions fields for use with the Regional Modeling System for Aerosols and Deposition (REMSAD) and the Community Multiscale Air Quality model modified with the Model of Aerosol Dynamics, Reaction, Ionization and Dissolution (CMAQ-MADRID). The compilation of the inventory, supporting model input data, and issues encountered during the development of the inventory are documented. A comparison of the BRAVO emissions

  6. Detailed Observation of Multiphoton Emission Enhancement from a Single Colloidal Quantum Dot Using a Silver-Coated AFM Tip.

    Science.gov (United States)

    Takata, Hiroki; Naiki, Hiroyuki; Wang, Li; Fujiwara, Hideki; Sasaki, Keiji; Tamai, Naoto; Masuo, Sadahiro

    2016-09-14

    The enhancement of multiphoton emission from a single colloidal nanocrystal quantum dot (NQD) interacting with a plasmonic nanostructure was investigated using a silver-coated atomic force microscopy tip (AgTip) as the plasmonic nanostructure. Using the AgTip, which exhibited a well-defined localized surface plasmon (LSP) resonance band, we controlled the spectral overlap and the distance between the single NQD and the AgTip. The emission behavior of the single NQD when approaching the AgTip at the nanometer scale was measured using off-resonance (405 nm) and resonance (465 nm) excitation of the LSP. We directly observed the conversion of the single-photon emission from a single NQD to multiphoton emission with reduction of the emission lifetime at both excitation wavelengths as the NQD-AgTip distance decreased, whereas a decrease and increase in the emission intensity were observed at 405 and 465 nm excitation, respectively. By combining theoretical analysis and the numerical simulation of the AgTip, we deduced that the enhancement of the multiphoton emission was caused by the quenching of the single-exciton state due to the energy transfer from the NQD to the AgTip and that the emission intensity was increased by enhancement of the excitation rate due to the electric field of the LSP on the AgTip. These results provide evidence that the photon statistics and the photon flux from the single NQD can be manipulated by the plasmonic nanostructure through control of the spectral overlap and the distance. PMID:27501388

  7. Estimating Amazonian methane emissions through 4D-Var inverse modelling with satellite observations from GOSAT and IASI

    Science.gov (United States)

    Wilson, C. J.; Chipperfield, M.; Gloor, M.; McNorton, J.; Miller, J. B.; Gatti, L. V.; Siddans, R.; Bloom, A. A.; Basso, L. S.; Boesch, H.; Parker, R.; Monks, S. A.

    2015-12-01

    Methane (CH4) is emitted from a range of anthropogenic and natural sources, and since the industrial revolution its mean atmospheric concentration has climbed dramatically. CH4 produces a relatively high radiative forcing effect upon the Earth's climate, and its atmospheric lifetime of approximately 10 years makes it an appealing target for the mitigation of climate change. However, the spatial and temporal variation of CH4 emissions are not well understood, though in recent years a number of top-down and bottom-up studies have attempted to construct improved emission budgets. However, some top-down studies suffer from poor observational coverage near the Amazon basin, particularly in the planetary boundary layer. Since emissions from this region, coming mainly from wetland and burning sources, are thought to be relatively high, additional observations in this region would greatly help to constrain the geographical distribution of the global CH4 emission budget. To this end, regular flask measurements of CH4 and other trace gases have been taken during flights over four Amazonian sites since 2010, as part of the AMAZONICA project. The GOSAT has been used to retrieve global column-average CH4 concentrations since mid-2009, whilst IASI, on-board Metop-A, has also been measuring atmospheric CH4 concentrations since its launch in 2006. We present an assessment of Amazonian methane emissions for 2010 and 2011 using the TOMCAT Chemical Transport Model and the new variational inverse model, INVICAT. These models are used to attribute methane variations at each Amazon site to a source type and region, to assess the ability of our current CH4 flux estimates to reproduce these observations and to produce improved posterior emission estimates through assimilation of atmospheric observations. This study represents the first use of the INVICAT scheme to constrain emissions of any atmospheric trace gas. Whilst there is generally good agreement between the model and the

  8. Fermi large area telescope observations of the cosmic-ray induced γ-ray emission of the Earth's atmosphere

    International Nuclear Information System (INIS)

    We report on measurements of the cosmic-ray induced γ-ray emission of Earth's atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded ∼6.4x106 photons with energies >100 MeV and ∼250 hours total live time for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission--often referred to as Earth albedo gamma-ray emission--has a power-law shape up to 500 GeV with spectral index Γ=2.79±0.06.

  9. Inverse Modeling of Texas NOx Emissions Using Space-Based and Ground-Based NO2 Observations

    Science.gov (United States)

    Tang, Wei; Cohan, D.; Lamsal, L. N.; Xiao, X.; Zhou, W.

    2013-01-01

    Inverse modeling of nitrogen oxide (NOx) emissions using satellite-based NO2 observations has become more prevalent in recent years, but has rarely been applied to regulatory modeling at regional scales. In this study, OMI satellite observations of NO2 column densities are used to conduct inverse modeling of NOx emission inventories for two Texas State Implementation Plan (SIP) modeling episodes. Addition of lightning, aircraft, and soil NOx emissions to the regulatory inventory narrowed but did not close the gap between modeled and satellite observed NO2 over rural regions. Satellitebased top-down emission inventories are created with the regional Comprehensive Air Quality Model with extensions (CAMx) using two techniques: the direct scaling method and discrete Kalman filter (DKF) with Decoupled Direct Method (DDM) sensitivity analysis. The simulations with satellite-inverted inventories are compared to the modeling results using the a priori inventory as well as an inventory created by a ground-level NO2 based DKF inversion. The DKF inversions yield conflicting results: the satellite based inversion scales up the a priori NOx emissions in most regions by factors of 1.02 to 1.84, leading to 3-55% increase in modeled NO2 column densities and 1-7 ppb increase in ground 8 h ozone concentrations, while the ground-based inversion indicates the a priori NOx emissions should be scaled by factors of 0.34 to 0.57 in each region. However, none of the inversions improve the model performance in simulating aircraft-observed NO2 or ground-level ozone (O3) concentrations.

  10. Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line

    CERN Document Server

    Arnold, N D; Banks, G; Bechtold, R; Beczek, K; Benson, C; Berg, S; Berg, W; Biedron, S G; Biggs, J A; Boerste, K; Borland, M; Bosek, M; Brzowski, W R; Budz, J; Carwardine, J A; Castro, P; Chae, Y C; Christensen, S; Clark, C; Conde, M; Crosbie, E A; Decker, G A; Dejus, Roger J; Deleon, H; Den Hartog, P K; Deriy, B N; Dohan, D; Dombrowski, P; Donkers, D; Doose, C L; Dortwegt, R J; Edwards, G A; Eidelman, Y; Erdmann, M J; Error, J J; Ferry, R; Flood, R; Forrestal, J; Freund, H; Friedsam, H; Gagliano, J; Gai, W; Galayda, J N; Gerig, R; Gilmore, R L; Gluskin, E; Goeppner, G A; Goetzen, J; Gold, C; Grelick, A E; Hahne, M W; Hanuska, S; Harkay, K C; Harris, G; Hillman, A L; Hogrefe, R; Hoyt, J; Huang, Z; Jagger, J M; Jansma, W G; Jaski, M; Jones, S J; Keane, R T; Kelly, A L; Keyser, C; Kim, K J; Kim, S H; Kirshenbaum, M; Klick, J H; Knoerzer, K; Knott, M; Koldenhoven, R J; Labuda, S; Laird, R; Lang, J; Lenkszus, F R; Lessner, E S; Lewellen, J W; Li, Y; Lill, R M; Lumpkin, Alex H; Makarov, O A; Markovich, G M; McDowell, M; McDowell, W P; McNamara, P E; Meier, T; Meyer, D; Michalek, W; Milton, S V; Moe, H; Moog, E; Morrison, L; Nassiri, A; Noonan, J R; Otto, R; Pace, J; Pasky, S J; Penicka, J M; Pietryla, A F; Pile, G; Pitts, C; Power, J; Powers, T; Putnam, C C; Puttkammer, A J; Reigle, D; Reigle, L; Ronzhin, D; Rotela, E R; Russell, E F; Sajaev, Vadim; Sarkar, S; Scapino, J C; Schröder, K; Seglem, R A; Sereno, N S; Sharma, S K; Sidarous, J F; Singh, O; Smith, T L; Soliday, R; Sprau, G A; Stein, S J; Stejskal, B; Svirtun, V; Teng, L C; Theres, E; Thompson, K; Tieman, B J; Torres, J A; Trakhtenberg, E; Travish, G; Trento, G F; Vacca, J; Vasserman, I B; Vinokurov, N A; Walters, D R; Wang, J; Wang, X J; Warren, J; Wesling, S; Weyer, D L; Wiemerslage, G; Wilhelmi, K; Wright, R; Wyncott, D; Xu, S; Yang, B X; Yoder, W; Zabel, R B

    2001-01-01

    Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

  11. Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, N.D.; Attig, J.; Banks, G.; Bechtold, R.; Beczek, K.; Benson, C.; Berg, S.; Berg, W.; Biedron, S.G.; Biggs, J.A.; Borland, M.; Boerste, K.; Bosek, M.; Brzowski, W.R.; Budz, J.; Carwardine, J.A.; Castro, P.; Chae, Y.-C.; Christensen, S.; Clark, C.; Conde, M.; Crosbie, E.A.; Decker, G.A.; Dejus, R.J.; DeLeon, H.; Den Hartog, P.K.; Deriy, B.N.; Dohan, D.; Dombrowski, P.; Donkers, D.; Doose, C.L.; Dortwegt, R.J.; Edwards, G.A.; Eidelman, Y.; Erdmann, M.J.; Error, J.; Ferry, R.; Flood, R.; Forrestal, J.; Freund, H.; Friedsam, H.; Gagliano, J.; Gai, W.; Galayda, J.N.; Gerig, R.; Gilmore, R.L.; Gluskin, E.; Goeppner, G.A.; Goetzen, J.; Gold, C.; Gorski, A.J.; Grelick, A.E.; Hahne, M.W.; Hanuska, S.; Harkay, K.C.; Harris, G.; Hillman, A.L.; Hogrefe, R.; Hoyt, J.; Huang, Z.; Jagger, J.M.; Jansma, W.G.; Jaski, M.; Jones, S.J.; Keane, R.T.; Kelly, A.L.; Keyser, C.; Kim, K.-J.K.-J.; Kim, S.H.; Kirshenbaum, M.; Klick, J.H.; Knoerzer, K.; Koldenhoven, R.J.; Knott, M.; Labuda, S.; Laird, R.; Lang, J.; Lenkszus, F.; Lessner, E.S.; Lewellen, J.W.; Li, Y.; Lill, R.M.; Lumpkin, A.H.; Makarov, O.A.; Markovich, G.M.; McDowell, M.; McDowell, W.P.; McNamara, P.E.; Meier, T.; Meyer, D.; Michalek, W.; Milton, S.V. E-mail: milton@aps.anl.gov; Moe, H.; Moog, E.R.; Morrison, L.; Nassiri, A.; Noonan, J.R.; Otto, R.; Pace, J.; Pasky, S.J.; Penicka, J.M.; Pietryla, A.F.; Pile, G.; Pitts, C.; Power, J.; Powers, T.; Putnam, C.C.; Puttkammer, A.J.; Reigle, D.; Reigle, L.; Ronzhin, D.; Rotela, E.R.; Russell, E.F.; Sajaev, V.; Sarkar, S.; Scapino, J.C.; Schroeder, K.; Seglem, R.A.; Sereno, N.S.; Sharma, S.K.; Sidarous, J.F.; Singh, O.; Smith, T.L.; Soliday, R.; Sprau, G.A.; Stein, S.J.; Stejskal, B.; Svirtun, V.; Teng, L.C.; Theres, E.; Thompson, K.; Tieman, B.J.; Torres, J.A.; Trakhtenberg, E.M.; Travish, G.; Trento, G.F.; Vacca, J.; Vasserman, I.B.; Vinokurov, N.A.; Walters, D.R.; Wang, J.; Wang, X.J.; Warren, J.; Wesling, S.; Weyer, D.L.; Wiemerslage, G.; Wilhelmi, K.; Wright, R.

