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Sample records for vlf emissions observed

  1. Characteristics of ELF/VLF drifting emissions observed at low latitude station Varanasi during geomagnetic substorms

    If the frequency within a set of periodic emissions changes significantly, the set is called drifting emissions. In this paper, characteristics of drifting ELF/VLF emissions are examined based on the ELF/VLF data recorded at low latitudes ground station Varanasi (geom. lat. 140 55/ N, long. 1540 E, L=1.07) during the period Jan., 1990 to Dec., 1990. Total seven strong events of drifting ELF/VLF emissions have been observed on 28-29 April, 1990 at pre-midnight sector out of which 3 events were analyzed in detail. The observed ELF/VLF emissions exhibit a regular frequency drifts, increasing as well as decreasing drift. The ELF/VLF emissions observed are mainly periodic emissions of rising and falling tone chorus. These emissions were observed during a geomagnetic storm period, when minimum Dst-index was -98 nT and KP-index ≥ 5. The repetition period, sweep rate and the frequency drift rate have been evaluated for all events. We have also computed the spectral power density, location of plasmapause, maximum intensity and maximum frequency attained. The generation mechanism of these drifting ELF/VLF emissions is explained in terms of a quasi-linear electron synchrotron instability model for wave excitation. The frequency drift in these emissions have been interpreted in terms of a combined effect of L-shell drift of energetic electrons and the change in convections electric field during the substorm developments. The computed maximum spectral power density of the wave varies between 1.8 x 10-21 to 4.08 x 10-22 Gauss2/Hz. The computed frequency drift rates of these drifting emissions are found in good agreement with that of experimentally observed values.

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

    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

    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 67 March, 1986

    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 2426?N; geomagnetic longitude 147 09?E, L = 1.28) during moderate magnetic storm activity ( $K^{?}_{P}} = 32$, $K_P$ 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. Quasi-periodic VLF emissions observed during daytime at a low latitude Indian ground station Jammu

    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.

  6. Auroral pulsations and accompanying VLF emissions

    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 Sodankyl (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 0.30.4 s formed the main ELF-VLF activity in the frequency range 1.02.5 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 4550 km and luminosity propagated inside it with velocity of about 1012 kms. We discuss a new approach to explain the 515 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

  7. VLF emissions from ionospheric/magnetospheric plasma

    R P Patel; R P Singh

    2001-05-01

    VLF emissions such as hiss, chorus, oscillating tones, hiss-triggered chorus and whistler triggered emissions have been observed at low latitude Indian stations. In this paper we present dynamic spectra of these emissions and discuss their various observed features. It is argued that most of the emissions are generated during Doppler shifted cyclotron resonance interaction between the whistler mode wave and counter streaming energetic electrons. Resonance energy of the participating electron and interaction length are evaluated to explain the generation mechanism of some of these emissions observed at Indian stations.

  8. Ground-based ELF/VLF chorus observations at subauroral latitudes—VLF-CHAIN Campaign

    Shiokawa, Kazuo; Yokoyama, Yu; Ieda, Akimasa; Miyoshi, Yoshizumi; Nomura, Reiko; Lee, Sungeun; Sunagawa, Naoki; Miyashita, Yukinaga; Ozaki, Mitsunori; Ishizaka, Kazumasa; Yagitani, Satoshi; Kataoka, Ryuho; Tsuchiya, Fuminori; Schofield, Ian; Connors, Martin

    2014-09-01

    We report observations of very low frequency (VLF) and extremely low frequency (ELF) chorus waves taken during the ELF/VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) of 17-25 February 2012 at subauroral latitudes at Athabasca (L=4.3), Canada. ELF/VLF waves were measured continuously with a sampling rate of 100 kHz to monitor daily variations in ELF/VLF emissions and derive their detailed structures. We found quasiperiodic (QP) emissions whose repetition period changes rapidly within a period of 1 h without corresponding magnetic pulsations. QP emissions showed positive correlation between amplitude and frequency sweep rate, similarly to rising-tone elements. We found an event of nearly simultaneous enhancements of QP emissions and Pc1/electromagnetic ion cyclotron wave intensities, suggesting that the temperature anisotropy of electrons and ions developed simultaneously at the equatorial plane of the magnetosphere. We also found QP emissions whose intensity suddenly increased in association with storm sudden commencement without changing their frequency. Falling-tone ELF/VLF emissions were observed with their rate of frequency change varying from 0.7 to 0.05 kHz/s over 10 min. Bursty-patch emissions in the lower and upper frequency bands are often observed during magnetically disturbed periods. Clear systematic correlation between these various ELF/VLF emissions and cosmic noise absorption was not obtained throughout the campaign period. These observations indicate several previously unknown features of ELF/VLF emissions in subauroral latitudes and demonstrate the importance of continuous measurements for monitoring temporal variations in these emissions.

  9. Identification of the source of quasiperiodic VLF emissions using ground-based and Van Allen Probes satellite observations

    Titova, E. E.; Kozelov, B. V.; Demekhov, A. G.; Manninen, J.; Santolík, Ondřej; Kletzing, C. A.; Reeves, G.

    2015-01-01

    Roč. 42, č. 15 (2015), s. 6137-6145. ISSN 0094-8276 R&D Projects: GA ČR(CZ) GAP209/11/2280 Institutional support: RVO:68378289 Keywords : energetic electrons * quasiperiodic emissions * Van Allen Probes * VLF waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 4.456, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2015GL064911/full

  10. Simultaneous observations of quasi-periodic ELF/VLF wave emissions and electron precipitation by DEMETER satellite: A case study

    Hayosh, Mykhaylo; Pasmanik, D. L.; Demekhov, A. G.; Santolík, Ondřej; Parrot, M.; Titova, E. E.

    2013-01-01

    Roč. 118, č. 7 (2013), s. 4523-4533. ISSN 2169-9380 R&D Projects: GA ČR(CZ) GAP209/11/2280; GA MŠk LH12231 Institutional support: RVO:68378289 Keywords : quasi-periodic ELF/VLF emissions in the magnetosphere * wave-particle interactions * demeter spacecraft measurements * whistler-mode waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/jgra.50179/abstract

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

    Hayosh, Mykhaylo; Němec, F.; Santolík, Ondřej; Parrot, M.

    2016-01-01

    Roč. 43, č. 3 (2016), s. 1007-1014. ISSN 0094-8276 R&D Projects: GA ČR(CZ) GAP209/11/2280; GA ČR(CZ) GA14-31899S; GA MŠk(CZ) LH15304 Institutional support: RVO:68378289 Keywords : quasiperiodic emissions * wave propagation in ionosphere * DEMETER spacecraft http://onlinelibrary.wiley.com/doi/10.1002/2015GL067373/pdf

  12. Simultaneous direction finding of VLF emissions in Japan and Europe, (1)

    It was clarified that the VLF (very low frequency) emission observed at low latitude as that in Moshiri is not propagated from the auroral zone but generated as a result of the interaction between waves and particles in the vicinity of plasma pause. For the purpose of further pursuit for that point, the direction finding of VLF emissions accompanying mainly magnetic storms was performed at Moshiri and other two points in Europe (Brorfelde, Denmark and Chambon-la-Foret, France) in order to clarify the generating and propagating mechanisms of VLF emissions at the time of disturbances. The project was conducted for 3 years from the fiscal 1976, and the observations were successful, being able to obtain a number of significant data. The objects of observation were the intensity and incident direction of VLF emissions (Hiss), whistler, and isolated VLF emissions (riser, hook, and trigged emission). Incident direction finding was carried out by the field analysis method and the direction finding using a goniometer, which are complementary each other. The final conclusion is not yet presented because the data arrangement is underway. However, the following is due: most VLF emissions (Hiss) occurred accompanying geomagnetism disturbances. It is mainly generated at dawn. In European stations, most of VLF emissions were observed simultaneously, and were considered to be the same events by the comparison of spectra by means of sonagram and the comparison of hiss record. (Wakatsuki, Y.)

  13. Early VLF perturbations observed in association with elves

    . Mika; Haldoupis, C.; Neubert, T.; Su, H.T.; Hsu, R. R.; Steiner, R. J.; Marshall, R. A.

    2006-01-01

    VLF remote sensing is used to detect lower-ionospheric electron density changes associated with a certain type of transient luminous events known as elves. Both ground- and satellite-based observations of elves are analysed in relation to VLF data acquired at various receiver sites in Europe, the United States and Antarctica. Ground-based observations were performed during the EuroSprite2003 campaign, when five elves were captured by low-light cameras located in the Pyrenees. Analysis of VLF ...

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

    Kachakhidze, Manana; Kachakhidze, Nino

    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 earthquak...

  15. Polarization analysis of VLF/ELF waves observed at subauroral latitudes during the VLF-CHAIN campaign

    Martinez-Calderon, Claudia; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Ozaki, Mitsunori; Schofield, Ian; Connors, Martin

    2015-02-01

    Chorus wave emissions are one of the most intense naturally occurring phenomena in the very low (VLF) and extremely low frequency (ELF) ranges. They are believed to be one of the major contributors to acceleration and loss of electrons in the radiation belts. During the VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) from 17 to 25 February 2012, several types of VLF/ELF emissions, including chorus, were observed at subauroral latitudes in Athabasca, Canada. To our knowledge, there has not been any comprehensive study of the physical properties of such emissions at these latitudes. In this study, we calculate spectral and polarization parameters of VLF/ELF waves with high temporal resolution. We found that the polarization angle of several emissions depended on both frequency and time. We suggest that the frequency-dependent events, which usually last several tens of minutes, might be the consequence of the broadening of the ray path that the waves follow from their generation region to the ground. Furthermore, time-dependent events, also lasting tens of minutes, have a polarization angle that changes from negative to positive values (or vice versa) every few minutes. We suggest that this could be due to variations of the wave duct, either near the generation region or along the wave propagation path. Using another ground station in Fort Vermillion, Canada, about 450 km northwest of Athabasca, we tracked the movements of the ionospheric exit point of three chorus emissions observed simultaneously at both stations. Although we found that movement of the ionospheric exit point does not follow a general direction, it is subject to hovering motion, suggesting that the exit point can be affected by small-scale plasma processes.

  16. Magnetosphere VLF observation by satellite ISIS

    On the basis of the VLF (50 Hz -- 30 kHz) electric field data from the satellite ISIS, the following works carried out in The Radio Research Laboratories are described: deuteron whistler and whistler duct, detection of plasmapause by LHR hiss, and the origin of 5 kHz hiss at low/middle latitudes. The deuteron whistlers are observable distinctly only at low latitude because of gyro-frequency and the frequency resolution of spectral analyzers. Whistler echo occurs when a whistler moves back and forth through a duct along the line of magnetic force, so it is considered that the ISIS satellite crosses the duct. The variation in ion composition around plasmapause obtained through LHR hiss is explainable by the plasamapause position and the magnetic storm effect on the plasamapause. Concerning the narrow band hiss of 5 kHz +- 1.0 kHz frequently observed on the ground at low/middle latitudes, it may occur around plasmapause, propagate through the ionosphere and then to the ground in waveguide mode, or otherwise, it may occur above the ionosphere and then propagate directly to the ground penetrating through the ionosphere. (J.P.N.)

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

    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.

  18. VLF emission triggering by a highly anisotropic energetic electron plasma

    Nunn, D.; Demekhov, A.; Trakhtengerts, V.; Rycroft, M. J.

    2003-02-01

    A recent paper (Bell et al., 2000) reports observations from the POLAR spacecraft of highly anisotropic hot electron distribution functions in the equatorial region of the magnetosphere at L= 3.4. The particle instrument HYDRA measures electron fluxes from 1 20 keV. VLF emissions triggered by pulses from Omega (Norway) are found to coincide with "pancake" type electron distributions with average pitch angles >70 degrees, such distributions being effectively confined to the equatorial zone. We examine the linear and nonlinear wave particle interaction process between pancake distributions and continuous wave (CW) or narrow band ducted whistler mode signals. It is concluded that the pitch angle range of 67 76 degrees dominates the interaction process, and that with induct wave saturation amplitudes of 6 pT strong nonlinear trapping occurs for these particles. Using these data, a 1-D Vlasov Hybrid Simulation VLF code was run to simulate numerically risers triggered by a 1 s Omega pulse. The integrated linear trans-equatorial amplification of ~ 15 dB agrees well with figures calculated by Bell et al. (2000) from the HYDRA data. Fallers, hooks and oscillating tones have also been simulated.

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

    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.

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

    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.

  1. The theory and simulation of falling frequency VLF emissions

    Nunn, D.; Omura, Y.

    2012-12-01

    Recently a lot of progress has been made in the numerical simulation and theoretical understanding of rising frequency triggered emissions and rising frequency chorus. Both PIC[3,4,5] and Vlasov[1,2] codes produce risers in the negative inhomogeneity region downstream from the equator, and Vlasov codes have simulated fallers but with difficulty. In this paper using a Vlasov VHS simulation code[1] we confine the interaction region to be the positive inhomogeneity region upstream from the equator, thus suppressing the tendency of the code to only trigger risers. The emission generation region is in reality a thin cylindrical field aligned from which the generated fields radiate out. It is unreasonable to assume the fields radiated from a faller GR are transmitted to the downstream region without spreading loss or Landau damping. Furthermore due to energetic resonant electron drift and the fact that the mean group velocity will not be aligned with ambient B field we do not expect phase coherent wave particle interaction across the equator With this reduced interaction region it is found that the VHS code easily and reproducibly triggers falling tones. One example is presented of the numerical simulation of a faller. It is analysed in detail and is compared with VHS simulations of rising frequency emission and also rising frequency chorus. Following Omura [3] it is found that the sweeping frequency is due entirely to the frequency/wavenumber advective term. It has recently been shown [5,6] that the non linear resonant particle current component Jb plays a key role in setting up the required spatial gradient of frequency. The plots of in phase current in z/t space point to a generation point upstream from the equator where initial sweep rate is determined as being nonlinear frequency shift ω1 divided by the set up time which is of the order of the trapping time [5,6]. In the generation region itself we find that the current component parallel to Bw (Jb) is positive, whereas it is negative for risers. In addition examination of the resonant particle distribution function reveals an enhanced distribution function or 'hill' in the resonant particle trap, which is as expected for positive inhomogeneity factor S, again in contrast to the riser case where one has a 'hole' in velocity space in the trap. References 1. Nunn,D., Y. Omura, H. Matsumoto, I. Nagano, and S. Yagitani,(1997) "The numerical simulation of VLF chorus and discrete emissions observed on the Geotail satellite using a Vlasov code," J. Geophys. Res., 102, pp 27083-27097. 2.Nunn,D., O. Santolik, M. Rycroft, and V. Trakhtengerts,(2009), "On the numerical modelling of VLF chorus dynamical spectra," Ann. Geophys., 27, pp1-19. 3. Omura,Y., Y. Katoh, and D. Summers,(2008), "Theory and simulation of the generation of whistler-mode chorus," J.Geophys. Res., 113, A04223, doi:10.1029/2007JA012622. 4. Omura,Y., M. Hikishima, Y. Katoh, D. Summers, and S. Yagitani,(2009) "Nonlinear mechanisms of lower-band and upperband VLF chorus emissions in the magnetosphere," J. Geophys. Res., 114,. A07217, doi:10.1029/2009JA014206. 5. Omura, Y. and D. Nunn (2011),Triggering process of whistler mode chorus emissions in the magnetosphere, J. Geophys. Res., 116, A05205, doi:10.1029/2010JA016280. 6. Nunn,D. and Y. Omura (2012), A computational and theoretical analysis of falling frequency VLF emissions, J. Geophys. Res., in press.

  2. On the frequency modulation of VLF emissions

    M. Goncharova

    Full Text Available The VLF-wave frequency modulation efficiency as a function of magnetosphere plasma parameters under the weak pitch-angle diffusion regime is studied. The study is based on the VLF growth-rate modulation both in the magnetosphere equatorial plane and after integrating along the magnetic field line. It is shown that for the typical quiet magnetosphere plasma parameters the relative shift of the maximum intensity frequency ??m/?m is approximately equal to relative disturbance of the magnetic field in the magnetosphere equatorial plane, but may exceed it when both electron temperature anisotropy and the parameter ???are small; here ? is the total-to-warm electron content ratio and ?? is the electron parallel beta. It is also shown that relative shift of the maximum intensity frequency ??m/?m after integrating along the field line is not less than 50% from its value at the equatorial plane, which allows the use of the equatorial-plasma-parameter data to estimate the VLF frequency modulation on the ground. The upper cut-off frequency modulation is considered as well. The calculated theoretical sonagrams show that this frequency modulation may be related to the non-dispersive and to the "inverted-V'' structures of QP hiss.

  3. Polarization analysis of VLF/ELF chorus waves observed at two ground stations at subauroral latitudes

    Martinez C., C.; Shiokawa, K.; Miyoshi, Y.; Ozaki, M.; Schofield, I.; Connors, M. G.

    2013-12-01

    Chorus waves are naturally occurring and very intense electromagnetic whistler-mode wave emissions, generated near the geomagnetic equator and propagating through the geomagnetic field lines to the ionosphere. They are believed to be of a major contribution to the acceleration and loss of radiation belt particles (Omura et al., 2007, Inan et al., 1982). The spatial and temporal variations of the acceleration region of radiation belt electrons might be directly linked to the spatial and temporal variations of Very Low Frequency/Extremely Low Frequency (VLF/ELF) ionospheric exit point. Hence this research will focus on studying VLF/ELF chorus characteristics at frequencies of 0.003-30kHz with the objective of locating their ionospheric exit point. During February 17 - 25, 2012, the VLF-CHAIN campaign observed VLF/ELF emissions at subauroral latitudes using two loop antennas at Athabasca (MLAT=61.31, L=4.3) and Fort Vermillion (MLAT=64.51, L=5.4), Canada. Since the end of this campaign, continuous measurements of VLF/ELF waves with a sampling rate of 100 kHz, have been made at Athabasca. We have developed a polarization and spectral analysis method that has been successfully tested with an artificial wave with known polarization parameters. We intend to apply this process to raw data from both ground stations. The objective is to study the temporal variations of polarization parameters for several types of chorus wave emissions observed during the VLF-CHAIN campaign, such as, quasi-periodic emissions, falling-tone and rising-tone chorus, as well as bursty-patch emissions.

  4. VLF saucers observed by multiple Cluster spacecraft in the AAR

    Masson, A.; Berthomier, M.; Fazakerley, A. N.; Andre, M.; Taylor, M. G.; Escoubet, C. P.; Rauch, J.; Décréau, P.; Pickett, J. S.; Laakso, H. E.

    2012-12-01

    VLF saucer is a natural radio-wave phenomenon observed in the auroral zone since the 1960's. It has a characteristic V-shaped signature on electric field spectrograms in the VLF range. Many properties of VLF saucers have been established in the 1970's based on Alouette and Isis spacecraft. Further investigations continued thanks to satellites flying over the auroral zone such as Viking, Polar and FAST. Since 2006, the orbits of the ESA/NASA Cluster satellites are slowly evolving from a nominal polar orbit to an oblique one. Meanwhile, the original 19,000 km perigee of their orbits went down to a few hundred kilometres and then back up. During spring 2009, early winter 2009/2010 and late 2011, Cluster scientists could make use of this natural orbital drift to target a new key region of the magnetosphere: the Auroral Acceleration Region (AAR). We present new observations of VLF saucers with upward electron beams by multiple Cluster satellites in the AAR region and how these observations improve our knowledge on the VLF saucers source region.

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

    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...

  6. Statistical study of ELF/VLF emissions at subauroral latitudes in Athabasca, Canada

    Martinez-Calderon, Claudia; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Ozaki, Mitsunori; Schofield, Ian; Connors, Martin

    2015-10-01

    We present the first statistical analysis of ELF/VLF emissions observed on the ground at subauroral latitudes that includes their features, occurrences, and association with solar wind and geomagnetic variations. Using a 100 kHz sampling loop antenna located in Athabasca, Canada (54.60°N, 246.36°E, L = 4.3), we monitored these emissions, including chorus, quasiperiodic emissions, and hiss, from November 2012 to October 2013. We found a maximum occurrence rate in the morning sector (06-07 MLT, magnetic local time) and a minimum in the night sector (˜18 to 02 MLT), in agreement with previous satellite measurements in the inner magnetosphere. We also found correlation between the ongoing substorm and storm activity and the increase of occurrence rates. The observed waves usually had a central frequency ˜1-3 kHz lower than the half-gyrofrequency at the conjugate equatorial plane, indicating a wave source at higher latitudes. A superposed epoch analysis showed that the starting time of the ELF/VLF emissions is preceded by a rise in AE both on short (hours) and long (days) terms. Solar wind speed also started slowly rising ˜1.5 days before, while density and dynamic pressure decreased shortly afterward. This may signify that high-speed solar wind conditions also contribute to the generation of ELF/VLF emissions detected at subauroral latitudes.

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

    NaitAmor, S.; AlAbdoadaim, M. A.; Cohen, M. B.; Cotts, B. R. T.; Soula, S.; Chanrion, Olivier Arnaud; Neubert, Torsten; Abdelatif, T.

    ) were captured over the Mediterranean Sea by cameras at Pic du Midi (42.94N, 0.14E) and at Centre de Recherches Atmospheriques (CRA) in southwestern France (43.13N, 0.37E). The cameras observations are compared to collected VLF AWESOME data. We consider early VLF perturbations observed on 12-13, 17...

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

    Mika, A.; Haldoupis, C.; Marshall, R.A.; Neubert, Torsten; Inan, U.S.

    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...

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

    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.

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

    Moore, R C; Fujimaru, S; Kotovsky, D A; Go?kowski, 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 ?1 and ?2, with |?2-2?1| 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 ?2-?1 and the polarization current density associated with the lower frequency HF wave at frequency ?1. 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

  11. A computational and theoretical analysis of falling frequency VLF emissions

    Nunn, David; Omura, Yoshiharu

    2012-08-01

    Recently much progress has been made in the simulation and theoretical understanding of rising frequency triggered emissions and rising chorus. Both PIC and Vlasov VHS codes produce risers in the region downstream from the equator toward which the VLF waves are traveling. The VHS code only produces fallers or downward hooks with difficulty due to the coherent nature of wave particle interaction across the equator. With the VHS code we now confine the interaction region to be the region upstream from the equator, where inhomogeneity factor S is positive. This suppresses correlated wave particle interaction effects across the equator and the tendency of the code to trigger risers, and permits the formation of a proper falling tone generation region. The VHS code now easily and reproducibly triggers falling tones. The evolution of resonant particle current JE in space and time shows a generation point at -5224 km and the wavefield undergoes amplification of some 25 dB in traversing the nonlinear generation region. The current component parallel to wave magnetic field (JB) is positive, whereas it is negative for risers. The resonant particle trap shows an enhanced distribution function or `hill', whereas risers have a `hole'. According to recent theory (Omura et al., 2008, 2009) sweeping frequency is due primarily to the advective term. The nonlinear frequency shift term is now negative (-12 Hz) and the sweep rate of -800 Hz/s is approximately nonlinear frequency shift divided by TN, the transition time, of the order of a trapping time.

  12. Interaction between ELF-VLF emission and magnetic pulsations: quasi-periodic ELF-VLF emissions associated with Pc 3--4 magnetic pulsations and their geomagnetic conjugacy

    Sato, N.; Kokubun, S.

    1980-01-01

    The characteristics of quasi-periodic (QP) ELF-VLF emissions with periods of 10--150 s and their relationships to magnetic pulsations are studied by using data obtained from Syowa and Mizuho Stations in Antarctica and at Husafell in Iceland, which is located near the geomagnetic conjugate point of Syowa. From the coherency analysis between QP emissions and Pc 3--4 magnetic pulsations it is found that the coherency between the D component of magnetic pulsations and the intensity fluctuations of QP's is much higher than that between the H component of magnetic pulsations and QP's. It is also found that the propagation time of magnetic pulsations (HM waves) from the interaction region between magnetic pulsations and QP's in the magnetosphere to the ground is 20--30 s. These properties are observed at conjugate-pair stations with good conjugacy. The results strongly suggest that QP emissions are modulated by compressional mode Pc 3--4 magnetic pulsations near the equatorial plane in the outer magnetosphere.

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

    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-seismicity statistical correlation means probably that passive scattering prevails upon nonlinear (active one.

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

    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.

  15. VLF transmission experiments in space

    Koons, H. C.

    1982-01-01

    It is noted that VLF electromagnetic radiation has played an important role in the discovery, exploration, and understanding of the earth's space environment. Before 1968, the data comprised passive observations of emissions generated by charged particles in the radiation belts and auroral zones. Since then, controlled wave-injection experiments have been carried out using ground-based VLF transmitters. The diagnostics have been flown on several types of spacecraft. Future experiments will test antenna configurations for the VLF transmitters to be flown on Space Test Program and Space Lab Space Shuttle missions. Both electric dipole and magnetic loop antennas are under consideration for these missions.

  16. Simulation of VLF chorus emissions in the magnetosphere and comparison with THEMIS spacecraft data

    Demekhov, A.; Taubenschuss, U.; Santolík, Ondřej

    Prague : International Union of Geodesy and Geophysics, 2015. IUGG-0723. [Earth and Environmental Sciences for Future Generations. General Assembly of International Union of Geodesy and Geophysics /26./. 22.06.2015-02.07.2015, Prague] Institutional support: RVO:68378289 Keywords : VLF chorus emissions * magnetosphere Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.iugg2015prague.com/abstractcd/data/HtmlApp/main.html#

  17. Direct observation of radiation belt electrons precipitation by the controlled injection of VLF signals from a ground-based transmitter

    Radiation belt electrons precipitated by controlled injection of VLF signals from a ground based transmitter have been directly observed for the first time. These observations were part of the SEEP (Stimulated Emission of Energetic Particles) experiment conducted during May-December 1982. Key elements of SEEP were the controlled modulation of VLF transmitters and a sensitive low altitude satellite payload to detect the precipitation. An outstanding example of time-correlated wave and particle data occurred from 8680 to 8740 seconds. U. T. on 17 August 1982 when the satellite passed near the VLF transmitter at Cutler, Maine (NAA) as it was being modulated with a repeated ON (3--s)/OFF (2--s) pattern. During each of twelve consecutive pulses from the transmitter the electron counting rate increased significantly after start of the ON period and reached a maximum about 2 seconds later. The measured energy spectra revealed that approximately 15 to 50 percent of the enhanced electron flux was concentrated near the resonant energies for first order cyclotron interactions occurring close to the magnetic equator with the nearly monochromatic waves emitted from the transmitter

  18. In connection with identification of VLF emissions before L'Aquila earthquake

    M. K. Kachakhidze; Z. A. Kereselidze; Kachakhidze, N. K.; G. T. Ramishvili; Kukhianidze, V. J.

    2012-01-01

    The present paper deals with an attempt to check the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data.

    Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. Besides, the model enables us to associate telluric character geoelectric and geomagnetic perturbations incited by rock pol...

  19. Observation of magntosphere and ionosphere through HF and VLF standard waves

    The observation of magnetosphere and ionosphere through HF and VLF standard waves is a part of the IMS research subject I on the structure and dynamics of the earth's plasmasphere. By receiving the HF and VLF standard waves with high accuracy, and through the changes of the phase and frequency, continuous observation is made concerning the lower plasmasphere at equator and middle/low latitudes and the upper layers in polar regions. In this way, the dynamic state at the time of disturbance such as magnetic storm can be explored. The following matters are described: features of standard-wave observation, purpose and observation plans, the exhcange of data with overseas countries and satellites, and the results of observation expected. (Mori, K.)

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

    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.

  1. Observation of lightning-induced signals on the summit of La Grande Montagne: part 2-interferometry and VLF measurements

    Santolík, Ondřej; Kolmašová, Ivana; Uhlíř, Luděk; Lán, Radek

    Parc d'activités de Courtabœuf : EDP Sciences, 2014 - (Febvre, P.; DiBorgo, E.; CoulieCastellani, K.) ISSN 2267-1242. - (E3S Web of Conferences. 4). [International conference i-DUST /5th/. Apt (FR), 05.05.2014-07.05.2014] Institutional support: RVO:68378289 Keywords : VLF instrumentation * VLF observation * VLF measurement Subject RIV: BL - Plasma and Gas Discharge Physics http://www.e3s-conferences.org/articles/e3sconf/pdf/2014/03/e3sconf-idust2014-04003.pdf

  2. Shipborne LF-VLF oceanic lightning observations and modeling

    Zoghzoghy, F. G.; Cohen, M. B.; Said, R. K.; Lehtinen, N. G.; Inan, U. S.

    2015-10-01

    Approximately 90% of natural lightning occurs over land, but recent observations, using Global Lightning Detection (GLD360) geolocation peak current estimates and satellite optical data, suggested that cloud-to-ground flashes are on average stronger over the ocean. We present initial statistics from a novel experiment using a Low Frequency (LF) magnetic field receiver system installed aboard the National Oceanic Atmospheric Agency (NOAA) Ronald W. Brown research vessel that allowed the detection of impulsive radio emissions from deep-oceanic discharges at short distances. Thousands of LF waveforms were recorded, facilitating the comparison of oceanic waveforms to their land counterparts. A computationally efficient electromagnetic radiation model that accounts for propagation over lossy and curved ground is constructed and compared with previously published models. We include the effects of Earth curvature on LF ground wave propagation and quantify the effects of channel-base current risetime, channel-base current falltime, and return stroke speed on the radiated LF waveforms observed at a given distance. We compare simulation results to data and conclude that previously reported larger GLD360 peak current estimates over the ocean are unlikely to fully result from differences in channel-base current risetime, falltime, or return stroke speed between ocean and land flashes.

  3. In connection with identification of VLF emissions before L'Aquila earthquake

    Kachakhidze, M; Kachakhidze, N

    2012-01-01

    The present paper deals with an attempt to check up the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data. Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. It is worth to pay attention to the fact that frequency changes from MHz to kHz in electromagnetic emission spectrum comes to a good agreement with avalanche-like unstable model of fault formation. L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes. On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake predi...

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

    Hayosh, Mykhaylo; Němec, F.; Santolík, Ondřej; Parrot, M.

    2014-01-01

    Roč. 119, č. 10 (2014), s. 8063-8072. ISSN 2169-9380 R&D Projects: GA ČR(CZ) GAP209/11/2280; GA MŠk LH12231 Grant ostatní: Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR M100421206 Institutional support: RVO:68378289 Keywords : VLF waves in ionosphere * QP emissions * DEMETER spacecraft Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2013JA019731/abstract

  5. In connection with identification of VLF emissions before L'Aquila earthquake

    M. K. Kachakhidze

    2012-04-01

    Full Text Available The present paper deals with an attempt to check the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data.

    Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. Besides, the model enables us to associate telluric character geoelectric and geomagnetic perturbations incited by rock polarization and self-generated electromagnetic oscillations of lithosphere-atmosphere system.

    L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes.

    On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake prediction with certain accuracy.

  6. The natural VLF emission as diagnostics and estimation means of the fluxes of solar x ray bursts

    The possibility to detect the chromospheric flares based on the natural VLF emission intensity data on the Earth's surface is considered. Diagnostics of the change of solar x ray burst flux at 0.5 to 4A and its estimation are discussed as possible

  7. Analysis of time-of-arrival observations performed during ELF/VLF wave generation experiments at HAARP

    Fujimaru, S.; Moore, R. C.

    2011-06-01

    Modulated high frequency (HF) heating of the lower ionosphere in the presence of auroral electrojet currents has become an important method for generating electromagnetic waves in the extremely-low frequency (ELF) and very-low frequency (VLF) bands. Recent research efforts focus on improving the efficiency of ELF/VLF wave generation. One method to do so involves the spatial mapping of modulated currents that result from HF heating for comparison with HF heating models. As a first step toward providing a spatial map of the modulated ionospheric currents, we introduce time-of-arrival (TOA) observations performed during a series of experimental research campaigns conducted at the High-frequency Active Auroral Research Program (HAARP) in Gakona, Alaska. The TOA method provides a measurement of the ELF/VLF amplitude and phase detected at a ground-based receiver as a function of time, and this information may be used to estimate the distribution of ELF/VLF source currents within the HF heated region. In an effort to test and improve the TOA method, the University of Florida conducted ELF/VLF wave generation experiments using the HAARP HF transmitter under varying ionospheric conditions and using various transmission formats. In this paper, we summarize our experimental results and compare observations with the predictions of a theoretical model.

  8. Detection of VLF and LF emissions of fluorescent light for efficient management of power consumption

    In this research work, a detection probe of Very Low Frequency and Low Frequency (LF) emissions of fluorescent light is developed by using low cost loop antenna. The developed loop antenna is able to operate at VLF and LF bandwidth. The developed antenna is tested and measured with signal generator and oscilloscope in order to verify the usefulness of antenna. The developed antenna is subsequently used to detect the signal emitted by the fluorescent light. The antenna probe is located at different distance in order to obtain the peak voltage of received signal. Besides that, the fluorescent light is switch on and off respectively in order to verify the source of signal. From the oscilloscope, the received signal is operating at approximately 28 KHz. Hence, the developed antenna probe can be used for efficient management of power consumption as 28 KHz signal is detected if the light is on.

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

    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.

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

    NaitAmor, S.; AlAbdoadaim, M. A.; Cohen, M. B.; Cotts, B. R. T.; Soula, S.; Chanrion, Olivier Arnaud; Neubert, Torsten; Abdelatif, T.

    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...

  11. Whistler-triggered emissions observed by ISIS satellites

    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.

  12. Thunderstorm monitoring with VLF network and super dense meteorological observation system

    Takahashi, Yukihiro; Sato, Mitsuteru

    2015-04-01

    It's not easy to understand the inside structure and developing process of thunderstorm only with existing meteorological instruments since its horizontal extent of the storm cell is sometimes smaller than an order of 10 km while one of the densest ground network in Japan, AMEDAS, consists of sites located every 17 km in average and the resolution of meteorological radar is 1-2 km in general. Even the X-band radar realizes the resolution of 250 m or larger. Here we suggest a thunderstorm monitoring system consisting of the network of VLF radio wave receivers and the super dense meteorological observation system with simple and low cost plate-type sensors that can be used for measurement both of raindrop and vertical electric field change caused by cloud-to-ground lightning discharge, adding to basic equipments for meteorological measurements. The plate-type sensor consists of two aluminum plates with a diameter of 10-20 cm. We carried out an observation campaign in summer of 2013 in the foothills of Mt. Yastugatake, Yamanashi and Nagano prefectures in Japan, installing 6 plate-type sensors at a distance of about 4 km. Horizontal location, height and charge amount of each lightning discharge are estimated successfully based on the information of electric field changes at several observing sites. Moreover, it was found that the thunderstorm has a very narrow structure smaller than 300 m that cannot be measured by any other ways, counting the positive and negative pulses caused by attachment of raindrop to the sensor plate, respectively. We plan to construct a new super dense observation network in the north Kanto region, Japan, where the lightning activity is most prominent in summer Japan and surrounded by our VLF systems developed for detecting sferics from lightning discharge, distributing more than several tens of sensors at every 4 km or shorter, such as an order of 100 m at minimum. This kind of new type network will reveal the unknown fine structures of thunderstorms and open the door for constructing real time alert system of torrential rainfall and lightning stroke especially in the city area.

  13. Whistler-triggered emissions observed by ISIS satellites

    VLF emissions triggered by whistlers are often observed at middle and high latitudes in the topside ionosphere by ISIS satellites. Most of them are so-called LHR emissions lasting for a few seconds. Latitudinal distributions of the occurrence rate for the whistler-triggered emissions in the topside ionosphere have been obtained by using VLF electric field data received from the ISIS 1 and 2 satellites at Kashima station, Communications Research Laboratory, Japan. These VLF emissions are classified into two groups according to the type of whistlers, i.e., ducted whistlers with a continuous trace over the full frequency range of the spectrum and nonducted whistlers without a complete trace below fLHR. The latitudinal distribution of the occurrence rate for emissions triggered by ducted whistlers is considerably different from that for emissions triggered by nonducted whistlers, especially at high latitudes. The occurrence rate for the emissions by nonducted whistlers is distributed rather randomly in latitude between L = 2.0 and L = 4.2. The occurrence rate for emissions by ducted whistlers increases with latitudes between L = 1.5 and L = 2.9, and it attains a maximum of 0.33 at L = 2.7. It then abruptly drops to 0.1 at L = 3.0, and it remains below 0.1 between L = 3.0 and L = 4.0. The decrease of the occurrence rate for emissions by ducted whistlers at L = 3.0 seems to be caused by the decrease of the radiation belt electron flux near the slot region. These results suggest that the VLF emissions triggered by ducted whistlers in the topside ionosphere are generated by the cyclotron resonant interaction of ducted whistlers with the magnetospheric electrons near the geomagnetic equatorial plane

  14. VLF emissions from a modulated electron beam in the auroral ionosphere

    A discrete VLF frequency of 3 kHz was successfully radiated by a modulated electron beam on a rocket launched into an active aurora. Instrumentation on this flight included a programable electron accelerator on the aft section with various particle and field detectors on the aft sections as well as the ejected forward payload. The accelerator programmer included a current modulation period at fixed electron energy for 0.45-s duration approximately every 11 s throughout the flight. In each of these program steps, 4-kV electrons are current modulated at a 3-kHz rate between I/sub min/ = 0 or 10 mA and I/sub max/approx. =80 mA. The forward payload, which was ejected at about 10 m/s, included a pair of spherical double probes seperated by 2.75 m and connected to a VLF receiver operating between 30 Hz and 18 kHz. Both this broadband receiver output as well as various narrow band channel outputs were directly telemetered to ground. Post flight spectrum analysis of the broadband VLF data clearly indicates that signals during the 3-kHz accelerator modulation periods were propagated to the forward payload. A detailed analysis of these modulated pulses detected by the VLF receiver is presented. A time-delay analysis between the start of the modulation and detection at the forward payload indicates time delays up to 0.2 s. The electron beam is believed to have produced a beam-plasma discharge making a radiation efficiency calculation difficult. However, absolute received signal strength was about 1 mV/m at 1.4-km separation

  15. Multistation observations of the azimuth, polarization, and frequency dependence of ELF/VLF waves generated by electrojet modulation

    Maxworth, A. S.; Gołkowski, M.; Cohen, M. B.; Moore, R. C.; Chorsi, H. T.; Gedney, S. D.; Jacobs, R.

    2015-10-01

    Modulated ionospheric heating experiments are performed with the High Frequency Active Auroral Research Program facility in Gakona, Alaska, for the purpose of generating extremely low frequency (ELF) and very low frequency (VLF) waves. Observations are made at three different azimuths from the heating facility and at distances from 37 km to 99 km. The polarization of the observed waves is analyzed in addition to amplitude as a function of modulation frequency and azimuth. Amplitude and eccentricity are observed to vary with both azimuth and distance from the heating facility. It is found that waves radiated at azimuths northwest of the facility are generated by a combination of modulated Hall and Pedersen currents, while waves observed at other azimuths are dominated by modulated Hall currents. We find no evidence for vertical currents contributing to ground observations of ELF/VLF waves. Observed amplitude peaks near multiples of 2 kHz are shown to result from vertical resonances in the Earth-ionosphere waveguide, and variations of the frequency of these resonances can be used to determine the D region ionosphere electron density profile in the vicinity of the HF heater.

  16. Relationship between median intensities of electromagnetic emissions in the VLF range and lightning activity

    Němec, František; Santolík, Ondřej; Parrot, M.; Rodger, C. J.

    2010-01-01

    Roč. 115, - (2010), A08315/1-A08315/10. ISSN 0148-0227 R&D Projects: GA ČR GA205/09/1253; GA ČR GAP205/10/2279; GA MŠk ME09107 Grant ostatní: MŠMT(CZ) MSM0021620860 Institutional research plan: CEZ:AV0Z30420517 Keywords : lightning activity * VLF electromagnetic waves * DEMETER satellite Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010

  17. Additional attenuation of natural VLF electromagnetic waves observed by the DEMETER spacecraft resulting from preseismic activity

    Píša, David; Němec, F.; Santolík, Ondřej; Parrot, M.; Rycroft, M.

    2013-01-01

    Roč. 118, č. 8 (2013), s. 5286-5295. ISSN 2169-9380 R&D Projects: GA ČR(CZ) GAP209/11/2280; GA ČR GA205/09/1253 Grant ostatní: European Community Seventh Framework Programme (FP7/2007-2013),(XE) 262005; AV ČR(CZ) M100431206. Institutional support: RVO:68378289 Keywords : DEMETER * VLF waves * preseismic activity * Earth-ionosphere waveguide Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/jgra.50469/abstract

  18. Possible Seismic Influence on VLF Wave Intensity: Observations by a Low-Altitude Satellite

    Němec, František; Santolík, Ondřej; Parrot, M.

    Vol. 2. Praha : MATFYZPRESS, Praha, 2008 - (Šafranková, J.; Pavlů, J.), s. 168-171 ISBN 978-80-7378-066-1. [Week of Doctoral Students 2008 /17./. Prague (CZ), 03.06.2008-06.06.2008] R&D Projects: GA ČR GA205/06/1267 Grant ostatní: CNRS/DREI(FR) PICS-3725 Institutional research plan: CEZ:AV0Z30420517 Keywords : seismo-electromagnetic effects * VLF electromagnetic waves * DEMETER Subject RIV: BL - Plasma and Gas Discharge Physics http://oberon.troja.mff.cuni.cz/~nemef1am/work/articles/08wds.pdf

  19. The Ionospheric Precursor to the 2011 March 11 Earthquake Based upon Observations Obtained from the Japan-Pacific Subionospheric VLF/LF Network

    Masashi Hayakawa

    2013-01-01

    Full Text Available By using network observation of subionospheric VLF (very low frequency/LF (low frequency signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 March 11 Japan earthquake (EQ which occurred at sea proximate to the Tohoku area on the main island (Honshu of Japan was an exceptionally huge plate-type EQ. A remarkable anomaly (with a decrease in the nighttime amplitude and also with enhancement in dispersion was detected on March 5 and 6 along the propagation path from the NLK (Seattle, USA transmitter to Chofu (together with Kochi and Kasugai. We also have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 along the path from JJI (Miyazaki, Kyushu to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability. (1 How abnormal is this VLF/LF propagation anomaly? (2 What was the temporal evolution of terminator times? (3 Were there any solar-terrestrial effects (especially the effect from geomagnetic storms on the VLF/LF propagation anomaly? (4 The effect of any other EQs and foreshock activities on the VLF/LF anomaly? (5 Were there any correlations with other related phenomena? Finally, (6 are there any other examples of a VLF/LF propagation anomaly for oceanic EQs? We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude. Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly discussed.

  20. The ionospheric precursor to the 2011 March 11 earthquake as based on the Japan-Pacific subionospheric VLF/LF network observation

    Hayakawa, M.; Hobara, Y.; Rozhnoi, A.; Solovieva, M.; Ohta, K.; Izutsu, J.; Nakamura, T.; Yasuda, Y.; Yamaguchi, H.; Kasahara, Y.

    2013-01-01

    By using the network observation of subionospheric VLF/LF signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 3.11 Japan earthquake (EQ) in the off-sea of the Tohoku area, which was an exceptionally huge plate-type EQ. A remarkable anomaly (with decrease in the nighttime amplitude and also with enhancement in dispersion) has been detected on March 5 and 6 on the propagation path from the NLK (Seattle, USA) transmitter to Chofu (together with Kochi and Kasugai), and also we have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 on the path from JJI (Miyazaki, Kyushu) to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability: (1) How abnormal is this VLF/LF propagation anomaly ?, (2) how about the temporal evolution of terminator times ?, (3) any solar-terrestrial effects (especially the effect of geomagnetic storms) on the VLF/LF propagation anomaly ?, (4) the effect of any other EQs and foreshock activities on the VLF/LF anomaly ?, (5) any correlation with other related phenomena ?, and (6) any other examples of VLF/LF propagation anomaly for oceanic EQs ?. We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs, and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude. Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly commented.

  1. Building and Testing a Portable VLF Receiver

    McLaughlin, Robert; Krause, L.

    2014-01-01

    Unwanted emissions or signal noise is a major problem for VLF radio receivers. These can occur from man made sources such as power line hum, which can be prevalent for many harmonics after the fundamental 50 or 60 Hz AC source or from VLF radio transmissions such as LORAN, used for navigation and communications. Natural emissions can also be detrimental to the quality of recordings as some of the more interesting natural emissions such as whistlers or auroral chorus may be drowned out by the more common sferic emissions. VLF receivers must selectively filter out unwanted emissions and amplify the filtered signal to a record-able level without degrading the quality.

  2. Survey of ELF-VLF plasma waves in outer radiation belt observed by Cluster STAFF-SA experiment

    D. Pokhotelov

    2008-10-01

    Full Text Available Various types of plasma waves have profound effects on acceleration and scattering of radiation belt particles. For the purposes of radiation belt modeling it is necessary to know statistical distributions of plasma wave parameters. This paper analyzes four years of plasma wave observations in the Earth's outer radiation belt obtained by the STAFF-SA experiment on board Cluster spacecraft. Statistical distributions of spectral density of different plasma waves observed in ELF-VLF range (chorus, plasmaspheric hiss, magnetosonic waves are presented as a function of magnetospheric coordinates and geomagnetic activity indices. Comparison with other spacecraft studies supports some earlier conclusions about the distribution of chorus and hiss waves and helps to remove the long-term controversy regarding the distribution of equatorial magnetosonic waves. This study represents a step towards the development of multi-spacecraft database of plasma wave activity in radiation belts.

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

    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.

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

    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-Australia. The frequency of occurrence of such days was by far the largest in N-Australia. In accordance with radar observed storm structures, the intra-cloud stroke mean emission heights were found distinctly different in Germany (8 km as compared to the tropics (up to 12 km in N-Australia. The fraction of intra-cloud strokes (compared to all strokes was found to be relatively high in Brazil and Australia (0.83 and 0.74, respectively as compared to Benin and Germany (0.67 and 0.69, respectively.

    Using stroke peak currents and vertical location information, lightning NOx (LNOx production under defined standard conditions can be compared for the different areas of observation. LNOx production per standard stroke was found to be most efficient for the N-Australian and S-German thunderstorms whereas the yield from Brazilian and W-African strokes was nearly 40% less. On the other hand, the main NO contribution in Brazil was from intra-cloud (IC strokes whereas in Benin it was due to cloud-to-ground (CG components. For the German and Australian strokes both stroke types contributed similar amounts to the total NO outcome.

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

    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-Australia. The frequency of occurrence of such days was by far the largest in N-Australia. In accordance with radar observed storm structures, the intra-cloud stroke mean emission heights were found distinctly different in Germany (8 km as compared to the tropics (up to 12 km in N-Australia. The fraction of intra-cloud strokes (compared to all strokes was found to be relatively high in Brazil and Australia (0.83 and 0.82, respectively as compared to Benin and Germany (0.64 and 0.69, respectively.

    Using stroke peak currents and vertical location information, lightning NOx (LNOx production under defined standard conditions can be compared for the different areas of observation. LNOx production per standard stroke was found to be most efficient for the N-Australian and S-German thunderstorms whereas the yield from Brazilian and W-African strokes was nearly 40% less. On the other hand, the main NO contribution in Brazil was from intra-cloud (IC strokes whereas in Benin it was due to cloud-to-ground (CG components. For the German and Australian strokes both stroke types contributed similar amounts to the total NO outcome.

  6. Plasma waves produced by an ion beam: observations by the VLF experiment on Porcupine

    Results are presented from the VLF electric field experiments flown on Porcupine flights F3 and F4, which also had ejectable xenon ion sources. The xenon ion beam was found to produce plasma instabilities whose frequencies could be linked to the local proton gyrofrequency fsub(cH+). The main energy in the instabilities lies at approximately 3kHz for events when the Xe+ source is close to the rocket, and at approximately 7kHz when the source is farther away. Theory predicts that these frequencies should be the lower-hybrid-resonance and this implies that Xe+ is the dominant ion in the first case and that it is the ambient plasma that dominates later. There is no discernable antenna spin-modulation during the Xe events which indicates that the wave k-vectors are not unidirectional. A theory is cited based on the 'setting up' of the proton cyclotron harmonic waves by the Xe+ or O+ cyclotron harmonic waves. The second Xe+ event on both flights exhibited an, as yet, unexplained harmonic structure related to fsub(cH+)/2. (Auth.)

  7. Observed Barium Emission Rates

    Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.

    1993-01-01

    The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.

  8. Hiss emissions during quiet and disturbed periods

    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.

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

    Greenberg, E.; Price, C.; Yair, Y.; Haldoupis, C.; Chanrion, Olivier Arnaud; Neubert, Torsten

    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...

  10. ELF/VLF emissions generated in the ionosphere by heating facilities - a new tool for ionospheric and magnetospheric research

    A brief summary of ELF/VLF generation experiments using the SURA heating facility is presented. The possibilities of applications of the measured ionospherically generated low frequency signal parameters for diagnosing the physical phenomena in the ionosphere and the magnetosphere are discussed

  11. Modeling of long-path propagation characteristics of VLF radio waves as observed from Indian Antarctic station Maitri

    Sasmal, Sudipta; Palit, Sourav; Chakrabarti, Sandip K.

    2015-10-01

    Propagation of very low frequency (VLF) radio signal through the Earth-ionosphere waveguide depends strongly on the plasma properties of the ionospheric D layer. Solar extreme ultraviolet radiation plays the central role in controlling physical and chemical properties of the lower ionospheric layers and hence determining the propagation characteristics of a VLF signal. The nature of interference among different propagating modes varies widely with the length of the propagation path. For a very long path, exposure of solar radiation and thus the degree of ionization vary by a large amount along the path. This influences the VLF signal profile by modulating the sky wave propagation. To understand the propagation characteristics over such a long path, we need a thorough investigation of the chemical reactions of the lower ionosphere which is lacking in the literature. Study of radio signal characteristics in the Antarctic region during summer period in the Southern Hemisphere gives us a unique opportunity to explore such a possibility. In addition, there is an extra feature in this path—the presence of solar radiation and hence the D region for the whole day during summer in at least some sections of the path. In this paper, we present long-distance propagation characteristics of VLF signals transmitted from VTX (18.2 kHz) and NWC (19.8 kHz) transmitters recorded at the Indian permanent station Maitri (latitude 70°45'S, longitude 114°40'E) in 2007-2008. A very stable diurnal variation of the signal has been obtained with no signature of nighttime fluctuation due the presence of 24 h of sunlight. Using ion production and recombination profiles by solar irradiance and incorporating D region ion chemistry processes, we calculate the electron density profile at different heights. Using this profile in the Long Wavelength Propagation Capability code, we are able to reproduce the amplitude of VLF signal.

  12. Possible production of lower hybrid parametric instabilities by VLF ground transmitter and by natural emissions

    A parametric instability at the lower hybrid frequency which is known as the ion quasi-mode instability may be excited in the ionosphere. The instability considered is a three-wave interaction in which an incident whistler mode wave near the lower hybrid frequency dcays into a lower hybrid wave and an ion acoustic type of oscillation. Threshold calculations are made at intervals along the L = 4 magnetic field line starting at the earth's surface (the geomagnetic position of Siple Station, Antarctica) and proceeding to the equatorial plane. A model is developed for the ionospheric plasma parameters needed to evaluate the expression for threshold field strength. The field directly radiated by the Siple transmitter are not strong enough to meet the requirement for threshold. However, it is possible that the threshold can be met for Siple transmissions which are amplified by natural processes and also for natural emissions

  13. Propagation of beam-driven VLF waves from the ionosphere toward the ground

    Schriver, David; Sotnikov, Vladimir I.; Ashour-Abdalla, Maha; Ernstmeyer, James

    1995-01-01

    As part of the Cooperative High Altitude Rocket Gun Experiment (CHARGE-2B) rocket mission, an electron beam was injected into the ionosphere with a modulated beam current in an effort to generate very low frequency (VLF) waves. The propagation of the beam-driven VLF waves through the ionosphere is examined here to determine whether it is possible to detect these wave emissions with ground receivers. The paths of the VLF waves from where they were generated near the rocket were followed to the bottom of the ionosphere and the decrease in wave amplitude due to wave-particle resonance and collisional damping was calculated. It was found that due to collisional damping, which for these VLF waves becomes large at altitudes below about 150 km, wave amplitudes were decreased below the background atmospheric noise level. A number of different beam injection events have been examined and in all of these cases studied the waves were sufficiently damped such that detection on the ground would not be possible. This is in agreement with observations on the ground in which no wave emissions were observed during the CHARGE-2B mission. Control parameters that would be more favorable for beam-generated VLF propagation to the ground are discussed for future experiments of this type.

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

    Complete text of publication follows. During the summer of 2005, transient luminous events were optically imaged from the French Pyrenees as part of the EuroSprite campaign. Simultaneously, ELF (Extremely Low Frequency: 3-3000Hz) and broadband VLF (Very Low Frequency: 3-30 kHz) data were recorded continuously at two separate receivers 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 Meteorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation with the CMCs which were estimated using ELF methods. Additionally, more than one +CG was associated with 6 of the sprites, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space. Finally, for a significant number of events (33%) an ELF transient was not associated with sprite occurrence, suggesting that long continuing current of tens of msec may not always be a necessary condition for sprite production, a finding which influences the estimation of the global sprite rate based on Schumann Resonance (SR) measurements.

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

    Greenberg, E.; Price, C.; Yair, Y.; Haldoupis, C.; Chanrion, O.; Neubert, T.

    2009-08-01

    During the summer of 2005, transient luminous events were optically imaged from the French Pyrnes as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3-3000 Hz) and broadband very low frequency (VLF: 3-30 kHz) data were recorded continuously at two separate receivers 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 Mtorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation with the CMCs which were estimated using ELF methods. Additionally, more than one +CG was associated with six of the sprites, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space. Finally, for a significant number of events (33%) an ELF transient was not associated with sprite occurrence, suggesting that long continuing current of tens of ms may not always be a necessary condition for sprite production, a finding which influences the estimation of the global sprite rate based on Schumann resonance (SR) measurements.

  16. Observation and research on ULF and VLF seismo-electromagnetic radiation

    Yuan, Jia-Zhi; Takahashi, Kozo; Qian, Shu-Qing; Fujinawa, Yokio; Zhao, Hua-Xing; Ren, Ke-Xin

    1996-05-01

    It is attracting more and more attention of seismologists in the world that electromagnetic radiation (EMR) was observed before some strong earthquake occurrence (Takahashi, 1988; Warwick, 1982; Yoshino, 1986; Oike, 1985; Fujinawa, 1990; Qian, 1992, Zhang, 1992). The international co-operation have promoted the development of this kind of science for getting more data to study SEMR physical mechanism. The observation equipments were provided by Japan, the observation installations were provided by the Seismological Bureau of Yunnan Province. Two observatories were built by Prof. Kozo Takahashi and Yukio Fujinawa, and some Chinese seismologists at Xiao Shao, Kunming, and Yuexi, Dali in Nov. 3 7, 1992. Here, some characters of SEMR in Yunnan Province and prediction efficience of the methods of impending earthquake prediction are obtained. And it was found that before the Puer M6.3 earthquake of 1993, that the occurrence time of EMR signals before strong earthquakes approximately synchronizes some other precursors, for example, of water level, water radon and F-ion. That means the SEMR signals are generated by the activation of the tectonic belt in the seismogenic zone.

  17. Compton Gamma Ray Observatory/BATSE observations of energetic electrons scattered by cyclotron resonance with waves from powerful VLF transmitters

    Datlowe, Dayton W.; Imhof, William L.

    1994-01-01

    To obtain a better understanding of the wave-particle mechanisms responsible for the loss of electrons from the radiation belts, energetic electron data from the Burst and Transient Source Experiment (BATSE) on the NASA's Compton Gamma Ray Observatory (GRO) was studied. Powerful ground-based VLF transmitters resonantly scatter electrons from the inner radiation belt onto trajectories from which they precipitate into the atmosphere as they drift eastward. 563 instances in which the satellite traversed a cloud of energetic electrons which had been scattered into quasi-trapped trajectories were identified. From the longitude distribution, it was concluded that waves from the VLF transmitter NWC at 114 deg E are the origin of 257 of the events, and waves from UMSat 44 deg E related to 45 more. In another 177 cases the electrons had drifted from the longitude of these transmitters to a location in the western hemisphere. The previously reported seasonal variation in the frequency of occurrence of cyclotron resonance interaction is confirmed with the continuous coverage provided by GRO. The frequency of occurrence of the cyclotron resonance interactions is largest before sunrise, which we attribute to the diurnal variations in the transmission VLF waves through the ionosphere. For the first time, unique very narrow sheets of electrons occurring in the aftermath of a large geomagnetic storm are reported.

  18. Dependence of Characteristics of SURA Induced Artificial ULF/VLF Signals on Geomagnetic Activity

    Kotik, D. S.; Ryabov, A. V.; Ermakova, E. N.; Pershin, A. V.

    2015-10-01

    A comprehensive study of artificial ionospheric signal generation in the ULF/VLF bands at SURA facility in Russia was conducted during the past 4 years. We investigated the influence of geomagnetic activity on the characteristics of artificial low-frequency signals under the background of increasing solar activity. No correlation of artificial ULF signals with variations of Earth's magnetic field was observed for weak geomagnetic disturbances (Kp ? 3) while the VLF signals increased in the growth phase of the geomagnetic perturbation. In case of strong magnetic storm (Kp ? 5+) a tendency of the amplitude of the ULF/VLF signals decrease with increasing magnetic disturbance was observed. Sometimes, the modulation of artificial ULF signals with a period of 15-30 s was detected in the decay phase of magnetic storms. During storm time, a change in the polarization of artificial VLF emissions was detected. The right polarization becomes predominant. Interpretation of observed peculiarities of artificial VLF signals is given in the context of the physical mechanism of ionospheric current drive by RF pumping.

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

    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.

     

  20. Pulsating aurora and quasiperiodic VLF hiss in the auroral zone morning sector: The event of December 30, 2011

    Kozelov, B. V.; Manninen, J.; Titova, E. E.

    2016-01-01

    The spatial-temporal variations in aurora and VLF emissions during an weak intensification in the auroral zone morning sector on December 30, 2011, have been analyzed. The event was accompanied by a negative bay (~70 nT) in the X component of the magnetic field at ground stations in northern Scandinavia. At the recovery phase of this bay, the precipitation zone moved and VLF emission frequency simultaneously increased over ten minutes, which may indicate that waves and precipitating electrons had a common source. VLF noise bursts in the 600-1000 Hz band with a characteristic modulation scale of ~10 s and the corresponding aurora intensifications localized in the ~100 km region were observed during the following ten minutes, which also confirms that recorded waves are related to electron precipitation. This correspondence of the pulsating aurora periods and VLF noise modulation has been revealed for the first time. The role of VLF wave generation processes during the cyclotron interaction with electrons in the magnetosphere and the propagation of these waves from the magnetosphere to the observation point are discussed.

  1. Observations of whistler-type echoes on signals of a ground VLF transmitter on board the Interkosmos-19 satellite

    Whistler-type echoes were received on board the Interkosmos 19 satellite with signals at frequencies between 10.2 and 13.6 kHz from a VLF transmitter of the Omega navigation system located in the auroral zone (66.4 deg N, 13.2 deg E, L 5). The echoes occur predominately in periods of low geomagnetic activity the occurrence region in the outer ionosphere has the dimension of about 1000 km, and its position is about L 2.5 and L 4.4. The delay of the echo signal is practically the same during one satellite pass, but its values for different satellite revolutions lie between 2.5 and 3.5 s. The experimental results are consistent with the theory of nonlinear ducting assuming quasi-ducting of whistler waves in the equatorial region due to interaction with ion cyclotron waves that permanently exist in this region

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

    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.

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

    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.

  4. X ray microbursts and VLF chorus

    On January 4, 1978, at 1140 UT, a SuperArcas sounding rocket was launched from Siple Station, Antarctica (L = 4.2, 760S, 840W), during a geomagnetically disturbed period (Kp = 6--) with intense X ray and VLF chorus activity. The parachuted payload observed an intense microburst precipitation event of 10-minute duration. These data have been correlated with measurements of VLF chorus by receivers on the ground at both Siple and its magnetic conjugate point, Roberval, Quebec. Detailed one-to-one correspondence between the microbursts and the chorus was not a consistent feature of the data. Time series analysis of the data did indicate a significant correlation between the Siple X ray precipitation and the Roberval VLF waves with an arrival time delay of 0.1 +- 0.3 seconds

  5. Whistler precursors on a VLF transmitter signal

    Whistler precursors are discrete emissions which are occasionally seen just before two-hop whistlers. Most theories of precursors assume they are triggered emissions and focus on creating a triggering signal with the proper time delay from the causative sferic. Whistler precursors have now been seen on a signal from the Siple VLF transmitter. Phase analysis shows that these precursors are caused by a rapid increase in growth activity, and not by a triggering signal

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

    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.

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

    Hayosh, Mykhaylo; Santolík, Ondřej; Němec, F.; Parrot, M.; Hanzelka, M.

    San Francisco : American Geophysical Union, 2015. SM21A-2479. [AGU Fall Meeting 2015. 14.12.2015-18.12.2015, San Francisco] Institutional support: RVO:68378289 Keywords : whistler-mode waves * inner magnetosphere * plasmasphere Subject RIV: BL - Plasma and Gas Discharge Physics

  8. On the spectral broadening of the ground-based VLF transmitter signals in the high-latitude ionosphere observed from Intercosmos-19 and Aureol-3 satellites

    The effect of spectral broadening of VLF signals as they propagate through the turbulent polar ionosphere (300-500 HZ) is discussed. The two-satellite observation results have shown that (a) electric component prevails in a broadened signal (BS), (b) the effect is independent of transmitter power, (c) BS is in a good correlation with the appearance of ELF electrostatic noise, (d) the digital processing of BS reveals the 20-50 ms temporal variations and the harmonic components at a 30-40 recurrence frequency, (e) at altitudes of > 700 km a BS is as a rule no seshaped with the characteristic rate of frequency variation df/dt = 3 x 103 - 104 s-2. These facts seem to indicate an effective scattering of wistler waves by ion-cyclotron turbulence near the oxygen ion gyrofrequency (fBi ∼ 30 HZ) involving the transformation of an initial wave into the electrostatic plasme mode in the upper ionosphere. Theoretical estimates the proposed hypothesis are presented

  9. Effects of VLF heating of ionosphere on the transmission cone of MF waves propagating from ground to space

    Lefeuvre, F.; Pincon, J.; Parrot, M.

    2012-12-01

    Global maps of VLF-MF waves observed by the low-altitude (~700 km) DEMETER satellite (Parrot et al., 2009) have pointed out localized enhancements of wave energy above the most powerful VLF transmitters and their conjugate regions, both in the 18-25 kHz frequency range (VLF transmitters) and in the 2.-2.5 MHz frequency range (emissions associated with lightning discharges). Under hypothesis made for the computation of the refractive index by the Appleton-Hartree formula, simulations are conducted to estimate the effect of VLF heating on the transmission cone of MF waves propagating from ground to space. The method used consists in the computation of the vertical variations of the Real part of the refractive index n and of the ? attenuation factor (? = ?. Imag(n)/c), with an IRI electron density profile derived from the geophysical parameters of a DEMETER orbit and an hybrid collision frequency model taking into account of theoretical and experimental data. Half-angles of the transmission cone are estimated: first, at the X=1 (X=fpe2/f2) low altitude boundary (where Ordinary mode waves may be converted into Extraordinary mode waves), and second, at the high-altitude X=1 boundary (where Extraordinary mode waves may be converted into Ordinary mode waves). It is shown that enhancements in the collision frequencies, produced by VLF heating at altitudes where the product of the collision frequency ? by the electronic density Ne is maximum (i.e. at altitudes including the low-altitude and the high-altitude X=1 boundaries), open the half angle of the transmission cones for MF waves which cross the ionosphere, and so explain enhancements of wave energy observed in the 2. - 2.5 MHz band above the powerful VLF transmitters and their conjugate regions.

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

    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.

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

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

    2013-01-01

    The effects of ground-based very low frequency (VLF) transmitters on the lower ionosphere are investigated. Controlled modulation experiments are performed with the 21.4 kHz, 424 kW VLF transmitter NPM in Lualualei, Hawaii, and physical effects of the NPM transmissions are studied with a subionospherically propagating VLF probe signal. Observed perturbations to the probe signal are consistent neither with expectations from transmitter-induced electron precipitation nor to off-p...

  12. VLF-EM surveys at Chalk River, Ontario

    Airborne DIGHEMII electromagnetic (EM) and airborne and ground Very Low Frequency Electromagnetic (VLF-EM) surveys were carried out at Chalk River prior to September 1979. All surveys were run in two directions perpendicular to the azimuths of the two VLF transmitters used (NAA, Cutler, Maine and NSS, Annapolis, Maryland). Both airborne and ground data show responses corresponding to the fracture sets mapped geologically. the order of increasing sensitivity of the techniques to small rock fractures is airborne DIGHEMII, airborne VLF-EM and ground VLF-EM. Comparison of azimuthal distribution of EM anomaly sets with geological mapping demonstrates that a VLF-EM survey in one direction only will not give a complete picture of fracture distribution. With two transmitters whose azimuths are roughly orthogonal, and with a survey in the corresponding two directions responses will be observed from all fractures that are electrical conductors. In the Chalk River area, overburden is generally resistive, and does not strongly influence results. In areas of thick or conductive cover, VLF-EM techniques should be used with caution

  13. Observations of the coupling efficiency of VLF lightning-generated whistlers into the low-latitude plasmasphere

    Jacobson, A. R.; Holzworth, R. H., II; Pfaff, R. F., Jr.; Heelis, R. A.

    2014-12-01

    The C/NOFS satellite [de La Beaujardiere, 2004] has provided a vast archive of multi-sensor data on the low-latitude ionosphere/plasmasphere since 2008. As part of the project, the VEFI payload [Pfaff et al., 2010] has recorded the 3-D electric field from DC through 16 kHz with high fidelity. The relative calibrations track between the three E-field antennas with sufficient accuracy and stability to allow retrieval of the wave polarization for a wide range of lightning-generated whistler waves [Jacobson et al., 2014]. The wave polarization in turn allows retrieval of the wavevector (within a sign ambiguity), which in turn allows an inverse-raytrace of the whistler raypath from the satellite to the ionospheric entry point. We will compare the raytrace predictions with ground-truth from the WWLLN global lightning-monitoring system [Lay et al., 2004; Rodger et al., 2005; Rodger et al., 2004]. In addition to providing location and time of lightning strokes, WWLLN provides an estimate of the radiated radio energy in the whistler passband [Hutchins et al., 2012]. Finally, the CINDI payload [Heelis et al., 2009] on C/NOFS provides ion composition at the satellite, permitting the index of refraction to be inferred. We will compare these estimates to the Poynting fluence density observed by VEFI, thereby providing a direct test of the coupling of lightning radio energy into plasmaspheric whistlers.

  14. Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance

    S. Kumar

    2008-06-01

    Full Text Available Lightning generated signals recorded at a low-latitude station, Suva (18.2° S, 178.3° E Fiji, in the South Pacific region, during September 2003–July 2004, are used to study the propagation features and the reflection heights of tweek atmospherics in the waveguide formed by the Earth's surface and the lower ionosphere. Tweeks are observed only during the local night and the maximum harmonic (n recorded is six. The occurrence of tweeks with higher n progressively decreases as n increases. The dispersed part of tweeks decreases as n increases. The attenuation factor has been calculated for tweeks with n=1–3. The ionospheric reflection heights obtained assuming the transverse magnetic mode of propagation for tweek signals vary from 83–92 km. A higher harmonic of the same tweek is reflected from about 2.0 km higher than the lower harmonic. For 90% of tweeks, propagation distances are estimated to be between 1000–5000 km. Tweeks with lower n propagate longer distances than the tweeks with higher n.

  15. Midlatitude propagation of VLF to MF waves through nighttime ionosphere above powerful VLF transmitters

    Lefeuvre, François; Pinçon, Jean-Louis; Parrot, Michel

    2013-01-01

    [1] Midlatitude nighttime observations made by the DEMETER satellite in the very low frequency (VLF) to medium frequency (MF) bands (3 kHz to 3 MHz) have demonstrated the propagation of radio waves from the bottom of ionosphere up to the satellite altitude (~700 km). Propagation characteristics derived from the magneto-ionic theory [Budden, 1985] are used to explain the absence of wave observations between ~1 and 2 MHz. Under hypotheses made for the Appleton and Hartree (or Appleton and Lasse...

  16. On remote sensing of transient luminous events' parent lightning discharges by ELF/VLF wave measurements on board a satellite

    Lefeuvre, F.; Marshall, R.; PinOn, J. L.; Inan, U. S.; Lagoutte, D.; Parrot, M.; Berthelier, J. J.

    2009-09-01

    First recordings of satellite ELF/VLF waveform data associated with transient luminous event (TLE) observations are reported from the summer 2005 campaign coordinated by Stanford University and Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPCE). TLEs are optically observed from the U.S. Langmuir Laboratory, while ELF/VLF waveform data are simultaneously recorded on board the Centre National d'Etudes Spatiales microsatellite DEMETER and on the ground at Langmuir. Analyses of ELF/VLF measurements associated with sprite events observed on 28 July 2005 and 3 August 2005 are presented. Conditions to trace back the wave emissions from the satellite to the source region of the parent lightning discharge are discussed. The main results concern: (1) the identification from a low Earth orbit satellite of the 0+ whistler signatures of the TLE causative lightning; (2) the identification of the propagation characteristics of proton whistlers triggered by the 0+ whistlers of the causative lightning, and the potential use of those characteristics; (3) recognition of the difficulty to observe sprite-produced ELF bursts in the presence of proton-whistlers; (4) the use of geographical displays of the average power received by the DEMETER electric field antennas over the U.S. Navy transmitter North West Cape (NWC) located in Western Australia to evaluate VLF transmission cones which explain the presence (28 July events) or the absence (3 August events) of propagation links between sferics observed at ground and 0+ whistlers observed on DEMETER; and (5) owing to electron-collisions, an optimum transfer of energy from the atmosphere to the ionosphere for waves with k vectors antiparallel, or quasi-antiparallel, to Earth's magnetic field direction.

  17. VLF heating of the lower ionosphere

    A controlled wave-injection experiment with a 28.5 kHz transmitter having a radiated power of 100 kW has revealed evidence of ionospheric heating by the VLF waves. Calculations indicate that the observed effect can be attributed to the absorption of wave energy in the lower ionosphere, which is estimated to result in a 30% enhancement in the collision frequency at 85 km. This process also represents a new means of direct coupling of lightning energy to the lower ionosphere

  18. ARCADE 2 Observations of Galactic Radio Emission

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Mirel, P.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2011-06-01

    We use absolutely calibrated data from the ARCADE 2 flight in 2006 July to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index βsynch = -2.5 ± 0.1, with free-free emission contributing 0.10 ± 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc |b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of C II emission. Both methods are consistent with a single power law over the frequency range 22 MHz to 10 GHz, with total Galactic emission toward the north polar cap T Gal = 10.12 ± 0.90 K and spectral index β = -2.55 ± 0.03 at reference frequency 0.31 GHz. Emission associated with the plane-parallel structure accounts for only 30% of the observed high-latitude sky temperature, with the residual in either a Galactic halo or an isotropic extragalactic background. The well-calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust and is consistent with spinning dust contributing 0.4 ± 0.1 of the Galactic plane emission at 23 GHz.

  19. ARCADE 2 OBSERVATIONS OF GALACTIC RADIO EMISSION

    We use absolutely calibrated data from the ARCADE 2 flight in 2006 July to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index βsynch = -2.5 ± 0.1, with free-free emission contributing 0.10 ± 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc |b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of C II emission. Both methods are consistent with a single power law over the frequency range 22 MHz to 10 GHz, with total Galactic emission toward the north polar cap TGal = 10.12 ± 0.90 K and spectral index β = -2.55 ± 0.03 at reference frequency 0.31 GHz. Emission associated with the plane-parallel structure accounts for only 30% of the observed high-latitude sky temperature, with the residual in either a Galactic halo or an isotropic extragalactic background. The well-calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust and is consistent with spinning dust contributing 0.4 ± 0.1 of the Galactic plane emission at 23 GHz.

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

    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.

  1. Constraining CO emission estimates using atmospheric observations

    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 (mainly CO from oxidation of NMVOCs) that are 185 Tg CO/yr higher compared to the stations-only inversion. Second, MOPITT-only derived biomass burning emissions are reduced with respect to the prior which is in contrast to previous (inverse) modeling studies. Finally, MOPITT derived total emissions are significantly higher for South America and Africa compared to the stations-only inversion. This is likely due to a positive bias in the MOPITT V4 product. This bias is also apparent from validation with surface stations and ground-truth FTIR columns. In the final study we present the first inverse modeling study to estimate CO emissions constrained by both surface (NOAA) and satellite (MOPITT) observations using a bias correction scheme. This approach leads to the identification of a positive bias of maximum 5 ppb in MOPITT column-averaged CO mixing ratios in the remote Southern Hemisphere (SH). The 4D-Var system is used to estimate CO emissions over South America in the period 2006-2010 and to analyze the interannual variability (IAV) of these emissions. We infer robust, high spatial resolution CO emission estimates that show slightly smaller IAV due to fires compared to the Global Fire Emissions Database (GFED3) prior emissions. Moreover, CO emissions probably associated with pre-harvest burning of sugar cane plantations are underestimated in current inventories by 50-100%.

  2. Evidence of a VLF transmission amplitude perturbation induced by a discrete meteor

    Rault, Jean-Louis

    2011-01-01

    Modifications of the ionosphere D layer density and/or altitude by solar UV or XR bursts are frequently observed. inducing phase and/or amplitude modifications on VLF transmissions propagation. A perturbation of the amplitude of french and german VLF transmissions received at Pic du Midi observatory during the Geminids 2010 meteor shower has been observed, which is triggered by a large meteor ionized trail

  3. VLF wave injections from the ground

    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.

  4. Terrestrial VLF transmitter injection into the magnetosphere

    İnan, Umran Savaş; Cohen, M. B.

    2012-01-01

    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 global impacts of VLF waves are based on models of trans-ionospheric propagation to calculate the VLF energy reaching the magnetosphere. Limited comparisons of these models to individual sat...

  5. Quasi-periodic ELF/VLF wave emissions in the Earth's magnetosphere: comparison of satellite observations and modeling

    Pasmanik, D. L.; Titova, E. E.; Demekhov, A. G.; Trakhtengerts, V. Y.; Santolík, Ondřej; Jiříček, František; Kudela, K.; Parrot, M.

    2004-01-01

    Roč. 22, č. 12 (2004), s. 4351-4361. ISSN 0992-7689 R&D Projects: GA MŠk ME 650; GA ČR GA202/03/0832 Institutional research plan: CEZ:AV0Z3042911 Keywords : Magnetospheric physics (plasma waves and instabilities, energetic particles, precipitating, energetic particles, trapped) Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.610, year: 2004

  6. Simultaneous observations of quasi-periodic (QP) VLF wave emissions and related ULF fluctuations of the geomagnetic field

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

    Paříž : COSPAR, 2014. C0.4-37-14. [COSPAR Scientific Assembly /40th/. 02.08.2014-10.08.2014, in Moscow, Russia, Moskva] Institutional support: RVO:68378289 http://adsabs.harvard.edu/abs/2014cosp...40E1176H

  7. VLF-ELF measurement system

    Chum, Jaroslav; Vojta, Jaroslav

    Lindau : European Geophysical Society, 2001, s. PS12. ISSN 1029-7006. [26th General Assembly of European Geophysical Society. Nice (FR), 25.03.2001-30.03.2001] R&D Projects: GA MŠk ME 435; GA MŠk ME 391 Institutional research plan: CEZ:AV0Z3042911 Keywords : VLF-ELF measurement system Subject RIV: JV - Space Technology

  8. Observation of light emissions in superconducting cavities; Observation d`emissions lumineuses dans une cavite supraconductrice

    Caruette, A.; Fouaidy, M.; Hammoudi, N.; Junquera, T.; Le Goff, A.; Lesrel, J.; Maissa, S. [Services Techniques, Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1999-11-01

    In order to investigate the light emissions associated to the electron emission in a superconducting RF cavity, an optical observation system is mounted on the `mushroom` cavity. After an intentional contamination of the cavity with alumina particles, stable luminous spots are observed around the contaminated area. (authors) 3 refs., 2 figs.