    2001-12-21

    Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

  12. Possibilities for observations with the infrared space observatory of emission from shock-heated dust in SNRs

    International Nuclear Information System (INIS)

    The possibilities for observing infrared emission from shock-heated dust in SNRs with the future Infrared Space Observatory (ISO) are illustrated with calculations of the ISOPHOT-P and ISOPHOT-C flux densities and integration times for radiation from six selected SNRs in eight wavelength bands between 4 μm and 180 μm

  13. Global inventory of nitrogen oxide emissions constrained by space-based observations of NO2 columns

    Science.gov (United States)

    Martin, Randall V.; Jacob, Daniel J.; Chance, Kelly; Kurosu, Thomas P.; Palmer, Paul I.; Evans, Mathew J.

    2003-09-01

    We use tropospheric NO2 columns from the Global Ozone Monitoring Experiment (GOME) satellite instrument to derive top-down constraints on emissions of nitrogen oxides (NOx ≡ NO + NO2), and combine these with a priori information from a bottom-up emission inventory (with error weighting) to achieve an optimized a posteriori estimate of the global distribution of surface NOx emissions. Our GOME NO2 retrieval improves on previous work by accounting for scattering and absorption of radiation by aerosols; the effect on the air mass factor (AMF) ranges from +10 to -40% depending on the region. Our AMF also includes local information on relative vertical profiles (shape factors) of NO2 from a global 3-D chemical transport model (GEOS-CHEM); assumption of a globally uniform shape factor, as in most previous retrievals, would introduce regional biases of up to 40% over industrial regions and a factor of 2 over remote regions. We derive a top-down NOx emission inventory from the GOME data by using the local GEOS-CHEM relationship between NO2 columns and NOx emissions. The resulting NOx emissions for industrial regions are aseasonal, despite large seasonal variation in NO2 columns, providing confidence in the method. Top-down errors in monthly NOx emissions are comparable with bottom-up errors over source regions. Annual global a posteriori errors are half of a priori errors. Our global a posteriori estimate for annual land surface NOx emissions (37.7 Tg N yr-1) agrees closely with the GEIA-based a priori (36.4) and with the EDGAR 3.0 bottom-up inventory (36.6), but there are significant regional differences. A posteriori NOx emissions are higher by 50-100% in the Po Valley, Tehran, and Riyadh urban areas, and by 25-35% in Japan and South Africa. Biomass burning emissions from India, central Africa, and Brazil are lower by up to 50%; soil NOx emissions are appreciably higher in the western United States, the Sahel, and southern Europe.

  14. Suzaku observations of X-ray excess emission in the cluster of galaxies A 3112

    Science.gov (United States)

    Lehto, T.; Nevalainen, J.; Bonamente, M.; Ota, N.; Kaastra, J.

    2010-12-01

    Aims: We analysed the Suzaku XIS1 data of the A 3112 cluster of galaxies in order to examine the X-ray excess emission in this cluster reported earlier with the XMM-Newton and Chandra satellites. Methods: We performed X-ray spectroscopy on the data of a single large region. We carried out simulations to estimate the systematic uncertainties affecting the X-ray excess signal. Results: The best-fit temperature of the intracluster gas depends strongly on the choice of the energy band used for the spectral analysis. This proves the existence of excess emission component in addition to the single-temperature MEKAL in A 3112. We showed that this effect is not an artifact due to uncertainties of the background modeling, instrument calibration or the amount of Galactic absorption. Neither does the PSF scatter of the emission from the cool core nor the projection of the cool gas in the cluster outskirts produce the effect. Finally we modeled the excess emission either by using an additional MEKAL or powerlaw component. Due to the small differencies between thermal and non-thermal model we can not rule out the non-thermal origin of the excess emission based on the goodness of the fit. Assuming that it has a thermal origin, we further examined the differential emission measure (DEM) models. We utilised two different DEM models, a Gaussian differential emission measure distribution (GDEM) and WDEM model, where the emission measure of a number of thermal components is distributed as a truncated power law. The best-fit XIS1 MEKAL temperature for the 0.4-7.0 keV band is 4.7 ± 0.1 keV, consistent with that obtained using GDEM and WDEM models.

  15. The origin of emission and absorption features in Ton S180 Chandra observations

    OpenAIRE

    Różańska, A.; Czerny, B.; Siemiginowska, A.; Dumont, A. -M.; Kawaguchi, T.

    2003-01-01

    We present new interpretation of Ton S180 spectrum obtained by {\\it Chandra} Spectrometer (Low Energy Transmission Grating). Several narrow absorption lines and a few emission disk lines have been successfully fitted to the data. We have not found any significant edges accompanying line emission. We propose the interpretation of narrow lines consistent with the paper recently written by Krolik (2002), where warm absorber is strongly inhomogeneous. Such situation is possible in so called multi...

  16. Characteristics of fire-generated gas emission observed during a large peatland fire in 2009 at Kalimantan, Indonesia

    Science.gov (United States)

    Hamada, Yohei; Darung, Untung; Limin, Suwido H.; Hatano, Ryusuke

    2013-08-01

    To investigate the characteristics of gas emissions from a tropical peatland fire, ground-level measurement of fire-generated gases was conducted during a large fire event in Kalimantan, Indonesia in 2009. Concentrations of CO and CH4 showed positive linear correlations with that of CO2. The relationship between concentrations of N2O and CO2 were divided into two parts, suggesting the influence of additional N2O generation during sample storage. The CO2-normalized emission ratio was calculated for CO, CH4, and N2O. The molar ratio of these fire-generated gas emissions was summarized as CO2:CO:CH4:N2O = 1.00:0.382:0.0261:0.000156, whereas the emission ratio calculated on the global warming potential (GWP) basis was CO2:CH4:N2O = 1.00:0.237:0.0465. The GWP emission based on this ratio was 87.8-91.2% of a simple evaluation in which all carbon was assumed to be emitted as CO2. This is the first trial to evaluate the emission ratios of major greenhouse gases on the basis of ground-level observation during an actual tropical peatland fire.

  17. Chandra & XMM-Newton Observations of NGC5253. Analysis of the X-ray Emission from a Dwarf Starburst Galaxy

    CERN Document Server

    Summers, L K; Strickland, D K; Heckman, T M; Summers, Lesley K.; Stevens, Ian R.; Strickland, David K.; Heckman, Timothy M.

    2004-01-01

    We present Chandra and XMM-Newton X-ray data of NGC5253, a local starbursting dwarf elliptical galaxy, in the early stages of a starburst episode. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission, in the form of what appear to be multiple superbubbles, and smaller bubbles probably associated with individual star clusters. Chandra detects 17 sources within the optical extent of NGC5253 down to a completeness level corresponding to a luminosity of 1.5E37 erg/s.The slope of the point source X-ray luminosity function is -0.54, similar to that of other nearby dwarf starburst galaxies. Several different types of source are detected within the galaxy, including X-ray binaries and the emission associated with star-clusters. Comparison of the diffuse X-ray emission with the observed Halpha emission shows similarities in their extent. The best spectral fit to the diffuse emission is obtained with an absorbed, two temperature model giving temperatures for the two gas com...

  18. Fermi-LAT Observations of High-Energy Gamma-Ray Emission Toward the Galactic Center

    CERN Document Server

    ,

    2015-01-01

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission towards the Galactic centre (GC) in high-energy gamma-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a $15^\\circ \\times 15^\\circ$ region about the direction of the GC, and implications for the interstellar emissions produced by cosmic ray (CR) particles interacting with the gas and radiation fields in the inner Galaxy and for the point sources detected. Specialised interstellar emission models (IEMs) are constructed that enable separation of the gamma-ray emission from the inner $\\sim 1$ kpc about the GC from the fore- and background emission from the Galaxy. Based on these models, the interstellar emission from CR electrons interacting with the interstellar radiation field via the inverse Compton (IC) process and CR nuclei inelastically scattering off the gas producing gamma-rays via $\\pi^0$ decays from the inner $\\sim 1$ kpc is d...

  19. First Observation of Self-Amplified Spontaneous Emission in a Free-Electron Laser at 109 nm Wavelength

    CERN Document Server

    Andruszków, J; Ayvazyan, V T; Baboi, N I; Bakker, R; Balakin, V; Barni, D; Bazhan, A; Bernard, M; Bosotti, A; Bourdon, J C; Brefeld, W; Brinkmann, R; Bühler, S; Carneiro, J P; Castellano, M G; Castro, P; Catani, L; Chel, S; Cho, Y; Choroba, S; Colby, E R; Decking, W; Den Hartog, P; Desmons, M; Dohlus, M; Edwards, D; Edwards, H T; Faatz, B; Feldhaus, J; Ferrario, M; Fitch, M J; Flöttmann, K; Fouaidy, M; Gamp, A; Garvey, Terence; Geitz, M A; Gluskin, E S; Gretchko, V; Hahn, U; Hartung, W H; Hubert, D; Hüning, M; Ischebek, R; Jablonka, M; Joly, J M; Juillard, M; Junquera, T; Jurkiewicz, P; Kabel, A C; Kahl, J; Kaiser, H; Kamps, T; Katelev, V V; Kirchgessner, J L; Körfer, M; Kravchuk, L V; Kreps, G; Krzywinski, J; Lokajczyk, T; Lange, R; Leblond, B; Leenen, M; Lesrel, J; Liepe, M; Liero, A; Limberg, T; Lorenz, R; Lu, H H; Lu, F H; Magne, C; Maslov, M A; Materlik, G; Matheisen, A; Menzel, J; Michelato, P; Möller, W D; Mosnier, A; Müller, U C; Napoly, O; Novokhatskii, A V; Omeich, M; Padamsee, H; Pagani, C; Peters, F; Petersen, B; Pierini, P; Pflüger, J; Piot, P; Phung Ngoc, B; Plucinski, L; Proch, D; Rehlich, K; Reiche, S; Reschke, D; Reyzl, I; Rosenzweig, J; Rossbach, J; Roth, S; Saldin, E L; Sandner, W; Sanok, Z; Schlarb, H; Schmidt, G; Schmüser, P; Schneider, J R; Schneidmiller, E A; Schreiber, H J; Schreiber, S; Schütt, P; Sekutowicz, J; Serafini, L; Sertore, D; Setzer, S; Simrock, S; Sonntag, B F; Sparr, B; Stephan, F; Sytchev, V V; Tazzari, S; Tazzioli, F; Tigner, Maury; Timm, M; Tonutti, M; Trakhtenberg, E; Treusch, R; Trines, D; Verzilov, V A; Vielitz, T; Vogel, V; Von Walter, G; Wanzenberg, R; Weiland, T; Weise, H; Weisend, J G; Wendt, M; Werner, M; White, M M; Will, I; Wolff, S; Yurkov, M V; Zapfe, K; Zhogolev, P; Zhou, F

    2000-01-01

    We present the first observation of Self-Amplified Spontaneous Emission (SASE) in a free-electron laser (FEL) in the Vacuum Ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approx. 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width and intensity fluctuations all corroborate the existing models for SASE FELs.

  20. Estimation of NOx emissions from Delhi using Car MAX-DOAS observations and comparison with OMI satellite data

    OpenAIRE

    R. Shaiganfar; Beirle, S.; Sharma, M.; Chauhan, A; Singh, R P; Wagner, T

    2011-01-01

    We present the first Multi-Axis-(MAX-) DOAS observations in India performed during April 2010 and January 2011 in Delhi and nearby regions. The MAX-DOAS instrument was mounted on a car roof, which allowed us to perform measurements along individual driving routes. From car MAX-DOAS observations along closed circles around Delhi, together with information on wind speed and direction, the NOx emissions from the greater Delhi area were determined: our estimate of 4.4 × 10...

  1. Atmospheric observation-based global SF6 emissions – comparison of top-down and bottom-up estimates

    Directory of Open Access Journals (Sweden)

    D. E. Worthy

    2009-12-01

    Full Text Available Emissions of sulphur hexafluoride (SF6, one of the strongest greenhouse gases on a per molecule basis, are targeted to be collectively reduced under the Kyoto Protocol. Because of its long atmospheric lifetime (≈3000 years, the accumulation of SF6 in the atmosphere is a direct measure of its global emissions. Examination of our extended data set of globally distributed high-precision SF6 observations shows an increase in SF6 abundance from near zero in the 1970s to a global mean of 6.7 ppt by the end of 2008. In-depth evaluation of our long-term data records shows that the global source of SF6 decreased after 1995, most likely due to SF6 emission reductions in industrialised countries, but increased again after 1998. By subtracting those emissions reported by Annex I countries to the United Nations Framework Convention of Climatic Change (UNFCCC from our observation-inferred SF6 source leaves a surprisingly large gap of more than 70–80% of non-reported SF6 emissions in the last decade.

  2. DE-1 and COSMOS 1809 observations of lower hybrid waves excited by VLF whistler mode waves

    Science.gov (United States)

    Bell, T. F; Inan, U. S.; Lauben, D.; Sonwalkar, V. S.; Helliwell, R. A.; Sobolev, Ya. P.; Chmyrev, V. M.; Gonzalez, S.

    1994-01-01

    Past work demostrates that strong lower hybrid (LH) waves can be excited by electromagnetic whistler mode waves throughout large regions of the topside ionosphere and magnetosphere. The effects of the excited LH waves upon the suprathermal ion population in the topside ionosphere and magnetosphere depend upon the distribution of LH wave amplitude with wavelength lambda. The present work reports plasma wave data from the DE-1 and COSMOS 1809 spacecraft which suggests that the excited LH wave spectrum has components for which lambda less than or equal to 3.5 m when excitation occurs at a frequency roughly equal to the local lower hybrid resonance frequency. This wavelength limit is a factor of approximately 3 below that reported in past work and suggests that the excited LH waves can interact with suprathermal H(+) ions with energy less than or equal to 6 eV. This finding supports recent work concerning the heating of suprathermal ions above thunderstorm cells.

  3. Free-free and H42α emission from the dusty starburst within NGC 4945 as observed by ALMA

    Science.gov (United States)

    Bendo, G. J.; Henkel, C.; D'Cruze, M. J.; Dickinson, C.; Fuller, G. A.; Karim, A.

    2016-11-01

    We present observations of the 85.69 GHz continuum emission and H42α line emission from the central 30 arcsec within NGC 4945. Both sources of emission originate from nearly identical structures that can be modelled as exponential discs with scalelengths of ˜2.1 arcsec (or ˜40 pc). An analysis of the spectral energy distribution based on combining these data with archival data imply that 84 ± 10 per cent of the 85.69 GHz continuum emission originates from free-free emission. The electron temperature is 5400 ± 600 K, which is comparable to what has been measured near the centre of the Milky Way Galaxy. The star formation rate (SFR) based on the H42α and 85.69 GHz free-free emission (and using a distance of 3.8 Mpc) is 4.35 ± 0.25 M⊙ yr-1. This is consistent with the SFR from the total infrared flux and with previous measurements based on recombination line emission, and it is within a factor of ˜2 of SFRs derived from radio data. The Spitzer Space Telescope 24 μm data and Wide-field Infrared Survey Explorer 22 μm data yield SFRs ˜10× lower than the Atacama Large Millimeter/submillimeter Array measurements, most likely because the mid-infrared data are strongly affected by dust attenuation equivalent to AV = 150. These results indicate that SFRs based on mid-infrared emission may be highly inaccurate for dusty, compact circumnuclear starbursts.

  4. Dust aerosol emission over the Sahara during summertime from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations

    Science.gov (United States)

    Todd, Martin C.; Cavazos-Guerra, Carolina

    2016-03-01

    Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. Inadequate surface observations ensure that satellite data remain the primary source of this information over extensive and remote desert regions. Here, we develop estimates of the relative magnitude of active dust emission over the Sahara desert based on data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Utilising the unique vertical profile of aerosol characteristics provided by CALIOP our algorithm identifies emission from aerosol extinction and lidar backscatter in the near surface layers. From the long-term CALIOP archive of day and night-time orbits over 2006-13 we construct coarse resolution maps of a new dust emission index (DEI) for the Sahara desert during the peak summer dust season (June to September). The spatial structure of DEI indicates highest emission over a broad zone focused on the border regions of Southern Algeria, Northern Mali and northwest Niger, displaced substantially (∼7°) to the east of the mean maximum in satellite-derived aerosol optical depth. In this region night-time emission exceeds that during the day. The DEI maps substantially corroborate recently derived dust source frequency count maps based on back-tracking plumes in high temporal resolution SEVIRI imagery. As such, a convergence of evidence from multiple satellite data sources using independent methods provides an increasingly robust picture of Saharan dust emission sources. Various caveats are considered. As such, quantitative estimates of dust emission may require a synergistic combined multi-sensor analysis.

  5. The VLF Transmitter Signal as a Diagnostic of Thunderstorm-Ionosphere Coupling

    Science.gov (United States)

    Cohen, M.

    2015-12-01

    Very Low Frequency (VLF) transmitter remote sensing has evolved into a useful diagnostic for the D-region ionosphere, particularly in the presence of lightning-associated disturbances. All it requires is a VLF radio receiver monitoring the amplitude and/or phase of a beacon signal over time, which perturbs during ionospheric disturbances. For much of this field's history, amplitude and phase were analyzed and presented as individual data streams. A clever formulation known as scattered field analysis was recently reintroduced, which combines amplitude and phase into a single measurement, and calculates the phasor of the scattered field, providing insights that would otherwise be missed by either amplitude or phase individually. In this presentation we describe another useful formulation that goes one step further, combining the amplitude and phase of two horizontal magnetic field channels into a single measurement: polarization ellipse. This allows insights that would otherwise by missed by examining one channel at a time. Using this formulation, we take a new look at ionospheric disturbances from thunderstorms, including early/fast events and lightning-induced electron precipitation.

  6. An 80 KW SCR VLF power source for drift-pump-coil excitation

    International Nuclear Information System (INIS)

    The drift-pump antenna coils in the end regions of the TMX-U mirror machine at LLNL require kiloamperes of current excitation in the 10 to 30 kHz range during the 75 ms shots. The coil's self-inductance will be series-resonated at the operating frequency f/sub 0/ with a high-Q inductor and capacitor. The overall tank Q≥200. The resonator acts as a current multiplier and VLF energy reservoir whose time constant tau=Q/πf/sub 0/. The sources to be described are modular SCR pulse generators which are inductively coupled to the resonator, and deliver alternate-polarity, half-sine-wave current pulses which are 35μs wide. As in a Class C vacuum-tube harmonic generator, the coupled resonator selectively extracts the Fourier component of the pulse current nearest f/sub 0/, and allows other components to pass unimpeded. DC to VLF efficiencies >80% have been measured. Resonator fill-up at the start of a shot is a problem for the pulse generator, since the only circuit damping is provided by the gradual buildup of the coupled resonator voltage. A clamping circuit across the generator's capacitor bank limits its voltage to a level safe for the SCRs, with the clamped current being returned to the main dc supply. The clamped pulse generator behaves like a current source for any load resistance from zero up to a critical value where SCR commutation failure occurs

  7. Solar flare induced D-region ionospheric perturbations evaluated from VLF measurements

    Science.gov (United States)

    Singh, Ashutosh K.; Singh, A. K.; Singh, Rajesh; Singh, R. P.

    2014-03-01

    The results of very low frequency (VLF) wave amplitude measurements carried out at the low latitude station Varanasi (geom. lat. 14∘55'N, long. 154∘E), India during solar flares are presented for the first time. The VLF waves (19.8 kHz) transmitted from the NWC-transmitter, Australia propagated in the Earth-ionosphere waveguide to long distances and were recorded at Varanasi. Data are analyzed and the reflection height H' and the sharpness factor β are evaluated. It is found that the reflection height decreases whereas sharpness factor increases with the increase of solar flare power. The H' is found to be higher and β smaller at low latitudes than the corresponding values at mid and high latitudes. The sunspot numbers were low during the considered period 2011-2012, being the rising phase of solar cycle 24 and as a result cosmic rays may impact the D-region ionosphere. The increased ionization from the flare lowers the effective reflecting height, H', of the D-region roughly in proportion to the logarithm of the X-ray flare intensity from a typical mid-day unperturbed value of about 71-72 km down to about 65 km for an X class flare. The sharpness ( β) of the lower edge of the D-region is also significantly increased by the flare but reaches a clear saturation value of about 0.48 km-1 for flares of magnitude greater than about X1 class.

  8. New observations of VOC emissions and concentrations in, above, and around the Central Valley of California

    Science.gov (United States)

    Goldstein, A. H.; Fares, S.; Gentner, D. R.; Park, J.; Weber, R.; Ormeno, E.; Holzinger, R.; Misztal, P. K.; Karl, T. R.; Guenther, A. B.; Fischer, M. L.; Harley, R. A.; Karlik, J. F.

    2011-12-01

    Large portions of the Central Valley of California are out of compliance with current state and federal air quality standards for ozone and particulate matter, and the relative importance of biogenic and anthropogenic VOC emissions to their photochemical production in this region remains uncertain. In 2009-2011 multiple measurement campaigns were completed investigating the VOC emission inventory and concentration distributions. In 2009 BVOC emissions from more than 20 species of major agricultural crops in California were measured in a greenhouse using branch enclosures by both PTRMS and in-situ GC. Overall, crops were found to emit low amounts of BVOC compared to the natural forests surrounding the valley. Crops mainly emitted methanol and terpenes, with a broad array of other species emitted at lower levels, and all the measured crops showed negligible emissions of isoprene. Navel oranges were the largest crop BVOC emitters measured so a full year of flux measurements were made in an orange grove near Visalia in 2010 by eddy covariance(EC)-PTRMS with two multi-week periods of concentration measurements by hourly in-situ GC, and one month of high mass resolution flux measurements by EC-PTR-TOF-MS. The dominant BVOC emissions from the orange grove were methanol and terpenes, followed by acetone, acetaldehyde, and a low level of emissions for many other species. In 2011 aircraft eddy covariance measurements of BVOC fluxes were made by EC-PTRMS covering a large area of California as part of the California Airborne Bvoc Emission Research in Natural Ecosystem Transects (CABERNET) campaign aimed at improving BVOC emission models on regional scales, mainly profiling BVOC emissions from oak woodlands surrounding the Central Valley. In 2010, hourly in-situ VOC measurements were made via in-situ GC in Bakersfield, CA as part of the CalNex experiment. Additionally, in-situ measurements of fresh motor vehicle exhaust were made in Oakland's Caldecott tunnel. Measurements by

  9. Atmospheric observation-based global SF6 emissions - comparison of top-down and bottom-up estimates

    OpenAIRE

    Levin, Ingeborg; Naegler, Tobias; Heinz, Renate; Osusko, Daniel; Cuevas, Emilio; Engel, Andreas; Ilmberger, Johann; Langenfelds, Ray L.; Neininger, Bruno; Rohden, Christoph von; Steele, L. Paul; Weller, Rolf; Worthy, Douglas E. W; Zimov, Sergej A.

    2010-01-01

    Emissions of sulphur hexafluoride (SF6), one of the strongest greenhouse gases on a per molecule basis, are targeted to be collectively reduced under the Kyoto Protocol. Because of its long atmospheric lifetime (estimated as 800 to 3200 years), the accumulation of SF6 in the atmosphere is a direct measure of its global emissions. Examination of our extended data set of globally distributed high-precision SF6 observations shows an increase in SF6 abundance from near zero in the 1970s to a glob...