  9. Monitoring the Ground-Based VLF transmissions from Space using IMAGE RPI

    Paznukhov, V.; Song, P.; Reinisch, B.; Sales, G.; Khmyrov, G.

    2003-12-01

    Using the global network of ground-based VLF transmitters operating at frequency between 10 and 30 kHz, we have monitored the occurrence of whistler mode VLF signals with the RPI instrument on the IMAGE satellite. Our objective was to study the power and effective spatial scales of the whistler waves propagating trough the ionosphere into the magnetosphere. We have identified signals from 20 stations in the plasmasphere region with L shells ranging from 1.1 to 5.2. Ten of these stations have high radiated power, 200 kW to 1 MW. The spatial region where VLF signals were observed was significantly smaller during the dayside measurements than during the nightside ones. We also present azimuthal and radial characteristics of the VLF signal amplitude.

  10. Observations of Diffuse Ultraviolet Emission from Draco

    Sujatha, N V; Suresh, Rahul; Henry, Richard Conn; Bianchi, Luciana

    2010-01-01

    We have studied small scale (2 arcmin) spatial variation of the diffuse UV radiation using a set of 11 GALEX deep observations in the constellation of Draco. We find a good correlation between the observed UV background and the IR 100 micron flux, indicating that the dominant contributor of the diffuse background in the field is the scattered starlight from the interstellar dust grains. We also find strong evidence of additional emission in the FUV band which is absent in the NUV band. This is most likely due to Lyman band emission from molecular hydrogen in a ridge of dust running through the field and to line emissions from species such as C IV (1550 A) and Si II (1533 A) in the rest of the field. A strong correlation exists between the FUV/NUV ratio and the FUV intensity in the excess emission regions in the FUV band irrespective of the optical depth of the region. The optical depth increases more rapidly in the UV than the IR and we find that the UV/IR ratio drops off exponentially with increasing IR due ...

  11. Modeling the relaxation of early VLF perturbations associated with transient luminous events

    Complete text of publication follows. Studies show that Early VLF perturbations, characterized by abrupt signal onsets and long recoveries, occur often in relation with Transient Luminous Events (TLEs), that is, sprites, sprite halos, and elves. Also, most of the Early VLF events are attributed to forward scattering of sub-ionospheric VLF transmissions incident upon horizontally elongated disturbances of elevated ionization in the upper D region between about 70 and 90 km. This concept is supported by the similarity of Early VLF event recoveries to those of LEPs (Lightning induced Electron Precipitation events), which are due to electron density enhancements in the upper D region caused by lightning and whistler-induced precipitation of radiation belt electrons. Here, the simplified Glukhov-Pasko-Inan (GPI) model, that has been developed for LEP investigations, is applied to simulate Early VLF event recoveries observed simultaneously with sprites in the D region. The present study shows that: 1) Early VLF events with long (short) recoveries are likely to come from higher altitudes of about 80 to 90km (lower altitudes of about 70 to 80 km) and under conditions of low (high) electron density elevations relative to ambient values, 2) although negative ion and positive cluster ion production plays a role in electron density relaxation at lower heights, the electron-single ion dissociative recombination is likely the key process at upper D region heights that defines the relaxation of Early VLF perturbations, and 3) the estimated electron density increases responsible for Early VLF events reach typical values between 104 and 105 cm-3 in the upper D region ionosphere.

  12. Airborne observations of the infrared emission bands

    Earlier airborne studies of the infrared bands between 5 and 8 microns have now been extended to a sample of southern sources selected from the IRAS Low Resolution Spectra (LRS) atlas. The correlation between the strongest bands at 6.2 and 7.7 microns is now based on a total sample of 40 sources and is very strong. A new emission band at 5.2 microns, previously predicted for polycyclic aromatic hydrocarbons (PAHs), is recognized in 27 sources; it too correlates with the dominant 7.7 micron band, showing that the 5.2 micron feature also belongs to the generic spectrum of PAH features at 3.3, 5.6, 6.2, 6.2, 7.7, 8.7, 11.3, and 12.7 microns. Sufficient sources are had now to define the relative strengths of most of these bands in three separate nebular environments: planetaries, H II regions, and reflection nebulae. Significant variations are detected in the generic spectra of PAHs in these different environments which are echoed by variations in the exact wavelength of the strong 7.7 micron peak. The earlier suggestion that, in planetaries, the fraction of total emission observed by IRAS that is carried by the PAH emissions is correlated with nebular gas-phase C/O ratio is supported by the addition of newly-observed southern planetaries, including the unusually carbon-rich (WC10) nebular nuclei. These (WC10) nuclei also exhibit a strong plateau of emission linking the 6.2 and 7.7 micron features

  13. Influence of power line harmonic radiation on the VLF wave activity in the upper ionosphere: Is it capable to trigger new emissions?

    Němec, František; Parrot, M.; Santolík, Ondřej

    2010-01-01

    Roč. 115, - (2010), A11301/1-A11301/9. ISSN 0148-0227 R&D Projects: GA ČR GA205/09/1253; GA MŠk ME09107 Grant ostatní: MŠMT(CZ) MSM0021620860 Institutional research plan: CEZ:AV0Z30420517 Keywords : PLHR events * triggered emissions * DEMETER satellite Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010

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

    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

  15. Outer zone electron precipitation produced by a VLF transmitter

    By means of high-resolution pitch angle measurements made by a magnetic-focusing electron spectrometer on the S3-3 satellite while in the drift loss cone region of the magnetosphere, characteristics of fluxes of 108- to 654-keV electron precipitated in the inner zone, in the slot region, and in the outer zone of the magnetosphere are all shown to be consistent with the precipitation's having been produced by the same ground-based VLF transmitter, UMS. Pitch angle measurements are used to locate the longitude of precipitation. The temporal pattern of transmitter operation obtained from synoptic data from a ground-based VLF receiver is used along with drift rate calculations to predict the electron energies as a function of L shell which should be observable by the S3-3 instrument. The predicted energy response is then compared with the in situ observations, getting complete agreement. Finally, wave-particle resonance calculations are made for each of the three regions. The study indicates that ground-based VLF transmitters, which have previously been shown to produce precipitation in the inner zone and slot regions, are almost certainly instrumental in precipitating electrons in the outer zone also. copyright American Geophysical Union 1988

  16. Binding of the baculovirus very late expression factor 1 (VLF-1 to different DNA structures

    Mikhailov Victor S

    2002-09-01

    Full Text Available Abstract Background Baculovirus genomes encode a gene called very late expression factor 1 (VLF-1 that is a member of the integrase (Int family of proteins. In this report we describe the binding properties of purified Autographa californica multiple capsid nucleopolyhedrovirus (AcMNPV VLF-1 to a number of different DNA structures including homologous regions. In addition, its enzymatic activity was examined. Results VLF-1 was expressed in a recombinant baculovirus as a fusion with both HA and HIS6 tags and its binding activity to different DNA structures was tested. No binding was evident to single and double strand structures, very low binding was observed to Y-forks, more binding was observed to three-way junctions, whereas cruciform structures showed high levels of binding. VLF-1 binding was affected by divalent cations; optimal binding to three-way junctions and cruciforms was 2 and 0 mM MgCl2, respectively. Homologous region (hr sequences was also examined including oligomers designed to expose the hr palindrome as a hairpin, linear double strand, or H-shaped structure. Efficient binding was observed to the hairpin and H-shaped structure. No topoisomerase or endonuclease activity was detected. Sedimentation analysis indicated that *VLF-1 is present as a monomer. Conclusions An HA- and HIS-tagged version of AcMNPV VLF-1 showed structure-dependent binding to DNA substrates with the highest binding affinity to cruciform DNA. These results are consistent with the involvement of VLF-1 in the processing of branched DNA molecules at the late stages of viral genome replication. We were unable to detect enzymatic activity associated with these complexes.

  17. Plasma heating near a VLF antenna

    A collisionless plasma heating due to a strong parametric instability of VLF oscillations, excited in the near zone of an antenna in the ionospheric plasma, is considered. An expression for the temperature is derived. (author)

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

    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.

  19. New Observations of UV Emissions from Europa

    McGrath, Melissa; Sparks, William

    2009-01-01

    The recent top prioritization of the Europa Jupiter System Mission for the next outer solar system flagship mission is refocusing attention on Europa and the other Galilean satellites and their contextual environments in the Jupiter system. Surface sputtering by magnetospheric plasma generates a tenuous atmosphere for Europa, dominated by 02 gas. This tenuous gas is in turn excited by plasma electrons, producing ultraviolet and visible emissions. Two sets of imaging observations have been published to date, UV images from the Hubble Space Telescope, and visible eclipse images from Cassini. Three additional sets of HST UV observations were acquired in February 2007, April 2007 and June 2009. The signal to noise ratio in these data are not high, however, given the paucity of data and its increasing importance in terms of planning for EJSM, we have attempted to extract as much new information as possible from these data. This talk will summarize our analysis to date, and discuss them in terms of existing models, which attempt to explain the image morphology either in terms of the underlying source production and loss processes, or in terms of the plasma interaction with the exosphere.

  20. ARCADE 2 Observations of Galactic Radio Emission

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Mirel, P.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2010-01-01

    We use absolutely calibrated data from the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 0.31 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust, and is consistent with spinning dust contributing 0.4 +/- 0.1 of the Galactic plane emission at 23 GHz.

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

    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

    We present a comparative study of seismic and non-seismic sub-ionospheric VLF anomalies. Our method is based on parameter variations of the sub-ionospheric VLF waveguide formed by the surface and the lower ionosphere. The used radio links working in the frequency range between 10 and 50 kHz, the receivers are part of the European and Russian networks. Various authors investigated the lithopsheric-atmospheric-ionospheric coupling and predicted the lowering of the ionosphere over earthquake preparation zones [1]. The received nighttime signal of a sub-ionospheric waveguide depends strongly on the height of the ionospheric E-layer, typically 80 to 85 km. This height is characterized by a typical gradient of the electron density near the atmospheric-ionospheric boundary [2]. In the last years it has been turned out that one of the major issues of sub-ionospheric seismo-electromagnetic VLF studies are the non-seismic influences on the links, which have to be carefully characterized. Among others this could be traveling ionospheric disturbances, geomagnetic storms as well as electron precipitation. Our emphasis is on the analysis of daily, monthly and annual variations of the VLF amplitude. To improve the statistics we investigate the behavior and typical variations of the VLF amplitude and phase over a period of more than 2 years. One important parameter considered is the rate how often the fluctuations are falling below a significant level derived from a mean value. The temporal variations and the amplitudes of these depressions are studied for several years for sub-ionospheric VLF radio links with the receivers in Graz and Kamchatka. In order to study the difference between seismic and non-seismic turbulences in the lower ionosphere a power spectrum analysis of the received signal is performed too. We are especially interested in variations T>6 min which are typical for atmospheric gravity waves causing the lithospheric-atmospheric-ionospheric coupling [3]. All 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.

  2. Ogo 5 observations of LHR noise, emissions, and whistlers near the plasmapause at several earth radii during a large magnetic storm.

    Scarf, F. L.; Fredricks, R. W.; Smith, E. J.; Frandsen, A. M. A.; Serbu, G. P.

    1972-01-01

    On May 15, 1969, Ogo 5 crossed the plasmapause during a major storm that produced severe geomagnetic disturbances (Kp up to 8-), large and rapid variations in ring-current intensity (as measured by Dst), intense low-latitude aurora, and persistent SAR arcs. Near the highly structured plasmasphere boundary, the electric- and magnetic-field sensors on Ogo 5 detected lower-hybrid-resonance noise bursts, whistlers, ELF hiss, and other discrete signals or emissions. Some LHR noise bursts were associated with whistlers, and these high-altitude phenomena resembled the corresponding ionospheric ones. This report contains a description of the VLF observations. We also show that intense ULF magnetic signals were present near the plasmapause, and we attempt to relate these observations to the predictions of various theories of proton ring-current decay and SAR-arc formation.

  3. ARCADE 2 Observations of Galactic Radio Emission

    Kogut, A; Levin, S M; Limon, M; Lubin, P M; Mirel, P; Seiffert, M; Singal, J; Villela, T; Wollack, E; Wünsche, C A

    2009-01-01

    We use absolutely calibrated data from the ARCADE 2 flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 1 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emi...

  4. VLF saucers source region and generation revealed by the four Cluster satellites

    Masson, A.; Berthomier, M.; Pickett, J. S.; Fazakerley, A. N.; Forsyth, C.; Escoubet, C.; Laakso, H. E.; Rauch, J.; Décréau, P.

    2013-12-01

    A VLF saucer is a natural radio-wave phenomenon observed in the auroral zone since the 1960's. It has a characteristic V-shaped signature on electric field spectrograms in the VLF range. Many properties of VLF saucers have been established in the 1970's based on Alouette and Isis spacecraft. Further investigations continued thanks to satellites flying over the auroral zone, such as Viking, Polar and FAST. Since 2006, the orbits of the ESA/NASA Cluster satellites are slowly evolving from a nominal polar orbit to an oblique one. Meanwhile, the perigee of their orbits, originally at 19,000 km, naturally decreased to a few hundred kilometres and since 2011 have been steadily increasing back to the original perigee. Since spring 2009, Cluster scientists can make use of this natural orbital drift to target a new key region of the magnetosphere: the Auroral Acceleration Region (AAR). The AAR continues to be targeted by the Cluster mission, with a recent data campaign achieved successfully in Spring 2013. On rare occasions, VLF saucers are observed by the Cluster spacecraft, as they need to fly close enough to their source to catch them. Unique observations of electrostatic VLF saucers by the four Cluster satellites will be presented. These data not only enable for the first time to triangulate their source region, but they also allow revisiting some of the hypotheses commonly used so far in the analysis of their source region. Finally, the multi-point observations of VLF saucers question fundamental aspects of their generation. Indeed, it is difficult to understand, based on previously published studies, how transient structures such as electron holes are able to support the continuous generation of these electrostatic waves during several minutes, as observed by Cluster.

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

    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 detail...

  6. Detection of local and long-path VLF/ELF radiation from modulated ionospheric current systems

    Lunnen, R. J.; Ferraro, A. J.; Lee, H. S.; Allshouse, R.; Carroll, K.; Werner, D.; Collins, T. W.

    1985-06-01

    The characteristics of long-path VLF/ELF radiation detected in an RF-heated region of the ionosphere are described. The heating transmitter was modulated by a VLF/ELF frequency. Transmitters were located at sites in Puerto Rico, Norway and Peru, and receivers were in Puerto Rico and Pennsylvania. Heating was carried out at 3.17 MHz. The data indicated that the heating radiation traveled for thousands of kilometers in the atmospheric waveguide. The development of automated FFTs and correlators is recommended in order to take advantage of the communications opportunities offered by the long paths observed.

  7. Lightning and radar observations of hurricane Rita landfall

    Henderson, Bradley G [Los Alamos National Laboratory; Suszcynsky, David M [Los Alamos National Laboratory; Hamlin, Timothy E [Los Alamos National Laboratory; Jeffery, C A [Los Alamos National Laboratory; Wiens, Kyle C [TEXAS TECH U.; Orville, R E [TEXAS A& M

    2009-01-01

    Los Alamos National Laboratory (LANL) owns and operates an array of Very-Low Frequency (VLF) sensors that measure the Radio-Frequency (RF) waveforms emitted by Cloud-to-Ground (CG) and InCloud (IC) lightning. This array, the Los Alamos Sferic Array (LASA), has approximately 15 sensors concentrated in the Great Plains and Florida, which detect electric field changes in a bandwidth from 200 Hz to 500 kHz (Smith et al., 2002). Recently, LANL has begun development of a new dual-band RF sensor array that includes the Very-High Frequency (VHF) band as well as the VLF. Whereas VLF lightning emissions can be used to deduce physical parameters such as lightning type and peak current, VHF emissions can be used to perform precise 3d mapping of individual radiation sources, which can number in the thousands for a typical CG flash. These new dual-band sensors will be used to monitor lightning activity in hurricanes in an effort to better predict intensification cycles. Although the new LANL dual-band array is not yet operational, we have begun initial work utilizing both VLF and VHF lightning data to monitor hurricane evolution. In this paper, we present the temporal evolution of Rita's landfall using VLF and VHF lightning data, and also WSR-88D radar. At landfall, Rita's northern eyewall experienced strong updrafts and significant lightning activity that appear to mark a transition between oceanic hurricane dynamics and continental thunderstorm dynamics. In section 2, we give a brief overview of Hurricane Rita, including its development as a hurricane and its lightning history. In the following section, we present WSR-88D data of Rita's landfall, including reflectivity images and temporal variation. In section 4, we present both VHF and VLF lightning data, overplotted on radar reflectivity images. Finally, we discuss our observations, including a comparison to previous studies and a brief conclusion.

  8. Multi-spacecraft observations of quasiperiodic emissions

    Němec, F.; Pickett, J. S.; Hospodarsky, G.; Santolík, Ondřej; Bezděková, B.; Hayosh, Mykhaylo; Parrot, M.; Kurth, W.; Kletzing, C.

    Göttingen : European Geosciences Union, 2016. EGU 2016-2629-1. ISSN 1607-7962. [EGU General Assembly 2016. 17.04.2016-22.04.2016, Vienna] Institutional support: RVO:68378289 Keywords : QP emissions * inner magnetosphere Subject RIV: DG - Athmosphere Sciences, Meteorology http://meetingorganizer.copernicus.org/EGU2016/EGU2016-2629-1.pdf

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

    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...

  10. VLF Waves as Instigators and Diagnostics of Magnetosphere-Ionosphere Coupling

    Collier, Andrew

    In the terrestrial environment Very Low Frequency (VLF) radio waves originate principally from two sources: lightning discharges and wave-particle interactions. Whereas the former occur within the troposphere, the latter prevail in the ionosphere and magnetosphere. Within the magnetosphere the VLF signals propagate in the whistler mode, and are thus guided by the Earth's magnetic field while being subjected to dispersion. Lightning strokes, which liberate a brief but intense pulse of radiation, lead to the production of whistlers. During its passage through the magnetosphere the initial impulse is dispersed into a signal with a well defined frequency-time structure. Careful analysis of whistler traces allows the diagnosis of magnetospheric parameters. The identification of whistlers in broadband VLF data and their subsequent analysis has traditionally been an arduous process. However, recent advances have allowed for automated whistler detection and analysis. Extensive magnetospheric studies using whistler data are thus now feasible and there is the probability of real time analysis. Chorus and hiss are VLF phenomena which originate within the magnetosphere. Chorus is thought to arise via the amplification of VLF signals by an unstable electron population. The mechanism invoked is Doppler-shifted Cyclotron Resonance, where the wave frequency is Doppler-shifted up to the gyration frequency of the counter-streaming electrons. As energy is transferred from the particles to the waves, the particles' pitch angles are reduced and there is a diffusion of electrons into the loss cone. These electrons are subsequently precipitated into the ionosphere. Within the cavity formed by the surface of the Earth and the base of the ionosphere, VLF waves propagate in a waveguide mode. Under quiescent conditions both the upper and lower bound-aries of the waveguide are stable. However, the precipitation of electrons into the ionosphere causes a perturbation in the upper boundary, which leads to a modification in the propagation conditions within the waveguide. Signals from stable VLF transmitters are affected by these perturbations and may be used to study modifications in the profile of the lower ionosphere. Such modifications may also arise from solar flares and gamma-ray bursts. The study of VLF waves as a diagnostic tool for magnetosphere-ionosphere coupling will be reviewed and possibilities for linking ground and satellite observations will be discussed.

  11. Prompt Emission Observations of Swift BAT Bursts

    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.

  12. Showa Station and Iceland conjugate-point observations

    Joint observations with France were conducted for 52 days from July 29 to September 18, 1977, at Husafell about 100 km away from the capital of Iceland, Reykjavik. Husafell is about 60 km distant from the geomagnetic conjugate point of Showa Station. The items observed in Iceland were two horizontal components of geomagnetic pulsation, VLF natural radio waves, fixed-direction photometer (4278 A) and aurora TV camera. These have been all observed continuously at Showa Station, so that detailed analyses of conjugate-point observations are possible. The observation point was at Husafell, while geomagnetic stations are at Reykjavik, Showa Station and Mizuho Station. This report is described on the intensity ratio of ELF/VLF band natural radiowaves, spectral analyses, the conjugate natures of QP emission, aurora chorus and aurora hiss, and the relation of QP emission to geomagnetic pulsation. (J.P.N.)

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

    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

  14. OBSERVATION OF CORRELATED OPTICAL AND GAMMA EMISSIONS FROM GRB 081126

    We present an analysis of time-resolved optical emissions observed from the gamma-ray burst GRB 081126 during the prompt phase. The analysis employed time-resolved photometry using optical data obtained by the TAROT telescope, using BAT data from the Swift spacecraft, and time-resolved spectroscopy at high energies from the GBM instrument onboard the Fermi spacecraft. The optical emission of GRB 081126 is found to be compatible with the second gamma emission pulse shifted by a positive time lag of 8.4 3.9 s. This is the first well-resolved observation of a time lag between optical and gamma emissions during a gamma-ray burst. Our observations could potentially provide new constraints on the fireball model for gamma-ray burst early emissions. Furthermore, observations of time lags between optical and gamma ray photons provides an exciting opportunity to constrain quantum gravity theories.

  15. Excitation of whistler mode signals via injection of polarized VLF waves with the Siple transmitter

    Whistler mode waves of various polarizations were transmitted by the Siple Station, Antarctica, VLF transmitter and received near the geomagnetic conjugate point at Lake Mistissini, Quebec. Crossed 21-km horizontal dipole antennas on top of the 2-km-thick ice sheet were used to transmit 2- to 4-kHz waves alternately with right-hand circular, left-hand circular, and linear polarizations. Excitation of a multiplicity of magnetospheric propagation paths and the received signal strength were observed to depend on the transmitter antenna polarization. Where whistler mode growth and emission triggering occurred, saturated peak values of received signals were independent of antenna polarization and initial injected power levels, in agreement with previous findings. Propagation paths of ducted Siple signals observed at Lake Mistissini were identified with propagation paths deduced from natural whistlers, from which the L shell values and equatorial number densities for the paths were calculated. A combination of L shell data and models of antenna coupling into the whistler mode may aid in the location of ducts. Dynamics Explorer I satellite recordings of unducted Siple signals showed trends similar to the ground data on ducted signals. The observations are discussed in the context of a simplified model of the coupling from the Siple antenna into the ionosphere, which provides reasonable agreement with observations. 14 refs

  16. ELF and VLF radiation from the polar electrojet antenna

    Barr, R.; Stubbe, P.

    1984-07-01

    An approximate evaluation is made of the ELF/VLF dipole moment of the polar electrojet antenna established by ionospheric heating via the use of powerful HF waves amplitude modulated with frequencies in the ELF/VLF range. The theory of reciprocity is used to determine the magnitude of the ELF/VLF waveguide excitation produced by such a dipole immersed in the ionosphere. Propagation under a series of ionospheres ranging from quiet auroral nighttime to disturbed auroral daytime is considered. 32 references.

  17. Effects of Geomagnetic effect on Sub-ionospheric VLF-LF Signals Propagation

    Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Verma, Shivali; Kasde, Satish Kumar; Sonakia, Anjana

    Abstract: To investigate the effect of geomagnetic storm on subionospheric VLF-LF signal propagation, we analyze the variation in amplitude of VLF-LF signal using advanced complex continuous wavelet transform techniques. We analyze the VLF signal transmitted form ICV (20.27 kHz) located at Isola di Tavolara (40.55o N, 9.430 E), Italy and DH038 (23.40 kHz) Rhauderfehn (53.040 N, 7.340 E) Germany and one LF signal transmitted form NRK (37.50 kHz) transmitter located at Grindavik (63.510 N, 22.280 E), Iceland. We observed significant absorption in amplitude of these signals during the geomagnetic storm compared to their ambient values for the same period during the adjacent 7 days. The signal strength along their propagation paths was controlled by the storm associated decrease in ionization in the D-region of the ionosphere. Waveguide mode theory calculations show that the elevation of the height of lower ionosphere boundary of Earth-ionosphere waveguide was significantly decreased during this period. Key words: Subionospheric VLF-LF propagation, Complex Wavelet Transform, Geomagnetic activity and Earth-ionosphere waveguide

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

    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.

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

    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.

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

    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.

  1. Power line emission 50/60 Hz and Schumann resonances observed by microsatellite Chibis-M in the Earth's ionosphere

    Dudkin, Denys; Pilipenko, Vyacheslav; Dudkin, Fedir; Pronenko, Vira; Klimov, Stanislav

    2015-04-01

    The overhead power lines are the sources of intense wideband electromagnetic (EM) emission, especially in ELF-VLF range, because of significant length (up to a few thousand kilometers) and strong 50/60 Hz currents with noticeable distortion. The radiation efficiency of the power line emission (PLE) increases with the harmonic order, so they are well observed by ground-based EM sensors. However their observations by low orbiting satellites (LEO) are very rare, particularly at basic harmonic 50/60 Hz, because of the ionospheric plasma opacity in ELF band. The Schumann resonance (SR) is the narrow-band EM noise that occurs due to the global thunderstorm activity in the Earth-ionosphere cavity. The first five eigenmodes of the SR are 7.8, 14.3, 20.8, 27.3 and 33.8 Hz and, thus, SR harmonics are also strongly absorbed by the Earth ionosphere. The published numerical simulations show that the penetration depth of such an ELF emission into the Earth's ionosphere is limited to 50-70 km for electric field and 120-240 km for magnetic field. From this follows, that PLE and SR can hardly ever be detected by LEO satellites, i.e. above the F-layer of ionosphere. In spite of this fact, these emissions were recently observed with use of the electric field antennas placed on the satellites C/NOFS (USA) and Chibis-M (Russia). Microsatellite Chibis-M was launched on January 24, 2012, at 23:18:30 UTC from the cargo ship "Progress M-13M" to circular orbit with altitude ~500 km and inclination ~52° . Chibis-M mass is about 40 kg where one third is a scientific instrumentation. The dimensions of the microsatellite case are 0.26x0.26x0.54 m with the outside mounted solar panels, service and scientific instrumentation. The main scientific objective of Chibis-M is the theoretical model verification for the atmospheric gamma-ray bursts. It requires the study of the accompanying EM processes such as the plasma waves produced by the lightning discharges in the VLF band. Chibis-M decayed on 15 October 2014. The Chibis-M electric sensor has a small 0.42 m tip-to-tip base and was developed in Lviv Centre of Institute for Space Research, Ukraine. The sensor provides the measurement of one electric field component, which is perpendicular to the orbital plane, in the frequency range of 0.1-40,000 Hz with the noise spectral density 0.8-0.04 (μV/m)/Hz0.5 (in the band 1-100 Hz the noise is 0.2-0.04 (μV/m)/Hz0.5). We present the space distribution of the observed PLE and SR harmonics in the latitude range ±52o and connection of the PLE sources with the high-voltage overhead power lines. The electric field data have been analyzed for all Chibis-M operating time (~ 2.5 years). The fact of PLE and SR detection by LEO satellites C/NOFS and Chibis-M suggests that the model of the transionospheric ELF EM field propagation should be refined.

  2. VLF radio propagation conditions. Computational analysis techniques

    Complete text of publication follows. Very low frequency (VLF) radio waves propagate within the Earth-ionosphere waveguide with very little attenuation. Modifications of the waveguide geometry effect the propagation conditions, and hence, the attenuation. Changes in the ionosphere, such as the presence of the D-region during the day, or the precipitation of energetic particles, are the main causes of this modification. Using narrowband receivers monitoring VLF transmitters, the amplitude and phase of these signals are recorded. Multivariate data analysis techniques, namely Principal Component Analysis (PCA) and Singular Spectrum Analysis (SSA), are applied to the data in order to determine parameters, such as seasonal and diurnal changes, affecting the variation of these signals. Transient effects may then be easier to detect.

  3. Egret observations of the extragalactic gamma-ray emission

    Sreekumar, P.; Bertsch, D.L.; Dingus, B.L.; Esposito, J.A.; Fichtel, C.E.; Hartman, R.C.; Hunter, S.D.; Kanbach, G.; Kniffen, D.A.; Lin, Y.C.; Mayer-Hasselwander, H.A.; Michelson, P.F.; von Montigny, C.; Mucke, A.; Mukherjee, R.; Nolan, P.L.; Pohl, M.; Reimer, O.; Schneid, E.; Stacy, J.G.; Stecker, F.W.; Thompson, D.J.; Willis, T.D.

    1998-01-01

    the local interstellar gas and radiation, as well as an almost uniformly distributed component that is generally believed to originate outside the Galaxy. Through a careful study and removal of the Galactic diffuse emission, the flux, spectrum, and uniformity of the extragalactic emission are deduced......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 with...

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

    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.

  5. Dust Obscuration and Observable Emission of Active Galactic Nuclei

    Levenson, Nancy A.; Ichikawa, Kohei; Lopez-Rodriguez, Enrique; Nikutta, Robert; Packham, Christopher C.; Alonso-Herrero, Almudena

    2016-01-01

    The presence of toroidal distributions of obscuring material around active galactic nuclei (AGN) coherently accounts for many of their diverse observed properties. However, high spatial resolution observations that show dust emission extended along the polar axis in some cases would seem to contradict this basic geometric picture. We present simulations of clumpy dust distributions to demonstrate the variety of emission patterns that may emerge, which are dependent on wavelength and spatial scale. Data from ALMA currently and JWST in the future may distinguish some of the physical properties of the different AGN environments in detail. Fundamentally, the distribution of the emission does not necessarily match the distribution of material.

  6. MSX Observations of Diffuse UV Emission in Orion

    Murthy, J; Paxton, L J; Price, S D; Murthy, Jayant

    2001-01-01

    We have observed intense diffuse radiation in the UV (1400 A - 2600 A) from three fields around M42 in Orion. Intensities of 20000 photons cm-2 s-1 sr-1 A-1 were observed to the east and west of M42 with 8000 photons cm-2 s-1 sr-1 A-1 south of the nebula. Enhanced emission, perhaps associated with a nearby complex of molecular clouds observed in CO, was detected in one of the fields. The IRAS 100 micron emission in that region is highly correlated with the UV intensity with a UV-IR ratio of 40 photons cm-2 s-1 sr-1 A-1 (MJy sr-1)-1. In the other two fields there was no structure in the diffuse emission nor was there any correlation with the IRAS emission.

  7. Solar eclipse effects on HF and VLF propagation

    A multifrequency oblique-incidence experiment performed during the 10 July 1972 total solar eclipse is described. A definite correlation of VLF phase, HF signal strength, and geomagnetic field behaviour on eclipse day is demonstrated. Because of the relatively high transmitter powers available, ionospheric non-linearities observed during the eclipse period provided additional diagnostic information on oblique-incidence phenomena which are particularly sensitive to inverted Δ.E is not equal to 0 along the propagation path. Turbulence is suggested as a major suppressant of charge-coupled effects in the lower ionosphere. If the observed eclipse behaviour is interpreted entirely in terms of atmospheric irregularities, severe but realistic constraints on mid-eclipse conditions are implied. At mid-eclipse a nearly impulsive perturbation presumably caused by a re-entering rocket was also noted. (author)

  8. A tiered observational system for anthropogenic methane emissions

    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 methane point sources associated with oil and gas production and distribution, feedlots, and urban landfills in California.

  9. SCIAMACHY formaldehyde observations: constraint for isoprene emissions over Europe?

    G. Dufour

    2008-11-01

    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, never studied before, 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. Observed columns present a bias less than 20% on average. The differences are discussed according to the errors on the model and the observations and the 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. Perspectives of using SCIAMACHY observations as constraint for biogenic isoprene emissions with an adapted averaging are approached: this new constraint should help to reduce their uncertainties more than 50% in region of intense emissions.

  10. Direct observation of phonon emission from hot electrons: spectral features in diamond secondary electron emission

    In this work we use high-resolution synchrotron-based photoelectron spectroscopy to investigate the low kinetic energy electron emission from two negative electron affinity surfaces of diamond, namely hydrogenated and lithiated diamond. For hydrogen-terminated diamond electron emission below the conduction band minimum (CBM) is clearly observed as a result of phonon emission subsequent to carrier thermalization at the CBM. In the case of lithiated diamond, we find the normal conduction band minimum emission peak is asymmetrically broadened to higher kinetic energies and argue the broadening is a result of ballistic emission from carriers thermalized to the CBM in the bulk well before the onset of band-bending. In both cases the spectra display intensity modulations that are the signature of optical phonon emission as the main mechanism for carrier relaxation. To our knowledge, these measurements represent the first direct observation of hot carrier energy loss via photoemission. (paper)

  11. Observations of gamma-ray emission in solar flares

    This paper reviews the observations of gamma-ray emission made from the OSO-7 satellite in connection with two solar flares in early August 1972. The details of the measurements and a preliminary interpretation of some of the observed features are given. (U.S.)

  12. Effect of a heated patch of auroral ionosphere on VLF-radio wave propagation

    The development of a unique high frequency heating facility near Tromso, Norway, has made the generation of movable controlled anomalies in the D-region become possible. The authors describe here some initial observations, made in Norway, of the effect of such a movable D-region anomaly on the VLF signals received from the 12.1-kHz Omega transmitter at Aldra. The observations confirm the validity of earlier theoretical predictions. (author)

  13. Upper Limits on O VI Emission from Voyager Observations

    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.

  14. Understanding NOx emission trends in China based on OMI observations

    Wang, Y.; Ga, D.; Smeltzer, C. D.; Yi, R.; Liu, Z.

    2012-12-01

    We analyze OMI observations of NO2 columns over China from 2005 to 2010. Simulations using a regional 3-D chemical transport model (REAM) are used to derive the top-down anthropogenic NOx emissions. The Kendall method is then applied to derive the emission trend. The emission trend is affected by the economic slowdown in 2009. After removing the effect of one year abnormal data, the overall emission trend is 4.35±1.42% per year, which is slower than the linear-regression trend of 5.8-10.8% per year reported for previous years. We find large regional, seasonal, and urban-rural variations in emission trend. The annual emission trends of Northeast China, Central China Plain, Yangtze River Delta and Pearl River Delta are 44.98±1.39%, 5.24±1.63%, 3.31±1.02% and -4.02±1.87%, respectively. The annual emission trends of four megacities, Beijing, Shanghai, Guangzhou and Shenzhen are 0.7±0.27%, -0.75±0.31%, -4.08±1.21% and -6.22±2.85%,, considerably lower than the regional averages. These results appear to suggest that a number of factors, including migration of high-emission industries, vehicle emission regulations, emission control measures of thermal power plants, increased hydro-power usage, have reduced or reversed the increasing trend of NOx emissions in more economically developed megacities and southern coastal regions.

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

    Smida, R.; Werner, F; Engel, R.; Arteaga-Velazquez, J. C.; Bekk, K.; Bertaina, M.; Bluemer, J.; Bozdog, H.(Institut fr Kernphysik, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany); Brancus, I. M.; Chiavassa, A.; Cossavella, F.; Di Pierro, F.; Doll, P.(Institut fr Kernphysik, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany); Fuchs, B.; Fuhrmann, D.

    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 o...

  16. Quantifying surface emissions of methanol using observations from the Tropospheric Emission Spectrometer

    Wells, K. C.; Millet, D. B.; Cady-Pereira, K. E.; Shephard, M. W.; Luo, M.; Henze, D. K.

    2012-12-01

    Methanol is the most abundant non-methane organic compound in the atmosphere, and a precursor of carbon monoxide, formaldehyde and ozone. Biogenic emissions from terrestrial plants constitute the largest fraction of the global methanol source, while biomass burning and anthropogenic emissions can make significant contributions on a regional scale. The recent availability of tropospheric methanol observations from space provides a powerful new constraint for understanding methanol emission processes on a global scale. Here we employ two years of global methanol observations from the Tropospheric Emission Spectrometer (TES) with the adjoint of the GEOS-Chem CTM to quantify the surface methanol flux, and interpret the results in terms of emission rates from different plant functional types. The satellite data imply a downward revision of the model emissions in portions of the tropics, and an upward revision in midlatitudes. The largest increases to the model emissions occur in areas that are dominated by shrubs and grasses, suggesting a refinement in methanol emission factors as a function of plant functional type. Applying the optimized emission rates in the model results in an improvement of the simulation as compared to an ensemble of airborne and ground-based observations.

  17. Solar flare impulsive phase emission observed with SDO/EVE

    Kennedy, Michael B.; Milligan, Ryan O.; Mathioudakis, Mihalis; Keenan, Francis P., E-mail: mkennedy29@qub.ac.uk [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2013-12-10

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T{sub e} = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

  18. Solar flare impulsive phase emission observed with SDO/EVE

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log Te = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

  19. Solar Flare Impulsive Phase Emission Observed with SDO/EVE

    Kennedy, Michael B.; Milligan, Ryan O.; Mathioudakis, Mihalis; Keenan, Francis P.

    2013-12-01

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log Te = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

  20. Reflection of VLF radio waves from distant mountain ranges

    Thomson, N. R.

    1985-04-01

    A computer cross-correlation technique is being used to determine the group delays and directions of arrival of man-made subionospheric VLF signals which have reached the receiver by paths other than the direct great circle path. The 200-baud MSK signals transmitted by NWC, NPM, and NLK allow time resolution to at least 5 ms and, with 15 min of integration, the sensitivity can be as low as about 100 nV/m in quiet conditions. Reflections from the Andes, the Rockies, and the mountains of southeast Asia have now been identified at Dunedin, New Zealand. Round-the-world and round-the-world-the-other-way signals have also been observed.

  1. Statistical analysis of VLF radio emissions triggered by power line harmonic radiation and observed by the low-altitude satellite DEMETER

    Parrot, M.; Němec, F.; Santolík, Ondřej

    2014-01-01

    Roč. 119, č. 7 (2014), s. 5744-5754. ISSN 2169-9380 R&D Projects: GA ČR GAP205/10/2279; GA MŠk LH12231 Institutional support: RVO:68378289 Keywords : man-made waves * ionosphere Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020139/abstract

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

    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.