  10. Assessment of cardiac single-photon emission computed tomography performance using a scanning linear observer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chih-Jie; Kupinski, Matthew A.; Volokh, Lana [College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); GE Healthcare, Haifa 39120 (Israel)

    2013-01-15

    Purpose: Single-photon emission computed tomography (SPECT) is widely used to detect myocardial ischemia and myocardial infarction. It is important to assess and compare different SPECT system designs in order to achieve the highest detectability of cardiac defects. Methods: Whitaker et al.'s study ['Estimating random signal parameters from noisy images with nuisance parameters: linear and scanning-linear methods,' Opt. Express 16(11), 8150-8173 (2008)] on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than with reconstruction data. Thus, this observer model assesses the overall hardware performance independent of any reconstruction algorithm. In addition, the computation time of image quality studies is significantly reduced. In this study, three systems based on the design of the GE cadmium zinc telluride-based dedicated cardiac SPECT camera Discovery 530c were assessed. This design, which is officially named the Alcyone Technology: Discovery NM 530c, was commercialized in August, 2009. The three systems, GE27, GE19, and GE13, contain 27, 19, and 13 detectors, respectively. Clinically, a human heart can be virtually segmented into three coronary artery territories: the left-anterior descending artery, left-circumflex artery, and right coronary artery. One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can accurately predict in which territory the defect exists [http://www.asnc.org/media/PDFs/PPReporting081511.pdf, Guideline from American Society of Nuclear Cardiology]. A good estimation of the extent of the defect from the projection images is also very helpful for determining the seriousness of the myocardial ischemia. In this study, both the location and extent of defects were estimated by the SLO, and the system performance was assessed by

  11. Growth in NOx emissions from power plants in China: bottom-up estimates and satellite observations

    Directory of Open Access Journals (Sweden)

    Y. Lei

    2012-05-01

    Full Text Available Using OMI (Ozone Monitoring Instrument tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem, we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005–2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005–2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005–2007, with 92.2% of the total capacity additions coming from generator units with size ≥300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79–0.82 with OMI measurements over grids dominated by power plant emissions, with only 7–14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8–17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite

  12. Growth in NOx emissions from power plants in China: bottom-up estimates and satellite observations

    Directory of Open Access Journals (Sweden)

    Y. Lei

    2012-01-01

    Full Text Available Using OMI (Ozone Monitoring Instrument tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem, we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005–2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005–2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005–2007, with 92.2% of the total capacity additions coming from generator units with size ≥300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79–0.82 with OMI measurements over grids dominated by power plant emissions, with only 7–14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8–17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite

  13. Pervasive faint Fe XIX emission from a solar active region observed with EUNIS-13: Evidence for nanoflare heating

    Energy Technology Data Exchange (ETDEWEB)

    Brosius, Jeffrey W. [Catholic University of America at NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771 (United States); Daw, Adrian N. [NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771 (United States); Rabin, D. M., E-mail: Jeffrey.W.Brosius@nasa.gov [NASA Goddard Space Flight Center, Heliophysics Science Division, Code 670, Greenbelt, MD 20771 (United States)

    2014-08-01

    We present spatially resolved EUV spectroscopic measurements of pervasive, faint Fe XIX 592.2 Å line emission in an active region observed during the 2013 April 23 flight of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectral resolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 Å (formed at temperature T ≈ 8.9 MK) and Fe XII at 592.6 Å (T ≈ 1.6 MK). The Fe XIX line emission, observed over an area in excess of 4920 arcsec{sup 2} (2.58 × 10{sup 9} km{sup 2}, more than 60% of the active region), provides strong evidence for the nanoflare heating model of the solar corona. No GOES events occurred in the region less than 2 hr before the rocket flight, but a microflare was observed north and east of the region with RHESSI and EUNIS during the flight. The absence of significant upward velocities anywhere in the region, particularly the microflare, indicates that the pervasive Fe XIX emission is not propelled outward from the microflare site, but is most likely attributed to localized heating (not necessarily due to reconnection) consistent with the nanoflare heating model of the solar corona. Assuming ionization equilibrium we estimate Fe XIX/Fe XII emission measure ratios of ∼0.076 just outside the AR core and ∼0.59 in the core.

  14. Pervasive faint Fe XIX emission from a solar active region observed with EUNIS-13: Evidence for nanoflare heating

    International Nuclear Information System (INIS)

    We present spatially resolved EUV spectroscopic measurements of pervasive, faint Fe XIX 592.2 Å line emission in an active region observed during the 2013 April 23 flight of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectral resolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 Å (formed at temperature T ≈ 8.9 MK) and Fe XII at 592.6 Å (T ≈ 1.6 MK). The Fe XIX line emission, observed over an area in excess of 4920 arcsec2 (2.58 × 109 km2, more than 60% of the active region), provides strong evidence for the nanoflare heating model of the solar corona. No GOES events occurred in the region less than 2 hr before the rocket flight, but a microflare was observed north and east of the region with RHESSI and EUNIS during the flight. The absence of significant upward velocities anywhere in the region, particularly the microflare, indicates that the pervasive Fe XIX emission is not propelled outward from the microflare site, but is most likely attributed to localized heating (not necessarily due to reconnection) consistent with the nanoflare heating model of the solar corona. Assuming ionization equilibrium we estimate Fe XIX/Fe XII emission measure ratios of ∼0.076 just outside the AR core and ∼0.59 in the core.

  15. Suzaku observations of X-ray excess emission in the cluster of galaxies A3112

    CERN Document Server

    Lehto, T; Bonamente, M; Ota, N; Kaastra, J

    2010-01-01

    We analysed the Suzaku XIS1 data of the A3112 cluster of galaxies in order to examine the X-ray excess emission in this cluster reported earlier with the XMM-Newton and Chandra satellites. The best-fit temperature of the intracluster gas depends strongly on the choice of the energy band used for the spectral analysis. This proves the existence of excess emission component in addition to the single-temperature MEKAL in A3112. We showed that this effect is not an artifact due to uncertainties of the background modeling, instrument calibration or the amount of Galactic absorption. Neither does the PSF scatter of the emission from the cool core nor the projection of the cool gas in the cluster outskirts produce the effect. Finally we modeled the excess emission either by using an additional MEKAL or powerlaw component. Due to the small differencies between thermal and non-thermal model we can not rule out the non-thermal origin of the excess emission based on the goodness of the fit. Assuming that it has a therma...

  16. Statistical study of seismo-ionospheric perturbations around Japan by using VLF/LF transmitters with a focal mechanism

    Science.gov (United States)

    Kawano, Tomoki; Hobara, Yasuhide; Tatsuta, Kenshin

    2016-04-01

    In this paper we perform the statistical analysis to study the response of the lower ionosphere prior to major seismic activities focusing on different earthquake types. The lower ionospheric condition is represented by daily averaged nighttime electric amplitude from various VLF/LF transmitter signals received in Japan by UEC team. Six-year record of ionospheric conditions are used for our data analysis. Over 200 earthquakes occurred around the VLF/LF transmitter - receiver paths during the time period of analysis. They are characterized into three different groups based on the Centroid-Moment-Tensor (CMT) solution such as reverse fault type, normal fault type and stress slip type. The ionospheric anomaly is identified by a large change (2 sigma criteria) in the VLF/LF daily nighttime amplitude. As a result, the highest occurrence rate of ionospheric anomaly is obtained for reverse type fault for both sea and ground earthquakes. The occurrence rate for these earthquakes are statistically significant because they are significantly large in comparison to those calculated from random test. The difference of occurrence rate of the ionospheric perturbations may indicate the coupling efficiency of seismic activity into the overlaying ionosphere originated from the pre-seismic condition of earth's crust. We also perform the trend-based earthquake prediction. Alarm threshold in nighttime VLF amplitude with ‑3.5 sigma is found to be most effective and significant for the earthquake prediction by using lower ionospheric perturbations.

  17. Comparative study of measured amplitude and phase perturbations on VLF and LF radio signals induced by solar flares

    CERN Document Server

    Sulic, D M

    2014-01-01

    Very Low Frequency, VLF and Low Frequency, LF signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares. The aim was to understand processes in propagation VLF/LF radio signals over short paths, and to estimate specific characteristics of each short path. The receiver at Belgrade station continuously monitor the amplitude and phase of coherent and subionospherically propagating LF signal operated in Sicily, NSC at 45.90, kHz and VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with great circle distances of 953 km and 976 km, respectively. Geographical locations of transmitters and receiver site result that these short paths have many similarity. The main difference is in transmitter frequencies. In period from 2008 to February 2014 were selected around 200 events for further examination. In all selected examples amplitude and phase on VLF and LF signals were perturbed by occurrence of solar X-ray flares. This six years period covers minimum and maximum of so...

  18. Penetration Characteristics of VLF Wave From Atmosphere Into the Lower Ionosphere%VLF波从大气层到低电离层的传输特性分析

    Institute of Scientific and Technical Information of China (English)

    赵庶凡; 申旭辉; 潘威炎; 张学民

    2011-01-01

    Many papers have indicated that earthquake happens associated with a width frequency band of VLF (Very Low Frequency), ULF (Ultra Low Frequency), ELF (Extremely Low Frequency)electromagnetic radiation, which have been recorded by satellites in the ionosphere and low magnetosphere.In this paper, the reflection and transmission coefficient of the homogeneous half-space ionosphere has been calculated using propagation matrix method.Simultaneously the Booker quartic equation is solved to get the refractive index in the ionosphere.The analysis of the factors which influence the reflection and transmission coefficient of the ionosphere and the propagation characteristics in the ionosphere of VLF wave have been performed, such as wave frequency, incident angle, geomagnetic inclination, electron density and collision frequency in the ionosphere to provide fundamental basis for further studies on numerical calculation of propagation of ULF/VLF waves in the stratified ionosphere and support the study of seismo-ionosphere coupling mechanism.The results show that it is easier for the TE (Traverse Electric) wave radiated by vertical electric dipole to penetrate into the ionosphere, but the TM (Traverse Magnetic) wave radiated by horizontal electric dipole is reflected again and again in the ground-ionosphere waveguide.It is easier to observe the VLF wave anomaly when the electron density is lower or at the high-latitude region.The O wave experiences severer attenuation than X wave, so X wave is a penetration mode whereas O wave is a non penetration mode in the ionosphere.The attenuation of the two characteristic wave decrease as the decrease of the angle between the geomagnetic field and wave vector, that is to say the attenuation is the smallest when longitudinal propagation.When the geomagnetic field is considered, the ULF/VLF wave related with earthquake can penetrate into the ionosphere which is confirmed by the satellite observation.But the further physical mechanism will

  19. Observational studies on the near-infrared unidentified emission bands in galactic H II regions

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Tamami I.; Onaka, Takashi; Sakon, Itsuki; Ohsawa, Ryou; Bell, Aaron C. [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Ishihara, Daisuke [Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Shimonishi, Takashi, E-mail: morii@astron.s.u-tokyo.ac.jp [Department of Earth and Planetary Sciences, Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada Kobe 657-8501 Japan (Japan)

    2014-03-20

    Using a large collection of near-infrared spectra (2.5-5.4 μm) of Galactic H II regions and H II region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a director's time program. In addition to the well known 3.3-3.6 μm features, most spectra show a relatively weak emission feature at 5.22 μm with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 μm band (previously reported). By careful analysis, we find good correlations between the 5.25 μm band and both the aromatic hydrocarbon feature at 3.3 μm and the aliphatic hydrocarbon features at around 3.4-3.6 μm. The present results give us convincing evidence that the astronomical 5.25 μm band is associated with C-H vibrations, as suggested by previous studies, and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic-to-aromatic ratio of I {sub 3.4-3.6} {sub μm}/I {sub 3.3} {sub μm} decreases against the ratio of the 3.7 μm continuum intensity to the 3.3 μm band, I {sub cont,} {sub 3.7} {sub μm}/I {sub 3.3} {sub μm}, which is an indicator of the ionization fraction of PAHs. The midinfrared color of I {sub 9} {sub μm}/I {sub 18} {sub μm} also declines steeply against the ratio of the hydrogen recombination line Brα at 4.05 μm to the 3.3 μm band, I {sub Brα}/I {sub 3.3} {sub μm}. These facts indicate possible dust processing inside or at the boundary of ionized gas.

  20. Submillimeter Wave Astronomy Satellite Observations of Extended Water Emission in Orion

    CERN Document Server

    Snell, R L; Ashby, M L N; Bergin, E A; Chin, G; Erickson, N R; Goldsmith, P F; Harwit, M; Kleiner, S C; Koch, D G; Neufeld, D A; Patten, B M; Plume, R; Schieder, R; Stauffer, J R; Tolls, V; Wang, Z; Winnewisser, G; Zhang, Y F; Melnick, G J

    2000-01-01

    We have used the Submillimeter Wave Astronomy Satellite to map the ground-state 1_{10}-1_{01} transition of ortho-water at 557 GHz in the Orion molecular cloud. Water emission was detected in Orion over an angular extent of about 20 arcmin, or nearly 3 pc. The water emission is relatively weak, with line widths (3-6 km s^{-1}) and V_{LSR} velocities (9-11 km s^{-1}) consistent with an origin in the cold gas of the molecular ridge. We find that the ortho-water abundance relative to H_2 in the extended gas in Orion varies between 1 and 8x10^{-8}, with an average of 3x10^{-8}. The absence of detectable narrow-line ortho-H_2^{18}O emission is used to set a 3-sigma upper limit on the relative ortho-water abundance of 7x10^{-8}.

  1. First estimates of volume distribution of HF-pump enhanced emissions at 6300 and 5577 Å : a comparison between observations and theory

    OpenAIRE

    Gustavsson, B.; M. Kosch; Wong, A.; Pedersen, T.; Heinselman, C.; Mutiso, C.; Bristow, B.; Hughes, J; Wang, W

    2008-01-01

    We present bi-static observations of radio-wave induced optical emissions at 6300 and 5577 Å from a night-time radio-induced optical emission ionospheric pumping experiment at the HIPAS (Fairbanks) facility in Alaska. The optical observations were made at HIPAS and from HAARP located 285 km south-east. From these observations the altitude distribution of the emissions is estimated with tomography-like methods. These estimates are compared with theoretical m...

  2. ELF/VLF Perturbations Above the Haarp Transmitter Recorded by the Demeter Satellite in the Upper Ionosphere

    Science.gov (United States)

    Titova, E. E.; Demekhov, A. G.; Mochalov, A. A.; Gvozdevsky, B. B.; Mogilevsky, M. M.; Parrot, M.

    2015-08-01

    In the studies of the data received from DEMETER (orbit altitude above the Earth is about 700 km), we detected for the first time electromagnetic perturbations, which are due to the ionospheric modification by HAARP, a high-power high-frequency transmitter, simultaneously in the extremely low-frequency (ELF, below 1200 Hz) and very low-frequency (VLF, below 20 kHz) ranges. Of the thirteen analyzed flybys of the satellite above the heated area, the ELF/VLF signals were detected in three cases in the daytime (LT = 11-12 h), when the minimum distance between the geomagnetic projections of the satellite and the heated area center on the Earth's surface did not exceed 31 km. During the nighttime flybys, the ELF/VLF perturbations were not detected. The size of the perturbed region was about 100 km. The amplitude, spectrum, and polarization of the ELF perturbations were analyzed, and their comparison with the characteristics of natural ELF noise above the HAARP transmitter was performed. In particular, it was shown that in the daytime the ELF perturbation amplitude above the heated area can exceed by a factor of 3 to 8 the amplitude of natural ELF noise. The absence of the nighttime records of artificial ELF/VLF perturbations above the heated area can be due to both the lower frequency of the heating signal, at which the heating occurs in the lower ionosphere, and the higher level of natural noise. The spectrum of the VLF signals related to the HAARP transmitter operation had two peaks at frequencies of 8 to 10 kHz and 15 to 18 kHz, which are close to the first and second harmonics of the lower-hybrid resonance in the heated area. The effect of the whistler wave propagation near the lower-hybrid resonance region on the perturbation spectrum recorded in the upper ionosphere for these signals has been demonstrated. In particular, some of the spectrum features can be explained by assuming that the VLF signals propagate in quasiresonance, rather than quasilongitudinal, regime

  3. All-Sky Observational Evidence for An Inverse Correlation Between Dust Temperature and Emissivity Spectral Index

    Science.gov (United States)

    Liang, Z.; Fixsen, D. J.; Gold, B.

    2012-01-01

    We show that a one-component variable-emissivity-spectral-index model (the free- model) provides more physically motivated estimates of dust temperature at the Galactic polar caps than one- or two-component fixed-emissivity-spectral-index models (fixed- models) for interstellar dust thermal emission at far-infrared and millimeter wavelengths. For the comparison we have fit all-sky one-component dust models with fixed or variable emissivity spectral index to a new and improved version of the 210-channel dust spectra from the COBE-FIRAS, the 100-240 micrometer maps from the COBE-DIRBE and the 94 GHz dust map from the WMAP. The best model, the free-alpha model, is well constrained by data at 60-3000 GHz over 86 per cent of the total sky area. It predicts dust temperature (T(sub dust)) to be 13.7-22.7 (plus or minus 1.3) K, the emissivity spectral index (alpha) to be 1.2-3.1 (plus or minus 0.3) and the optical depth (tau) to range 0.6-46 x 10(exp -5) with a 23 per cent uncertainty. Using these estimates, we present all-sky evidence for an inverse correlation between the emissivity spectral index and dust temperature, which fits the relation alpha = 1/(delta + omega (raised dot) T(sub dust) with delta = -.0.510 plus or minus 0.011 and omega = 0.059 plus or minus 0.001. This best model will be useful to cosmic microwave background experiments for removing foreground dust contamination and it can serve as an all-sky extended-frequency reference for future higher resolution dust models.

  4. Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field

    Science.gov (United States)

    Jelić, V.; de Bruyn, A. G.; Mevius, M.; Abdalla, F. B.; Asad, K. M. B.; Bernardi, G.; Brentjens, M. A.; Bus, S.; Chapman, E.; Ciardi, B.; Daiboo, S.; Fernandez, E. R.; Ghosh, A.; Harker, G.; Jensen, H.; Kazemi, S.; Koopmans, L. V. E.; Labropoulos, P.; Martinez-Rubi, O.; Mellema, G.; Offringa, A. R.; Pandey, V. N.; Patil, A. H.; Thomas, R. M.; Vedantham, H. K.; Veligatla, V.; Yatawatta, S.; Zaroubi, S.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bentum, M. J.; Best, P.; Bonafede, A.; Bregman, J.; Breitling, F.; Broderick, J.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Conway, J. E.; de Gasperin, F.; de Geus, E.; Deller, A.; Dettmar, R.-J.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R. A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hassall, T. E.; Haverkorn, M.; Heald, G.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Horneffer, A.; van der Horst, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; van Leeuwen, J.; Maat, P.; Mann, G.; McKay-Bukowski, D.; McKean, J. P.; Munk, H.; Nelles, A.; Norden, M. J.; Paas, H.; Pandey-Pommier, M.; Pietka, G.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Rowlinson, A.; Scaife, A. M. M.; Schwarz, D.; Serylak, M.; Smirnov, O.; Steinmetz, M.; Stewart, A.; Tagger, M.; Tang, Y.; Tasse, C.; ter Veen, S.; Thoudam, S.; Toribio, C.; Vermeulen, R.; Vocks, C.; van Weeren, R. J.; Wijers, R. A. M. J.; Wijnholds, S. J.; Wucknitz, O.; Zarka, P.

    2014-08-01

    Aims: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for extracting of the cosmological 21 cm signal from the LOw-Frequency ARray - Epoch of Reionization (LOFAR-EoR) data. Methods: We used the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes. Results: The brightness temperature of the detected Galactic emission is on average ~4 K in polarized intensity and covers the range from -10 to + 13 rad m-2 in Faraday depth. The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to ≈1.5%. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies Conclusions: The wide frequency range, high angular resolution, and high sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of ~1-2 rad m-2 in Faraday depth. The different polarized patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarized foregrounds is a serious complication for epoch of reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%.

  5. HST-COS Observations on Hydrogen, Helium, Carbon, and Nitrogen Emission from the SN 1987A Reverse Shock

    Science.gov (United States)

    France, Kevin; McCray, Richard; Penton, Steven V.; Kirshner, Robert P.; Challis, Peter; Laming, J. Martin; Bouchet, Patrice; Chevalier, Roger; Garnavich, Peter M.; Fransson, Claes; Heng, Kevin; Larsson, Josefin; Lawrence, Stephen; Lundqvist, Peter; Panagia, Nino; Pun, Chun S. J.; Smith, Nathan; Sollerman, Jesper; Sonneborn, George; Sugerman, Ben; Wheeler, J. Craig

    2011-01-01

    We present the most sensitive ultraviolet observations of Supernova 1987 A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (Delta v approximates 300 km/s) emission lines from the circumstellar ring, broad Delta v approximates 10-20 x 10(exp 3) km/s) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Ly-alpha emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at lambda > 1350 A can be explained by H-I two-photon (2s(exp 2)S(sub 1/2)-l(exp 2)S(sub 1/2)) emission from the same region. We confirm our earlier, tentative detection of N V lambda 1240 emission from the reverse shock and present the first detections of broad He II lambda1640, C IV lambda 1550, and N IV ] lambda1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 +/- 0.06. The N V /H alpha line ratio requires partial ion-electron equilibration (T(sub e)/T(sub p) approximately equal to 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expUlsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expUlsion of the circumstellar ring.

  6. HST-COS OBSERVATIONS OF HYDROGEN, HELIUM, CARBON, AND NITROGEN EMISSION FROM THE SN 1987A REVERSE SHOCK

    Energy Technology Data Exchange (ETDEWEB)

    France, Kevin; Penton, Steven V. [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); McCray, Richard [JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309 (United States); Kirshner, Robert P.; Challis, Peter [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Laming, Martin J. [Naval Research Laboratory, Code 7674L, Washington, DC 20375 (United States); Bouchet, Patrice [Service d' Astrophysique DSM/IRFU/SAp CEA - Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Chevalier, Roger [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Garnavich, Peter M. [225 Nieuwland Science, University of Notre Dame, Notre Dame, IN 46556-5670 (United States); Fransson, Claes; Larsson, Josefin; Lundqvist, Peter; Sollerman, Jesper [Department of Astronomy, The Oskar Klein Centre, Stockholm University, S-106 91 Stockholm (Sweden); Heng, Kevin [ETH Zuerich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Lawrence, Stephen [Department of Physics and Astronomy, Hofstra University, Hempstead, NY 11549 (United States); Panagia, Nino [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Pun, Chun S. J. [Department of Physics, University of Hong Kong, Pok Fu Lam Road, Hong Kong (China); Smith, Nathan [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Sonneborn, George [NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Sugerman, Ben, E-mail: kevin.france@colorado.edu [Department of Physics and Astronomy, Goucher College, 1021 Dulaney Valley Road, Baltimore, MD 21204 (United States); and others

    2011-12-20

    We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow ({Delta}v {approx} 300 km s{sup -1}) emission lines from the circumstellar ring, broad ({Delta}v {approx} 10-20 Multiplication-Sign 10{sup 3} km s{sup -1}) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Ly{alpha} emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at {lambda} > 1350 A can be explained by H I two-photon (2s {sup 2} S{sub 1/2}-1s {sup 2} S{sub 1/2}) emission from the same region. We confirm our earlier, tentative detection of N V {lambda}1240 emission from the reverse shock and present the first detections of broad He II {lambda}1640, C IV {lambda}1550, and N IV] {lambda}1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 {+-} 0.06. The N V/H{alpha} line ratio requires partial ion-electron equilibration (T{sub e} /T{sub p} Almost-Equal-To 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expulsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expulsion of the circumstellar ring.

  7. Estimating domestic wood burning emissions in Nordic countries using ambient air observations, receptor and dispersion modelling

    Science.gov (United States)

    Denby, B.; Karl, M.; Laupsa, H.; Johansson, C.; Pohjola, M.; Karppinen, A.; Kukkonen, J.; Ketzel, M.; Wåhlin, P.