  3. The effect of weather on VLF measurements

    Complete text of publication follows. The VLF experiment running at SANAE IV, Antarctica, has long been plagued by an unknown form of intermittent interference. Previously the prime suspect for this interference was the HF Radar, part of the SUPERDarn network, operated at SANAE IV. However, this instrument was not operational during the second half of 2008, and yet the interference was still prevalent. It is well known that the wind can set up mechanical oscillations in the antenna elements, causing periodic modulations in the loop area. We show evidence linking high wind speeds to this interference.

  4. Terrestrial FeO Continuum Emission Observed in Sky Spectra

    Slanger, Tom G.; Melchiorri, R.; Saran, D. V.

    2011-01-01

    The terrestrial continuum emission in the visible spectral region has often been studied by both astronomers and aeronomers, in order to clarify backgrounds and the nature of the emissions. New observations from the ESI spectrograph on the Keck II telescope, as well as from the OSIRIS/Odin spectrograph and orbiter, have established that a major component of the emission originates with the FeO molecule [Evans et al., 2010]. This quasi-continuum peaks at 5950 A and extends from 5000 A well into the infrared. The identity has been demonstrated by comparison with meteor trains and laboratory measurements [Jenniskens et al., 2000]. Early studies of the continuum show consistency with the FeO emission as presently observed [Gadsden and Marovich, 1973]. Analysis of spectra from Kitt Peak [Neugent and Massey, 2010] demonstrates the great similarity between FeO emission in a clean atmosphere and high pressure sodium lamp emission in a polluted atmosphere. This research was supported by NSF Aeronomy under Grant ATM-0637433 . Evans, W.F.J., et al., Geophys. Res. Lett. [in press, 2010] Gadsden, M. and E. Marovich, J. Atm. Terr. Phys., 35, 1601-1614 [1973] Jenniskens, P., et al., Earth, Moon and Planets, 82-83, 429-434 [2000] Neugent, K.F. and P. Massey, PASP [in press, 2010

  5. The influence of ionospheric absorption on mid-latitude whistler mode signal occurrence from VLF transmitters

    Clilverd, M. A.; Thomson, N. R.; Smith, A. J.

    1993-08-01

    Whistler mode signals from VLF transmitters received at Faraday (Antarctica) during 1986-1991 show an annual variation in the number of hours over which signals are observed, with a maximum in June and a minimum in December. The variation was larger at solar minimum than at maximum and can be understood in terms of changes in absorption of VLF signals in the D-region, where the high geographic latitude of Faraday plays an important role in producing low attenuation levels during the austral winter. In contrast, very little such variation was observed at Dunedin (New Zealand) in 1991. Nighttime whistler mode signals have start and end time trends that are consistent with the influence of F-region absorption. Increases in whistler mode occurrence appear to be associated with periods of high geomagnetic activity at solar maximum but not during solar minimum. A possible mechanism involving decreased F-region absorption is discussed.

  6. Absorption of very low frequency (VLF) waves in the whistler mode propagation in Jovian ionosphere

    Ahmad, M. M.; Ahmad, Altaf; Lalmani

    1992-08-01

    Making use of currently available theory of wave absorption, an attempt has been made to estimate the refractive indices and absorption coefficients for different wave frequencies during day and night times in the Jovian ionosphere. The results obtained have striking similarity with the corresponding results in the case of the Earth's ionosphere. It is concluded that VLF signals can be observed more easily during night times.

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

    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.

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

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

    2012-01-01

    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 propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy ...

  9. Isoprene and monoterpene emission rate variability: Observations with Eucalyptus and emission rate algorithm development

    Guenther, Alex B.; Monson, Russell K.; Fall, Ray

    1991-06-01

    Variability in the emission rates of isoprene and monoterpenes from individual leaves of Eucalyptus globulus was investigated with a laboratory gas exchange system and an environmental control leaf cuvette. For individual leaves, with constant environmental conditions, short-term (1 hour) fluctuations in isoprene emission rates were less than 3% while day-to-day fluctuations averaged 14%. Leaf-to-leaf variations were much larger (62%). Fluctuations with time and leaf-to-leaf variability in CO2 assimilation rates were of the same order as isoprene, while monoterpene variations were higher. Leaf age was identified as one of the factors contributing to leaf-to-leaf variability in CO2 assimilation and isoprene and monoterpene emission rates. Monoterpene emission rates were not influenced by light intensity or CO2 mixing ratio. The observed temperature dependence was the same for α-pinene and 1,8-cineole (an oxygenated monoterpene) and is similar to the temperature dependence of monoterpene emission rates reported by other investigators. Isoprene emissions were slightly dependent on humidity (1-3% increase in emission per 10% increase in relative humidity) and responded only to very low (600 ppm) CO2 mixing ratios. Isoprene emission was associated with the abaxial leaf side, which contains stomatal pores, while monoterpenes were emitted primarily from the adaxial side, which lacks stomatal pores. The temperature and light dependence of isoprene emission closely resembles relationships observed for electron transport in plant chloroplasts. For this reason, we have used a mechanistic electron transport model as the basis for an empirical isoprene emission rate model. The emission rate variation predicted by this model was within 10% of observed values for 62% of the 255 observations at light-saturated conditions and temperatures between 23° and 33°C. The entire data base includes over 600 observations at leaf temperatures ranging between 12° and 50°C and light intensities between 0 and 2000 μmol m-2 s-1. Nearly two thirds of the emission rates predicted for the entire data base were within a factor of 1.25, and 89% were within a factor of 2. The algorithms developed in this study provide a solid physiological basis for future efforts to model the biogenic flux of isoprene and monoterpenes into the atmosphere.

  10. Iras observations of Hα selected emission-line galaxies

    Rego Fernández, Manuel; Cordero Gracia, M.; Zamorano Calvo, Jaime; Gallego Maestro, Jesús

    1993-01-01

    We present the results of IRAS observations of the UCM (Universidad Complutense de Madrid) sample of emission-line galaxies, which have been selected from wide-dispersion H_α objective-prism plates. These data are intended to provide a convenient summary of the relevant far-infrared (FIR) properties of these galaxies. Color-color diagrams, as interpreted by theoretical models, suggest that emission from UCM galaxies is mainly due to dust heated directly by photons emitted in active star-formi...

  11. Assessing methane emissions from global space-borne observations.

    Frankenberg, C; Meirink, J F; van Weele, M; Platt, U; Wagner, T

    2005-05-13

    In the past two centuries, atmospheric methane has more than doubled and now constitutes 20% of the anthropogenic climate forcing by greenhouse gases. Yet its sources are not well quantified, introducing uncertainties in its global budget. We retrieved the global methane distribution by using spaceborne near-infrared absorption spectroscopy. In addition to the expected latitudinal gradient, we detected large-scale patterns of anthropogenic and natural methane emissions. Furthermore, we observed unexpectedly high methane concentrations over tropical rainforests, revealing that emission inventories considerably underestimated methane sources in these regions during the time period of investigation (August through November 2003). PMID:15774724

  12. Solar Flare Impulsive Phase Emission Observed with SDO/EVE

    Kennedy, Michael B; Mathioudakis, Mihalis; Keenan, Francis P

    2013-01-01

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T = 5.8 - 7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3 - 4 MK, and we use spatially-unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied the DEMs exhibited a two component distribution during the impulsive phase, a low temperature component with peak temperature of 1 - 2 MK, and a broad high temperature one from 7 - 30 MK. A bimodal high temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emissi...

  13. Observations of H? emission profiles in Aditya tokamak

    Emissions from the hydrogen Balmer alpha (? = 656.28 nm) has been recorded for a large number of plasma discharges in the Aditya tokamak using a 1m Czerny-Turner spectrometer equipped with an 1800 grooves/mm reflection grating. Eight simultaneous vertically collimated line-of-sights, using individual lens fiber combination from a top port of the tokamak view a poloidal cross-section of the plasma. The line-of-sights can be moved along the major radius to obtain emissions from different major-radial positions on a shottoshot basis. Abel-like matrix inversion has been performed to obtain radial profile of volume emissivities from these chord-integrated intensities. Considerable H? emission is observed in the bulk plasma indicating a considerable neutral penetration. Further, a second peak in the H? radial profile has been observed at ?(r/a) ? +/- 0.3 -- +/- 0.5 in majority of discharges irrespective of the plasma column position. This observation suggests a considerable accumulation of neutrals in the region of ?(r/a) ? +/- 0.3 -- +/- 0.5. CV to CIII line ratio variations at the same location also suggest a substantial presence of neutrals explained by the charge-exchange, involving collisions between H-like carbon ions and neutral hydrogen atoms. (author)

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

    Avaria, G.; Ruiz, M.; Guzmn, 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 H? 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.

  15. Biogenic nonmethane hydrocarbon emissions estimated from tethered balloon observations

    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.

  16. Deep 1.4-GHz observations of diffuse polarized emission

    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...

  17. GALEX Observations of Diffuse Ultraviolet Emission from Draco

    Sujatha, N. V.; Murthy, Jayant; Suresh, Rahul; Conn Henry, Richard; Bianchi, Luciana

    2010-11-01

    We have studied small-scale (2') spatial variation of the diffuse ultraviolet (UV) radiation using a set of 11 Galaxy Evolution Explorer deep observations in the constellation of Draco. We find a good correlation between the observed UV background and the infrared (IR) 100 μm flux, indicating that the dominant contributor of the diffuse background in the field is scattered starlight from the interstellar dust grains. We also find strong evidence of additional emission in the far-ultraviolet (FUV) band which is absent in the near-ultraviolet (NUV) band. This is most likely due to Lyman band emission from molecular hydrogen in a ridge of dust running through the field and to line emissions from species such as C IV (1550 Å) and Si II (1533 Å) in the rest of the field. A strong correlation exists between the FUV/NUV ratio and the FUV intensity in the excess emission regions in the FUV band irrespective of the optical depth of the region. The optical depth increases more rapidly in the UV than the IR and we find that the UV/IR ratio drops off exponentially with increasing IR due to saturation effects in the UV. Using the positional details of Spitzer extragalactic objects, we find that the contribution of extragalactic light in the diffuse NUV background is 49 ± 13 photons cm-2 sr-1 s-1 Å-1 and is 30 ± 10 photons cm-2 sr-1 s-1 Å-1 in the FUV band.

  18. GALEX OBSERVATIONS OF DIFFUSE ULTRAVIOLET EMISSION FROM DRACO

    We have studied small-scale (2') spatial variation of the diffuse ultraviolet (UV) radiation using a set of 11 Galaxy Evolution Explorer deep observations in the constellation of Draco. We find a good correlation between the observed UV background and the infrared (IR) 100 μm flux, indicating that the dominant contributor of the diffuse background in the field is scattered starlight from the interstellar dust grains. We also find strong evidence of additional emission in the far-ultraviolet (FUV) band which is absent in the near-ultraviolet (NUV) band. This is most likely due to Lyman band emission from molecular hydrogen in a ridge of dust running through the field and to line emissions from species such as C IV (1550 A) and Si II (1533 A) in the rest of the field. A strong correlation exists between the FUV/NUV ratio and the FUV intensity in the excess emission regions in the FUV band irrespective of the optical depth of the region. The optical depth increases more rapidly in the UV than the IR and we find that the UV/IR ratio drops off exponentially with increasing IR due to saturation effects in the UV. Using the positional details of Spitzer extragalactic objects, we find that the contribution of extragalactic light in the diffuse NUV background is 49 ± 13 photons cm-2 sr-1 s-1 A-1 and is 30 ± 10 photons cm-2 sr-1 s-1 A-1 in the FUV band.

  19. Polar cap optical emissions observed from the ISIS2 satellite

    The application of polar orbiting scientific satellites to the study of polar cap phenomena has led to significant advances in our understanding of polar cap processes. The ISIS2 satellite, which is in a circular orbit 1400 km above the earth's surface, has provided monochromatic optical images of the high latitude region since April 1971. The 5577 Angstroem emission from atomic oxygen and the 3914 Angstroem emission from the First Negative bands of N2+ have been monitored by the auroral scanning photometer, and the 6300 Angstroem emission from atomic oxygen has been obtained by means of the red line photometer. In order to view the entire polar cap during a single pass of the satellite, several restrictive conditions have to be met which limit the quantity of useful data. Nevertheless, there have been a sufficient number of satisfactory observations to allow the characteristic features of high latitude emission to be identified. In the sections that follow, a summary of results of observations of dayside aurora and polar cap arcs is given. (orig./WL)

  20. XMM-Newton Observations of Solar Wind Charge Exchange Emission

    Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

    2004-01-01

    We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

  1. TIMS observations of surface emissivity in HAPEX-Sahel

    Schmugge, Thomas; Hook, Simon; Kahle, Anne

    1995-01-01

    The Thermal Infrared Multispectral Scanner (TIMS) was flown on the NASA C-130 aircraft for a series of 12 flights during HAPEX-Sahel at altitudes ranging from 0.25 to 6 km (0.6 to 15 m resolution). TIMS provides coverage of the 8 to 12 micrometer thermal infrared band in 6 contiguous channels. Thus it is possible to observe the spectral behavior of the surface emissivity over this wavelength interval.

  2. EUV emission lines and diagnostics observed with Hinode/EIS

    Young, P R; Mason, H E; Dere, K P; Landi, E; Landini, M; Doschek, G A; Brown, C M; Culhane, J L; Harra, L K; Watanabe, T; Hara, H

    2007-01-01

    Quiet Sun and active region spectra from the Hinode/EIS instrument are presented, and the strongest lines from different temperature regions discussed. A list of emission lines recommended to be included in EIS observation studies is presented based on analysis of blending and diagnostic potential using the CHIANTI atomic database. In addition we identify the most useful density diagnostics from the ions covered by EIS.

  3. Coherent whistler emissions in the magnetosphere – Cluster observations

    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.

  4. Observation of microwave emission from extensive air showers with CROME

    Wilczyński H.

    2013-06-01

    Full Text Available We report on the measurement of microwave radio signals from air showers with the CROME (Cosmic Ray Observation via Microwave Emission experiment. CROME is located in the center of the KASCADE-Grande air shower array. The radio signals of the CROME antennas are stored for each high-energy trigger from the KASCADE-Grande array and matched offine with the KASCADE-Grande data. After almost one year of data taking microwave signals have been observed for more than ten air showers.

  5. Observation of microwave emission from extensive air showers with CROME

    Wilczy?ski H.; Werner F.; Weber M; Unger M.; Stasielak J.; Schieler H.; Salamida F.; Riegel M; Roth M; Rautenberg J.; Pekala J.; Neunteufel P.; Mathys S.; Ludwig M.; Krmer O.

    2013-01-01

    We report on the measurement of microwave radio signals from air showers with the CROME (Cosmic Ray Observation via Microwave Emission) experiment. CROME is located in the center of the KASCADE-Grande air shower array. The radio signals of the CROME antennas are stored for each high-energy trigger from the KASCADE-Grande array and matched o?ine with the KASCADE-Grande data. After almost one year of data taking microwave signals have been observed for more than ten air showers.

  6. Observation of microwave emission from extensive air showers with CROME

    mda, R.; Baur, S.; Bertaina, M.; Blmer, J.; Chiavassa, A.; Engel, R.; Haungs, A.; Huege, T.; Kampert, K.-H.; Klages, H.; Kleifges, M.; Krmer, O.; Ludwig, M.; Mathys, S.; Neunteufel, P.; Pekala, J.; Rautenberg, J.; Riegel, M.; Roth, M.; Salamida, F.; Schieler, H.; Stasielak, J.; Unger, M.; Weber, M.; Werner, F.; Wilczy?ski, H.; Wochele, J.

    2013-06-01

    We report on the measurement of microwave radio signals from air showers with the CROME (Cosmic Ray Observation via Microwave Emission) experiment. CROME is located in the center of the KASCADE-Grande air shower array. The radio signals of the CROME antennas are stored for each high-energy trigger from the KASCADE-Grande array and matched offine with the KASCADE-Grande data. After almost one year of data taking microwave signals have been observed for more than ten air showers.

  7. XMM-Newton Observation of Solar Wind Charge Exchange Emission

    Snowden, S L; Kuntz, K D

    2004-01-01

    We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by probable C VI lines at 0.37 keV and 0.46 keV, an O VII line at 0.56 keV, O VIII lines at 0.65 keV and ~0.8 keV, Ne IX lines at ~0.92 keV, and Mg XI lines at ~1.35 keV. This spectrum is consistent with that expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy (E<1.5 keV) spectral enhancement in one of a series of four observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by ACE, Wind, and SoHO spacecraft. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has a significantly enhanced O^{+7}/O^{+6} ratio. Besides being of interest in its own right for studies of the solar system, this emission can hav...

  8. Observation of Field-Emission Dependence on Stored Energy.

    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

    2015-12-31

    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. PMID:26764996

  9. Energetic electron precipitation and VLF phase disturbances at middle latitudes following the magnetic storm of December 6, 1971

    Enhanced fluxes of electrons precipitating over middle latitudes (L approx. 3--4) were detected by the polar-orbiting satellite 1971-089A following a period of magnetic activity starting on December 16, 1971. The electron fluxes measured in 256 differential channels between 130 and 2800 keV have been coordinated with phase observations of VLF radio waves propagating in the earth-ionosphere waveguide. The VLF paths in question, NLK (near Seattle, Washington) and GBR (at Rugby, England) to APL (near Washington, D. C.), cover approx. =1200 in longitude and range from L approx. 2.5 to L approx. 4.0 in invariant latitude. These paths showed marked daytime and nighttime phase advances from 1650 UT on December 17 (in excess of 10 μs during maximum disturbance). The phase values did not return to prestorm levels before December 22--23. The unusual presence of these daytime VLF disturbances is offered as evidence for the widespread precipitation at low L shell vales of nearly relativistic electrons (E/sub e/> approx.200 keV) which would be required to penetrate below approx.70-km altitude to affect the daytime VLF transmissions. Wave guide mode calculations using D region electron density profiles deduced from the satellite particle data predict phase advances which agree reasonably well with the observed values. It is concluded that the observed long-lived VLF phase disturbances can be explained by excess D region ionization caused by energetic electrons precipitating from the earth's radiation belt following their injection deep into the magnetosphere during the magnetic storm

  10. Correlations between SAMPEX detected relativistic electron precipitation and perturbations in ground based VLF signals during periods of extreme geomagnetic disturbance

    Complete text of publication follows. Bursts of relativistic (>1 MeV) electron precipitation from Earth's radiation belts are detected by the Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX), a low Earth orbiting satellite. During periods of enhanced geomagnetic activity, perturbations can be found in very low frequency (VLF) signals received by the Antarctic-Arctic Radiation-belt (Dynamic) Deposition - VLF Atmospheric Research Konsortium (AARDDVARK). One such class of these VLF perturbations have been termed FAST events, which are characterised by their large perturbation amplitude, both positive and negative, their temporal brevity (t?6. These FAST events are observed across multiple VLF channels and are thought to be caused by a 'rainstorm' of spatially small (tens of kilometres or less) bursts of precipitation striking the atmosphere. It is seen that periods of FAST event activity coincide with periods of SAMPEX detected relativistic electron precipitation, which are termed microbursts. SAMPEX is usually measuring both the drift and bounce-loss cones, while the AARDDVARK measurements are of local precipitation from the bounce-loss cone. A statistical analysis of the nature of the correlation between FAST events and SAMPEX precipitation during times of enhanced geomagnetic disturbance is currently being undertaken. Emphasis is being placed on periods during which SAMPEX was viewing the bounce-loss cone but not the drift-loss cone.

  11. Doppler-Shifted Flare Emissions Observed by SDO/EVE

    Chamberlin, Phillip C.

    2012-01-01

    The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) has been obtaining unprecedented observations of solar variation on times scales of seconds during flares and over the rising phase of Solar Cycle 24 since its start of normal operations in May 2010. Unexpectedly, as first pointed out in Hudson et. al., Ap.j. (2011), even with EVE's spectral resolution of 0.1 nm and 'irradiance' measurements, EVE has the ability to very accurately determine Doppler shifts in all emissions during solar flares and coronal mass ejections (CMEs). The technique for deriving these absolute velocities is not straightforward, as the optical and instrumental effects must first be eliminated in order to separate the absolute plasma velocities from the instrument effects. This talk will discuss these efforts to eliminate the instrumental component, as well as show some of the first results of absolute velocities of multiple emissions at a wide range of temperatures during solar flares.

  12. Airborne observations of the Orion molecular hydrogen emission spectrum

    We have observed the Orion near-IR H2 emission spectrum from an altitude of 12.5 km in order to measure line intensities free from interference by terrestrial H2O. Three new transitions [H n = 6→4 and H2 v = 1→0 O(2) and Q(7)] have been detected. Analysis of the data indicate that earlier estimates of source extinction, temperature, and luminosity are all too high. We find E/sub 2.1-2.4/ μm = 0.59 +- 0.06, T(v = 1) = 1540 +- 100 K and L2(vib) = 200--400 L. There is strong evidence for an anomalous 3.5:1 ortho/para H2 abundance ratio for the excited H2. Line luminosities and line-of-sight position constraints support a mass outflow model for the emission region. Subject headings: infrared: spectra: interstellar: molecules: nebulae: Orion Nebula

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

    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.

  14. Observations of microwave continuum emission from air shower plasmas

    Gorham, P. W.; Lehtinen, N. G.; 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.; Ruckman, L.; Saltzberg, D.; Stokes, B. T.; Walz, D.

    2008-08-01

    We investigate a possible new technique for microwave detection of cosmic-ray 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 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 the Stanford Linear Accelerator Center in the summer of 2004 confirmed the major features of the previous Argonne Wakefield Accelerator observations with better precision. Prompted by these results we built a prototype detector using satellite television technology and have made measurements suggestive of the detection of cosmic-ray extensive air showers. The method, if confirmed by experiments now in progress, could provide a high-duty cycle complement to current nitrogen fluorescence observations.

  15. VLF wave activity during a magnetic storm: A case study of the role of power line radiation

    Ground-based data on magnetospheric wave activity in the American longitude sector are studied for a 13-day period that includes a major magnetic storm and some isolated substorm activity. The wave intensity in the 0.5- to 10- kHz range shows clear association with geomagnetic activity. A detailed examination of VLF spectra shows that the strongest waves emerging from the middle magnetosphere during the storm recovery period and during isolated substorm activity are often emissions stimulated by radiation from the electrical power distribution system. Several different types of power line radiation effects are illustrated by using broadband spectral data from stations in Antarctica and North America. It appears that man-made VLF noise has a strong influence on the energetic particle population in the magnetosphere

  16. Airborne observations of aircraft aerosol emissions I: Total nonvolatile particle emission indices

    Anderson, B. E.; Cofer, W. R.; Bagwell, D. R.; Barrick, J. W.; Hudgins, C. H.; Brunke, K. E.

    We report airborne measurements of total and nonvolatile (at T aerosol emission indices (EI's) generated by a variety of jet aircraft. The data were obtained using an instrumented jet aircraft, flown repeatedly through aircraft wakes. These aircraft were observed to produce 0.5hyphen;10 × 1015 nonvolatile particles kg-1 of fuel burned. Their numbers varied as a function of aircraft type, age, and engine operating parameters, but less with atmospheric conditions. Large numbers of volatile aerosols were measured in all cases. Volatile EI's ranged from 0.1 to 40×1016 kg-1 fuel burned. The observed soot emissions are estimated to have only a minor impact on atmospheric aerosol loading, but a future fleet producing such high concentrations of implied sulfate aerosols could perturb cloud formation and heterogeneous chemical processes in the upper troposphere/lower stratosphere.

  17. VLF-HISS from electrons in the earth's magnetosphere

    Maeda, K.

    1973-01-01

    Intensities of auroral and magnetospheric hiss generated by the Cherenkov radiation process of electrons in the lower magnetosphere were calculated with respect to a realistic model of the earth's magnetosphere. In this calculation, the magnetic field was expressed by the Mead-Fairfield Model, and a static model of the iono-magnetospheric plasma distribution was constructed by accumulated data obtained by recent satellite observations. The energy range of hiss producing electrons and the frequency range of produced VLF in the computation are 100 eV to 200 keV, and 2 to 200 kHz, respectively. The maximum hiss intensity produced by soft electrons is more than one order higher than that of hard electron produced hiss. Higher rate of hiss occurrence in the daytime side, particularly in the soft electron precipitation zone in the morning sector, and less association of auroral hiss in nighttime sectors must be, therefore, due to the local time dependence of the energy spectra of precipitating electrons rather than the difference in the geomagnetic field and in the geoplasma distributions.

  18. Electron precipitation in the vicinity of a VLF transmitter

    Using high-resolution pitch angle measurements made by a magnetic focusing electron spectrometer on the S3-3 satellite, angular distributions of 235-keV electrons precipitated in the slot region of the magnetosphere by a ground-based VLF transmitter are compared with the pitch angle distributions that would be produced by various patterns of longitudinal interaction regions.The observed electrons are in the drift loss cone, necessitating the use of a trace-back-to-longitude-of-origin technique coupled with a two-dimensional convolution program describing the response of the electron spectrometer. The data are well fit both with theoretical calculations of ionospheric field intensity patterns above a transmitter and with a similar pattern of received field intensities measured along a traverse in the conjugate region. The agreement between the data dna field patterns implies a linear or quasi-linear wave-particle interaction. The energy-frequency relationship between the electrons and the waves implies an interaction region low on the magnetic field line rather than near the equator, as has been determined for similar precipitations in the inner zone

  19. Precipitation of inner zone electrons by whistler mode waves from the VLF transmitters UMS and NWC

    The precipitation of energetic electrons which are commonly observed in the drift loss cone east of 600 east longitude between Lapprox.1.6 and Lapprox.1.8 can be accounted for by a Doppler-shifted cyclotron resonance between the electrons and nonducted whistler mode waves from high-power, ground-based VLF transmitters. A ray-tracing analysis using a diffusive-equilibrium model shows that 17.1-kHz waves starting with vertical wave normals between 230 and 310 magnetic latitude cross the magnetic equator between Lapprox.1.6 and f Lapprox.1.8 with wave normals of approximately 630. A relativistic cyclotron-resonance analysis for the same model plasmasphere using the ray-tracing results gives an energy versus L shell dependence for the precipitated ray electron which is in excellent agreement with the observed dependence. The primary VLF transmitter is most probably the UMS transmitter located near Gorki, USSR. It transmits on 17.1 kHz. VLF records covering this frequency band were available for only three of the time periods when electrons were observed. In two cases UMS was transmitting at the time required to account for the observations. In the third case a higher frequency is required to fit the data. At the time, the NWC transmitter at North West Cape, Australia was operating at 22.3 kHz. These data are consistent with a model in which weak pitch angle scattering by whistler mode waves from NWC does not completely fill the drift loss cone at the longitude of NWC

  20. Surface slope characteristics from Thermal Emission Spectrometer emission phase function observations

    Edwards, C. S.; Bandfield, J. L.; Christensen, P. R.

    2006-12-01

    It is possible to obtain surface roughness characteristics, by measuring a single surface from multiple emission angles and azimuths in the thermal infrared. Surfaces will have different temperatures depending on their orientation relative to the sun. A different proportion of sunlit versus shaded surfaces will be in the field of view based on the viewing orientation, resulting in apparent temperature differences. This difference in temperature can be utilized to calculate the slope characteristics for the observed area. This technique can be useful for determining surface slope characteristics not resolvable by orbital imagery. There are two main components to this model, a surface DEM, in this case a synthetic, two dimensional sine wave surface, and a thermal model (provided by H. Kieffer). Using albedo, solar longitude, slope, azimuth, along with several other parameters, the temperature for each cell of the DEM is calculated using the thermal model. A temperature is then predicted using the same observation geometries as the Thermal Emission Spectrometer (TES) observations. A temperature difference is calculated for the two complementary viewing azimuths and emission angles from the DEM. These values are then compared to the observed temperature difference to determine the surface slope. This method has been applied to TES Emission Phase Function (EPF) observations for both the spectrometer and bolometer data, with a footprint size of 10s of kilometers. These specialized types of TES observations measure nearly the same surface from several angles. Accurate surface kinetic temperatures are obtained after the application of an atmospheric correction for the TES bolometer and/or spectrometer. Initial results include an application to the northern circumpolar dunes. An average maximum slope of ~33 degrees has been obtained, which makes physical sense since this is near the angle of repose for sand sized particles. There is some scatter in the data from separate observations, which may be due to the large footprint size. This technique can be better understood and characterized by correlation with high resolution imagery. Several different surface maps will also be tested in addition to the two dimensional sine wave surface. Finally, by modeling the thermal effects on different particle sizes and land forms, we can further interpret the scale of these slopes.

  1. On the numerical modelling of VLF chorus dynamical spectra

    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.

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

    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 the region and employ the LWPC code to find the VLF signal amplitude. To tackle the uncertainty in the values of the recombination coefficients we explore a range of values in the chemical evolution model. We achieve two goals by this exercise: First, we have been able to reproduce the trends, if not the exact signal variation, of the VLF signal modulations during a solar eclipse at two different receiving stations with sufficient accuracy purely from theoretical modeling, and second our knowledge of some of the D-region ion-chemistry parameters is now improved.

  3. Proton precipitation by a whistler-mode wave from a VLF transmitter

    Protons with 50 keV< E<530 keV were detected by sensors aboard satellite 1972-76B at an altitude of 700 km in the region conjugate to the transportable very-low-frequency (TVLF) transmitter which was being operated near Anchorage, Alaska Lapprox.4). Temporal maxima in the proton count rates can be identified on a one-to-one basis with short pulsed transmissions by the VLF transmitter. The observed time delay between the center of a transmitted pulse and the detection of the next maximum in the proton count rate at the sensor agrees well with the delay predicted from a simple plasmaspheric model. (auth)

  4. Source location of chorus emissions observed by Cluster

    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

  5. Airborne observations of the Orion molecular hydrogen emission spectrum

    Davis, D. S.; Larson, H. P.; Smith, H. A.

    1982-01-01

    The Orion near-infrared H2 emission spectrum was observed from an altitude of 12.5 km in order to measure line intensities free from interference by terrestrial H2O. For the peak source, the observations indicate that the differential extinction between 4126 and 4712 per cm is 0.59 + or -0.06 mag, and the relative line intensities are consistent with those expected from a homogeneous source in approximate LTE at 1540 + or -100 K. An anomalous ortho/para H2 abundance ratio of 3.5(+ or - 0.2):1 is found, and the estimated total luminosity in vibrationally excited H2 lines is 300 + or - 100 solar luminosities. Rough molecular abundance limits, based on the missing H2 Q(6) line and the good agreement between other line intensities and the LTE model, place the H2 region no deeper within OMC-1 than the IR cluster and no shallower than 50 percent of the depth to the cluster.

  6. Emission Patterns of Solar Type III Radio Bursts: Stereoscopic Observations

    Thejappa, G.; MacDowall, R.; Bergamo, M.

    2012-01-01

    Simultaneous observations of solar type III radio bursts obtained by the STEREO A, B, and WIND spacecraft at low frequencies from different vantage points in the ecliptic plane are used to determine their directivity. The heliolongitudes of the sources of these bursts, estimated at different frequencies by assuming that they are located on the Parker spiral magnetic field lines emerging from the associated active regions into the spherically symmetric solar atmosphere, and the heliolongitudes of the spacecraft are used to estimate the viewing angle, which is the angle between the direction of the magnetic field at the source and the line connecting the source to the spacecraft. The normalized peak intensities at each spacecraft Rj = Ij /[Sigma]Ij (the subscript j corresponds to the spacecraft STEREO A, B, and WIND), which are defined as the directivity factors are determined using the time profiles of the type III bursts. It is shown that the distribution of the viewing angles divides the type III bursts into: (1) bursts emitting into a very narrow cone centered around the tangent to the magnetic field with angular width of approximately 2 deg and (2) bursts emitting into a wider cone with angular width spanning from [approx] -100 deg to approximately 100 deg. The plots of the directivity factors versus the viewing angles of the sources from all three spacecraft indicate that the type III emissions are very intense along the tangent to the spiral magnetic field lines at the source, and steadily fall as the viewing angles increase to higher values. The comparison of these emission patterns with the computed distributions of the ray trajectories indicate that the intense bursts visible in a narrow range of angles around the magnetic field directions probably are emitted in the fundamental mode, whereas the relatively weaker bursts visible to a wide range of angles are probably emitted in the harmonic mode.

  7. Aperture synthesis observations of solar and stellar radio emission

    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 ? ? 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

  8. Airborne Observations of Aerosol Emissions from F-16 Aircraft

    Anderson, B. E.; Cofer, W. R.; McDougal, D. S.

    1999-01-01

    We presented results from the SASS Near-Field Interactions Flight (SNIF-III) Experiment which was conducted during May and June 1997 in collaboration with the Vermont and New Jersey Air National Guard Units. The project objectives were to quantify the fraction of fuel sulfur converted to S(VI) species by jet engines and to gain a better understanding of particle formation and growth processes within aircraft wakes. Size and volatility segregated aerosol measurements along with sulfur species measurements were recorded in the exhaust of F-16 aircraft equipped with F-100 engines burning fuels with a range of fuel S concentrations at different altitudes and engine power settings. A total of 10 missions were flown in which F-16 exhaust plumes were sampled by an instrumented T-39 Sabreliner aircraft. On six of the flights, measurements were obtained behind the same two aircraft, one burning standard JP-8 fuel and the other either approximately 28 ppm or 1100 ppm S fuel or an equal mixture of the two (approximately 560 ppm S). A pair of flights was conducted for each fuel mixture, one at 30,000 ft altitude and the other starting at 35,000 ft and climbing to higher altitudes if contrail conditions were not encountered at the initial flight level. In each flight, the F-16s were operated at two power settings, approx. 80% and full military power. Exhaust emissions were sampled behind both aircraft at each flight level, power setting, and fuel S concentration at an initial aircraft separation of 30 m, gradually widening to about 3 km. Analyses of the aerosol data in the cases where fuel S was varied suggest results were consistent with observations from project SUCCESS, i.e., a significant fraction of the fuel S was oxidized to form S(VI) species and volatile particle emission indices (EIs) in comparably aged plumes exhibited a nonlinear dependence upon the fuel S concentration. For the high sulfur fuel, volatile particle EIs in 10-second-old-plumes were 2 to 3 x 10 (exp 17) / kg of fuel burned and exhibited no obvious trend with engine power setting or flight altitude. In contrast, about 8-fold fewer particles were observed in similarly aged plumes from the same aircraft burning fuel with 560 ppm S content and EIs of 1 x 10(exp 15)/ kg of fuel burned were observed in the 28 ppm S fuel case. Moreover, data recorded as a function of plume age indicates that formation and growth of the volatile particles proceeds more slowly as the fuel S level is reduced. For example, ultrafine particle concentrations appear to stabilize within 5 seconds after emission in the 1100 ppm S cases but are still increasing in 20-second old plumes produced from burning the 560 ppm S fuel.

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

    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 four seaweed species which correlated with high levels of halocarbons (CH3I, CH2Br2, CH2BrI and CH2BrCl up to 100ppt, CHBr3 up to 600ppt). These results, the similarities and differences in the emission behavior and implications for atmospheric chemistry are discussed.

  10. Simultaneous observation of NMR spin noise and maser spontaneous emission

    Jurkiewicz, Antoni

    2015-03-01

    Spin noise emission, absorbed noise, and spontaneous maser emission are distinguished in the hexanol molecule by changing spin noise dynamics along with coupling the spin system to a probe circuit. Inverted magnetization leads to spontaneous maser emission of methyl and methylene resonances permitting separation from broad overlapped peaks. The maser emission resonance shows random intensity the scattering range of which depends on the length of the gradient following magnetization inversion. Combination of thermal noise and spin noise can be altered by varying magnetization orientation. This results in radiation damping which alters how fluctuation signals are coupled with the probe circuit.

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

    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.

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

    Cohen, M. B.; Lehtinen, N. G.; Inan, U. S.

    2012-12-01

    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 propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy into electrostatic modes may be responsible for the error. We utilize a newly available extensive record of VLF transmitter energy reaching the magnetosphere, taken from the DEMETER satellite, and perform a direct comparison with a sophisticated full wave model of trans-ionospheric propagation. Although the model does not include the effect of ionospheric irregularities, it correctly predicts the average total power injected into the magnetosphere within several dB. The results, particularly at nighttime, appear to be robust against the variability of the ionospheric electron density. We conclude that the global effect of irregularity scattering on whistler mode conversion to quasi-electrostatic may be no larger than 6 dB.

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

    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...

  14. Detection of Exomoons Through Observation of Radio Emissions

    Noyola, Joaquin P.; Satyal, Suman; Musielak, Zdzislaw E.

    2013-01-01

    In the Jupiter-Io system, the moon's motion produces currents along the field lines that connect it to Jupiter's polar regions. The currents generate, and modulate radio emissions along their paths via the electron-cyclotron maser instability. Based on this process, we suggest that such modulation of planetary radio emissions may reveal the presence of exomoons around giant planets in exoplanetary systems. A model explaining the modulation mechanism in the Jupiter-Io system is extrapolated, a...

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

    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.

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

    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 for automobile air-conditioning had been retained, ADEME initiated a campaign for evaluating exhaust emissions and consumption by two-wheel vehicles in laboratory tests. This campaign makes it possible to obtain a 'photo' of present two-wheel emissions and consumption and to better gauge the stakes associated to the evolution of this category of vehicle. The goal of this present document is to establish the state of the art of what actually exists concerning the fleet and the levels of pollutant emissions through the findings of this testing campaign. (author)

  17. Very exceptional cases of VLF/LF ionospheric perturbations for deep oceanic earthquakes offshore the Japan island

    Yamaguchi, Hiroki; Hayakawa, Masashi

    2015-12-01

    It is so far believed that ionospheric perturbations as detected by subionospheric VLF/LF (very low frequency/low frequency) propagation, are generated above and around the earthquake (EQ) epicenter. This paper presents very rare cases, which are in complete contrast to the above fact. We have found that in extremely rare cases when EQs happened (i) in the Pacific Ocean or (ii) offshore the Soya cape (Hokkaido) both with very large depths (300-400 km), corresponding ionospheric perturbations take place far away from the EQ epicenter and above the regions with considerable seismic intensity at the time of each EQ. Two EQs happened in the Torishima area of Izu islands (magnitude ∼7 and depth ∼400 km), and corresponding seismic intensity was observed in the Tokyo and Ibaraki districts. Our VLF data have indicated that the ionospheric perturbation takes place over such regions with high seismic intensity. Another group is two EQs (magnitude ∼5) offshore the Soya cape of Hokkaido, and the spatial distribution of seismic intensity at the time of each EQ is just around Aomori prefecture. VLF data have indicated the ionospheric perturbations taken place over the same Aomori area, which is in complete coincidence with the spatial distribution of seismic intensity. As a conclusion, these exceptional examples are, in principle, very similar to the concept of 'selectivity' (or sensitive zone) of geoelectric measurement by the Greek group, and we try to interpret these cases in the context of lithosphere-atmosphere-ionosphere coupling.