    2009-04-01

    One of the major emission sources of primary PM2.5 in Nordic countries during winter is wood burning from domestic heating. In Norway alone it is estimated that 80% of PM2.5 is emitted through this source. Though direct measurements of wood burning emissions are possible under controlled conditions, emission inventories for domestic heating are difficult to calculate. Emissions vary from stove to stove as well as wood type, wood condition and burning habits. The consumption rate of wood burning is also strongly dependent on meteorological as well as societal conditions. As a result the uncertainty in wood burning emission inventories used in dispersion modelling is considered to be quite high. As an alternative method for estimating the emissions resulting from wood burning for domestic heating this paper combines ambient air measurements, chemical analysis of filter samples, receptor models, dispersion models, and simple inverse modelling methods to infer emission strengths. The methodology is applied in three Nordic cities, notably Oslo (Norway), Helsinki (Finland) and Lycksele (Sweden). In these cities daily filter samples over several months have been collected. The filter samples have been chemically analysed for a range of elemental and specific markers including OC/EC and Levoglucosan. The chemical analysis has been used as input for a range of receptor models, including UNMIX, PMF, PMF-2 and COPREM. From these calculations the source contributions at the measurement sites, with particular emphasis on wood burning, have been estimated. Though the receptor models have a common basis their application method varies, and as a result the number of identifiable sources and their contributions may differ. For the application here the contribution of wood burning was not found to vary significantly, irrespective of the model or user. It was also found that Levoglucosan as a wood burning tracer was essential for the identification of the wood burning sources. Source

  8. Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$

    CERN Document Server

    Lavrov, B P; Zhukov, A S

    2011-01-01

    For the first time the fine structure of rovibronic spectral lines in visible part of emission spectra of $D_2$ molecule has been observed. Observed splitting in visible doublets is about 0.2 cm$^{-1}$ in good accordance with previous observations in the infrared part of the spectrum ($a^3\\Sigma_g^+ \\to c^3\\Pi_u$ electronic transition) by means of FTIR and laser spectroscopy. Relative intensities of the fine structure components are in agreement with our calculations of adiabatic line strengths for Hund's case "b" coupling scheme.

  9. Experimental observation of acoustic emissions generated by a pulsed proton beam from a hospital-based clinical cyclotron

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Kevin C.; Solberg, Timothy D.; Avery, Stephen, E-mail: Stephen.Avery@uphs.upenn.edu [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Vander Stappen, François; Janssens, Guillaume; Prieels, Damien [Ion Beam Applications SA, Louvain-la-Neuve 1348 (Belgium); Bawiec, Christopher R.; Lewin, Peter A. [School of Biomedical Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Sehgal, Chandra M. [Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2015-12-15

    Purpose: To measure the acoustic signal generated by a pulsed proton spill from a hospital-based clinical cyclotron. Methods: An electronic function generator modulated the IBA C230 isochronous cyclotron to create a pulsed proton beam. The acoustic emissions generated by the proton beam were measured in water using a hydrophone. The acoustic measurements were repeated with increasing proton current and increasing distance between detector and beam. Results: The cyclotron generated proton spills with rise times of 18 μs and a maximum measured instantaneous proton current of 790 nA. Acoustic emissions generated by the proton energy deposition were measured to be on the order of mPa. The origin of the acoustic wave was identified as the proton beam based on the correlation between acoustic emission arrival time and distance between the hydrophone and proton beam. The acoustic frequency spectrum peaked at 10 kHz, and the acoustic pressure amplitude increased monotonically with increasing proton current. Conclusions: The authors report the first observation of acoustic emissions generated by a proton beam from a hospital-based clinical cyclotron. When modulated by an electronic function generator, the cyclotron is capable of creating proton spills with fast rise times (18 μs) and high instantaneous currents (790 nA). Measurements of the proton-generated acoustic emissions in a clinical setting may provide a method for in vivo proton range verification and patient monitoring.

  10. Tracing jet emission at the base of a high-mass YSO. First AMBER/VLTI observations of the Br\\gamma emission in IRAS 13481-6124

    CERN Document Server

    Garatti, A Caratti o; Weigelt, G; Schertl, D; Hofmann, K -H; Kraus, S; Oudmaijer, R D; de Wit, W J; Sanna, A; Lopez, R Garcia; Kreplin, A; Ray, T P

    2016-01-01

    To probe the circumstellar environment of IRAS 13481-6124, a 20 M_sun high-mass young stellar object (HMYSO) with a parsec-scale jet and accretion disc, we investigate the origin of its Br\\gamma-emission line through NIR interferometry. We present the first AMBER/VLTI observations of the Br\\gamma-emitting region in an HMYSO at R~1500. Our AMBER/VLTI observations reveal a spatially and spectrally resolved Br\\gamma-line in emission with a strong P Cygni profile, indicating outflowing matter with a terminal velocity of ~500 km/s. Visibilities, differential phases, and closure phases are detected in our observations within the spectral line and in the adjacent continuum. Both total visibilities (continuum plus line emitting region) and pure-line visibilities indicate that the Br\\gamma-emitting region is more compact (2-4 mas in diameter or ~6-13 au at 3.2 kpc) than the continuum-emitting region (~5.4 mas or ~17 au). The absorption feature is also spatially resolved at the longest baselines (81 and 85 m) and has a...

  11. Characteristics of VLF wave propagation in the Earth's magnetosphere in the presence of an artificial density duct

    Science.gov (United States)

    Pasmanik, Dmitry; Demekhov, Andrei

    We study the propagation of VLF waves in the Earth's ionosphere and magnetosphere in the presence of large-scale artificial plasma inhomogeneities which can be created by HF heating facilities like HAARP and ``Sura''. A region with enhanced cold plasma density can be formed due to the action of HF heating. This region is extended along geomagnetic field (up to altitudes of several thousand km) and has rather small size across magnetic field (about 1 degree). The geometric-optical approximation is used to study wave propagation. The plasma density and ion composition are calculated with the use of SAMI2 model, which was modified to take the effect of HF heating into account. We calculate ray trajectories of waves with different initial frequency and wave-normal angles and originating at altitudes of about 100 km in the region near the heating area. The source of such waves could be the lightning discharges, modulated HF heating of the ionosphere, or VLF transmitters. Variation of the wave amplitude along the ray trajectories due to refraction is considered and spatial distribution of wave intensity in the magnetosphere is analyzed. We show that the presence of such a density disturbances can lead to significant changes of wave propagation trajectories, in particular, to efficient guiding of VLF waves in this region. This can result in a drastic increase of the VLF-wave intensity in the density duct. The dependence of wave propagation properties on parameters of heating facility operation regime is considered. We study the variation of the spatial distribution of VLF wave intensity related to the slow evolution of the artificial inhomogeneity during the heating.

  12. FERMI-LAT OBSERVATIONS OF HIGH-ENERGY γ-RAY EMISSION TOWARD THE GALACTIC CENTER

    Energy Technology Data Exchange (ETDEWEB)

    Ajello, M. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Albert, A.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A.; Cameron, R. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B.; Caputo, R. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K. [Dept. of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin, Madison, WI 53706 (United States); Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Bonino, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, Montpellier (France); Bruel, P. [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); Buehler, R., E-mail: tporter@stanford.edu, E-mail: smurgia@uci.edu [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); and others

    2016-03-01

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy γ-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1–100 GeV from a 15° × 15° region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the γ-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner ∼1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15° × 15° region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with γ-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

  13. Spitzer observations of dust emission from H II regions in the Large Magellanic Cloud

    Energy Technology Data Exchange (ETDEWEB)

    Stephens, Ian W. [Now at Institute for Astrophysical Research, Boston University, Boston, MA 02215, USA. (United States); Evans, Jessica Marie; Xue, Rui; Chu, You-Hua; Gruendl, Robert A.; Segura-Cox, Dominique M., E-mail: ianws@bu.edu [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States)

    2014-04-01

    Massive stars can alter physical conditions and properties of their ambient interstellar dust grains via radiative heating and shocks. The H II regions in the Large Magellanic Cloud (LMC) offer ideal sites to study the stellar energy feedback effects on dust because stars can be resolved, and the galaxy's nearly face-on orientation allows us to unambiguously associate H II regions with their ionizing massive stars. The Spitzer Space Telescope survey of the LMC provides multi-wavelength (3.6-160 μm) photometric data of all H II regions. To investigate the evolution of dust properties around massive stars, we have analyzed spatially resolved IR dust emission from two classical H II regions (N63 and N180) and two simple superbubbles (N70 and N144) in the LMC. We produce photometric spectral energy distributions (SEDs) of numerous small subregions for each region based on its stellar distributions and nebular morphologies. We use DustEM dust emission model fits to characterize the dust properties. Color-color diagrams and model fits are compared with the radiation field (estimated from photometric and spectroscopic surveys). Strong radial variations of SEDs can be seen throughout the regions, reflecting the available radiative heating. Emission from very small grains drastically increases at locations where the radiation field is the highest, while polycyclic aromatic hydrocarbons (PAHs) appear to be destroyed. PAH emission is the strongest in the presence of molecular clouds, provided that the radiation field is low.

  14. Probing the origin of VHE emission from M 87 with MWL observations in 2010

    CERN Document Server

    Raue, Martin; Mazin, Daniel; Colin, Pierre; Hui, Michelle; Beilicke, Matthias; Walker, Craig; MAGIC,; VERITAS,

    2012-01-01

    The large majority of extragalactic very high energy (VHE; E>100 GeV) sources belongs to the class of active galactic nuclei (AGN), in particular the BL Lac sub-class. AGNs are characterized by an extremely bright and compact emission region, powered by a super-massive black hole (SMBH) and an accretion disk, and relativistic outflows (jets) detected all across the electro-magnetic spectrum. In BL Lac sources the jet axis is oriented close to the line of sight, giving rise to a relativistic boosting of the emission. In radio galaxies, on the other hand, the jet makes a larger angle to the line of sight allowing to resolve the central core and the jet in great details. The giant radio galaxy M 87 with its proximity (1 6Mpc) and its very massive black hole ((3-6) x 10^9 M_solar) provides a unique laboratory to investigate VHE emission in such objects and thereby probe particle acceleration to relativistic energies near SMBH and in jets. M 87 has been established as a VHE emitter since 2005. The VHE emission dis...

  15. NuSTAR observations of the bullet cluster: constraints on inverse compton emission

    DEFF Research Database (Denmark)

    Wik, Daniel R.; Hornstrup, Allan; Molendi, S.;

    2014-01-01

    The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Because all prior telescopes sensitive at E > 10 keV do not focus light a...

  16. Modelling the Soft X-Ray and EUV Emission in Classical Novae: EUVE and ROSAT Observations of V1974 Cygni

    Science.gov (United States)

    Stringfellow, Guy S.; Bowyer, Stuart

    1996-01-01

    We have conducted an extensive analysis of the observability of Classical Novae with the EUVE Lex/B and Al/Ti/C detectors. Predicted count rates have been computed using optically thin, isothermal plasma models for solar and metal-rich compositions, and hot ONeMg white dwarf model atmospheres. We find EUVE to be quite sensitive to both the EUV and soft X-ray emission emitted by the underlying hot white dwarf during novae outbursts, except for the coolest temperatures with very high intervening hydrogen column density. These results are used to interpret the emission detected during the EUVE all-sky survey of Nova Cygni 1992 (approx. = V1974 Cyg), 279-290 days after visual maximum. We find the best fit to the observed emission from V1974 Cyg arises from a hot ONeMg white dwarf with surface temperature approx. 4 x l0(exp 5) K and a mas of approx. 1.2 solar mass, and derive an interstellar hydrogen column density of approx. 3 x 10(exp 21)/sq cm. Virtually all this emission arises from supersoft X-rays rather than the EUV. We also report the detection of V1974 Cyg with the EUVE Deep Survey detector at 549 days after visual maximum. This observation is compatible with the above properties, indicating that the mechanism responsible for the soft X-ray emission, connected with the underlying white dwarf, had not yet entirely turned off. We also present analysis of a ROSAT PSPC observation which is contemporaneous with the EUVE survey observations; this independently confirms the high column density we derived from the EUVE survey observation. Light curves for the EUVE and ROSAT observations are presented. Statistical tests for variability show that all of these observations are indeed highly variable over various time scales. The EUVE survey data shows one day variations, the EUVE DS data show approx. 30 minute fluctuations, while the ROSAT data vary rapidly on time scales of seconds. The EUVE data shows no periodic variability on any time scale. The implications of the

  17. Modeling the magnetospheric X-ray emission from solar wind charge exchange with verification from XMM-Newton observations

    Science.gov (United States)

    Whittaker, Ian C.; Sembay, Steve; Carter, Jennifer A.; Read, Andrew M.; Milan, Steve E.; Palmroth, Minna

    2016-05-01

    An MHD-based model of terrestrial solar wind charge exchange (SWCX) is created and compared to 19 case study observations in the 0.5-0.7 keV emission band taken from the European Photon Imaging Cameras on board XMM-Newton. This model incorporates the Global Unified Magnetosphere-Ionosphere Coupling Simulation-4 MHD code and produces an X-ray emission datacube from O7+ and O8+ emission lines around the Earth using in situ solar wind parameters as the model input. This study details the modeling process and shows that fixing the oxygen abundances to a constant value reduces the variance when comparing to the observations, at the cost of a small accuracy decrease in some cases. Using the ACE oxygen data returns a wide ranging accuracy, providing excellent correlation in a few cases and poor/anticorrelation in others. The sources of error for any user wishing to simulate terrestrial SWCX using an MHD model are described here and include mask position, hydrogen to oxygen ratio in the solar wind, and charge state abundances. A dawn-dusk asymmetry is also found, similar to the results of empirical modeling. Using constant oxygen parameters, magnitudes approximately double that of the observed count rates are returned. A high accuracy is determined between the model and observations when comparing the count rate difference between enhanced SWCX and quiescent periods.