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

    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.

  19. Unexpected very low frequency (VLF) radio events recorded by the ionospheric satellite DEMETER

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

    2015-01-01

    Roč. 36, č. 3 (2015), s. 483-511. ISSN 0169-3298 R&D Projects: GA ČR(CZ) GA14-31899S; GA MŠk LH12231 Grant ostatní: Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100421206; Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100421206 Institutional support: RVO:68378289 Keywords : ionosphere * natural and man-made VLF radio emissions * anomalies Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.447, year: 2014 http://link.springer.com/article/10.1007%2Fs10712-015-9315-5

  20. A BATSE investigation of radiation belt electrons precipitated by VLF waves

    Datlowe, Dayton W.

    1995-01-01

    The Compton Observatory commonly encounters fluxes of energetic electrons which have been scattered from the inner radiation belt to the path of the satellite by resonant interactions with VLF waves from powerful man-made transmitters. The present investigation was motivated by the fact that in the Fall of 1993, the Gamma Ray Observatory was boosted from a 650 km altitude circular orbit to a 750 km altitude circular orbit. This was an opportunity, for the first time, to make observations at two different altitudes using the same instrument. We have examined DISCLA data from the Burst & Transient Source Experiment (BATSE) experiment from 1 Sep. 1993 to 29 Jan. 1994. During the period of study we identified 48 instances of the satellite encountering a cloud of energetic electrons which had been scattered by VLF transmitters. We find that boosting the altitude of the circular orbit from 650 km to 750 km increased the intensity of cyclotron resonance scattered electrons by a factor of two. To search for long term changes in the cyclotron resonance precipitation, we have compared the approx. 750 km altitude data from 106 days at the end of 1993 with data at the same altitudes and time of year in 1991. The cyclotron resonance events in 1991 were three times more frequent and 25% of those cases were more intense than any seen in the 1993 data. We attribute this difference to increased level of geomagnetic activity in 1991 near the Solar Maximum.

  1. VLF character and its geological interpretation in the middle region of Shule river fault zone

    The middle region of Shule River Fault Zone is an area for selecting the site of HLW repository, it is a blind basement fault zone. The VLF response is very good because of its large scale and being filled with the structural breccia of low resistivity. The VLF character for the fault zone was discussed. It is pointed that the effectiveness and limitation of searching blind fault with VLF method

  2. Detection of exomoons through observation of radio emissions

    Noyola, J. P.; Satyal, S.; Musielak, Z. E., E-mail: joaquin.noyola@mavs.uta.edu, E-mail: ssatyal@uta.edu, E-mail: zmusielak@uta.edu [The Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

    2014-08-10

    In the Jupiter-Io system, the moon's motion produces currents along the field lines that connect it to Jupiter's polar regions. The currents generate and modulate radio emissions along their paths via the electron-cyclotron maser instability. Based on this process, we suggest that such modulation of planetary radio emissions may reveal the presence of exomoons around giant planets in exoplanetary systems. A model explaining the modulation mechanism in the Jupiter-Io system is extrapolated and used to define criteria for exomoon detectability. A cautiously optimistic scenario of the possible detection of such exomoons around Epsilon Eridani b and Gliese 876 b is provided.

  3. Detection of exomoons through observation of radio emissions

    In the Jupiter-Io system, the moon's motion produces currents along the field lines that connect it to Jupiter's polar regions. The currents generate and modulate radio emissions along their paths via the electron-cyclotron maser instability. Based on this process, we suggest that such modulation of planetary radio emissions may reveal the presence of exomoons around giant planets in exoplanetary systems. A model explaining the modulation mechanism in the Jupiter-Io system is extrapolated and used to define criteria for exomoon detectability. A cautiously optimistic scenario of the possible detection of such exomoons around Epsilon Eridani b and Gliese 876 b is provided.

  4. Methane emissions from Alaska in 2012 from CARVE airborne observations.

    Chang, Rachel Y-W; Miller, Charles E; Dinardo, Steven J; Karion, Anna; Sweeney, Colm; Daube, Bruce C; Henderson, John M; Mountain, Marikate E; Eluszkiewicz, Janusz; Miller, John B; Bruhwiler, Lori M P; Wofsy, Steven C

    2014-11-25

    We determined methane (CH4) emissions from Alaska using airborne measurements from the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Atmospheric sampling was conducted between May and September 2012 and analyzed using a customized version of the polar weather research and forecast model linked to a Lagrangian particle dispersion model (stochastic time-inverted Lagrangian transport model). We estimated growing season CH4 fluxes of 8 2 mg CH4?m(-2)?d(-1) averaged over all of Alaska, corresponding to fluxes from wetlands of 56(-13)(+22) mg CH4?m(-2)?d(-1) if we assumed that wetlands are the only source from the land surface (all uncertainties are 95% confidence intervals from a bootstrapping analysis). Fluxes roughly doubled from May to July, then decreased gradually in August and September. Integrated emissions totaled 2.1 0.5 Tg CH4 for Alaska from May to September 2012, close to the average (2.3; a range of 0.7 to 6 Tg CH4) predicted by various land surface models and inversion analyses for the growing season. Methane emissions from boreal Alaska were larger than from the North Slope; the monthly regional flux estimates showed no evidence of enhanced emissions during early spring or late fall, although these bursts may be more localized in time and space than can be detected by our analysis. These results provide an important baseline to which future studies can be compared. PMID:25385648

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

    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.

  6. Can the envisaged reductions of fossil fuel CO2 emissions be detected by atmospheric observations?

    Levin, Ingeborg; Rödenbeck, Christian

    2007-01-01

    The lower troposphere is an excellent receptacle, which integrates anthropogenic greenhouse gases emissions over large areas. Therefore, atmospheric concentration observations over populated regions would provide the ultimate proof if sustained emissions changes have occurred. The most important anthropogenic greenhouse gas, carbon dioxide (CO2), also shows large natural concentration variations, which need to be disentangled from anthropogenic signals to assess changes in associated emission...

  7. Detection of karst structures using airborne EM and VLF

    Through the combined use of multi-frequency helicopter electromagnetic and VLF data, it is possible to detect and delineate a wide variety of karst structures and possibly to assess their interconnectedness. Multi-frequency EM Can detect karst features if some element of the structure is conductive. This conductive aspect may derive from thick, moist soils in the depression commonly associated with a doline, from conductive fluids in the cavity, or from conductive sediments in the cavity if these occupy a significant portion of it. Multiple loop configurations may also increase the likelihood of detecting karst features. Preliminary evidence indicates total field VLF measurements may be able to detect interconnected karst pathways, so long as the pathways are water or sediment filled. Neither technique can effectively detect dry, resistive air-filled cavities

  8. A generation mechanism of chorus emissions using BWO theory

    In this paper, discrete VLF chorus emissions recorded at low latitude ground station Jammu (geomag. Lat. = 220 26/ 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.

  9. Infrared emission from X-ray binaries - IRAS observations

    Theoretical calculations show that detectable amounts of FIR radiation can be produced by accretion disks around compact sources. Here, the HEAO A-1 Catalog (Wood et al., 1984) and Bradt and McClintock (1983) are used to select a likely set of candidate sources, and the IRAS Point Source Catalog and IRAS Serendipitous Survey Catalog are used to search for characteristic IR emission from sources in fields around them. Eighty-one candidates with 242 IRAS field sources were examined and color corrected. Eight of these have IR flux measurements which are consistent with emisison from an accretion disk S/N, although other mechanisms for their IR emission cannot yet be ruled out. Most have poor positional corespondences and must be considered suspect as identifications. 34 refs

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

    Caledonia, G. E.; R. E. Murphy; Nadile, R. M.; Ratkowski, A. J.

    1995-01-01

    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 kine...

  11. Rashba-type surface emission observed on W(110)

    In this contribution we discuss surface related spectral features of bcc W(110) by means of angle- and spin-resolved photoemission. For more than thirty years Tungsten serves as a prototypical material for studying spin-orbit effects in simple metals. Also, it is used for a quite long time in electron polarimeters. Nevertheless, there still remain some pecularities in its electronic structure concerning surface emission. It is known that a surface resonance exists on W(110) dispersing around anti ? in the vicinity of the Fermi level. But not much is understood concerning surface emission for higher binding energies. From our investigation we found that surface emission dominates the E(k parallel) intensity distribution measured along ?N. The spin analysis reveals a Rashba-like behavior for features related to the spin-orbit induced symmetry gap existing at anti ?. The theoretical analysis has been performed in the framework of the fully relativistic version of the one-step model of photoemission.

  12. Rashba-type surface emission observed on W(110)

    Braun, Juergen; Minar, Jan; Ebert, Hubert [Department Chemie, LMU, Muenchen (Germany); Kimura, Akio; Miyamoto, Koji [Graduate School of Science, Hiroshima University, Higashi-Hiroshima (Japan); Donath, Markus [Physikalisches Institut, Universitaet Muenster (Germany)

    2011-07-01

    In this contribution we discuss surface related spectral features of bcc W(110) by means of angle- and spin-resolved photoemission. For more than thirty years Tungsten serves as a prototypical material for studying spin-orbit effects in simple metals. Also, it is used for a quite long time in electron polarimeters. Nevertheless, there still remain some pecularities in its electronic structure concerning surface emission. It is known that a surface resonance exists on W(110) dispersing around anti {gamma} in the vicinity of the Fermi level. But not much is understood concerning surface emission for higher binding energies. From our investigation we found that surface emission dominates the E(k {sub parallel}) intensity distribution measured along {gamma}N. The spin analysis reveals a Rashba-like behavior for features related to the spin-orbit induced symmetry gap existing at anti {gamma}. The theoretical analysis has been performed in the framework of the fully relativistic version of the one-step model of photoemission.

  13. Observations on some thermoluminescence emission centres in geological quartz

    We report measurements of three-dimensional thermoluminescence emission spectra of samples of geological quartz, derived from Australian sediments. The emphasis is on peaks of particular practical interest for thermoluminescence sediment dating, viz. the 110oC peak, which is used for pre-dose dating and the peak at 325oC, which is of significance for partial and selective bleach techniques and for optically stimulated luminescence (OSL) dating. Because the 325oC peak can be bleached to essentially zero, it can be isolated in a given spectrum by subtracting the bleached spectrum from the unbleached spectrum. By including both peaks in the same spectrum, it is demonstrated that they do not emit at the same wavelength, although this does not necessarily mean that the emission is from different emission centres. The 375oC peak, which is important in total bleach methods, emits at a distinguishable wavelength. The use of bleaching and subtraction in practical dating is discussed. (Author)

  14. Study of electromagnetic emissions associated with seismic activity in Kamchatka region

    V. Gladychev

    2001-01-01

    Full Text Available A review of data processing of electromagnetic emission observation collected at the Complex Geophysical Observatory Karimshino (Kamchatka peninsula during the first 5 months (July–November, 2000 of its operation is given. The main goal of this study addresses the detection of the phenomena associated with Kamchatka seismic activity. The following observations have been conducted at CGO: variations of ULF/ELF magnetic field, geoelectric potentials (telluric currents, and VLF signals from navigation radio transmitters. The methods of data processing of these observations are discussed. The examples of the first experimental results are presented.

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

    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 from large diameter fuels to total fire emissions, which would lower the overall modified combustion efficiency (MCE and NOx emission factor, and offset the higher combustion efficiency of dryer fine fuels. We evaluated the OMI derived NOx emission factors with SCIAMACHY NO2 tropospheric column observations and found improved model performance in regions dominated by fire emissions.

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

    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.

  17. Sawtooth-like X-ray emission observed in EBIT

    Radtke, R.; Biedermann, C.; Bachmann, P

    2003-01-01

    The evolution of a mixture of highly charged Ar and Ba ions was measured in an electron beam ion trap (EBIT) by recording the characteristic X-ray emission from trapped ions. A special feature in the spectra are sawtooth-like intensity variations caused by a periodic collapse of the ion inventory in the trap. The effect requires favorable conditions to become present and is very sensitive to the trapping conditions. Analysis of the measurements is based on a time-dependent calculation of the ...

  18. Subionospheric VLF/LF radio waves propagation characteristics before, during and after the Sofia, Bulgaria Mw=5.6 earthquake occurred on 22 May 2012

    Moldovan, Iren Adelina; Emilian Toader, Victorin; Nenovski, Petko; Biagi, Pier Francesco; Maggipinto, Tommaso; Septimiu Moldovan, Adrian; Ionescu, Constantin

    2013-04-01

    In 2009, INFREP, a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers, was put into operation in Europe having as principal goal, the study of disturbances produced by the earthquakes on the propagation properties of these signals. On May 22nd, 2012 an earthquake with Mw=567 occurred in Bulgaria, near Sofia, inside the "sensitive" area of the INFREP VLF/LF electromagnetic network. The data collected on different frequencies, during April-May 2012 were studied using different methods of analysis: daily correlation methods, spectral approaches and terminator time techniques, in order to find out possible connections between the seismic activity and the subionospheric propagation properties of radio waves. The studies were performed with the help of a specially designed LabVIEW application, which accesses the VLF/LF receiver through internet. This program opens the receiver's web-page and automatically retrieves the list of data files to synchronize the user-side data with the receiver's data. Missing zipped files are also automatically downloaded. The application performs primary, statistical correlation and spectral analysis, appends daily files into monthly and annual files and performs 3D colour-coded maps with graphic representations of VLF and LF signals' intensities versus the minute-of-the-day and the day-of-the-month, facilitating a near real-time observation of VLF and LF electromagnetic waves' propagation. Another feature of the software is the correlation of the daily recorded files for the studied frequencies by overlaying the 24 hours radio activity and taking into account the sunrise and sunset. Data are individually processed (spectral power, correlations, differentiation, filtered using bandpass, lowpass, highpass). JTFA spectrograms (Cone-Shaped Distribution CSD, Gabor, Wavelet, short-time Fourier transform STFT, Wigner-Ville Distribution WVD, Choi-Williams Distribution CWD) are used, too.

  19. Observations of twilight helium 10830 A emission with an tilting filter photometer

    A tilting filter photometer was used to observe the helium 10830 A emission in twilight. The observed intensities of the helium emission show the seasonal variation. The enhancement occurs in winter. It agrees with the previous observation of Christensen et al. It was observed also that the solar zenith angle dependencies of the intensity variations differ in the evening and morning twilights. It can be explained by the asymmetry of the exospheric temperature in evening and morning qualitatively. (author)

  20. Detection of Long-Term Change in Methane Emissions Using Atmospheric Network Observations

    Bruhwiler, L.

    2014-12-01

    The number of sites in the Arctic at which observations of atmospheric CH4 are collected has grown over the past several decades. Some of these sites now have observation records that span several decades; from the early 1980s to present. At the same time, Arctic temperatures have increased at double the rate of the global average increase. A recent comparison of models of CH4 emissions from wetlands (the "WETCHIMP" study) found that many models predict increased emissions in response to higher temperatures. Given the temperature sensitivity of the wetland emission models, and the observed Arctic temperature increase, the change in annual CH4 emissions is likely small, however, the cumulative extra emissions over this period may be at the detection level of the atmospheric network. Even so there is still no firm evidence from the atmospheric network that emissions are changing. In this study, we explore the sensitivity of the atmospheric network to changing emissions. How large do the emissions have to be before they can be seen in the network observations? Can changes be detected by using spatial gradients of observed methane? Can changes in the amplitude and phase of the annual cycle be used to detect increasing emissions during the growing season? Furthermore, by using atmospheric assimilation techniques, network observations provide a strong constraint on total Arctic emissions. Using results from a suite of atmospheric CH4 assimilations we show that total emissions from the Arctic are ~25 TgCH4/yr (with a range from 18 to 29 TgCH4/yr). This is lower than many bottom-up analyses, and implies that emissions from Arctic lakes, the Eastern Siberian Arctic Sea, wetlands and possible geologic sources cannot all be accommodated in the Arctic atmospheric budget of CH4. Finally, we address the issue of how the observation network can be augmented to allow timely trend detection.

  1. Estimating Aerosol Emissions by Assimilating Remote Sensing Observations into a Global Transport Model

    Teruyuki Nakajima; Makiko Nakata; Nick Schutgens

    2012-01-01

    We present a fixed-lag ensemble Kalman smoother for estimating emissions for a global aerosol transport model from remote sensing observations. We assimilate AERONET AOT and AE as well as MODIS Terra AOT over ocean to estimate the emissions for dust, sea salt and carbon aerosol and the precursor gas SO2. For January 2009, globally dust emission decreases by 26% (to 3,244 Tg/yr), sea salt emission increases by 190% (to 9073 Tg/yr), while carbon emission increases by 45% (to 136 Tg/yr), compare...

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

    Castellanos, P.; Boersma, K. F.; van der Werf, G. R.

    2014-04-01

    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 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 patterns 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). 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 1.8 higher than GFED v3 values. For savanna, woodland, and deforestation fires, early dry season NOx emission factors were a factor of ~1.5-2 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, supporting the hypothesis that prolonged dry spells may lead to an increase in the contribution of smoldering combustion from large-diameter fuels, offsetting the higher combustion efficiency of dryer fine fuels. We evaluated the OMI-derived NOx emission factors with SCIAMACHY NO2 tropospheric column observations and found improved model performance in regions dominated by fire emissions.

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

    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.

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

    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.

  5. Radio emission observed by Galileo in the inner Jovian magnetosphere during orbit A-34

    Menietti, J. Douglas; Gurnett, Donald A.; Groene, Joseph B.

    2005-10-01

    The Galileo spacecraft encountered the inner magnetosphere of Jupiter on its way to a flyby of Amalthea on November 5, 2002. During this encounter, the spacecraft observed distinct spin modulation of plasma wave emissions. The modulations occurred in the frequency range from a few hundred hertz to a few hundred kilohertz and probably include at least two distinct wave modes. Assuming transverse EM radiation, we have used the swept-frequency receivers of the electric dipole antenna to determine the direction to the source of these emissions. Additionally, with knowledge of the magnetic field some constraints are placed on the wave mode of the emission based on a comparative analysis of the wave power versus spin phase of the different emissions. The emission appears in several bands separated by attenuation lanes. The analysis indicates that the lanes are probably due to blockage of the freely propagating emission by high density regions of the Io torus near the magnetic equator. Radio emission at lower frequencies (40 kHz) appears to emanate from sources at high latitude and is not attenuated. Emission at f>80kHz is consistent with O-mode and Z-mode. Lower frequency emissions could be a mixture of O-mode, Z-mode and whistler mode. Emission for fplasma torus, similar to the generation of nKOM and continuum emission observed in the outer Jovian magnetosphere and in the terrestrial magnetosphere from source regions near the plasmapause.

  6. Optimizing the emission inventory of volatile organic compounds (VOCs) based on network observations

    Chen, Sheng-Po; Liu, Wen-Tzu; Ou-Yang, Chang-Feng; Chang, Julius S.; Wang, Jia-Lin

    2014-02-01

    Hourly observations of 56 non-methane hydrocarbons (NMHCs) performed by a network of photochemical assessment monitoring stations (PAMS) at 11 locations across Taiwan were used to evaluate 56 speciated emissions and the resulting simulations of an air quality model. Based on the PAMS observations at two urban sites, emission modification was made for the 56 PAMS species in the model. To further test the applicability of this emission correction approach, the same modified emissions were subject to seven different meteorological conditions and comparison with observations of all the 11 PAMS sites. Originally there was a minimum of only 8 of 56 species showed agreement with observations for the worst of the 11 PAMS sites and 28 of 56 species for the best site. With modified emissions, the number increased to 13-52 species across the 11 PAMS sites, demonstrating that the simple urban based correction procedure has broad applicability. When applying this modification of PAMS emissions to the simulations of other air quality gases, SO2 and NOx showed small changes compared with observations (-0.27% and -2.51%, respectively), while total VOC concentrations showed significant changes (+15.28%) as a result of the adjustment in VOC emissions (+26.7%). Although VOCs are the precursor of ozone, the relatively large changes in VOC did not seem to affect ozone formation to the similar extent, only resulting in the changes of average O3 by 2.9 ppb (+9.41%). It shows that although the emission modification improves individual VOC simulations, the performance in oxidant simulation is still largely unaltered. Although the original U.S. VOC emission profiles can capture the general features of ambient VOCs, further optimization of emissions may still be needed by referencing extensive observations, so that emissions can better fit domestic conditions and accuracy in model simulations can be improved.

  7. Observation of fast ion behaviour with a neutron emission profile monitor in MAST

    Cecconello, M.; Sangaroon, S.; Turnyanskiy, M.; Conroy, S.; Wodniak, I.; Akers, R. J.; Ericsson, G.; the MAST Team

    2012-09-01

    Preliminary measurements of neutron emissivity at the Mega Amp Spherical Tokamak (MAST) along collimated lines-of-sight show a clear correlation between the neutron emissivity temporal and spatial evolution and the evolution of different MHD instabilities. In particular, the variations in neutron emissivity during sawtooth oscillations are compared with changes in the classical fast ion slowing-down time, while fast ion losses are observed in bursts during fishbones or as a continuous process during long-lived modes.

  8. Validation of the Swiss methane emission inventory by atmospheric observations and inverse modelling

    Henne, S.; Brunner, D.; B. Oney; Leuenberger, M; Eugster, W; Bamberger, I.; Meinhardt, F.; Steinbacher, M.; Emmenegger, L.

    2015-01-01

    Atmospheric inverse modelling has the potential to provide observation-based estimates of greenhouse gas emissions at the country scale, thereby allowing for an independent validation of national emission inventories. Here, we present a regional scale inverse modelling study to quantify the emissions of methane (CH4) from Switzerland, making use of the newly established CarboCount-CH measurement network and a high resolution Lagrangian transport model. Overall we estimate na...

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

    M. Zavala; W. Lei; 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...

  10. Cassini VIMS observations of H3+ emission on the nightside of Jupiter

    Stallard, Tom S.; Melin, Henrik; Miller, Steve; Badman, Sarah V.; Baines, Kevin H.; Brown, Robert H.; Blake, James S. D.; O'Donoghue, James; Johnson, Rosie E.; Bools, Bethany; Pilkington, Nathan M.; East, Oliver T. L.; Fletcher, Mark

    2015-08-01

    We present the first detailed analysis of H3+ nightside emission from Jupiter, using Visual and Infrared Mapping Spectrometer (VIMS) data from the Cassini flyby in 2000-2001, producing the first Jovian maps of nightside H3+ emission, temperature, and column density. Using these, we identify and characterize regions of H3+ nightside emission, compared against past observations of H3+ emission on the dayside. We focus our investigation on the region previously described as "mid-to-low latitude emission," the source for which has been controversial. We find that the brightest of this emission is generated at Jovigraphic latitudes similar to the most equatorward extent of the main auroral emission but concentrated at longitudes eastward of this emission. The emission is produced by enhanced H3+ density, with temperatures dropping away in this region. This emission has a loose association with the predicted location of diffuse aurora produced by pitch angle scattering in the north, but not in the south. This emission also lays in the path of subrotating winds flowing from the aurora, suggesting a transport origin. Some differences are seen between dayside and nightside subauroral emissions, with dayside emission extending more equatorward, perhaps caused by the lack of sunlight ionization on the nightside, and unmeasured changes in temperature. Ionospheric temperatures are hotter in the polar region (~1100-1500 K), dropping away toward the equator (as low as 750 K), broadly similar to values on the dayside, highlighting the dominance of auroral effects in the polar region. No equatorial emission is observed, suggesting that very little particle precipitation occurs away from the polar regions.

  11. ALMA capabilities for observations of spectral line emission

    Wootten, Alwyn

    2008-01-01

    The Atacama Large Millimeter/submillimeter Array (ALMA) (The Enhanced Atacama Large Millimeter/submillimeter Array (known as ALMA) is an international astronomy facility. ALMA is a partnership between North America, Europe, and Japan/Taiwan, in cooperation with the Republic of Chile, and is funded in Europe by the European Southern Observatory (ESO) and Spain, in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC), and in Japan by the National Institutes of Natural Sciences (NINS) in cooperation with the Academia Sinica in Taiwan. ALMA construction and operations are led on behalf of Japan/Taiwan by the National Astronomical Observatory of Japan (NAOJ), on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI), and on behalf of Europe by ESO) combines large collecting area and location on a high dry site to provide it with unparalleled potential for sensitive millimeter/submillimeter spectral line observations. Its wide frequency coverage, superb receivers and flexible spectrometer will ensure that its potential is met. Since the 1999 meeting on ALMA Science (Wootten, ASP Conf. Ser. 235, 2001), the ALMA team has substantially enhanced its capability for line observations. ALMAs sensitivity increased when Japan joined the project, bringing the 16 antennas of the Atacama Compcat Array (ACA), equivalent to eight additional 12 m telescopes. The first four receiver cartridges for the baseline ALMA (Japans entry has brought two additional bands to ALMAs receiver retinue) have been accepted, with performance above the already-challenging specifications. ALMAs flexibility has increased with the enhancement of the baseline correlator with additional channels and flexibility, and with the addition of a separate correlator for the ACA. As an example of the increased flexibility, ALMA is now capable of multi-spectral-region and multi-resolution modes. With the former, one might observe e.g. four separate transitions anywhere within a 2 GHz band with a high resolution bandwidth. With the latter, one might simultaneously observe with low spectral resolution over a wide bandwidth and with high spectral resolution over a narrow bandwidth; this mode could be useful for observations of pressure-broadened lines with narrow cores, for example. Several science examples illustrate ALMAs potential for transforming millimeter and submillimeter astronomy.

  12. Solar Flare Impulsive Phase Footpoint Emission Observed with SDO/EVE

    Kennedy, Michael; Milligan, R. O.; Mathioudakis, M.

    2013-07-01

    The differential emission measure of solar flare plasmas was constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range Log T = 5.8 - 7.4 allow for the evolution of the DEM to be studied over a wide temperature range at 10s cadence. The DEM construction technique is applied to several M and X-class flares where impulsive phase EUV emission is observable in the disk-integrated EVE spectra. The emission is verified using AIA images to be originating from the flare ribbons and footpoints and EVE observations are used to infer the thermal structure of the EUV emitting flare chromosphere. For the nine events studied the constructed differential emission measures have a two component distribution during the impulsive phase. The low temperature component has peak temperatures of 1 - 2 MK, and a high temperature component peaking at 10 MK.

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

    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.

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

    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...

  15. Neutron emission observed from spent thermal reactor fuel assemblies

    A scoping experiment to characterize the neutron field generated from a Light Water Reactor spent fuel assembly has been successfully completed. Solid State Track Recorder (SSTR) neutron dosimeters have been exposed at the surface of a spent fuel assembly from a Pressurized Water Reactor. Acceptable track densities were obtained. From these SSTR neutron dosimetry observations, an absolute neutron flux of roughly 8000 n/(cm2.sec) was obtained at the surface of the spent fuel assembly three years after discharge. The deduced neutron energy spectrum, with a mean neutron energy of roughly 1.3 MeV, is intimately dependent upon the actinide content of the spent fuel. Hence, the results of this preliminary experiment have demonstrated that, with suitable calibration, SSTR neutron dosimetry can be successfully applied for non-destructive spent fuel actinide assay and for characterization of the radiation environment associated with spent reactor fuel assemblies

  16. Observation of radio frequency emissions from electrochemical loading experiments

    Palladium foil cathodes were electrochemically loaded with deuterium from alkaline solutions of heavy water in specially designed closed calorimeter cells. Here, one cell is described that showed low levels of constant heat (1-7 mW) and radio frequency (RF) emanations, but the RF was not correlated with the heat production. This cell is compared with Pd90Rh10 alloy cathodes that showed excess energy bursts of 2.4-44.3 kJ. In these cells, RF coincident with the bursts was observed peaking at different frequencies from about 450 kHz and extending into the MHz range. Some of the excess energy production in LENR may be in the MHz RF range, which has no conventional explanation in electrochemistry. (author)

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

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

    2016-02-01

    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 self-gravity in the local approximation are relatively weak when compared to amplitudes produced by tidal interactions, or spirals launched at Lindblad resonances due to embedded planets in the disc. As such, we ultimately caution against diagnosing spiral features as being due to self-gravity, unless the disc exists in the very narrow region of parameter space where the spiral wave amplitudes are large enough to produce detectable features, but not so large as to cause the disc to fragment.

  18. Observations of OI 7774 emission excited by conjugate photoelectrons. [ionosonde data analhysis

    Christensen, A. B.

    1975-01-01

    Observations and computer calculations of O I 7774 A airglow emissions excited by conjugate photoelectrons have been carried out. The observations were made at McDonald Observatory, Texas using a 2 m grille spectrometer from December 1972 to June 1973. The zenithal emission intensity during conjugate photoelectron precipitation was fairly constant at 2-4 R until conjugate sunset, after which it diminished steadily and ceased near a conjugate solar zenith angle of 105 (plus or minus 3) deg. A predawn enhancement in both O I 7774 A and forbidden O I 6300 A was observed to commence near 102 deg. The computations utilize the two-stream technique of Nagy and Banks (1970) to obtain the escaping photoelectron flux and the local excitation rates of the oxygen emissions. Good agreement with the observations is obtained for the dependence of the emission rate on conjugate solar zenith angle.

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

    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 * = 4520 120 K), giving the planet a modest equilibrium temperature of T 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 ?m and 0.382% 0.015% and 1514 25 K at 4.5 ?m. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347436 1.4 107 days) and put an upper limit on the eccentricity (e=0.010?0.007+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.

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

    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.

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

    Menietti, J. D.; Shprits, Y. Y.; Horne, R. B.; Woodfield, E. E.; 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...

  2. Temperature and Emission-Measure Profiles Along Long-Lived Solar Coronal Loops Observed with TRACE

    Lenz, Dawn D.; DeLuca, Edward E.; Golub, Leon; Rosner, Robert; Bookbinder, Jay A.

    1999-01-01

    We report an initial study of temperature and emission measure distributions along four steady loops observed with the Transition Region and Coronal Explorer (TRACE) at the limb of the Sun. The temperature diagnostic is the filter ratio of the extreme-ultraviolet 171-angstrom and 195-angstrom passbands. The emission measure diagnostic is the count rate in the 171-angstrom passband. We find essentially no temperature variation along the loops. We compare the observed loop structure with theore...

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

    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 ?m 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.

  4. The observation of chemiluminescent NiO* emissions in the laboratory and in the night airglow

    W. F. J. Evans

    2011-09-01

    Full Text Available The recent finding of an orange spectral feature in OSIRIS/Odin spectra of the night airglow near 87 km has raised interest in the origin of the emission. The feature was positively identified as the chemiluminescent FeO* emission where the iron is of meteoric origin. Since the meteorite source of atomic metals in the mesosphere contains both iron and nickel, with Ni being typically 6 % of Fe, it is expected that faint emissions involving Ni should also be present in the night airglow. The present study summarizes the laboratory observations of chemiluminescent NiO* emissions and includes a search for the NiO* signature in the night airglow. A very faint previously unidentified "continuum" extending longwave of 440 nm has been detected in the night airglow spectra obtained with two space-borne limb viewing instruments. Through a comparison with laboratory spectra this continuum is identified as arising from the NiO* emission. The altitude profile of the new airglow emission has also been measured. The similarity of the altitude profiles of the FeO* and NiO* emissions also suggests the emission is NiO as both can originate from reaction of the metal atoms with mesospheric ozone. The observed NiO* to FeO* ratio exhibits considerable variability; possible causes of this observed variation are briefly discussed.

  5. Estimating Aerosol Emissions by Assimilating Remote Sensing Observations into a Global Transport Model

    Teruyuki Nakajima

    2012-11-01

    Full Text Available We present a fixed-lag ensemble Kalman smoother for estimating emissions for a global aerosol transport model from remote sensing observations. We assimilate AERONET AOT and AE as well as MODIS Terra AOT over ocean to estimate the emissions for dust, sea salt and carbon aerosol and the precursor gas SO2. For January 2009, globally dust emission decreases by 26% (to 3,244 Tg/yr, sea salt emission increases by 190% (to 9073 Tg/yr, while carbon emission increases by 45% (to 136 Tg/yr, compared with the standard emissions. Remaining errors in global emissions are estimated at 62% (dust, 18% (sea salt and 78% (carbons, with the large errors over land mostly due to the sparseness of AERONET observations. The new emissions are verified by comparing a forecast run against independent MODIS Aqua AOT, which shows significant improvement over both ocean and land. This paper confirms the usefulness of remote sensing observations for improving global aerosol modelling.

  6. Observation of density fluctuations from the infrared bremsstrahlung emission on TFTR

    The infrared emission of beam heated TFTR discharges is studied using the high collection efficiency TFTR Thompson scattering system. It is found that emission in the vicinity of 9800 A can be used to study fluctuations in the bremsstrahlung emission. Low-frequency (200 kHz) bursts of fluctuations are observed. Both coherent and incoherent fluctuations exist. In some cases, the observed coherent fluctuations can be interpreted as being due to density fluctuations as high as 5%. The rms value of broadband density turbulence in the near central regions of the plasma is estimated to be about 1%

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

    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 NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the base case. We further performed emissions perturbations from the gasoline fleet, diesel fleet, all mobile (gasoline plus diesel and all emission sources (anthropogenic plus biogenic. The results suggest that although large ozone reductions obtained in the past were from changes in emissions from gasoline vehicles, currently significant benefits could be achieved with additional emission control policies directed to regulation of VOC emissions from diesel and area sources that are high emitters of alkenes, aromatics and aldehydes.

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

    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 NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the base case. We further performed emissions perturbations from the gasoline fleet, diesel fleet, all mobile (gasoline plus diesel and all emission sources (anthropogenic plus biogenic. The results suggest that although large ozone reductions obtained in the past were from changes in emissions from gasoline vehicles, currently significant benefits could be achieved with additional emission control policies directed to regulation of VOC emissions from diesel and area sources that are high emitters of alkenes, aromatics and aldehydes.

  9. Pioneer 10 ultraviolet photometer observations of Jovian UV emission in 1973

    Wu, F. M.; Gangopadhyay, P.; Judge, D. L.

    1995-01-01

    The Pioneer 10 ultraviolet measurements obtained during the Jupiter encounter in 1973 have been further examined by using improved data handling and analysis techniques. The Pioneer 10 observations of Jupiter and its satellites during the encounter have been carefully reviewed in order to improve our understanding of the morphology of the Io plasma torus and Jupiter's upper atmosphere and to investigate the possible existence of other emission source such as Europa. In addition, the morphology of Io's bimodal torus observed during the Pioneer 10 encounter has been compared with the Voyager observations obtained approximately 6 years after the Pioneer 10 flyby and significant differences in the torus characteristics are found. The Io torus in 1973 was more similar to the 1992 Ulysses observations of a longitudinally asymmetric ring than to the complete ring observed by Voyager. Pioneer 10 observed a significantly dimmer Io torus and Jupiter upper atmosphere in the EUV compared to the Voyager observations. Apart from the torus and Jupiter, Pioneer 10 observed additional emissions which have been attributed to Io itself. Three distinct possibilities have been discussed to explain these additional emissions. The most likely is that Pioneer 10 observed volcanism on Io. There is also evidence of Pioneer 10 observing emissions from Europa. The present analysis clearly shows that the Jovian system in 1973 was significantly different from that observed in 1979.

  10. Observation of Solar Wind Charge Exchange Emission from Exospheric Material in and Outside Earth's Magnetosheath

    Snowden, S. L.; Collier, M. R.; Cravens, T.; Kuntz, K. D.; Lepri, S. T.; Robertson, I.; Tomas, L.

    2008-01-01

    A long XMM-Newton exposure is used to observe solar wind charge exchange (SWCX) emission from exospheric material in and outside Earth s magnetosheath. The light curve of the O VII (0.5-0.62 keV) band is compared with a model for the expected emission, and while the emission is faint and the light curve has considerable scatter, the correlation is significant to better than 99.9%. This result demonstrates the validity of the geocoronal SWCX emission model for predicting a contribution to astrophysical observations to a scale factor of order unity (1.36). The results also demonstrate the potential utility of using X-ray observations to study global phenomena of the magnetosheath which currently are only investigated using in situ measurements.

  11. Resistivity soundings and VLF profiles for siting groundwater wells in a fractured basement aquifer in the Arabian Shield, Saudi Arabia

    Ammar, A. I.; Kruse, S. E.

    2016-04-01

    Seasonal shortages of groundwater are common in parts of the Arabian Shield, where complex basement hydrogeology can make siting of water wells difficult. To identify optimal production well locations, six 200-400 m-long Very Low Frequency (VLF) electromagnetic traverses and ten Vertical Electrical Soundings (VESes) were run at the western edge of the Arabian Shield near At-Taif town, Saudi Arabia. Here wadi sediments overlie fractured Precambrian basement, which in turn overlies unfractured basement. The fractured basement forms the water supply aquifer. Both VLF and VES data indicate significant lateral heterogeneity in the electrical conductivity of both wadi and basement deposits over lengths scales as small as ∼100 m. VES results correlate closely with data from two wells in the study area. The change in resistivity at the wadi-to-fractured basement contact is relatively subtle, but the transition from low resistivity fractured basement to high resistivity unfractured basement is well resolved. Inferred wadi thicknesses range from 0 to 14 m; the electrically conductive fractured basement extends from wadi down to 12-32 m depth. VES data indicate the fractured basement aquifer thickens progressively to the south in this area. A production well, sited on the basis of the VES analysis, successfully yielded 70m3/day. The relationship between VLF and VES data is complex, suggesting that the terrain is heterogeneous on the scale of the different effective sampling volumes of the two methods, and/or that fracture azimuth is locally heterogeneous. Overall resistivities in this study are similar to those observed at other locations in Saudi Arabia, suggesting these methods may be widely applicable for siting of groundwater wells in the complex basement of the Arabian Shield.

  12. Assimilation of FRP Observations for Global Fire Emission Estimation in MACC-II

    Kaiser, J. W.; Benedetti, A.; Detmers, R.; Heil, A.; Morcrette, J.-J.; Schultz, M. G.; van der Werf, G. R.; Wooster, M. J.; Xu, W.

    2012-04-01

    We present the Global Fire Assimilation System (GFAS) that is run routinely at ECMWF by the MACC-II project in preparation of the operational GMES atmospheric service. The GFAS currently combines Fire Radiative Power (FRP) observations from the polar orbiting MODIS instruments and applies a quality control, a partial cloud cover correction and observation gap filling with a Kalman filter to generate daily global FRP maps. These are subsequently used to calculate the daily average dry matter combustion rate and emission rates for 40 atmospheric trace constituents in real time with a time lag of 7 hours. The emission estimates are consistent with the GFED3 emission dataset, but FRP appears to have a lower detection threshold than the burnt area observations used in GFED3. The emissions are further validated with the atmospheric composition models of MACC by comparing the simulated smoke plumes with atmospheric observations. The temporal and spatial patterns of the emissions are shown to be realistic. However, a general mismatch between various aerosol smoke emission rates from bottom-up and top-down inventories is evident. Upcoming upgrades of GFAS will include FRP observations from the geostationary instruments aboard Meteosat-9, GOES-East and GOES-West and improve the temporal resolution to one hour.

  13. Fading of VLF signals along the NAA-Apatity line during solar proton injections

    Investigations of very-low-frequency (VLF) radiowave propagation in the Earth atmosphrere during solar proton injections are made. For the analysis data of proton flux measurements made by the IMP 7 and IMP-8 satellites in the energy range 4-12.5 MeV are used. It is shown that on high-latitude heterogeneous VLF-routes of the NAA-Apatity radioline type the changes in geomagnetic activity during proton injections affect but slightly the value of VLF-field fading

  14. Searching for meteor ELF /VLF signatures

    Rault, J.-L.

    2010-01-01

    For more than two centuries, credible reports about various audible sounds appearing simultaneously with visible meteors have been collected. Knowing that the sound velocity is much lower than the light velocity, it was impossible to explain such a phenomenon until some theories predicted that an electromagnetic wave vector could be the reason for such simultaneous light and sound observations. Several optical/sound/radio recording campaigns have been performed in the last decades but with no...

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

    Tibbs, Christopher T; Dickinson, Clive; Davies, Rodney D; Davis, Richard J; del Burgo, Carlos; Franzen, Thomas M O; Gnova-Santos, Ricardo; Grainge, Keith; Hobson, Michael P; Padilla-Torres, Carmen P; Rebolo, Rafael; Rubio-Martn, Jse 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...

  16. White-light continuum emission from solar flare and plages: observations and modeling

    Berlicki, Arkadiusz; Awasthi, Arun Kumar; Heinzel, Petr

    2015-08-01

    Observations of flares in optical continuum emission are very rare. Therefore, the analysis of such observations is very useful and may contribute to our understanding of the flaring chromosphere. We study the white-light continuum emission observed during the X6.9 flare observed on August 09, 2011. This emission comes not only from the flare ribbons but also form the nearby plage area observed within the active region. The main aim of this work is to disentangle the flare and plage emission and to understand the physical mechanisms responsible for the production of white-light continuum.There are two main mechanisms which can be responsible for the optical continuum emission of the solar atmosphere: enhanced photospheric H- continuum due to the temperature increase below the temperature minimum region, or hydrogen recombination continua (Balmer, Paschen) formed in solar chromosphere. In our work we analyse the physical conditions in solar active atmosphere in order to obtain the contribution from these two mechanisms to the whole continuum emission of the flare and plage.We analyzed the spatial, spectral and temporal evolution study of the flare and plage parameters by analyzing multi-wavelength observations obtained from ground and space based solar observatories. We study the morphological correlation of the white-light continuum emission observed with different instruments. Moreover, we also explore the non-thermal electron beam properties by forward fitting the observed X-ray spectra.The unique opportunity of an intense X6.9 flare occurrence close to the limb enabled us to explore the origin of white-light continuum with better visibility. The analysis of multi-wavelength data revealed the origin of this emission from the foot-points of the loops. Spatial association of HXR foot-points synthesized from RHESSI observations confirmed this finding. In addition, we found a good temporal correlation of hard (>30 keV) X-ray with the white-light emission. However, some active region areas which produce the continuum emission correspond rather to plages than to the flare kernels.

  17. Theory of weakly nonlinear VLF interactions

    A mathematical description of the weakly nonlinear regime of the coherent cyclotron resonance instability in the magnetosphere which has hitherto been neglected in the literature is developed. Using the concept that the fundamental role played by the inhomogeneity of the Earth's magnetic field is to limit the interaction time between the resonance electrons and whistler mode wave, perturbation expansions of the current equations to third order have been obtained. It is then found that the real component of resonance current can qualitatively account for excess growth found in some magnetospheric transmissions while the imaginary component gives a good quantitative estimate of frequency shifts observed in transmissions of the mains harmonics. (author)

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

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

    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 rural and remote sites, attributed partly to weaker atmospheric oxidation and SOC formation compared to summer. Enhanced SOC formation from oxidization and anthropogenic activities like biomass combustion is judged to have crucial effects on severe haze events characterized by high particle concentrations. Several observational studies indicate an increasing trend in ambient OC/EC (but not in OC or EC individually from 2000 to 2010, confirming increased atmospheric oxidation of OC across the country. Combining the results of emission estimation and observations, the improvement over prior emission inventories is indicated by inter-annual comparisons and correlation analysis. It is also indicated, however, that the estimated growth in emissions might be faster than observed growth, and that some sources with high primary OC/EC like burning of biomass are still underestimated. Further studies to determine changing emission factors over time in the residential sector and to compare to other measurements such as satellite observations are thus suggested to improve understanding of the levels and trends of primary carbonaceous aerosol emissions in China.

  20. Jiamusi Pulsar Observations: I. Abnormal emission events of PSR B0919+06

    Han, Jun; Peng, Ling-Xiang; Tang, De-Yu; Wang, Jun; Li, Jun-Qiang; Wang, Chen; Yu, Ye-Zhao; Dong, Bin

    2016-01-01

    PSR B0919+06 generally radiates radio pulses in a normal phase range. It has been known for its occasional perplexing abnormal emission events wherein individual pulses come to an earlier phase range for a few tens of periods and then returns to its usual phase. Heretofore, only a few such events have been available for study. We observed PSR B0919+06 for about 30 hours using the Jiamusi 66-m telescope at Jiamusi Deep Space Station at S-band, and detected 92 abnormal emission events. We identify four types of events based on the abrupted or gradual phase-shifting of individual pulses. The abnormal emission events are seen to occur randomly some every 1000 to 3000 periods, and they affect the leading edge of the mean profile by up to 2\\% in amplitude. The abnormal emission events are probably related to gradual changes of emission processing in the pulsar magnetosphere.

  1. Observations of the microwave emission of Venus from 1.3 to 3.6 cm

    An account is given of the methodology as well as the results of coordinated Venus emission observations conducted at four wavelengths between 1.35 and 3.6 cm; the results are compared with other observations and with calculated mission spectra, with a view to suggestions that the microwave spectrum of Venus could be sensitive to the subcloud abundance of such constituents as SO2 and gaseous H2SO4. The observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions of about 5 ppm. An upper limit is established for the subcloud SO2 abundance. 19 refs

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

    Cui, H.; Mao, P.; Zhao, Y.; Nielsen, C. P.; Zhang, J.

    2015-08-01

    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 74-78, 17-21, and 4-6 % of the total emissions of OC, respectively, and 49-55, 30-34, and 14-18 % of EC. Updated emission factors (EFs) based on the most recent local field measurements, particularly for biofuel stoves, led 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 higher OC / EC ratios are found in southern sites, due to the joint effects of primary emissions and meteorology. Higher OC / EC 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 rural and remote sites, attributed partly to weaker atmospheric oxidation and SOC formation compared to summer. Enhanced SOC formation from oxidization and anthropogenic activities like biomass combustion is judged to have crucial effects on severe haze events characterized by high particle concentrations. Several observational studies indicate an increasing trend in ambient OC / EC (but not in OC or EC individually) from 2000 to 2010, confirming increased atmospheric oxidation of OC across the country. Combining the results of emission estimation and observations, the improvement over prior emission inventories is indicated by inter-annual comparisons and correlation analysis. It is also indicated, however, that the estimated growth in emissions might be faster than observed growth, and that some sources with high primary OC / EC, such as burning of biomass, are still underestimated. Further studies to determine changing EFs over time in the residential sector and to compare to other measurements, such as satellite observations, are thus suggested to improve understanding of the levels and trends of primary carbonaceous aerosol emissions in China.

  3. Backside observation of large-scale integrated circuits with multilayered interconnections using laser terahertz emission microscope

    Yamashita, Masatsugu; Otani, Chiko; Kawase, Kodo; Matsumoto, Toru; Nikawa, Kiyoshi; Kim, Sunmi; Murakami, Hironaru; Tonouchi, Masayoshi

    2009-05-01

    We have developed a laser terahertz emission microscope utilizing excitation laser pulses at 1.06 μm wavelength for the inspection and localization of electrical failures in large-scale integrated circuits with multilayered interconnection structures. The system enables to measure terahertz emission images from the backside of a large-scale integrated circuits chip with a multilayered interconnection structure that prevents the observation from the front side. By comparing the terahertz emission images, we successfully distinguish a normal circuit from damaged ones with different positions of the interconnection defects without any electrical probing.

  4. GRB 050713A: High Energy Observations of the GRB Prompt and Afterglow Emission

    Morris, D. C.; Reeves, J; Pal'shin, V.; Garczarczyk, M.; Falcone, A. D.; D. N. Burrows(PSU, USA;); Krimm, H.; Galante, N.; Gaug, M.; Mizobuchi, S.; Pagani, C.; A. Stamerra(Universitá di Siena, and INFN Pisa, I-53100 Siena, Italy); Teshima, M.; Beardmore, A. P.; Godet, O.

    2006-01-01

    Swift discovered GRB 050713A and slewed promptly to begin observing with its narrow field instruments 72.6 seconds after the burst onset, while the prompt gamma-ray emission was still detectable in the BAT. Simultaneous emission from two flares is detected in the BAT and XRT. This burst marks just the second time that the BAT and XRT have simultaneously detected emission from a burst and the first time that both instruments have produced a well sampled, simultaneous dataset covering multiple ...

  5. Conjugate observations of quasi-periodic emissions by Cluster and DEMETER spacecraft

    Němec, F; Santolík, O; Parrot, M.; Pickett, J. S.; Hayosh, M.; N. Cornilleau-Wehrlin

    2013-01-01

    Quasi-periodic (QP) emissions are electromagnetic emissions at frequencies of about 0.5-4 kHz that are characterized by a periodic time modulation of the wave intensity. Typical periods of this modulation are on the order of minutes. We present a case study of a large-scale long-lasting QP event observed simultaneously on board the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) and the Cluster spacecraft. The measurements by the Wide-Band Data instrument...

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

    Schillaci, Alessandro; Battistelli, Elia; Giuseppe D'Alessandro; 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.

  7. Tropospheric methanol observations from space: retrieval evaluation and constraints on the seasonality of biogenic emissions

    Wells, K. C.; Millet, D. B.; Hu, L.; Cady-Pereira, K. E.; Xiao, Y.; Shephard, M. W.; Clerbaux, C. L.; Clarisse, L.; Coheur, P.-F.; Apel, E. C.; de Gouw, J.; Warneke, C.; Singh, H. B.; Goldstein, A. H.; Sive, B. C.

    2012-07-01

    Methanol retrievals from nadir-viewing space-based sensors offer powerful new information for quantifying methanol emissions on a global scale. Here we apply an ensemble of aircraft observations over North America to evaluate new methanol measurements from the Tropospheric Emission Spectrometer (TES) on the Aura satellite, and combine the TES data with observations from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A satellite to investigate the seasonality of methanol emissions from northern midlatitude ecosystems. Using the GEOS-Chem chemical transport model as an intercomparison platform, we find that the TES retrieval performs well when the degrees of freedom for signal (DOFS) are above 0.5, in which case the model:TES regressions are generally consistent with the model:aircraft comparisons. Including retrievals with DOFS below 0.5 degrades the comparisons, as these are excessively influenced by the a priori. The comparisons suggest DOFS >0.5 as a minimum threshold for interpreting retrievals of trace gases with a weak tropospheric signal. We analyze one full year of satellite observations and find that GEOS-Chem, driven with MEGANv2.1 biogenic emissions, underestimates observed methanol concentrations throughout the midlatitudes in springtime, with the timing of the seasonal peak in model emissions 1-2 months too late. We attribute this discrepancy to an underestimate of emissions from new leaves in MEGAN, and apply the satellite data to better quantify the seasonal change in methanol emissions for midlatitude ecosystems. The derived parameters (relative emission factors of 11.0, 0.26, 0.12 and 3.0 for new, growing, mature, and old leaves, respectively, plus a leaf area index activity factor of 0.5 for expanding canopies with leaf area index methanol concentrations in midlatitudes on the basis of both the IASI and TES measurements.

  8. Tropospheric methanol observations from space: retrieval evaluation and constraints on the seasonality of biogenic emissions

    K. C. Wells

    2012-02-01

    Full Text Available Methanol retrievals from nadir-viewing space-based sensors offer powerful new information for quantifying methanol emissions on a global scale. Here we apply an ensemble of aircraft observations over North America to evaluate new methanol measurements from the Tropospheric Emission Spectrometer (TES on the Aura satellite, and combine the TES data with observations from the Infrared Atmospheric Sounding Interferometer (IASI on the MetOp-A satellite to investigate the seasonality of methanol emissions from northern midlatitude ecosystems. Using the GEOS-Chem chemical transport model as an intercomparison platform, we find that the TES retrieval performs well when the degrees of freedom for signal (DOFS are above 0.5, in which case the model : TES regressions are generally consistent with the model : aircraft comparisons. Including retrievals with DOFS below 0.5 degrades the comparisons, as these are excessively influenced by the a priori. The comparisons suggest DOFS > 0.5 as a minimum threshold for interpreting retrievals of trace gases with a weak tropospheric signal. We analyze one full year of satellite observations and find that GEOS-Chem, driven with MEGANv2.1 biogenic emissions, underestimates observed methanol concentrations throughout the midlatitudes in springtime, with the timing of the seasonal peak in model emissions 1–2 months too late. We attribute this discrepancy to an underestimate of emissions from new leaves in MEGAN, and apply the satellite data to better quantify the seasonal change in methanol emissions for midlatitude ecosystems. The derived parameters (relative emission factors of 11.0, 1.0, 0.05 and 8.6 for new, growing, mature, and old leaves, respectively, plus a leaf area index activity factor of 0.75 for expanding canopies with leaf area index < 2.0 provide a more realistic simulation of seasonal methanol concentrations in midlatitudes on the basis of IASI, TES, and ground-based measurements.

  9. Tropospheric methanol observations from space: retrieval evaluation and constraints on the seasonality of biogenic emissions

    K. C. Wells

    2012-07-01

    Full Text Available Methanol retrievals from nadir-viewing space-based sensors offer powerful new information for quantifying methanol emissions on a global scale. Here we apply an ensemble of aircraft observations over North America to evaluate new methanol measurements from the Tropospheric Emission Spectrometer (TES on the Aura satellite, and combine the TES data with observations from the Infrared Atmospheric Sounding Interferometer (IASI on the MetOp-A satellite to investigate the seasonality of methanol emissions from northern midlatitude ecosystems. Using the GEOS-Chem chemical transport model as an intercomparison platform, we find that the TES retrieval performs well when the degrees of freedom for signal (DOFS are above 0.5, in which case the model:TES regressions are generally consistent with the model:aircraft comparisons. Including retrievals with DOFS below 0.5 degrades the comparisons, as these are excessively influenced by the a priori. The comparisons suggest DOFS >0.5 as a minimum threshold for interpreting retrievals of trace gases with a weak tropospheric signal. We analyze one full year of satellite observations and find that GEOS-Chem, driven with MEGANv2.1 biogenic emissions, underestimates observed methanol concentrations throughout the midlatitudes in springtime, with the timing of the seasonal peak in model emissions 1–2 months too late. We attribute this discrepancy to an underestimate of emissions from new leaves in MEGAN, and apply the satellite data to better quantify the seasonal change in methanol emissions for midlatitude ecosystems. The derived parameters (relative emission factors of 11.0, 0.26, 0.12 and 3.0 for new, growing, mature, and old leaves, respectively, plus a leaf area index activity factor of 0.5 for expanding canopies with leaf area index <1.2 provide a more realistic simulation of seasonal methanol concentrations in midlatitudes on the basis of both the IASI and TES measurements.

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

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

    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 ...

  11. Coordinated NIR/mm observations of flare emission from Sagittarius A*

    Kunneriath, D.; Witzel, G.; A. Eckart; Zamaninasab, M.; übel, R. Gieß; Schödel, R; Baganoff, F. K.; Morris, M. R.; Dovčiak, M.; Duschl, W. J.; García-Marín, M.; Karas, V.; König, S; Krichbaum, T. P.; Krips, M

    2010-01-01

    We report on a successful, simultaneous observation and modelling of the millimeter (mm) to near-infrared (NIR) flare emission of the Sgr A* counterpart associated with the supermassive black hole at the Galactic centre (GC). We present a mm/sub-mm light curve of Sgr A* with one of the highest quality continuous time coverages and study and model the physical processes giving rise to the variable emission of Sgr A*.

  12. Observations of the 10 micrometer natural laser emission from the mesospheres of Mars and Venus

    Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model the flux observed from Venus is 74% of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T 204 + or - 10 K

  13. Nonlinear VLF Wave Physics in the Radiation Belts

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

    2014-12-01

    Electromagnetic VLF waves, such as whistler mode waves, both control the lifetime of trapped electrons in the radiation belts by pitch-angle scattering and are responsible for the energization of electrons during storms. Traditional approaches to understanding the influence of waves on trapped electrons have assumed that the wave characteristics (frequency spectrum, wave-normal angle distribution, etc.) were both stationary in time and amplitude independent from event to event. In situ data from modern satellite missions, such as the Van Allen probes, are showing that this assumption may not be justified. In addition, recent theoretical results [Crabtree et al. 2012] show that the threshold for nonlinear wave scattering can often be met by naturally occurring VLF waves in the magnetosphere, with wave magnetic fields of the order of 50-100 pT inside the plasmapause. Nonlinear wave scattering (Nonlinear Landau Damping) is an amplitude dependent mechanism that can strongly alter VLF wave propagation [Ganguli et al. 2010], primarily by altering the direction of propagation. Laboratory results have confirmed the dramatic change in propagation direction when the pump wave has sufficient amplitude to exceed the nonlinear threshold [Tejero et al. 2014]. Nonlinear scattering can alter the macroscopic dynamics of waves in the radiation belts leading to the formation of a long-lasting wave-cavity [Crabtree et al. 2012] and, when amplification is present, a multi-pass amplifier [Ganguli et al., 2012]. Such nonlinear wave effects can dramatically reduce electron lifetimes. Nonlinear wave dynamics such as these occur when there are more than one wave present, such a condition necessarily violates the assumption of traditional wave-normal analysis [Santolik et al., 2003] which rely on the plane wave assumption. To investigate nonlinear wave dynamics using modern in situ data we apply the maximum entropy method [Skilling and Bryan, 1984] to solve for the wave distribution function [Storey and Lefeuvre, 1979] to yield the power distribution as a function of wave-normal angle and local azimuthal angle. We have validated this technique in the NRL space chamber and applied this methodology to Van Allen probe data to demonstrate that traditional wave-normal analaysis can give misleading results when multiple waves are present.

  14. Numerical Simulations Of The Effect Of Localised Ionospheric Perturbations On Subionospheric VLF Propagation

    Sulic, D; Sreckovic, V

    2014-01-01

    Electron density and temperature changes in the D-region of the ionosphere are sensitively manifested as changes in the amplitude and phase of subionospheric Very Low Frequency (VLF) signals propagating beneath the perturbed region. Disturbances (either in electron density or temperature) in the D region cause significant scattering of VLF waves propagating in the earth-ionosphere waveguide, leading to measurable changes in the amplitude and phase of the VLF waves. We analyze Lightning-induced electron precipitation (LEP) events during period 2008 - 2009 at Belgrade station on subionospheric VLF signals from four transmitters (DHO/23.4 kHz, Germany; GQD/22.1 kHz, UK; NAA/24.0 kHz USA and ICV/20.9 kHz Italy).

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

    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

  16. Toward observationally constrained high space and time resolution CO2 urban emission inventories

    Maness, H.; Teige, V. E.; Wooldridge, P. J.; Weichsel, K.; Holstius, D.; Hooker, A.; Fung, I. Y.; Cohen, R. C.

    2013-12-01

    The spatial patterns of greenhouse gas (GHG) emission and sequestration are currently studied primarily by sensor networks and modeling tools that were designed for global and continental scale investigations of sources and sinks. In urban contexts, by design, there has been very limited investment in observing infrastructure, making it difficult to demonstrate that we have an accurate understanding of the mechanism of emissions or the ability to track processes causing changes in those emissions. Over the last few years, our team has built a new high-resolution observing instrument to address urban CO2 emissions, the BErkeley Atmospheric CO2 Observing Network (BEACON). The 20-node network is constructed on a roughly 2 km grid, permitting direct characterization of the internal structure of emissions within the San Francisco East Bay. Here we present a first assessment of BEACON's promise for evaluating the effectiveness of current and upcoming local emissions policy. Within the next several years, a variety of locally important changes are anticipated--including widespread electrification of the motor vehicle fleet and implementation of a new power standard for ships at the port of Oakland. We describe BEACON's expected performance for detecting these changes, based on results from regional forward modeling driven by a suite of projected inventories. We will further describe the network's current change detection capabilities by focusing on known high temporal frequency changes that have already occurred; examples include a week of significant freeway traffic congestion following the temporary shutdown of the local commuter rail (the Bay Area Rapid Transit system).

  17. MULTIWAVELENGTH OBSERVATIONS OF GRB 110731A: GeV EMISSION FROM ONSET TO AFTERGLOW

    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 ? ? 500-550.

  18. CAN A LONG NANOFLARE STORM EXPLAIN THE OBSERVED EMISSION MEASURE DISTRIBUTIONS IN ACTIVE REGION CORES?

    All theories that attempt to explain the heating of the high-temperature plasma observed in the solar corona are based on short bursts of energy. The intensities and velocities measured in the cores of quiescent active regions, however, can be steady over many hours of observation. One heating scenario that has been proposed to reconcile such observations with impulsive heating models is the 'long nanoflare storm', where short-duration heating events occur infrequently on many sub-resolution strands; the emission of the strands is then averaged together to explain the observed steady structures. In this Letter, we examine the emission measure distribution predicted for such a long nanoflare storm by modeling an arcade of strands in an active region core. Comparisons of the computed emission measure distributions with recent observations indicate that the long nanoflare storm scenario implies greater than five times more 1 MK emission than is actually observed for all plausible combinations of loop lengths, heating rates, and abundances. We conjecture that if the plasma had 'super coronal' abundances, the model may be able to match the observations at low temperatures.

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

    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 obtained from FLEXPART 20-day backward simulations based on ECMWF input data averaged for the period 2006-2012 for all three stations. Black dots represent the corresponding measurement stations.

  20. Solar flares detected by the new narrowband VLF receiver at SANAE IV

    Stephen Meyer

    2011-09-01

    Full Text Available A narrowband receiver was installed at the SANAE IV base in Antarctica to monitor specific very low frequency (VLF radio signals from transmitters around the world. VLF waves propagating through the Earth–Ionosphere Waveguide are excellent probes of the varying properties of the lower region of the ionosphere. This paper describes the set-up of the narrowband system and demonstrates its capabilities with data from a set of solar flares on 08 February and 12 February 2010.

  1. AMI OBSERVATIONS OF THE ANOMALOUS MICROWAVE EMISSION IN THE PERSEUS MOLECULAR CLOUD

    We present observations of the known anomalous microwave emission region, G159.618.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.618.5 at microwave wavelengths. By combining these microwave data with infrared observations between 5.8 and 160 ?m from the Spitzer Space Telescope, we investigate the existence of a microwave-infrared correlation on angular scales of ?2'. We find that the overall correlation appears to increase toward shorter infrared wavelengths, which is consistent with the microwave emission being produced by electric dipole radiation from small, spinning dust grains. We also find that the microwave-infrared correlation peaks at 24 ?m (6.7?), suggesting that the microwave emission is originating from a population of stochastically heated small interstellar dust grains rather than polycyclic aromatic hydrocarbons.

  2. Comparison of seasonal variation between anthropogenic and natural emission inventory and Satellite observation in Southeast Asia

    Kurata, G.; Lalitaporn, P.

    2012-12-01

    Since the economic growth of the countries in Southeast Asia is significantly rapid, the emission of air pollutant from the anthropogenic activity, such as industry, power generation and transportation is rapidly increasing. Moreover, biomass burning due to unsuitable agricultural management, deforestation and expansion of farmland are discharging large amount of pollutants, such as Carbon monoxide, volatile organic compound and particulate matter. Especially, the particulate matter from biomass burning causes the serious haze pollution in surrounding area in Southeast Asia. Furthermore, the biomass fuel used for cooking at residential sector discharges harmful pollutants including a particulate matter, and causes the adverse health impact to people on indoor and outdoor. In this study, we evaluated the spatial distribution and the seasonal variation of emission inventory for Southeast Asia region by comparing with satellite observation data in order to improve the accuracy of the impact assessment of air pollution by regional atmospheric chemistry transport model (WRF and CMAQ). As an emission inventory data, we used our original regional emission inventory for Southeast Asia region developed from detail transportation and industry data sets as well as a several existing emission inventories. As satellite observation data, the vertical column density of NO2, Particulate matter and Carbon monoxide obtained by various satellite, such as GOME, GOME2, SCIAMACY, OMI and so on. As a result of comparisons between satellite observation and emission inventories from 1996 to 2011, in the case of anthropogenic emission, seasonal variation was comparatively well in agreement with the seasonal variation of satellite data. However, the uncertainty of the seasonal variation was large on several large cities. In the case of emission from biomass burning, the seasonal variation was clear, but inter-annual variation was also large due to large scale climate condition.

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

    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

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

    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...

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

    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

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

    Struminsky, A.; Gan, W.

    2015-08-01

    We considered 18 solar flares observed between June 2010 and July 2012, in which high energy >100 MeV ?-emission was registered by the Large Area Telescope (LAT) aboard FermiGRO. We examined for these ?-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 ?0-decay ?-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 y-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 during the impulsive phase of the flare and subsequently trapped by some magnetic structure. In-situ energetic particle measurements by GOES and STEREO (High Energy Telescope, HET) shows that five of these y-events were not accompanied by SEP events at 1 AU, even when multi-point measurements including STEREO are taken into account. Therefore accelerated protons are not always released into the heliosphere. A longer delay between the maximum temperature and the maximum emission measure characterises flares with prolonged high energy ?-emission and solar proton events.

  7. Observationally constraining gravitational wave emission from short gamma-ray burst remnants

    Lasky, Paul D.; Glampedakis, Kostas

    2016-05-01

    Observations of short gamma-ray bursts indicate ongoing energy injection following the prompt emission, with the most likely candidate being the birth of a rapidly rotating, highly magnetized neutron star. We utilize X-ray observations of the burst remnant to constrain properties of the nascent neutron star, including its magnetic field-induced ellipticity and the saturation amplitude of various oscillation modes. Moreover, we derive strict upper limits on the gravitational wave emission from these objects by looking only at the X-ray light curve, showing the burst remnants are unlikely to be detected in the near future using ground-based gravitational wave interferometers, such as Advanced LIGO.

  8. Optical emission and mass spectra observations during hydrogen combustion in atmospheric pressure microwave plasma

    We experimentally investigated hydrogen combustion by atmospheric pressure plasma generated by a 2.45 GHz microwave discharge. Small amounts of hydrogen and oxygen were mixed in the operational argon gas during discharge. To clarify the details of combustion, optical emission was measured. The constituents of combustion-processed gases were observed by a quadruple mass spectrometer. The degree of hydrogen oxidation, the so-called conversion rate, increased with input microwave power. The maximum hydrogen conversion rate was greater than 80% under these experimental conditions. During discharge, an optical emission peak due to OH radicals was observed. (author)

  9. Observation of surface modification and secondary particle emission in HCI-surface interaction

    We have observed secondary particle emission in collision of HCI with Si and HOPG surfaces. For HOPG, we have measured the number of secondary electrons and the number of dot structures on the surface as the imprint of the incidence by STM. The single ion impact is surely observable with almost 100% efficiency by detecting an event of the secondary electron emission. For hydrogen terminated Si(111), H+, H2+, H3+, C+ and Si+ ions have been detected. The proton sputtering yield, which depends on the charge of HCI, has been examined

  10. Observationally constraining gravitational wave emission from short gamma-ray burst remnants

    Lasky, Paul D

    2015-01-01

    Observations of short gamma-ray bursts indicate ongoing energy injection following the prompt emission, with the most likely candidate being the birth of a rapidly rotating, highly magnetised neutron star. We utilise X-ray observations of the burst remnant to constrain properties of the nascent neutron star, including its magnetic field-induced ellipticity and the saturation amplitude of various oscillation modes. Moreover, we derive strict upper limits on the gravitational wave emission from these objects by looking only at the X-ray light curve, showing the burst remnants are unlikely to be detected in the near future using ground-based gravitational wave interferometers such as Advanced LIGO.

  11. Observationally constraining gravitational wave emission from short gamma-ray burst remnants

    Lasky, Paul D.; Glampedakis, Kostas

    2016-02-01

    Observations of short gamma-ray bursts indicate ongoing energy injection following the prompt emission, with the most likely candidate being the birth of a rapidly rotating, highly magnetised neutron star. We utilise X-ray observations of the burst remnant to constrain properties of the nascent neutron star, including its magnetic field-induced ellipticity and the saturation amplitude of various oscillation modes. Moreover, we derive strict upper limits on the gravitational wave emission from these objects by looking only at the X-ray light curve, showing the burst remnants are unlikely to be detected in the near future using ground-based gravitational wave interferometers such as Advanced LIGO.

  12. Resolving Urban to Rural CH4 Emissions Across California with Multi-site Observations

    Fischer, M. L.; Novakovskaia, E.; Jeong, S.; Andrews, A. E.; Bianco, L.; Graven, H. D.; Hsu, Y.; Newman, S.; Vaca, P.; Van Pelt, A. D.; Weiss, R. F.; Keeling, R. F.

    2012-12-01

    Methane emissions are included in California's commitment (Assembly Bill 32) to return total greenhouse gas emissions to 1990 levels by 2020. We will present atmospheric inversion estimates of California's total CH4 emissions for summer 2012, using data from more than a dozen tower sites covering urban and rural areas of California's South Coast Air Basin, Central Valley, San Francisco Bay Area, and North Coast. We use Bayesian inversions to estimate the CH4 emissions from discrete regions of California by combining the local measurements, background CH4 , two 0.1 degree prior model emission maps (one specific to California and one global), and predicted atmospheric transport from WRF-STILT. We quantify site-specific model-measurement uncertainties due to transport using meteorological data from a network of atmospheric profilers and in-situ sensors, due to background using oceanic and aircraft observations, and the prior emissions using the spread results obtained with the two different maps and a prior-free model. We expect the results of this study will significantly improve upon existing work in providing a regionally specific separation of emission from the urban and rural CH4 sources.

  13. On the statistical correlation between the ionospheric perturbations as detected by subionospheric VLF/LF propagation anomalies and earthquakes

    Y. Kasahara

    2008-07-01

    Full Text Available Relatively long-period (4 years data on different propagation paths by means of Japanese-Pacific VLF/LF network observation, are used to obtain further statistical significance on the correlation of ionospheric perturbations as revealed by VLF/LF propagation anomalies with earthquakes. Earthquakes with magnitude greater than 6.0, taken place only within the fifth Fresnel zone of each great-circle path are selected for the correlation study. It is finally found based on the superimposed epoch analysis that the nighttime trend (average amplitude exhibits a significant decrease exceeding 2σ (σ: standard deviation several days before the earthquake and the nighttime fluctuation exceeds the corresponding 2σ again several days before the earthquake when the earthquake depth is smaller than 30 km (shallow earthquakes. However, when we treat all earthquakes including deep earthquakes, the trend shows a significant decrease (just approaching 2σ line, and the nighttime fluctuation shows a less significant broad enhancement before the EQ.

  14. On the effectiveness of the vlf-em method For ground water prospecting in the Basement terrains, Sinai, Egypt

    Shendi, El-Arabi Hendi [العربيى هندي شندي

    1997-01-01

    The VLF-EM method is proved to be an effective, fast and inexpensive tool for ground water prospecting in the basement terrains of Southern Sinai. The resistive shallow alluvial deposits increase the penetration depth of the received VLF waves to as deep as 40 meters which is very reasonable to detect the water bearing alluvium in the studied areas. The measured horizontal and vertical components of the resultant VLF-EM field were used to calculate the apparent resistivities of the conductive...

  15. Coronal loop hydrodynamics. The solar flare observed on November 12, 1980 revisited: The UV line emission

    Betta, R. M.; Peres, G.; Reale, F.; Serio, S.

    2001-12-01

    We revisit a well-studied solar flare whose X-ray emission originating from a simple loop structure was observed by most of the instruments on board SMM on November 12, 1980. The X-ray emission of this flare, as observed with the XRP, was successfully modeled previously. Here we include a detailed modeling of the transition region and we compare the hydrodynamic results with the UVSP observations in two EUV lines, measured in areas smaller than the XRP rasters, covering only some portions of the flaring loop (the top and the foot-points). The single loop hydrodynamic model, which fits well the evolution of coronal lines (those observed with the XRP and the Fe XXI 1354.1 line observed with the UVSP) fails to model the flux level and evolution of the O V 1371.3 line.

  16. Validation of the Swiss methane emission inventory by atmospheric observations and inverse modelling

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

    2016-03-01

    Atmospheric inverse modelling has the potential to provide observation-based estimates of greenhouse gas emissions at the country scale, thereby allowing for an independent validation of national emission inventories. Here, we present a regional-scale inverse modelling study to quantify the emissions of methane (CH4) from Switzerland, making use of the newly established CarboCount-CH measurement network and a high-resolution Lagrangian transport model. In our reference inversion, prior emissions were taken from the "bottom-up" Swiss Greenhouse Gas Inventory (SGHGI) as published by the Swiss Federal Office for the Environment in 2014 for the year 2012. Overall we estimate national CH4 emissions to be 196 ± 18 Gg yr-1 for the year 2013 (1σ uncertainty). This result is in close agreement with the recently revised SGHGI estimate of 206 ± 33 Gg yr-1 as reported in 2015 for the year 2012. Results from sensitivity inversions using alternative prior emissions, uncertainty covariance settings, large-scale background mole fractions, two different inverse algorithms (Bayesian and extended Kalman filter), and two different transport models confirm the robustness and independent character of our estimate. According to the latest SGHGI estimate the main CH4 source categories in Switzerland are agriculture (78 %), waste handling (15 %) and natural gas distribution and combustion (6 %). The spatial distribution and seasonal variability of our posterior emissions suggest an overestimation of agricultural CH4 emissions by 10 to 20 % in the most recent SGHGI, which is likely due to an overestimation of emissions from manure handling. Urban areas do not appear as emission hotspots in our posterior results, suggesting that leakages from natural gas distribution are only a minor source of CH4 in Switzerland. This is consistent with rather low emissions of 8.4 Gg yr-1 reported by the SGHGI but inconsistent with the much higher value of 32 Gg yr-1 implied by the EDGARv4.2 inventory for this sector. Increased CH4 emissions (up to 30 % compared to the prior) were deduced for the north-eastern parts of Switzerland. This feature was common to most sensitivity inversions, which is a strong indicator that it is a real feature and not an artefact of the transport model and the inversion system. However, it was not possible to assign an unambiguous source process to the region. The observations of the CarboCount-CH network provided invaluable and independent information for the validation of the national bottom-up inventory. Similar systems need to be sustained to provide independent monitoring of future climate agreements.

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

    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

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

    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.

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

    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 model was driven by analysis fields from the non-hydrostatic numerical weather predication model COSMO at horizontal resolutions of up to 7 km x 7 km. As a result spatially resolved, annual mean CH4 fluxes for Switzerland were obtained. In general total Swiss CH4 emission remained close to the 'bottom-up' estimates, while considerable shifts in the regional distribution of the emissions were obtained. Reductions in CH4 emissions, as compared to the prior estimates, were established in regions with large emissions from ruminants, while increases resulted in the Western part of the Swiss Plateau, which is dominated by mixture of large water bodies and crop and vegetable farming. Sensitivity inversions were applied to assess the overall robustness and the uncertainty of the inversion system.

  20. GRB 050713A: High Energy Observations of the GRB Prompt and Afterglow Emission

    Morris, D C; Burrows, D N; Falcone, A D; Galante, N; Garczarczyk, M; Gaug, M; Gehrels, N; Godet, O; Krimm, H; Mizobuchi, S; Pagani, C; Palshin, V D; Reeves, J; Stamerra, A; Teshima, M

    2006-01-01

    Swift discovered GRB 050713A and slewed promptly to begin observing with its narrow field instruments 72.6 seconds after the burst onset, while the prompt gamma-ray emission was still detectable in the BAT. Simultaneous emission from two flares is detected in the BAT and XRT. This burst marks just the second time that the BAT and XRT have simultaneously detected emission from a burst and the first time that both instruments have produced a well sampled, simultaneous dataset covering multiple X-ray flares. The temporal rise and decay parameters of the flares are consistent with the internal shock mechanism. In addition to the Swift coverage of GRB 050713A, we report on the Konus-Wind (K-W) detection of the prompt emission in the energy range 18-1150 keV, an upper limiting GeV measurement of the prompt emission made by the MAGIC imaging atmospheric Cherenkov telescope and XMM-Newton observations of the afterglow. Simultaneous observation between Swift XRT and XMM-Newton produce consistent results, showing a bre...