  18. Evaluating Observational Constraints on N2O Emissions via Information Content Analysis Using GEOS-Chem and its Adjoint

    Science.gov (United States)

    Wells, K. C.; Millet, D. B.; Bousserez, N.; Henze, D. K.; Chaliyakunnel, S.; Griffis, T. J.; Dlugokencky, E. J.; Prinn, R. G.; O'Doherty, S.; Weiss, R. F.; Dutton, G. S.; Elkins, J. W.; Krummel, P. B.; Langenfelds, R. L.; Steele, P.

    2015-12-01

    Nitrous oxide (N2O) is a long-lived greenhouse gas with a global warming potential approximately 300 times that of CO2, and plays a key role in stratospheric ozone depletion. Human perturbation of the nitrogen cycle has led to a rise in atmospheric N2O, but large uncertainties exist in the spatial and temporal distribution of its emissions. Here we employ a 4D-Var inversion framework for N2O based on the GEOS-Chem chemical transport model and its adjoint to derive new constraints on the space-time distribution of global land and ocean N2O fluxes. Based on an ensemble of global surface measurements, we find that emissions are overestimated over Northern Hemisphere land areas and underestimated in the Southern Hemisphere. Assigning these biases to particular land or ocean regions is more difficult given the long lifetime of N2O. To quantitatively evaluate where the current N2O observing network provides local and regional emission constraints, we apply a new, efficient information content analysis technique involving radial basis functions. The technique yields optimal state vector dimensions for N2O source inversions, with model grid cells grouped in space and time according to the resolution that can actually be provided by the network of global observations. We then use these optimal state vectors in an analytical inversion to refine current top-down emission estimates.

  19. Assessment of Models of Galactic Thermal Dust Emission Using COBE/FIRAS and COBE/DIRBE Observations

    Science.gov (United States)

    Odegard, N.; Kogut, A.; Chuss, D. T.; Miller, N. J.

    2016-09-01

    Accurate modeling of the spectrum of thermal dust emission at millimeter wavelengths is important for improving the accuracy of foreground subtraction for cosmic microwave background (CMB) measurements, for improving the accuracy with which the contributions of different foreground emission components can be determined, and for improving our understanding of dust composition and dust physics. We fit four models of dust emission to high Galactic latitude COBE/FIRAS and COBE/DIRBE observations from 3 mm to 100 μm and compare the quality of the fits. We consider the two-level systems (TLS) model because it provides a physically motivated explanation for the observed long wavelength flattening of the dust spectrum and the anti-correlation between emissivity index and dust temperature. We consider the model of Finkbeiner et al. because it has been widely used for CMB studies, and the generalized version of this model that was recently applied to Planck data by Meisner and Finkbeiner. For comparison we have also fit a phenomenological model consisting of the sum of two graybody components. We find that the two-graybody model gives the best fit and the FDS model gives a significantly poorer fit than the other models. The Meisner and Finkbeiner model and the TLS model remain viable for use in Galactic foreground subtraction, but the FIRAS data do not have a sufficient signal-to-noise ratio to provide a strong test of the predicted spectrum at millimeter wavelengths.

  20. Intergalactic medium emission observations with the cosmic web imager. II. Discovery of extended, kinematically linked emission around SSA22 Lyα BLOB 2

    International Nuclear Information System (INIS)

    The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter- (CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Lyα blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on- and off-source exposure, CWI has revealed that LAB2 has extended Lyα emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Lyα emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 1011 M ☉, and the dark halo mass is at least 2 × 1012 M ☉. The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas have significant and

  1. Delineation of subsurface structures using resistivity, VLF and radiometric measurement around a U-tailings pond and its hydrogeological implication

    Science.gov (United States)

    Banerjee, K. S.; Sharma, S. P.; Sarangi, A. K.; Sengupta, D.

    The hydrogeological characteristics of the uranium mill tailings pond in the vicinity of Jaduguda (Jharkhand, India) were investigated to examine possible contamination and suggest suitable remedial measures, if required. As the hydrogeological characteristics of subsurface geology are closely related to the electrical properties of the subsurface, geophysical measurements using electrical resistivity coupled with Very Low Frequency electromagnetic method and radiation study were used to investigate the geophysical and geological condition of mill tailings in order to characterize the subsurface structures of the tailings pond. The resistivity interpretation depicted the thickness of the soil cover and thickness of tailings in the pond, as well as the depth to the basement. It also suggested the possible flow direction of leachate. It was observed that the resistivity of the top layer decreases in the direction opposite to the dam axis, which in turn, indicated that the groundwater movement occurs in the opposite direction of the dam axis (in the northwest direction). The VLF method depicted the fractures through which groundwater moves, and also showed the current density alignment in the northwest direction at 10 m depth. The radiation measurement showed relatively higher counts in the northwest direction. This correlated well with the resistivity measurement. The current density at a depth of 20 m showed a closed contour suggesting no groundwater movement in the area at this depth, and that high conductivity material was confined to the tailings area only. It was concluded that groundwater moves in opposite direction of the dam axis at shallower depth only. It was found that continuation of fractures do not extend to deeper depths, which suggested that the tailings storage facility at Jaduguda was reasonably safe from any downward contamination.

  2. Radio-emission of pre-main sequence stars of the Rho Ophiuchi cloud: observations and interpretation

    International Nuclear Information System (INIS)

    Observations of the radio continuum emission of a young star population have been made at VLA on the whole molecular cloud Rho Ophiuchi, one of the closest site of star formation. A dozen of stellar sources have been detected. Radio emission of some identified objects seems to have a magnetic nature and be produced by gyrosynchrotron mechanism. In particular, one of the sources shows a radio radiation circularly polarized; two other stars have a radiation strongly variable probably due to magnetic eruptions more important than those detected in X radiation. More generally, radio observations select probably a specific population of young stars characterized by magnetic field presence extended on several stellar radii and by absence of dense circumstellar environment. Spatial distribution of these objects suggest, they are younger than most of the pre-main sequence stars

  3. Near infrared spectral and polarization imaging observation of coronal emission lines during the 2008 total solar eclipse

    Institute of Scientific and Technical Information of China (English)

    BAO XingMing; WANG XiaoFan; ZHANG ZhiYong; DENG Jian; HU KeLiang; XUAN WeiJia; LIU YangBing; ZHANG HongQi; DENG YuanYong; WANG DongGuang

    2009-01-01

    During the 2008 total solar eclipse, the coronal emission lines were observed by using optical fibre spectrometric and polarization imaging system in near infrared waveband. The profiles of the coronal emission lines Including Fe ⅩⅢ 10747 A, 10798 A and He 1 10830 A were obtained with dispersion of 0.5 A/pix. The intensity of Fe ⅩⅢ 10747 A remained unchanged In the two different coronal regions while the intensity of He I 10830 A varied considerably in the two coronal locations no matter whether the prominence appeared or not. The coronal polarization images were observed at Fe XI 7892 A with a bandpass of 30 A in a series of exposure times.

  4. Observations of soft X-ray emission and plasma dynamics of a compact capillary discharge operated in xenon

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, J. C.; Wyndham, E. S.; Favre, M.; Chuaqui, H. [Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago (Chile)

    2013-09-15

    We report observations of a low stored energy, low inductance compact capillary discharge operated in xenon. Even though the stored electrical energy is less than 1 J, significant output in the optical windows at 110 and 135 Å is measured. The soft X-ray emission is time-resolved and the conversion energy of the source is obtained. A lower bound to the conversion efficiency at 110 Å ± 2% and 135 Å ± 1% of 3.6% and 1.6% is obtained, respectively. The use of moiré-schlieren optical diagnostic allows the evolution of the line electron density. In particular, we observe a significant degree of compression in a tight on axis pinch as well as radial compression waves. The temporal evolution of the X-ray emission, which occurs during the current reversal and later, is discussed in relation to work in argon discharges and in relation to model calculations.

  5. Near infrared spectral and polarization imaging observation of coronal emission lines during the 2008 total solar eclipse

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    During the 2008 total solar eclipse, the coronal emission lines were observed by using optical fibre spectrometric and polarization imaging system in near infrared waveband. The profiles of the coronal emission lines including Fe XIII 10747 , 10798  and He I 10830  were obtained with dispersion of 0.5 /pix. The intensity of Fe XIII 10747  remained unchanged in the two different coronal regions while the intensity of He I 10830  varied considerably in the two coronal locations no matter whether the prominence appeared or not. The coronal polarization images were observed at Fe XI 7892  with a bandpass of 30  in a series of exposure times.

  6. A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations

    CERN Document Server

    Araya, E D; Goss, W M; Linz, H; Kurtz, S; Olmi, L

    2008-01-01

    We report the results of our third survey for formaldehyde (H2CO) 6cm maser emission in the Galaxy. Using the Very Large Array, we detected two new H2CO maser sources (G23.01-0.41 and G25.83-0.18), thus increasing the sample of known H2CO maser regions in the Galaxy to seven. We review the characteristics of the G23.01-0.41 and G25.83-0.18 star forming regions. The H2CO masers in G23.01-0.41 and G25.83-0.18 share several properties with the other known H2CO masers, in particular, emission from rich maser environments and close proximity to very young massive stellar objects.

  7. Theoretical quasar emission-line profiles. I - Curve-of-growth effects on observed profiles

    Science.gov (United States)

    Hubbard, E. N.; Puetter, R. C.

    1983-01-01

    Radiative transfer effects are examined in an investigation of the kinematics of quasar and Seyfert emission-line regions with pancake cloud geometries. Consideration is given only to the effects of limb brightening with the aspect angle of pancake clouds, assuming that all lines lie on a single portion of the curve of growth. This effect is coupled with several simple but plausible ensemble geometries and dynamics, and a number of theoretical emission-line profiles have been generated. It is shown that these profiles differ substantially depending on both the ensemble geometry and the portion of the curve of growth considered; for a given ensemble geometry, optically thick line profiles are different from optically thick profiles. It is shown that, for radiatively driven clouds, ensembles of clouds which have maximum velocities approaching the terminal velocity of the acceleration mechanism never produce acceptable profiles unless the cloud luminosity is a strongly decreasing function of radius.

  8. In situ transmission electron microscopy observations of individually selected freestanding carbon nanotubes during field emission

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Monja [Philips Research Laboratories, High Tech Campus 11, 5656 AE Eindhoven (Netherlands)]. E-mail: m.kaiser@philips.com; Doytcheva, Maya [Philips Research Laboratories, High Tech Campus 11, 5656 AE Eindhoven (Netherlands); Verheijen, Marcel [Philips Research Laboratories, High Tech Campus 11, 5656 AE Eindhoven (Netherlands); Jonge, Niels de [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6030 (United States)

    2006-08-15

    For the successful application of carbon nanotubes (CNTs) as electron sources in various applications it is important to understand the relation between the morphology of the CNT and its emission properties. A method was developed to study individual, freestanding and pre-selected CNTs with high-resolution transmission electron microscopy (TEM). The technique provided important parameters of the CNT, such as the number of carbon walls and the nature of its apex. The resolution with which the freestanding apices were imaged depended linearly on the ratio of the length and the radius. CNTs were also imaged in situ in the TEM while emitting electrons. It was found that the structure of a CNT was highly stable below a certain threshold emission current of typically 2 {mu}A, while various structural changes occurred above the threshold, leading to either damaging or repair of the structure at the apex of the CNT.