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

    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.

  2. Worldwide biogenic soil NOx emissions inferred from OMI NO2 observations

    Vinken, G. C. M.; Boersma, K. F.; Maasakkers, J. D.; Adon, M.; Martin, R. V.

    2014-09-01

    Biogenic NOx emissions from soils are a large natural source with substantial uncertainties in global bottom-up estimates (ranging from 4 to 15 Tg N yr-1). We reduce this range in emission estimates, and present a top-down soil NOx emission inventory for 2005 based on retrieved tropospheric NO2 columns from the Ozone Monitoring Instrument (OMI). We use a state-of-science soil NOx emission inventory (Hudman et al., 2012) as a priori in the GEOS-Chem chemistry transport model to identify 11 regions where tropospheric NO2 columns are dominated by soil NOx emissions. Strong correlations between soil NOx emissions and simulated NO2 columns indicate that spatial patterns in simulated NO2 columns in these regions indeed reflect the underlying soil NOx emissions. Subsequently, we use a mass-balance approach to constrain emissions for these 11 regions on all major continents using OMI observed and GEOS-Chem simulated tropospheric NO2 columns. We find that responses of simulated NO2 columns to changing NOx emissions are suppressed over low NOx regions, and account for these non-linearities in our inversion approach. In general, our approach suggests that emissions need to be increased in most regions. Our OMI top-down soil NOx inventory amounts to 10.0 Tg N for 2005 when only constraining the 11 regions, and 12.9 Tg N when extrapolating the constraints globally. Substantial regional differences exist (ranging from -40% to +90%), and globally our top-down inventory is 4-35% higher than the GEOS-Chem a priori (9.6 Tg N yr-1). We evaluate NO2 concentrations simulated with our new OMI top-down inventory against surface NO2 measurements from monitoring stations in Africa, the USA and Europe. Although this comparison is complicated by several factors, we find an encouraging improved agreement when using the OMI top-down inventory compared to using the a priori inventory. To our knowledge, this study provides, for the first time, specific constraints on soil NOx emissions on all major continents using OMI NO2 columns. Our results rule out the low end of reported soil NOx emission estimates, and suggest that global emissions are most likely around 12.9 3.9 Tg N yr-1.

  3. PANCHROMATIC OBSERVATIONS OF THE TEXTBOOK GRB 110205A: CONSTRAINING PHYSICAL MECHANISMS OF PROMPT EMISSION AND AFTERGLOW

    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 gamma-ray burst (GRB) was still radiating in the γ-ray band, with optical light curve showing correlation with γ-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to γ-ray (1 eV to 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution during the prompt emission phase. In particular, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard synchrotron emission model in the fast cooling regime. Shortly after prompt emission (∼1100 s), a bright (R = 14.0) optical emission hump with very steep rise (α ∼ 5.5) was observed, which we interpret as the reverse shock (RS) emission. It is the first time that the rising phase of an RS component has been closely observed. The full optical and X-ray afterglow light curves can be interpreted within the standard reverse shock (RS) + forward shock (FS) model. In general, the high-quality prompt and afterglow data allow us to apply the standard fireball model to extract valuable information, including the radiation mechanism (synchrotron), radius of prompt emission (RGRB ∼ 3 × 1013 cm), initial Lorentz factor of the outflow (Γ0 ∼ 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

  4. Fermi Large Area Telescope observation of high-energy solar flares: constraining emission scenarios

    Omodei, Nicola; Pesce-Rollins, Melissa; Petrosian, Vahe; Liu, Wei; Rubio da Costa, Fatima

    2015-08-01

    The Fermi Large Area Telescope (LAT) is the most sensitive instrument ever deployed in space for observing gamma-ray emission >100 MeV. This has also been demonstrated by its detection of quiescent gamma-ray emission from pions produced by cosmic-ray protons interacting in the solar atmosphere, and from cosmic-ray electron interactions with solar optical photons. The Fermi LAT has also detected high-energy gamma-ray emission associated with GOES M-class and X-class X-ray flares, each accompanied by a coronal mass ejection and a solar energetic particle event increasing the number of detected solar flares by almost a factor of 10 with respect to previous space observations. During the impulsive phase, gamma rays with energies up to several hundreds of MeV have been recorded by the LAT. Emission up to GeV energies lasting several hours after the flare has also been recorded by the LAT. Of particular interest are the recent detections of two solar flares whose position behind the limb was confirmed by the STEREO-B satellite. 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.

  5. Modelling of X-ray emission supernova remnants observed by the European satellite XMM-Newton

    This thesis deals with the X-ray emission of supernova remnants (SNRs) observed by the European satellite XMM-Newton. In SNRs, the matter heated to millions of degrees shines brightly in X-rays. This emission depends on the hydrodynamical evolution of the SNR, on the chemical composition of the ejected matter and on the ambient medium. Moreover, the blast-wave is considered to be the prime site of the production and the acceleration of cosmic-rays in our Galaxy. XMM-Newton is one of the first to allow the investigation of these different aspects thanks to its spatially-resolved spectroscopy and its very good sensitivity. l first studied Kepler's SNR (SN 1604) whose X-ray emission is dominated by the ejecta. Its observation has allowed to obtain information on the nucleosynthesis products, on their spatial distribution and on the temperature structure in the shocked ejecta. This gives strong constraints on the physics of the explosion and on the progenitor's type. l have shown also that the X-ray emission at the shock is likely to be non-thermal. Then, l studied the SNR G347.3-0.5 whose X-ray emission is entirely due to the synchrotron radiation of relativistic (TeV) electrons accelerated at the shock. From five pointing, l made a full mapping of the X-ray emission characteristics (brightness, absorption and spectral index) at small scale. Combined to radio observations, these results have indicated a clear interaction between the SNR and molecular clouds located at 1 kpc and not at 6 kpc as previously estimated. Lastly, in the framework of a self-similar hydrodynamical model coupled with non-linear particle acceleration, l have obtained the synchrotron emission profile in SNRs, including the adiabatic and radiative losses of the accelerated electrons. (author)

  6. Long Wavelength Observations of Thermal Emission from Pluto and Charon with ALMA

    Butler, Bryan J.; Gurwell, Mark; Lellouch, Emmanuel; Moullet, Arielle; Moreno, Raphael; Bockelee-Morvan, Dominique; Biver, Nicolas; Fouchet, Thierry; Lis, Darek; Stern, Alan; Young, Leslie; Young, Eliot; Weaver, Hal; Boissier, Jeremie; Stansberry, John

    2015-11-01

    Long wavelength observations of Pluto can determine atmospheric temperatures, abundances, and vertical distributions for those molecules that have transitions at these wavelengths. In addition, observations of both Pluto and Charon can elucidate their surface and subsurface temperatures and surface compositions (and distribution, with enough resolution). We have used the Atacama Large Millimeter Array (ALMA) to observe the CO and HCN in the atmosphere of Pluto, and to observe thermal emission from the two bodies, where the resolution is enough to separate them (but not enough to resolve each individually). We report here on the thermal emission observations, and separately at this meeting on the CO [1] and HCN [2] observations. We observed the Pluto/Charon system with ALMA on June 12 and 13, 2015, at a wavelength of ~0.86 mm. Both days provide separate observations of the thermal emission from Pluto and Charon. We find a preliminary value of the brightness temperature of the two bodies of 35 K and 46 K with variation of less than 1 K between the two days and SNR of > 300 for Pluto and > 100 for Charon. This is similar to previous observations of the separate thermal emission of the two bodies with the Submillimeter Array (SMA) [3] and Very Large Array (VLA) [4]. We will discuss the implications of these measured brightness temperatures and the apparent lack of significant variation between the two days (longitudes).[1] Gurwell et al., this meeting. [2] Lellouch et al., this meeting. [3] Gurwell & Butler, BAAS 37, 2005. [4] Butler et al. BAAS 43, 2010.

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

    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 extended atmospheric transport model can be easily determined. Further, with the same singular vector analysis of the efficiency of observations, the sensitivity of observations can be identified by determining the directions of maximum perturbation. Finally, a 3D advection-diffusion toy model is presented to test the approach.

  8. Measurements at Trinidad Head, California during ITCT 2K2: Were Asian emissions observed?

    Goldstein, A. H.; Millet, D. B.; McKay, M.

    2002-12-01

    Measurements for a wide suite of trace gases and aerosols were made at Trinidad Head, California, from 19 April through 22 May 2002 as part of the NOAA ITCT research program. This talk will provide an introduction to the ITCT ground site, and will address one of the major scientific questions for the measurement campaign: What is the influence of Asian emissions on air masses entering North America in springtime? CO has been identified as one of the most useful tracers to look for Asian emission plumes because of its relatively long atmospheric lifetime and its emission from all combustion sources. Before assessing the influence of long range transport on the observations, local/regional influences must be filtered out of the data set. Methyl Tertiary Butyl Ether (MTBE) serves as a useful tracer because its emissions are associated with use as a fossil fuel additive in North America and its atmospheric lifetime is a few days. CO2 and radon also serve as useful tracers of regional continental influences, particularly at night when their concentrations are enhanced due to emissions under stable atmospheric conditions. Filtering out local influences removed 25 to 50% of the observations, depending on the constraints applied, and it decreased the mean CO mixing ratio by 4% to 147 ppb. After filtering the data to remove local influences, the variability and the absolute concentration in the remaining CO data can be examined for Asian influence by comparison with forecast models run as part of the ITCT campaign such as GEOS-CHEM (Harvard), MOZART (NCAR), and CFORS (IOWA). The observed variability in the filtered CO data is in general well simulated by the models, showing a dominant influence from North American fossil fuel emissions. Distinct Asian pollution plumes could not be identified in these ground based observations, because the magnitude of CO variability due to Asian emissions was small relative to the total observed variability. However, the relative contributions of emission sources to the total observed CO could be approximated through comparison of the measurements and model results. Comparison of all the ground based trace gas and aerosol measurements with the model results should utilize similar techniques to remove local influences that are unlikely to be captured by the models. Filtering out local influences decreases mean concentrations of aerosols and ozone precursors such as volatile organic compounds and oxides of nitrogen, but it increases the mean concentration of ozone.

  9. Validation of the Swiss methane emission inventory by atmospheric observations and inverse modelling

    Henne, S.; Brunner, D.; Oney, B.; Leuenberger, M.; Eugster, W.; Bamberger, I.; Meinhardt, F.; Steinbacher, M.; Emmenegger, L.

    2015-12-01

    Atmospheric inverse modelling has the potential to provide observation-based estimates of greenhouse gas emissions at the country scale, thereby allowing for an independent validation of national emission inventories. Here, we present a regional scale inverse modelling study to quantify the emissions of methane (CH4) from Switzerland, making use of the newly established CarboCount-CH measurement network and a high resolution Lagrangian transport model. Overall we estimate national CH4 emissions to be 196 18 Gg yr-1 for the year 2013 (1? uncertainty). This result is in close agreement with the recently revised "bottom-up" estimate of 206 33 Gg yr-1 published by the Swiss Federal Office for the Environment as part of the Swiss Greenhouse Gas Inventory (SGHGI). Results from sensitivity inversions using alternative prior emissions, covariance settings, baseline treatments, two different inverse algorithms (Bayesian and extended Kalman Filter), and two different transport models confirms the robustness and independent character of our estimate. According to the latest "bottom-up" inventory the main CH4 source categories in Switzerland are agriculture (78 %), waste handling (15 %) and natural gas distribution and combustion (6 %). The spatial distribution and seasonal variability of our posterior emissions suggest an overestimation of agricultural CH4 emissions by 10 to 20 % in the most recent national inventory, which is likely due to an overestimation of emissions from manure handling. Urban areas do not appear as emission hotspots in our posterior results suggesting that leakages from natural gas disribution are only a minor source of CH4 in Switzerland. This is consistent with rather low emissions of 8.4 Gg yr-1 reported by the SGHGI but inconsistent with the much higher value of 32 Gg yr-1 implied by the EDGARv4.2 inventory for this sector. Increased CH4 emissions (up to 30 % compared to the prior) were deduced for the north-eastern parts of Switzerland. This feature was common to most sensitivity inversions, which rules out an artefact of the transport model and the inversion system. However, it was not possible to assign an unambiguous source process to the region. The observations of the CarboCount-CH network provided invaluable and independent information for the validation of the national bottom-up inventory. Similar systems need to be sustained to provide independent monitoring of future climate agreements.

  10. Quantifying global terrestrial methanol emissions using observations from the TES satellite sensor

    K. C. Wells

    2013-08-01

    Full Text Available We employ new global space-based measurements of atmospheric methanol from the Tropospheric Emission Spectrometer (TES with the adjoint of the GEOS-Chem chemical transport model to quantify terrestrial emissions of methanol to the atmosphere. Biogenic methanol emissions in the model are based on MEGANv2.1 emission algorithms, using MODIS leaf area and GEOS-5 assimilated meteorological fields. We first carry out a pseudo observation test to validate the overall approach, and find that the TES sampling density is sufficient to accurately quantify regional- to continental-scale methanol emissions using this method. A global inversion of two years of TES data yields an optimized annual global surface flux of 117 Tg yr−1 (including biogenic, pyrogenic, and anthropogenic sources, an increase of 56% from the a priori global flux of 75 Tg yr−1. Global terrestrial methanol emissions are thus approximately 25% those of isoprene (~540 Tg yr−1, and are comparable to the combined emissions of all anthropogenic volatile organic compounds (~100–200 Tg yr−1. Our a posteriori terrestrial methanol source leads to a strong improvement of the simulation relative to an ensemble of airborne observations, and corroborates two other recent top-down estimates (114–120 Tg yr−1 derived using in-situ and space-based measurements. The TES data imply a relatively modest revision of model emissions over most of the tropics, but a significant upward revision in midlatitudes, particularly over Europe and North America. We interpret the inversion results in terms of specific source types using the methanol:CO correlations measured by TES, and find that biogenic emissions are overestimated relative to biomass burning and anthropogenic emissions in central Africa and southeastern China, while they are underestimated in regions such as Brazil and the US. Based on our optimized emissions, methanol accounts for >25% of the photochemical source of CO and HCHO over many parts of the northern extratropics during springtime, and contributes ~6% of the global secondary source of those compounds annually.

  11. Quantifying global terrestrial methanol emissions using observations from the TES satellite sensor

    Wells, K. C.; Millet, D. B.; Cady-Pereira, K. E.; Shephard, M. W.; Henze, D. K.; Bousserez, N.; Apel, E. C.; de Gouw, J.; Warneke, C.; Singh, H. B.

    2014-03-01

    We employ new global space-based measurements of atmospheric methanol from the Tropospheric Emission Spectrometer (TES) with the adjoint of the GEOS-Chem chemical transport model to quantify terrestrial emissions of methanol to the atmosphere. Biogenic methanol emissions in the model are based on version 2.1 of the Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1), using leaf area data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and GEOS-5 assimilated meteorological fields. We first carry out a pseudo observation test to validate the overall approach, and find that the TES sampling density is sufficient to accurately quantify regional- to continental-scale methanol emissions using this method. A global inversion of two years of TES data yields an optimized annual global surface flux of 122 Tg yr-1 (including biogenic, pyrogenic, and anthropogenic sources), an increase of 60% from the a priori global flux of 76 Tg yr-1. Global terrestrial methanol emissions are thus nearly 25% those of isoprene (~540 Tg yr-1), and are comparable to the combined emissions of all anthropogenic volatile organic compounds (~100-200 Tg yr-1). Our a posteriori terrestrial methanol source leads to a strong improvement of the simulation relative to an ensemble of airborne observations, and corroborates two other recent top-down estimates (114-120 Tg yr-1) derived using in situ and space-based measurements. Inversions testing the sensitivity of optimized fluxes to model errors in OH, dry deposition, and oceanic uptake of methanol, as well as to the assumed a priori constraint, lead to global fluxes ranging from 118 to 126 Tg yr-1. The TES data imply a relatively modest revision of model emissions over most of the tropics, but a significant upward revision in midlatitudes, particularly over Europe and North America. We interpret the inversion results in terms of specific source types using the methanol : CO correlations measured by TES, and find that biogenic emissions are overestimated relative to biomass burning and anthropogenic emissions in central Africa and southeastern China, while they are underestimated in regions such as Brazil and the US. Based on our optimized emissions, methanol accounts for > 25% of the photochemical source of CO and HCHO over many parts of the northern extratropics during springtime, and contributes ~6% of the global secondary source of those compounds annually.

  12. Multiwavelength Observations of AGN Jets: Untangling the Coupled Problems of Emission Mechanism and Jet Structure

    Perlman, Eric S.; Avachat, Sayali S.; Clautice, Devon; Georganopoulos, Markos; Meyer, Eileen; Cara, Mihai

    2016-04-01

    The discovery of X-ray and optical emission from large numbers of AGN jets is one of the key legacies of the Chandra X-ray Observatory and Hubble Space Telescope. Several dozen optical and X-ray emitting jets are now known, most of which are seen in both bands as well as in the radio, where they were first discovered. Jets carry prodigious amounts of energy and mass out from the nuclear regions out to tens to hundreds of kiloparsecs distant from the central black hole, depositing it into the host galaxy and cluster. Interpreting their multiwavelength emissions has not been easy: while in most jets, the optical and radio emission in many objects is believed to emerge via the synchrotron process, due to its characteristic spectral shape and high radio polarization, the X-ray emission has been a tougher nut to crack. In less powerful, FR I jets, such as M87, the X-ray emission is believed to be synchrotron emission from the highest energy electrons, requiring in situ particle acceleration due to the short radiative lifetimes of the particles. However, in FR II and quasar jets, a variety of emission mechanisms are possible. Until the last few years, the leading interpretation had been inverse-Comptonization of Cosmic Microwave Background photons (the IC/CMB mechanism). This requires the jet to be relativistic out to hundreds of kiloparsecs from the nucleus, and requires an electron spectrum that extends to very low Lorentz factors. However, that now appears less likely, due to observed high optical polarizations in jets where the optical and X-ray emission appears to lie on the same spectral component, as well as limits derived from Fermi observations in the GeV gamma-rays. It now appears more likely that the X-rays must arise as synchrotron emission from a second, high energy electron population. With this revelation, we must tackle anew the coupling between jet structure and emission mechanisms. Multiwavelength imaging and polarimetry can give us clues to the locations of the radiating particles in each band, as well as their kinematics and the jet's structure. We discuss new work that describes how observations in several bands can be knit together to form a more coherent picture of jet physics.

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

    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 emission estimates. Finally, NH3 observations from the TES instrument on NASA Aura satellite were validated with mobile measurements and aircraft observations. Improved validations will help to constrain NH3 emissions at continental to global scales. Ultimately, these efforts will improve the understanding of NH3 emissions from all scales, with implications on the global nitrogen cycle and atmospheric chemistry-climate interactions.

  14. Airborne Ethane Observations in the Barnett Shale: Quantification of Ethane Flux and Attribution of Methane Emissions.

    Smith, Mackenzie L; Kort, Eric A; Karion, Anna; Sweeney, Colm; Herndon, Scott C; Yacovitch, Tara I

    2015-07-01

    We present high time resolution airborne ethane (C2H6) and methane (CH4) measurements made in March and October 2013 as part of the Barnett Coordinated Campaign over the Barnett Shale formation in Texas. Ethane fluxes are quantified using a downwind flight strategy, a first demonstration of this approach for C2H6. Additionally, ethane-to-methane emissions ratios (C2H6:CH4) of point sources were observationally determined from simultaneous airborne C2H6 and CH4 measurements during a survey flight over the source region. Distinct C2H6:CH4 100% molar ratios of 0.0%, 1.8%, and 9.6%, indicative of microbial, low-C2H6 fossil, and high-C2H6 fossil sources, respectively, emerged in observations over the emissions source region of the Barnett Shale. Ethane-to-methane correlations were used in conjunction with C2H6 and CH4 fluxes to quantify the fraction of CH4 emissions derived from fossil and microbial sources. On the basis of two analyses, we find 71-85% of the observed methane emissions quantified in the Barnett Shale are derived from fossil sources. The average ethane flux observed from the studied region of the Barnett Shale was 6.6 0.2 10(3) kg hr(-1) and consistent across six days in spring and fall of 2013. PMID:26148554

  15. Observations of the 145.5 micron [O I] emission line in the Orion Nebula

    We have obtained a first set of observations of the [O I] 3P0 -3P1 (145.5 μm) transition. We observed the line both in a 1' x 1' beam centered on the Trapezium and in a 7' x 7' beam encompassing most of the Orion Nebula. We also have constructed a wide-beam (7' x 7') map of the region which shows that most of the emission is confined to the central regions of the nebula. These observations may be compared with reported measurement of the 3P1-3P2 (63.2 μm) transition in Orion and are consistent with optically thin emission in the 145.5 μm line and self-absorbed 63.2 μm emission lines. We discuss mechanisms for the excitation of neutral oxygen and conclude that much of the observed emission originates in the thin, radio recombination line-emitting C II/H I envelope bordering on the H II region

  16. Fermi-LAT Observation of Increased Gamma-ray Emission from the Microquasar Cygnus X-3

    Loh, Alan; Corbel, Stephane; Dubus, Guillaume; Corbet, Robin

    2016-01-01

    Recently, the hard X-ray emission from the high-mass X-ray binary Cygnus X-3 has drastically dropped since 2016 Jan 11 (MJD 57398, as observed by Swift/BAT http://swift.gsfc.nasa.gov/results/transients/CygX-3/, Krimm et al. 2013, ApJS 209, 14) indicating a possible transition to the soft state.

  17. The observation of chemiluminescent NiO* emissions in the laboratory and in the night airglow

    A. L. Broadfoot

    2011-04-01

    Full Text Available The recent finding of an orange spectral feature in OSIRIS/Odin spectra of the night airglow near 85 km has raised interest in the origin of the emission. The feature was positively identified as the chemiluminescent FeO* emission where the iron is of meteoric origin. Since the meteorite source of atomic metals in the mesosphere contains both iron and nickel, with Ni being typically 6% of Fe, it is expected that faint emissions involving Ni should also be present in the night airglow. The present study summarizes the laboratory observations of chemiluminescent NiO* emissions and includes a search for the NiO* signature in the night airglow. A faint previously unidentified "continuum" extending longwave of 440 nm has been identified in night airglow spectra obtained with two space-borne limb viewing instruments and through a comparison with laboratory spectra this continuum is identified as arising from the NiO* emission. The FeO* and NiO* emissions both originate from a reaction of the metal atoms with mesospheric ozone and so support the presence of NiO* in the night airglow.

  18. THE IMPORTANCE OF NEBULAR CONTINUUM AND LINE EMISSION IN OBSERVATIONS OF YOUNG MASSIVE STAR CLUSTERS

    In this spectroscopic study of infant massive star clusters, we find that continuum emission from ionized gas rivals the stellar luminosity at optical wavelengths. In addition, we find that nebular line emission is significant in many commonly used broadband Hubble Space Telescope (HST) filters including the F814W I-band, the F555W V-band, and the F435W B-band. Two young massive clusters (YMCs) in the nearby starburst galaxy NGC 4449 were targeted for follow-up spectroscopic observations after Reines et al. discovered an F814W I-band excess in their photometric study of radio-detected clusters in the galaxy. The spectra were obtained with the Dual Imaging Spectrograph (DIS) on the 3.5 m Apache Point Observatory (APO) telescope and have a spectral range of ?3800-9800 A. We supplement these data with HST and Sloan Digital Sky Survey photometry of the clusters. By comparing our data to the Starburst99 and GALEV evolutionary synthesis models, we find that nebular continuum emission competes with the stellar light in our observations and that the relative contribution from the nebular continuum is largest in the U- and I-bands, where the Balmer (3646 A) and Paschen jumps (8207 A) are located. The spectra also exhibit strong line emission including the [S III] ??9069, 9532 lines in the HST F814W I-band. We find that the combination of nebular continuum and line emission can account for the F814W I-band excess previously found by Reines et al. In an effort to provide a benchmark for estimating the impact of ionized gas emission on photometric observations of young massive stellar populations, we compute the relative contributions of the stellar continuum, nebular continuum, and emission lines to the total observed flux of a 3 Myr old cluster through various HST filter/instrument combinations, including filters in the Wide Field Camera 3. We urge caution when comparing observations of YMCs to evolutionary synthesis models since nebular continuum and line emission can have a large impact on magnitudes and colors of young (?<5 Myr) clusters, significantly affecting inferred properties such as ages, masses and extinctions.

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

    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 ...

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

    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...

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

    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 0.2500.362 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.

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

    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.

  3. Electron beam injection during active experiments. I - Electromagnetic wave emissions

    Winglee, R. M.; Kellogg, P. J.

    1990-01-01

    The wave emissions produced in Echo 7 experiment by active injections of electron beams were investigated to determine the properties of the electromagnetic and electrostatic fields for both the field-aligned and cross-field injection in such experiments and to evaluate the sources of free energy and relative efficiencies for the generation of the VLF and HF emissions. It is shown that, for typical beam energies in active experiments, electromagnetic effects do not substantially change the bulk properties of the beam, spacecraft charging, and plasma particle acceleration. Through simulations, beam-generated whistlers; fundamental z-mode and harmonic x-mode radiation; and electrostatic electron-cyclotron, upper-hybrid, Langmuir, and lower-hybrid waves were identified. The characteristics of the observed wave spectra were found to be sensitive to both the ratio of the electron plasma frequency to the cyclotron frequency and the angle of injection relative to the magnetic field.

  4. Observation of extreme ultraviolet hydrogen emission from incandescently heated hydrogen gas with certain catalysts

    Mills, R.L.; Dong, J.; Lu, Y. [BlackLight Power, Inc., Cranbury, NJ (United States)

    2000-10-01

    Typically the emission of extreme ultraviolet light from hydrogen gas is achieved via a discharge at high voltage, a high power inductively coupled plasma, or a plasma created and heated to extreme temperatures by RF coupling (e.g. > 10{sup 6} K) with confinement provided by a toroidal magnetic field. We report the observation of intense extreme ultraviolet (EUV) emission at low temperatures (e.g. <10{sup 3} K) from atomic hydrogen and certain atomized pure elements or certain gaseous ions which ionize at integer multiples of the potential energy of atomic hydrogen. (Author)

  5. RXTE Observation of PSR B1706-44 and Implications for Theoretical Models of Pulsar Emission

    Ray, A.; Harding, A. K.; Strickman, M. S.

    1998-01-01

    We report on results of an observation with the Rossi X-Ray Timing Explorer (RXTE) of PSR B1706-44 with a live time of 132 ks, to search for pulsed X-ray emission. PSR B1706-44 is a radio and high-energy gamma-ray pulsar (detected by EGRET), but no pulsed emission has been detected in the X-ray band. Since most of the other known gamma-ray pulsars emit pulsed X-rays, it is expected that PSR B1706-44 would also be an X-ray pulsar. However, while the ROSAT PSPC detected a source at the pulsar p...

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

    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, ...

  7. Observation of stimulated emission pumping spectra of jet-cooled NCS and C 3

    Northrup, F. J.; Sears, Trevor J.

    1989-07-01

    The observation of stimulated emission pumping (SEP) spectra of free-jet-cooled NCS and C 3 is reported. These species were generated by UV laser photolysis of a suitable precursor molecule in a large excess of inert gas in the throat of a supersonic free jet expansion. Individual rotational lines in the cold laser-induced fluorescence excitation spectrum were pumped and stimulated emission induced using two dye lasers pumped by a single excimer laser. The technique should be of general use in measuring vibronic level spacings in the ground electronic state of small free radicals.

  8. Chandra Observations of Nuclear X-ray Emission from a Sample of Radio Sources

    Gambill, J. K.; Sambruna, R. M.; Chartas, G.; Cheung, C. C.; L. Maraschi; Tavecchio, F.; Urry, C. M.; Pesce, J. E.

    2003-01-01

    We present the X-ray properties of a sample of 17 radio sources observed with the Chandra X-ray Observatory as part of a project aimed at studying the X-ray emission from their radio jets. In this paper, we concentrate on the X-ray properties of the unresolved cores. The sample includes 16 quasars (11 core-dominated and 5 lobe-dominated) in the redshift range z=0.30--1.96, and one low-power radio-galaxy at z=0.064. No diffuse X-ray emission is present around the cores of the quasars, except f...

  9. Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations

    Paulot, F.; Jacob, D. J.; Johnson, M. T.; Bell, T. G.; Baker, A. R.; Keene, W. C.; Lima, I. D.; Doney, S. C.; Stock, C. A.

    2015-08-01

    Current global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a-1, much lower than current literature values (7-23 TgN a-1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a-1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2-5 TgN a-1, comparable in magnitude to other natural sources from open fires and soils.

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

    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...

  11. Ultraviolet and Extreme-Ultraviolet Emissions at the Flare Footpoints Observed by Atmosphere Imaging Assembly

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

    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 A 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 the Atmosphere Imaging Assembly 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 approximate steady-state conditions are established in the loop. UV and EUV light curves of individual pixels may therefore be separated into contributions from two distinct physical mechanisms to shed light on the nature of energy transport in a flare.We demonstrate this technique using coordinated, spatially resolved observations of UV and EUV emissions from the footpoints of a C3.2 thermal flare.

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

    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...

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

    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.

  14. Hard X-ray emission from Serpens X-1 as observed by INTEGRAL

    Masetti, N.; Foschini, L.; Palazzi, E; Amati, L.; E. CAROLI; Di Cocco, G.; Frontera, F.; Orlandini, M

    2004-01-01

    We here report results of an INTEGRAL observation of the X-ray burst and atoll source Ser X-1 performed on May 2003. The object was observed for a total of 400 ks but nearly 8 degrees off-axis due to the amalgamation with an observation of SS 433, the pointing target source. Ser X-1 was detected up to 30 keV with unprecedented positional accuracy for a high-energy emission; a sharp spectral drop is evident beyond this energy. Significant variability is seen in the 20-30 keV light curve. Compa...

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

    Mebust, A. K.; Cohen, R. C.

    2014-03-01

    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 of NOx 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 (with 95% confidence) from the mean EC for the associated biome, and a similar number of ecoregion ECs falls outside the range of all mean biome ECs, implying that there are some regions where fuel type-specific global emission parameterizations fail to capture local fire NOx emissions.

  16. NOx lifetimes and emissions of cities and power plants in polluted background estimated by satellite observations

    Liu, Fei; Beirle, Steffen; Zhang, Qiang; Dörner, Steffen; He, Kebin; Wagner, Thomas

    2016-04-01

    We present a new method to quantify NOx emissions and corresponding atmospheric lifetimes from OMI NO2 observations together with ECMWF wind fields without further model input for sources located in a polluted background. NO2 patterns under calm wind conditions are used as proxy for the spatial patterns of NOx emissions, and the effective atmospheric NOx lifetime is determined from the change of spatial patterns measured at larger wind speeds. Emissions are subsequently derived from the NO2 mass above the background, integrated around the source of interest. Lifetimes and emissions are estimated for 17 power plants and 53 cities located in non-mountainous regions across China and the USA. The derived lifetimes for the ozone season (May-September) are 3.8 ± 1.0 h (mean ± standard deviation) with a range of 1.8 to 7.5 h. The derived NOx emissions show generally good agreement with bottom-up inventories for power plants and cities. Regional inventory shows better agreement with top-down estimates for Chinese cities compared to global inventory, most likely due to different downscaling approaches adopted in the two inventories.

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

    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 with localized absorption of HF waves in the ionospheric D layer enhanced by the energetic particle precipitation.

  18. Herschel HIFI observations of O2 toward Orion: special conditions for shock enhanced emission

    We report observations of molecular oxygen (O2) rotational transitions at 487 GHz, 774 GHz, and 1121 GHz toward Orion Peak A. The O2 lines at 487 GHz and 774 GHz are detected at velocities of 10-12 km s–1 with line widths ∼3 km s–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 O2 emission is ≅9'' (6 × 1016 cm) in size, and is located close to the H 2 Peak 1 position (where vibrationally excited H2 emission peaks), and not at Peak A, 23'' away. The peak O2 column density is ≅1.1 × 1018 cm–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 O2 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 × 104 cm–3, if a reasonable flux of UV radiation is present. The postshock O2 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 O2 emission has not been detected in the cores of other massive star-forming molecular clouds.

  19. Herschel HIFI Observations of O2 toward Orion: Special Conditions for Shock Enhanced Emission

    Chen, Jo-Hsin; Goldsmith, Paul F.; Viti, Serena; Snell, Ronald; Lis, Dariusz C.; Benz, Arnold; Bergin, Edwin; Black, John; Caselli, Paola; Encrenaz, Pierre; Falgarone, Edith; Goicoechea, Javier R.; Hjalmarson, Åke; Hollenbach, David; Kaufman, Michael; Melnick, Gary; Neufeld, David; Pagani, Laurent; van der Tak, Floris; van Dishoeck, Ewine; Yıldız, Umut A.

    2014-10-01

    We report observations of molecular oxygen (O2) rotational transitions at 487 GHz, 774 GHz, and 1121 GHz toward Orion Peak A. The O2 lines at 487 GHz and 774 GHz are detected at velocities of 10-12 km s-1 with line widths ~3 km s-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 O2 emission is sime9'' (6 × 1016 cm) in size, and is located close to the H 2 Peak 1 position (where vibrationally excited H2 emission peaks), and not at Peak A, 23'' away. The peak O2 column density is sime1.1 × 1018 cm-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 O2 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 × 104 cm-3, if a reasonable flux of UV radiation is present. The postshock O2 can explain the emission from the source if its line-of-sight dimension is sime10 times larger than its size on the plane of the sky. The special geometry and conditions required may explain why O2 emission has not been detected in the cores of other massive star-forming molecular clouds.

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

    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.

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

    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,...

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

    Saur, Joachim; Roth, Lorenz; Nimmo, Francis; Strobel, Darrell F; Retherford, Kurt D; McGrath, Melissa A; Schilling, Nico; Grard, 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...

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

    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...

  4. NuSTAR observations of the bullet cluster: constraints on inverse compton emission

    Wik, Daniel R.; Hornstrup, Allan; Molendi, S.; Madejski, G.; Harrison, F. A.; Zoglauer, A.; Grefenstette, B. W.; Gastaldello, F.; Madsen, K. K.; Westergaard, Niels Jrgen Stenfeldt; Ferreira, Desiree Della Monica; Kitaguchi, T.; Pedersen, K.; Boggs, S. E.; Christensen, Finn Erland; Craig, W. W.; Hailey, C. J.; Stern, D.; Zhang, W. 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. Because all prior telescopes sensitive at E > 10 keV do not focus light and...... 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...

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

    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.

  6. An explanation for experimental observations of harmonic cyclotron emission induced by fast ions

    An explanation, supported by numerical simulations and analytical theory, is given for the harmonic cyclotron emission induced by fast ions in tokamak plasmas - particular, for the emission observed at low harmonics in deuterium-deuterium md deuterium-tritium experiments in the Joint European Tokamak. We show that the first proton harmonic is one of the highest spectral peaks whereas the first alpha is weak. We also compare the relative spectral amplitudes of different harmonics. Our results axe consistent with the experimental observations. The simulations verify that the instabilities are caused by a weak relativistic mass effect. Simulation that a nonuniform magnetic field leads to no appreciable change in the growth and saturation amplitude of the waves

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

    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....

  8. The physical principles of the combined ELF/VLF method for single-station global location of lightning

    Mushtak, V.; Price, C.; Williams, E.

    Single -station electromagnetic methods for global lightning location are based on specific features of ELF wave propagation. First, ELF waves propagate with an extremely low attenuation not exceeding 1.5 dB/Mm up to 100 Hz. For this reason, the propagation has a resonant character (the Schumann resonance phenomena) imparting a unique pattern to the spectrum of a lightning waveform depending on the parent lightning's location relative to the given observer. The wave impedance technique realized by Kemp and Jones (1971) and widely adopted afterwards eliminates any need for the frequency dependence of the spectral density of the source's current moment for the location purpose. At the same time, an adequate single-mode propagation model can be applied for recovering this dependence and providing additional information about the source. As the only shortcoming of ELF location procedure, considerable error in estimates of the arrival directions of lightning waveforms was revealed by means of the satellite (OTD) identification of parent lightning events. These azimuthal deviations result in global location accuracies of 1-2 Mm (Boccippio et al, 1998) hardly acceptable in many geophysical problems. Price et al. (2002) found similar azimuthal errors in the ELF technique by means of the ground-truth (NLDN) identification of sprite-producing thunderstorms in Colorado when observing atmospherics in the Negev Desert, Israel. The location accuracy had been essentially improved - to better than 0.2 Mm on this 11 Mm path - by combining ELF distance estimates with VLF direction finding. Theoretical considerations show that this improvement is to be explained by a distinction between the ELF and VLF refraction effects at the day-night boundary of the Earth- ionosphere waveguide. While the difference between the day-time and night-time values of the phase velocity in the ELF range reaches 15%, it does not exceed 1% in the VLF range, with a corresponding diminishment of azimuthal errors. These effects are simulated both qualitatively and quantitatively on the basis of classical geometrical optics (Snell's law) as well as by means of the two-dimensional telegraph equation method for calculating ELF fields in a non-uniform waveguide (Kirillov et al., 1997). REFERENCES: Kemp, D.T., Jones, D.Ll., 1971. Journal of Atmospheric and Terrestrial Physics 33,567-572. Boccippio, D.J. et al., 1998. Journal of Atmospheric and Solar-Terrestrial Physics 60,701-712. Price, C., Mustafa, A., Lyons, W., Nelson, T., 2002. Geophysical Research Letters 29, 1.1-1.4. Kirillov, V.V., Kopeykin, V.N., Mushtak, V.C., 1997. Geomagnetism and Aeronomy 37, 114-120 [in Russian].