  9. Fermi observations of Cassiopeia and Cepheus: gamma-ray diffuse emission in the outer Galaxy

    CERN Document Server

    Tibaldo, L

    2009-01-01

    We have used measurements by the Fermi Large Area Telescope (LAT) to study the interstellar gamma-ray emission in a region of the second Galactic quadrant, at 100 deg < l < 145 deg and -15 deg < b < 30 deg. This region encompasses the prominent Gould-Belt clouds of Cassiopeia, Cepheus, and the Polaris flare, as well as large atomic and molecular complexes at larger distances in several spiral arms. The good kinematic separation in velocity between the local, Perseus, and outer arms, and the presence of massive complexes in each, make this region very well suited to probe the gamma-ray emission from the interstellar medium beyond the solar circle. The unprecedented sensitivity and angular resolution of the LAT provide improved constraints on the gradient of the cosmic-ray densities and on the increase of the CO-to-H2 conversion factor, Xco, in the outer Galaxy.

  10. The origin of emission and absorption features in Ton S180 Chandra observations

    CERN Document Server

    nska, A R; Siemiginowska, A L; Dumont, A M; Kawaguchi, T

    2004-01-01

    We present new interpretation of Ton S180 spectrum obtained by {\\it Chandra} Spectrometer (Low Energy Transmission Grating). Several narrow absorption lines and a few emission disk lines have been successfully fitted to the data. We have not found any significant edges accompanying line emission. We propose the interpretation of narrow lines consistent with the paper recently written by Krolik (2002), where warm absorber is strongly inhomogeneous. Such situation is possible in so called multi-phase medium, where regions with different ionization states, densities and temperatures may coexist in thermal equilibrium under constant pressure. We illustrate this scenario with theoretical spectra of radiation transfered through a stratified cloud with constant pressure (instead of constant density) computed by code {\\sc titan} in plane parallel approximation. Detected spectral features are faint and their presence do not alter the broad band continuum. We model the broad band continuum of Ton S180 assuming an irrad...

  11. Observation of Atomic Emission Enhancement by fs-ns Dual-Pulse Laser-Induced Breakdown Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    YAN Li-Xin; ZHANG Yong-Sheng; ZHANG Li-Rong; LIU Jing-Ru; CHENG Jian-Ping; L(U) Min

    2006-01-01

    An experiment of a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet synchronously with an ns frequency-doubled Nd:YAG laser pulse is performed in orthogonal configuration.Significant atomic emission enhancement of over forty-fold is observed with an optical multi-channel analyser.The enhancement effect is probably attributed to the different ionization mechanisms between fs and ns laser pulses.

  12. Observation of quasi-periodic frequency sweeping in electron cyclotron emission of nonequilibrium mirror-confined plasma

    CERN Document Server

    Viktorov, M E; Mansfeld, D A; Golubev, S V

    2016-01-01

    Chirping frequency patterns have been observed in the electron cyclotron emission from strongly nonequilibrium plasma confined in a table-top mirror magnetic trap. Such patterns are typical for the formation of nonlinear phase space structures in a proximity of the wave-particle resonances of a kinetically unstable plasma, also known as the "holes and clumps" mechanism. Our data provides the first experimental evidence for acting of this mechanism in the electron cyclotron frequency domain.

  13. Satellite observation of pollutant emissions from gas flaring activities near the Arctic

    Science.gov (United States)

    Li, Can; Hsu, N. Christina; Sayer, Andrew M.; Krotkov, Nickolay A.; Fu, Joshua S.; Lamsal, Lok N.; Lee, Jaehwa; Tsay, Si-Chee

    2016-05-01

    Gas flaring is a common practice in the oil industry that can have significant environmental impacts, but has until recently been largely overlooked in terms of relevance to climate change. We utilize data from various satellite sensors to examine pollutant emissions from oil exploitation activities in four areas near the Arctic. Despite the remoteness of these sparsely populated areas, tropospheric NO2 retrieved from the Ozone Monitoring Instrument (OMI) is substantial at ˜1 × 1015 molecules cm-2, suggesting sizeable emissions from these industrial activities. Statistically significant (at the 95% confidence level, corresponding uncertainties in parentheses) increasing trends of 0.017 (±0.01) × 1015 and 0.015 (±0.006) × 1015 molecules cm-2 year-1 over 2004-2015 were found for Bakken (USA) and Athabasca (Canada), two areas having recently experienced fast expansion in the oil industry. This rapid change has implications for emission inventories, which are updated less frequently. No significant trend was found for the North Sea (Europe), where oil production has been declining since the 1990s. For northern Russia, the trend was just under the 95% significance threshold at 0.0057 (±0.006) × 1015 molecules cm-2 year-1. This raises an interesting inconsistency as prior studies have suggested that, in contrast to the continued, albeit slow, expansion of Russian oil/gas production, gas flaring in Russia has decreased in recent years. However, only a fraction of oil fields in Russia were covered in our analysis. Satellite aerosol optical depth (AOD) data revealed similar tendencies, albeit at a weaker level of statistical significance, due to the longer lifetime of aerosols and contributions from other sources. This study demonstrates that synergetic use of data from multiple satellite sensors can provide valuable information on pollutant emission sources that is otherwise difficult to acquire.

  14. Synthesis of silver hollow nanoparticles and observation of photoluminescence emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Desarkar, H.S. [Nanoscience Laboratory, Department of Physics, National Institute of Technology Durgapur, Mahatma Gandhi Avenue, West Bengal 713209 (India); Kumbhakar, P., E-mail: nitdgpkumbhakar@yahoo.com [Nanoscience Laboratory, Department of Physics, National Institute of Technology Durgapur, Mahatma Gandhi Avenue, West Bengal 713209 (India); Mitra, A.K. [Nanoscience Laboratory, Department of Physics, National Institute of Technology Durgapur, Mahatma Gandhi Avenue, West Bengal 713209 (India)

    2013-02-15

    Preparation of hollow silver nanoparticles (HSNs) along-with solid silver nanoparticles are reported by Nd:YAG laser ablation of solid silver target immersed in water medium with a laser ablation time (LAT) duration of 50 min and with the incident laser fluence of 151 J/cm{sup 2}. It is found that only solid silver nanoparticles are produced when the experiment is carried out with smaller values of LAT duration. The synthesized samples are characterized by using transmission electron microscopy and UV-Visible absorption spectroscopy. The UV-Visible absorption spectra of the samples show sharp absorptions in the ultraviolet and in visible regions due to interband transition and surface plasmon resonance oscillations in Ag nanoparticles, respectively. It is found that all samples exhibit photoluminescence (PL) emission, at room temperature, in the UV-Visible region peaked at {approx}346 nm, due to the recombination of electrons with holes from sp conduction band to d band of Ag. The sample containing HSNs exhibits strong PL emission and the value of peak PL emission intensity is enhanced by the factor of 2.4 in comparison to that obtained from the sample synthesized with LAT duration of 20 min. The synthesized HSNs may find applications in catalysis and in chemical sensing. - Highlights: Black-Right-Pointing-Pointer Hollow silver nanoparticles of 15-60 nm particle sizes are prepared by laser ablation. Black-Right-Pointing-Pointer Prepared Ag nanoparticles show sharp absorptions in the UV and visible regions. Black-Right-Pointing-Pointer Strong interband transition along-with SPR oscillations is reported. Black-Right-Pointing-Pointer Enhancement (2.4 times) in photoluminescence emission in the UV region is reported.

  15. Optical observations geomagnetically conjugate to sprite-producing lightning discharges

    Directory of Open Access Journals (Sweden)

    R. A. Marshall

    2005-09-01

    Full Text Available Theoretical studies have predicted that large positive cloud-to-ground discharges can trigger a runaway avalanche process of relativistic electrons, forming a geomagnetically trapped electron beam. The beam may undergo pitch angle and energy scattering during its traverse of the Earth's magnetosphere, with a small percentage of electrons remaining in the loss cone and precipitating in the magnetically conjugate atmosphere. In particular, N2 1P and N2+1N optical emissions are expected to be observable. In July and August 2003, an attempt was made to detect these optical emissions, called "conjugate sprites", in correlation with sprite observations in Europe near . Sprite observations were made from the Observatoire du Pic du Midi (OMP in the French Pyrenées, and VLF receivers were installed in Europe to detect causative sferics and ionospheric disturbances associated with sprites. In the Southern Hemisphere conjugate region, the Wide-angle Array for Sprite Photometry (WASP was deployed at the South African Astronomical Observatory (SAAO, near Sutherland, South Africa, to observe optical emissions with a field-of-view magnetically conjugate to the Northern Hemisphere observing region. Observations at OMP revealed over 130 documented sprites, with WASP observations covering the conjugate region successfully for 30 of these events. However, no incidences of optical emissions in the conjugate hemisphere were found. Analysis of the conjugate optical data from SAAO, along with ELF energy measurements from Palmer Station, Antarctica, and charge-moment analysis, show that the lightning events during the course of this experiment likely had insufficient intensity to create a relativistic beam.

    Keywords. Ionosphere (Ionsophere-magnetosphere interactions; Ionospheric disturbances; Instruments and techniques

  16. Fermi observations of Cassiopeia and Cepheus: diffuse gamma-ray emission in the outer Galaxy

    CERN Document Server

    ,

    2009-01-01

    We present the analysis of the interstellar gamma-ray emission measured by the Fermi Large Area Telescope toward a region in the second Galactic quadrant at 100 deg < l < 145 deg and -15 deg < b < +30 deg. This region encompasses the prominent Gould-Belt clouds of Cassiopeia, Cepheus and the Polaris flare, as well as atomic and molecular complexes at larger distances, like that associated with NGC 7538 in the Perseus arm. The good kinematic separation in velocity between the local, Perseus, and outer arms, and the presence of massive complexes in each of them make this region well suited to probe cosmic rays and the interstellar medium beyond the solar circle. The gamma-ray emissivity spectrum of the gas in the Gould Belt is consistent with expectations based on the locally measured cosmic-ray spectra. The gamma-ray emissivity decreases from the Gould Belt to the Perseus arm, but the measured gradient is flatter than expectations for cosmic-ray sources peaking in the inner Galaxy as suggested by p...

  17. Suzaku Observation of Diffuse X-ray Emission from the Carina Nebula

    Science.gov (United States)

    Hamaguchi, Kenji; Petre, Robert; Matsumoti, Hironori; Tsujimoto, Masahiro; Holt, Stephan S.; Ezoe, Yuichiro; Ozawa, Hideki; Tsuboi, Yohko; Soong, Yang; Kitamoto, Shunji; Sekiguchi, Akiko; Kokubun, Motohide

    2007-01-01

    We studied extended X-ray emission from the Carina Nebula taken with the Suzaku CCD camera XIS on 2005 Aug. 29. The X-ray morphology, plasma temperature and absorption to the plasma are consistent with the earlier Einstein results. The Suzaku spectra newly revealed emission lines from various spices including oxygen, but not from nitrogen. This result restricts the N/O ratio significantly low, compared with evolved massive stellar winds, suggesting that the diffuse emission is originated in an old supernova remnant or a super shell produced by multiple supernova remnants. The X-ray spectra from the north and south of eta Car showed distinct differences between 0.3-2 keV. The south spectrum shows strong L-shell lines of iron ions and K-shell lines of silicon ions, while the north spectrum shows them weak in intensity. This means that silicon and iron abundances are a factor of 2-4 higher in the south region than in the north region. The abundance variation may be produced by an SNR ejecta, or relate to the dust formation around the star forming core.

  18. Suzaku Observation of Diffuse X-ray Emission from the Carina Nebula

    CERN Document Server

    Hamag