  9. Lightning as an embryonic source of VLF hiss

    Data from the DE 1 satellite show that lightning-generated whistlers often trigger hiss emissions that endure for up to 10- to 20-s periods. The data consist of the measured electric and magnetic fields in the frequency range of 1.5 kHz to 6.0 kHz, during 22 DE 1 passes during the period December 28, 1986 to January 18, 1987. The whistler-triggered hiss emissions were observed on 16 of the passes, and they generally exhibited the following characteristics: (1) emission spectra were wide band (1-2 kHz) and rather structureless, (2) well-defined and sustained fading patterns were observed at twice the spin frequency over 10- to 20-s periods, (3) the spin fading characteristics of the triggered hiss bursts were similar to those reported for background plasmaspheric hiss, indicating a large wave normal angle with respect to the ambient magnetic field. The results indicate that lightning-generated whistlers may be an important embryonic source for magnetospheric hiss and that whistlers and emissions triggered by them often constitute the dominant wave activity in the ∼ 1.5- to 6-kHz range on L shells of 3.5 to 5 in the afternoon sector during geomagnetically quiet periods. Through cyclotron and Landau resonant scattering, it is likely that these lightning-generated waves play a dominant role in the loss of ∼0.5- to 50-keV electrons trapped on these field lines in the afternoon sector. Through anisotropic proton instability, these waves can also interact with ring current protons in the range of several tens of keV leading to a loss mechanism for ring current protons

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

    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 sensitive to (1 the amount of methane transported through aerenchyma, (2 soil pH (±100 Tg CH4 yr−1, and (3 redox inhibition (±45 Tg CH4 yr−1. Results are sensitive to biases in the CLMCN and to errors in the satellite inundation fraction. In particular, the high latitude methane emission estimate may be biased low due to both underestimates in the high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4.

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

    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.

  12. Quasi-static ELF and VLF electric fields in the region of the main ionospheric trough

    Best, A. (Heinrich-Hertz-Institut fuer solar-terrestrische Physik, Berlin, East Germany); Lehmann, H.R. (Akademiia Nauk SSSR, Institut Zemnogo Magnetizma, Ionosfery i Rasprostraneniia Radiovoln, Moscow, USSR); Johanning, D. (Akademiia Nauk SSSR, Institut Kosmicheskikh Issledovanii, Moscow, USSR)

    1980-08-01

    The distribution of lower hybrid resonance noise and of quasi-static electric fields in the main middle-latitude trough of electron density is considered. It is shown that, as a rule, lower hybrid resonance noise occurs in the trough and that the lower cutoff frequency of the noise correlates well with electron density. Quasi-static electric fields having an average field intensity of 10-20 millivolts/m and more are registered in the bottom of the trough. The picture obtained turns out to be sufficiently regular. Observations of the trough made by the Intercosmos 10 satellite at 24-hour intervals confirm not only the similarity of the trough structure but also the similarity of the structure of the electromagnetic fields registered in the region of the trough. On the basis of the experimental data, hypotheses concerning the nature of the mechanism that ensures the correlation between the lower hybrid resonance noise and the electron density are discussed. These include noise excitation by epithermal proton fluxes and the reflection of VLF waves in the region of the trough.

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

    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 (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

  14. Impact of emission controls on air quality in Beijing during APEC 2014: lidar ceilometer observations

    Tang, G; Zhu, X.; Hu, B.; Xin, J.; Wang, L.; Münkel, C.; G. Mao; Wang, Y.

    2015-01-01

    The implementation of emission reductions during the 2014 Asia-Pacific Economic Cooperation (APEC) summit provides a valuable opportunity to study air pollution in Beijing. From 15 October to 30 November 2014, the height of the atmospheric mixing layer and the vertical attenuated backscattering coefficient profiles were observed online using a~lidar ceilometer. Compared with fine particulate matter (PM2.5) and aeros...

  15. Estimating the emissions from a nuclear accident using observations of radioactivity with dispersion model products

    The spread of material from fabricated nuclear releases simulated using the U.K. Met Office ''NAME'' long-range transport and dispersion model is used to test methods of modifying the modelled plume spread, and of assessing the release profiles, by comparing observed and modelled radioactivity. The method was also applied to reconstitute the first 108 h emissions from the Chernobyl incident. The results of the experiments were moderately encouraging. (Author)

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

    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 otherwise) of LLJs. However, the presence of a LLJ is not a guarantee of dust emission. Momentum calculations show that dust emission always occurs if momentum mixes down to the surface, but mix-down does not always happen - particularly if the surface temperature inversion is strong or ground heating is weak. Fennec findings are not only providing new insights into dust emission processes, they are also an excellent test-bed for models and satellite algorithms in a region where high-quality ';ground-truthing' measurements have been scarce. Conditions of (relatively) high water vapour appear to be a common cause of error. In one model, wind speeds in the core of monsoon LLJs are underestimated by 8.5m/s compared to observations.

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

    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.

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

    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.

  19. Recent increases in trifluoromethane (HFC-23) global emissions and early atmospheric changes observed for other hydrofluorocarbons

    Montzka, S. A.; Miller, B. R.; Battle, M. O.; Aydin, K. M.; Fahey, D. W.; Hall, B. D.; Miller, L.; Verhulst, K. R.; Saltzman, E.; McFarland, M.

    2009-12-01

    Trifluoromethane (HFC-23) is an unintended by-product of chlorodifluoromethane (HCFC-22) production and has a 100-yr global warming potential of 14,800. Firn-air and ambient air measurements of HFC-23 from three firn sampling excursions to Antarctica between 2001 and 2009 are used to construct a consistent atmospheric history for this chemical in the Southern Hemisphere. The results show continued increases in the atmospheric abundance of HFC-23 and imply substantial increases in HFC-23 global emissions since 2003. These emission increases are coincident with rapidly increasing HCFC-22 production in developing countries and are observed despite efforts in recent years to limit emissions of HFC-23 through the Kyoto Protocol’s Clean Development Mechanism. These results will be considered along with new observations of additional HFCs from archived air, firn air, and ongoing flask-air measurements. Considered together, atmospheric increases observed for hydrochlorofluorocarbons and hydrofluorocarbons accounted for ~9% of the increase in total direct radiative forcing from anthropogenic gases during 2003-2008, an addition that was slightly larger than attributable to N2O over this same period.

  20. Herschel HIFI observations of O$_2$ toward Orion: special conditions for shock enhanced emission

    Chen, Jo-Hsin; Viti, Serena; Snell, Ronald; Lis, Dariusz C; Benz, Arnold; Bergin, Edwin; Black, John; Caselli, Paola; Encrenaz, Pierre; Falgarone, Edith; Goicoechea, Javier R; Hjalmarson, Ake; Hollenbach, David; Kaufman, Michael; Melnick, Gary; Neufeld, David; Pagani, Laurent; van der Tak, Floris; van Dishoeck, Ewine; Yildiz, Umut A

    2014-01-01

    We report observations of molecular oxygen (O$_2$) rotational transitions at 487 GHz, 774 GHz, and 1121 GHz toward Orion Peak A. The O2 lines at 487 GHz and 774 GHz are detected at velocities of 10-12 km/s with line widths 3 km/s; 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$_2$ emission is 9" (6e16 cm) in size, and is located close to the H2 Peak 1position (where vibrationally-excited H$_2$ emission peaks), and not at Peak A, 23" away. The peak O2 column density is 1.1e18/cm2. The line velocity is close to that of 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$_2$ abundance compared to that generally found in dense interstellar clouds can be explained by passage of a low-velo...

  1. Groundbased Observations of Io [OI]6300 A Emission During the Galileo 124, 125, and Cassini Encounters

    Oliversen, R. J.; Morgenthaler, J. P.; Scherb, F.; Woodward, R. C.; Smyth, W. H.; Lupie, O. L.

    2003-01-01

    For the past 12 years, we have conducted a synoptic study of [OI] 6300 A emission from Io using the high-resolution (R 120,000) stellar spectrograph at the National Solar Observatory McMath-Pierce telescope. We showed in a recent paper that this emission allows us to use Io as a localized probe of the three-dimensional plasma torus structure. We report on selected recent spectroscopic observations of Io [OI] 6300 A emission obtained during the Galileo I24 (1999-Oct-11) and I25 (1999-Nov-26) encounters with Io and the Cassini Jupiter encounter (closest approach 2000-Dec-30). The exposure time for each spectrum was 15 minutes, with a 5.2 x 5.2 aperture centered on Io. We obtained over 100 spectra for the I24 encounter during 1999 October 9-13, over 100 spectra for the I25 encounter during 1999 November 24-30, and for the Cassini Jupiter flyby almost 600 spectra from 2000 December to 2001 January 21. We use our database of observations to track long- and short-term variations in torus structure. We compare our results to Galileo, Cassini, HST, and other groundbased contemporaneous observations to gain insight into torus variability and structure.

  2. Characterization of kraft pulp mill particulate emissionsA summary of existing measurements and observations

    Pinkerton, John E.; Blosser, Russell O.

    Particulate matter emission sources at a kraft pulp mill include kraft recovery furnaces, lime kilns, smelt dissolving tanks and power boilers. Chemical and physical characteristics of these paniculate emissions are reviewed. Measurements of particle size distributions for these sources made with cascade impactors and microscopic counting techniques both before and after paniculate control devices such as multiple cyclones, wet scrubbers, and electrostatic precipitalors are discussed. In general, particles with equivalent diameters less than 3 jim comprise the bulk of the controlled paniculate emissions from all sources. Sodium sulfate is the dominant paniculate emission from kraft recovery furnaces, smelt dissolving tanks and lime kilns. Results from a field investigation of the relationship between human observations of near-stack plume opacity and measured in-stack paniculate concentrations and opacities are summarized. Trained cenified panels of observers were used in the investigation to estimate plume opacities from two kraft recovery furnaces, a combination wood/coal-fired boiler, and a combination wood/oil-fired boiler at four different pulp mill locations. Plume opacities were varied from near-zero to 45 % by adjustment of the paniculate control equipment operation. The effects of different background viewing conditions, observer positions, observer experience levels, and plume characteristics are enumerated. It is concluded that there can be substantial variations between measured in-stack opacities and human perceptions of near-stack plume opacities. The degree of agreement between the human judgements and measured in-stack opacities is significantly affected by the background viewing conditions. It is further shown that even with a panel of six or seven trained observers with similar visual acuity, there can be significant departures of individual opacity readings from the panel mean opacity. Although this investigation deals with questions of human observations of near-stack opacity, it is likely that other studies concerned with human perceptions of visibility impairment at greater downwind distances will have to also address the inherently subjective nature of human visual observations and the effects of background viewing conditions. These factors will make it difficult to correlate human visual observations of plume characteristics to instrumental measures of opacity or opacity-related parameters made at the source.

  3. Observations of Far-Ultraviolet Diffuse Emission from the Small Magellanic Cloud

    Pradhan, Ananta C.; Murthy, Jayant; Pathak, Amit

    2011-01-01

    We report the first observations of far-ultraviolet (FUV: 1000 -- 1150 \\AA) diffuse radiation from the Small Magellanic Cloud (SMC) using observations from the {\\em Far Ultraviolet Spectroscopic Explorer (FUSE)}. The strength of FUV diffuse surface brightness in the SMC ranges from the detection limit of 2000 photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \\AA$^{-1}$ to a maximum of $3 \\times 10^{5}$ photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \\AA$^{-1}$ at 1004 \\AA. The contribution of diffuse emission to the...

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

    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 ...

  5. Submillimeter Array Observations of 321 GHz Water Maser Emission in Cepheus A

    Patel, N. A.; Curil, S.; Zhang, Q; Sridharan, T. K.; Ho, P. T. P.; Torrelles, J. M.

    2007-01-01

    Using the Submillimeter Array (SMA) we have imaged for the first time the 321.226 GHz, 10_{29}-9_{36} ortho-H2O maser emission. This is also the first detection of this line in the Cepheus A high-mass star-forming region. The 22.235 GHz, 6_{16}-5_{23} water masers were also observed with the Very Large Array 43 days following the SMA observations. Three of the nine detected submillimeter maser spots are associated with the centimeter masers spatially as well as kinematically, while there are ...

  6. Atmospheric observations of carbon monoxide and fossil fuel carbon dioxide emissions from East Asia

    Turnbull, J. C.; Tans, P. P.; Lehman, S. J.; Baker, D. F.; Conway, T. J.; Chung, Y. S.; Gregg, J.; Miller, J. B.; Southon, J. R.; Zhou, L.

    2011-12-01

    Flask samples from two sites in East Asia, Tae-Ahn Peninsula, Republic of Korea (TAP), and Shangdianzi, People's Republic of China (SDZ), were measured for a suite of trace gases and isotopes, including CO2, CO and Δ14CO2. We use the Δ14CO2 measurements to quantify the contribution of recently added fossil fuel CO2 (CO2ff) in each sample. Our five-year record from TAP, on the western edge of Korea, shows high pollution events when local air comes from the Korean Peninsula. Most samples at this site, however, reflect air masses from further afield in Northeastern China and typically have lower CO2ff values. SDZ is about 100km northeast of Beijing, and our small set of samples from winter 2009/2010 have strongly elevated CO2ff. Biospheric CO2 also contributes substantially to variability in total CO2 at both sites, even in winter when non-fossil CO2 sources (including photosynthesis, respiration, biomass burning and biofuel use) contribute 20-30% of the total CO2 enhancement over background. Carbon monoxide (CO) is also elevated, and correlates strongly with CO2ff. The SDZ samples, and the TAP far-field (China influenced) samples have CO to CO2ff emission ratios (RCO:CO2ff) of 47±2 and 44±3 ppb/ppm respectively, in agreement with recent bottom-up inventory estimates and consistent with other observational studies. Locally influenced TAP samples fall into two distinct datasets, ascribed to air sourced from either South Korea or North Korea. The South Korea samples are characterized by high CO2ff values and low RCO:CO2ff of 13±3 ppb/ppm, slightly higher than two available bottom-up inventory estimates, but quite consistent with emission ratios for other developed nations. We also compare our CO2ff observations with modeled CO2ff using the FLEXPART Lagrangian particle dispersion model, convolved with a bottom-up CO2ff emission inventory which includes the reported increase in Chinese emissions of 63% from 2004 to 2010. At SDZ, the model replicates the observations quite well. At TAP, the model performs well on an annual basis, although it is unable to capture the variability on individual days. The modeled time trend is consistent with our observations, whereas a model version which holds Chinese emissions flat at 2004 levels is unable to replicate the observed CO2ff.

  7. Soft and hard X-ray excess emission in Abell 3112 observed with Chandra

    Bonamente, M; Lieu, R

    2007-01-01

    Chandra ACIS-S observations of the galaxy cluster A3112 feature the presence of an excess of X-ray emission above the contribution from the diffuse hot gas, which can be equally well modeled with an additional non-thermal power-law model or with a low-temperature thermal model of low metal abundance. We show that the excess emission cannot be due to uncertainties in the background subtraction or in the Galactic HI column density. Calibration uncertainties in the ACIS detector that may affect our results are addressed by comparing the Chandra data to XMM MOS and PN spectra. While differences between the three instruments remain, all detect the excess in similar amounts, providing evidence against an instrumental nature of the excess. Given the presence of non-thermal radio emission near the center of A3112, we argue that the excess X-ray emission is of non-thermal nature and distributed throughout the entire X-ray bandpass, from soft to hard X-rays. The excess can be explained with the presence of a population...

  8. On the nature of prominence emission observed by SDO/AIA

    Parenti, Susanna; Heinzel, Petr; Golub, Leon

    2012-01-01

    The Prominence-Corona Transition Region (PCTR) plays a key role in the thermal and pressure equilibrium of solar prominences. Our knowledge of this interface is limited and several major issues remain open, including the thermal structure and, in particular, the maximum temperature of the detectable plasma. The high signal-to-noise ratio of images obtained by the Atmospheric Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory clearly show that prominences are often seen in emission in the 171 and 131 bands. We investigate the temperature sensitivity of these AIA bands for prominence observation, in order to infer the temperature content in an effort to explain the emission. Using the CHIANTI atomic database and previously determined prominence differential emission measure distributions, we build synthetic spectra to establish the main emission-line contributors in the AIA bands. We find that the Fe IX line always dominates the 171 band, even in the absence of plasma at > 10^6 K temperatures, while th...

  9. Volcanic emissions from AIRS observations: detection methods, case study, and statistical analysis

    Hoffmann, Lars; Griessbach, Sabine; Meyer, Catrin I.

    2014-10-01

    Monitoring volcanic emissions is important for many reasons, most notably for impacts on climate and possible hazards for human health or aviation safety. Satellite instruments allow for long-term monitoring of volcanic emissions on a global scale. In this paper we introduce new detection indices for volcanic ash and sulfur dioxide (SO2) that are optimized for radiance measurements of the Atmospheric InfraRed Sounder (AIRS). Radiative transfer calculations are used to determine the sensitivity of the ash index (AI) on the aerosol optical depth and the SO2 index (SI) on the SO2 column density. A case study on AIRS observations after the eruption of the Puyehue Cordon-Caulle, Chile, in June 2011 demonstrates that the new indices work in practice. A statistical analysis of a ten-year record (2002 to 2013) of AIRS data provides AI thresholds that help to better discriminate volcanic emissions from regular events such as dust storms. We compared our new SI with the AIRS operational product and found that it is more sensitive and better suppresses interfering background signals. Our new volcanic emission data products have been successfully applied in other scientific studies.

  10. Survey observations of emission-line stars in the Orion region

    Survey observations were conducted for H alpha-emission stars in the Orion region using the Kiso Schmidt telescope and partly the CTIO Curtis Schmidt telescope. In the area of about 25 square degrees, a total of 236 H alpha-emission objects, mostly supposed to be T Tau type stars, have been detected among which 155 are new ones including 6 non-stellar objects. Celestial coordinates and V-magnitude are measured for the detected objects. Eye estimation of the H alpha-emission intensity is also made at three epochs in a time span of about two years, where notable variation of H alpha intensity was found in 68 out of 236 objects. Besides a remarkable concentration along the northern dark cloud complex, a loose concentration is noticed near the Orion Belt region, fairly well coinciding with the distribution of the Orion OBIb association members. A comparison with the Av-map is also made to see the relationship between the distribution of emission-line objects and that of interstellar dust

  11. Recent observations of the OI 8446 A emission over Millstone Hill

    Lancaster, R. S.; Kerr, R. B.; Ng, K.; Noto, J.; Franco, M.; Solomon, Stanley C.

    1994-01-01

    Evening twilight spectra of the OI 8446 A emission were obtained during May and June of 1993 using a single-etalon, pressure scanning, Fabry-Perot interferometer located in the Millstone Hill Optical Facility. The goals of this work are to positively identify the 8446 A emission in the twilight airglow and to determine the intensity decay as a function of solar depression angle. Also, a study of the relative triplet line strengths is performed in hopes of establishing the importance of the primary excitation mechanisms (photoelectron impact or Bowen fluorescence) during the twilight period. Although absent in most of the data, a distinct auroral influence is also found to contribute considerably, on occasion, to the emission over Millstone Hill. The ratio of the combined 8446.26 A and 8446.38 A intensities to the 8446.76 A intensity varies as 0.13 +/- 0.03 per degree of solar depression angle, indicating that secondary excitation mechanisms are becoming increasingly important as evening twilight progresses. Bowen fluorescence is not found to be the primary excitation mechanism at any time during twilight, contributing just a few Rayleighs at most. These observations are an important first step toward a better characterization of highly variable thermospheric oxygen concentrations through ground-based measurements of the OI 8446 A emission.

  12. Fe XXIV emission in solar flares observed with the NRL/ATM XUV slitless spectrograph

    During the Skylab Mission, the NRL slitless spectrograph photographed a number of flares in the 170-600 A region with a spatial resolution approaching 2ins. At flare maximum the 2s 2Ssub(1/2) - 2p 2Psub(1/2,3/2) transitions of Fe XXIV are present and show the location of the (approx.)20 x 106deg plasma with respect to the surface magnetic field and chromospheric (HeII) emissions. Three examples are discussed (two only briefly). In the small, intense disk flare of 1973, August 9 the high temperature region appears at the foot of a low altitude arch. The estimated electron density is 5 x 1011cm-3. In the limb flare of 1974, January 15 the hot X-ray emitting component is at a very low altitude compared to the flare loops. In the impulsive double ribbon flare of 1973, June 15 the Fe XXIV emission is centered over the neutral line, forming a bridge-like structure between magnetic regions of opposite polarity. The estimated electron density is 5 x 1010cm-3. The Fe XXIV emission was visible 8 to 10 min as compared with a calculated cooling time by conduction of only 5 min. The lengthened life of the emission may be associated with the observed 'turbulence', which inhibits the heat conduction, or alternatively, with a slower energy release prolonged beyond the end of the burst phase. (Auth.)

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

    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.

  14. Observation and modeling of geocoronal charge exchange X-ray emission during solar wind gusts

    Solar wind charge exchange (SWCX) X-rays are emitted when highly charged solar wind ions such as O7+ collide with neutral gas, including the Earth's tenuous outer atmosphere (exosphere or geocorona) and hydrogen and helium from the local interstellar medium drifting through the heliosphere. This geocoronal and heliospheric emission comprises a significant and varying fraction of the soft X-ray background (SXRB) and is seen in every X-ray observation, with the intensity dependent on solar wind conditions and observation geometry. Under the right conditions, geocoronal emission can increase the apparent SXRB by roughly an order of magnitude for an hour or more. In this work, we study a dozen occasions when the near-Earth solar wind flux was exceptionally high. These gusts of wind lead to abrupt changes in SWCX X-ray emission around Earth, which may or may not be seen by X-ray observatories depending on their line of sight. Using detailed three-dimensional magnetohydrodynamical simulations of the solar wind's interaction with the Earth's magnetosphere, and element abundances and ionization states measured by ACE, we model the time-dependent brightness of major geocoronal SWCX emission lines during those gusts and compare with changes in the X-ray background measured by the Chandra X-ray Observatory. We find reasonably good agreement between model and observation, with measured geocoronal line brightnesses averaged over 1 hr of up to 136 photons s–1 cm–2 sr–1 in the O VII Kα triplet around 564 eV.

  15. Gamma-ray emission in dissipative pulsar magnetospheres: from theory to Fermi observations

    We compute the patterns of γ-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed γ-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model γ-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and γ-ray emission on the γ-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the γ-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

  16. Gamma-ray emission in dissipative pulsar magnetospheres: from theory to Fermi observations

    Kalapotharakos, Constantinos [University of Maryland, College Park (UMDCP/CRESST), College Park, MD 20742 (United States); Harding, Alice K.; Kazanas, Demosthenes, E-mail: constantinos.kalapotharakos@nasa.gov [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-10-01

    We compute the patterns of γ-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed γ-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model γ-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and γ-ray emission on the γ-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the γ-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

  17. Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: from Theory to Fermi Observations

    Kalapotharakos, Constantinos; Harding, Alice K.; Kazanas, Demosthenes

    2014-01-01

    We compute the patterns of gamma-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed gamma-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model gamma-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and gamma-ray emission on the gamma-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the gamma-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

  18. Inverse modeling of atmospheric mercury emissions using a global chemical transport model and surface observations

    Song, S.; Selin, N. E.

    2012-12-01

    We use inverse modeling in combination with worldwide observational data to constrain atmospheric mercury fluxes and associated uncertainties from anthropogenic and natural sources. Though atmospheric transport is a critical pathway of global mercury transport, large uncertainties exist in estimating the magnitudes and temporal variabilities of mercury emissions to the atmosphere from both natural and anthropogenic processes. Previous estimations have primarily used a so-called "bottom-up" approach, which extrapolates the few direct measurements to larger regions or uses simplified process models to estimate fluxes. Here, we apply a "top-down" or inverse modeling approach. Worldwide surface observations of total gaseous mercury (TGM) and simulations from a global chemical transport model (GEOS-Chem version 9-01-02 with a 2 by 2.5 degree horizontal resolution) are combined to estimate mercury fluxes. Time-invariant anthropogenic emission and seasonally varying fluxes (e.g., ocean evasion, biomass burning, and soil volatilization) are optimally estimated by Kalman filter between 2005 and 2009 at a monthly time resolution. The reference source spatial distributions are shown in Figure 1. We collected data from 16 measurement sites with high precision and frequency, covering most active stations during our period of study. The observations and reference model outputs at 4 representative sites are compared in Figure 2. We test the inverse model by comparing model-measurement fits between the reference model and optimized emissions.igure 1. Mercury reference source spatial distributions. Annually averaged patterns are shown in log scale. igure 2. Comparison of TGM monthly mean observations between observations (black, shown with standard deviations) and reference model results (red) at 4 representative sites.

  19. Direct Observation of Coronal Magnetic Fields by Vector Tomography of the Coronal Emission Line Polarizations

    Kramar, M; Tomczyk, S

    2015-01-01

    This article presents 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 observational measurements of the Fe {\\sc{xiii}} 10747 \\AA\\ Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and coronal density and temperature structures derived from scalar tomographic inversion of STEREO/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) simulation 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 rec...

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

    Straughn, A N; 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; Kimble, R A; Luppino, G; Paresce, F; Saha, A; Silk, J I; Trauger, J T; Walker, A R; Whitmore, B C; 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 covereage 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, \\OIII, and \\OII\\ emission lines detected in the redshift ranges 0.2$\\cle$z$\\cle$1.6, 1.2$\\cle$z$\\cle$2.4 and 2.0$\\cle$z$\\cle$3.6 respectively in the G102 (0.8--1.1 microns; R$\\sim$210) and G141 (1.1--1.6 microns; R$\\sim$130) grisms. The higher spectral resolution afforded by the WFC3 grisms also reveals emission lines not detectable with the G800L grism (e.g., \\SII\\ and \\SIII\\ lines). From these relatively shallow observations, line luminosities, star--formation rates, and grism s...

  1. Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS

    Acciari, V A; Arlen, T; Aune, T; Bautista, M; Beilicke, M; Benbow, W; Bradbury, S M; Buckley, J H; Bugaev, V; Butt, Y; Byrum, K; Cannon, A; Celik, O; Cesarini, A; Chow, Y C; Ciupik, L; Cogan, P; Colin, P; Cui, W; Daniel, M K; Dickherber, R; Duke, C; Dwarkadas, V V; Ergin, T; Fegan, S J; Finley, J P; Finnegan, G; Fortin, P; Fortson, L; Furniss, A; Gall, D; Gibbs, K; Gillanders, G H; Godambe, S; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Hays, E; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, Philip; Karlsson, N; Kertzman, M; Kieda, D; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; Le Bohec, S; Maier, G; McCann, A; McCutcheon, M; Millis, J; Moriarty, P; Ong, R A; Otte, A N; Pandel, D; Perkins, J S; Pohl, M; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Rose, H J; Schroedter, M; Sembroski, G H; Smith, A W; Steele, D; Swordy, S P; Theiling, M; Toner, J A; Valcarcel, L; Varlotta, A; Vasilev, V V; Vincent, S; Wagner, R G; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Weisgarber, T; Williams, D A; Wissel, S; Wood, M; Zitzer, B

    2009-01-01

    We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best-studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hours during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (sigma) before trials and 7.5 sigma after trials in a point-source search. The emission is centered at 06 16 51 +22 30 11 (J2000) +- 0.03_stat +- 0.08_sys degrees, with an intrinsic extension of 0.16 +- 0.03_stat +- 0.04_sys degrees. The VHE spectrum is well fit by a power law (dN/dE = N_0 * (E/TeV)^-Gamma) with a photon index of 2.99 +- 0.38_stat +- 0.3_sys and an integral flux above 300 GeV of (4.63 +- 0.90_stat +- 0.93_sys) * 10^-12 cm^-2 s^-1. These results are discussed in the context of existing ...

  2. Characterization of gaseous pollutant and particulate matter emission rates from a commercial broiler operation part I: Observed trends in emissions

    Roumeliotis, Taylor S.; Dixon, Brad J.; Van Heyst, Bill J.

    2010-10-01

    This paper characterizes the emission rates of size fractionated particulate matter, inorganic aerosols, acid gases, ammonia and methane measured over four flocks at a commercial broiler chicken facility. Mean emission rates of each pollutant, along with sampling notes, were reported in this paper, the first in a series of two. Sampling notes were needed because inherent gaps in data may bias the mean emission rates. The mean emission rates of PM 10 and PM 2.5 were 5.0 and 0.78 g day -1 [Animal Unit, AU] -1, respectively, while inorganic aerosols mean emission rates ranged from 0.15 to 0.46 g day -1 AU -1 depending on the season. The average total acid gas emission rate was 0.43 g day -1 AU -1 with the greatest contribution from nitrous and nitric acids and little contribution from sulfuric acid (as SO 2). Ammonia emissions were seasonally dependent, with a mean emission rate of 66.0 g day -1 AU -1 in the cooler seasons and 94.5 g day -1 AU -1 during the warmer seasons. Methane emissions were relatively consistent with a mean emission rate of 208 g day -1 AU -1. The diurnal pattern in each pollutant's emission rate was relatively consistent after normalizing the hourly emissions according to each daily mean emission rate. Over the duration of a production cycle, all the measured pollutants' emissions increased proportionally to the total live mass of birds in the house, with the exception of ammonia. Interrelationships between pollutants provide evidence of mutually dependent release mechanisms, which suggests that it may be possible to fill data gaps with minimal data requirements. In the second paper (Roumeliotis, T.S., Dixon, B.J., Van Heyst, B.J. Characterization of gaseous pollutants and particulate matter emission rates from a commercial broiler operation part II: correlated emission rates. Atmospheric Environment, 2010.), regression correlations are developed to estimate daily mean emission rates for data gaps and, using the normalized hourly diurnal patterns from this paper, emission factors were generated for each pollutant.

  3. VLF/LF Radio Sounding of Ionospheric Perturbations Associated with Earthquakes

    Masashi Hayakawa

    2007-01-01

    It is recently recognized that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes, seems to be very promising for short-term earthquake prediction. We have proposed a possible use of VLF/LF (very low frequency (3-30 kHz) /low frequency (30-300 kHz)) radio sounding of the seismo-ionospheric perturbations. A brief history of the use of subionospheric VLF/LF propagation for the short-term earthquake prediction is given,...

  4. A Spaceborne Multi-Arm Interferometer for VLF Gravitational Wave Detection (the Smile Project)

    Anderson, A. J.

    This project would be the next step in our ability to detect very low frequency (VLF) gravitational waves and the first committed spaceborn designed experiment. Present Deep Space spacecraft tracking experiments are severely limited in their detection capability. It is proposed to construct a space-borne multi-arm microwave interferometer using current elements of design applicable for the detection of VLF gravitational waves. The elements are outlined with particular emphasis placed on the utilization of small inexpensive get away special modules currently under development at JPL for launch in the 1990's.

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

    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...

  6. Observational study of generation conditions of substorm-associated low-frequency AKR emissions

    A. Olsson

    2004-11-01

    Full Text Available It has lately been shown that low-frequency bursts of auroral kilometric radiation (AKR are nearly exclusively associated with substorm expansion phases. Here we study low-frequency AKR using Polar PWI and Interball POLRAD instruments to constrain its possible generation mechanisms. We find that there are more low-frequency AKR emission events during wintertime and equinoxes than during summertime. The dot-AKR emission radial distance range coincides well with the region where the deepest density cavities are seen statistically during Kp>2. We suggest that the dot-AKR emissions originate in the deepest density cavities during substorm onsets. The mechanism for generating dot-AKR is possibly strong Alfvén waves entering the cavity from the magnetosphere and changing their character to more inertial, which causes the Alfvén wave associated parallel electric field to increase. This field may locally accelerate electrons inside the cavity enough to produce low-frequency AKR emission. We use Interball IESP low-frequency wave data to verify that in about half of the cases the dot-AKR is accompanied by low-frequency wave activity containing a magnetic component, i.e. probably inertial Alfvén waves. Because of the observational geometry, this result is consistent with the idea that inertial Alfvén waves might always be present in the source region when dot-AKR is generated. The paper illustrates once more the importance of radio emissions as a powerful remote diagnostic tool of auroral processes, which is not only relevant for the Earth's magnetosphere but may be relevant in the future in studying extrasolar planets.

  7. Observations of H2 emission from molecular clouds and Herbig-Haro objects

    Using a CVF spectrometer with a spectral resolution of approx.2%, we have searched a group of molecular clouds, HH sources, and related objects for emission in the v = 1 → 0 S(1) line of H2 at lambda0 = 2.122 μm. Included in this survey were H2O masers with high-velocity components as well as CO hotspots with broad radio emission lines indicative of high-speed molecular flows. Generally our 3sigma detection limit for the integrated S(1) line flux corresponded to 7 x 10-20W cm-2 in our 34'' diameter beam. We present results for six sources that we detected and mapped in the S(1) line (NGC 1333, HH 12, NGC 2071, S255, S140, and Cep A), and we report limits for another 18 regions that were searched but not detected (e.g., L1551). In the H2 sources that were mapped, we observed line emission over an extended area >0.2 pc in diameter. For NGC 1333 and Cep A, whose high velocity CO gas appears to be channeled into bipolar flows, we detected H2 emission from the blueshifted CO lobe but not from the redshifted radio lobe. If the redshifted gas lies relatively deeper within the molecular cloud, then differential 2 μm extinction from dust within the cloud might be sufficient to reduce the H2 emission from this part of the flow below our detection limit. By comparison with the Orion H2 source, the surface brightness and luminosity in the S(1) line of the regions detected in this survey are weaker by an order of magnitude or more

  8. Inclusive observables and hard gluon emission in neutrino deep inelastic scattering

    We derive the predictions of perturbative QCD together with non-perturbative corrections for a set of inclusive observables connected with the angular distribution of light-cone energy in deep inelastic neutrino scattering. Our particular choice of observables has been made in order to meet important physical requirements besides the necessary condition of infrared regularity. Our inclusive observables receive their dominant contribution from the quark fragmentation region. The non-perturbative contribution is calculable in a rather model-independent way and stays at an acceptable level in realistic experimental conditions. The QCD perturbative contribution, which takes the simple form of a convolution product, exhibits a strongly decreasing behaviour as a function of the Bjorken scaling variable x, superimposed on a constant background associated with the non-perturbative terms, allowing a rather clean separation of the two effects. The perturbative term being dominated by the process of hard-gluon emission, an experimental investigation of the observables discussed here may be a good way to detect the effect of gluon emission in deep inelastic neutrino scattering. (orig.)

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

    ,

    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 $0\\deg \\leq {\\theta} \\leq 0.1\\deg$ .

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

    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.

  11. Rocket observation of the N II 2143 A emission in an aurora

    Siskind, David E.; Barth, Charles A.

    1987-01-01

    Using a rocket-mounted spectrometer with a multichannel detector, the existence of the N II 2143 A doublet in the auroral ultraviolet spectrum was confirmed. The measured intensity is in agreement with previous auroral observations and is consistent with a peak electron-impact cross section of 1-2 x 10 to the -18th sq cm. By comparing an altitude profile of the 2143 A emission to the N2(+) 3914 A emission, a deactivation rate for the N(+)(5S) state was obtained. The most likely quencher is N2, although the possibility of a reaction with O2 cannot be ruled out. For N2, the deduced value of the quenching coefficient equals 5.5 x 10 to the -10th cu cm/s.

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

    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.

  13. Relations between observable parameters of collisionally broadened emission lines of rotating stars: a useful plot

    This paper emphasizes the importance of spectroscopy techniques and the need of additional assumptions in analyzing stellar spectra, when experimental data are mapped in terms of a few parameters. Collisionally broadened profiles of emission lines originated in circumstellar material surrounding rotating stars are analyzed. Theoretical relationships between the ratio of the central flux intensity to the equivalent width of the emission line Fij,0/Wij, and the half-width at half of the maximum HWHMij are found. The plane (HWHMij, Fij,0/Wij) shows general trends of the measurements and imposes bounds to the plasma parameters and the rotation velocities of the stars. With some educated guesses, it can be inferred whether the circumstellar material is spherically distributed or has a disc-like structure. As an example, an observational evaluation is made from data of gamma Cass. (paper)

  14. Ionospheric perturbations related to the earthquake in Vrancea area on November 22, 2014, as detected by electromagnetic VLF/LF frequency signals

    Maria Solovieva

    2015-11-01

    Full Text Available Data from the European network of very low/ low frequency (VLF/LF receivers has been used to study the response of the lower ionosphere to the earthquake of magnitude 5.5 in Vrancea area on November 22, 2014. Negative amplitude anomalies have been observed during 3 days before the earthquake and two days after, on the LF (45.9 kHz signal passed above the seismic area. No perturbations have been found for the same signal in control paths during this period. Other possible influences both from above and below which can produce perturbations in the ionosphere have been taken into consideration.

  15. Suzaku observations of the diffuse X-ray emission across the Fermi bubbles' edges

    We present Suzaku X-ray observations along two edge regions of the Fermi Bubbles, with eight ≅ 20 ks pointings across the northern part of the North Polar Spur (NPS) surrounding the north bubble and six across the southernmost edge of the south bubble. After removing compact X-ray features, diffuse X-ray emission is clearly detected and is well reproduced by a three-component spectral model consisting of unabsorbed thermal emission (temperature kT ≅ 0.1 keV) from the Local Bubble, absorbed kT ≅ 0.3 keV thermal emission related to the NPS and/or Galactic halo (GH), and a power-law component at a level consistent with the cosmic X-ray background. The emission measure (EM) of the 0.3 keV plasma decreases by ≅ 50% toward the inner regions of the northeast bubble, with no accompanying temperature change. However, such a jump in the EM is not clearly seen in the south bubble data. While it is unclear whether the NPS originates from a nearby supernova remnant or is related to previous activity within or around the Galactic center, our Suzaku observations provide evidence that suggests the latter scenario. In the latter framework, the presence of a large amount of neutral matter absorbing the X-ray emission as well as the existence of the kT ≅ 0.3 keV gas can be naturally interpreted as a weak shock driven by the bubbles' expansion in the surrounding medium, with velocity v exp ∼ 300 km s–1 (corresponding to shock Mach number M≃1.5), compressing the GH gas to form the NPS feature. We also derived an upper limit for any non-thermal X-ray emission component associated with the bubbles and demonstrate that, in agreement with the aforementioned findings, the non-thermal pressure and energy estimated from a one-zone leptonic model of its broadband spectrum, are in rough equilibrium with that of the surrounding thermal plasma.

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

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

    2009-12-01

    Blocks of igneous rocks such as anorthosite and granite subjected at one end to uniaxial stress have been shown to emit a small but distinct excess amount of infrared (IR) light (Freund, F. T., et al, JASTP, 71, 2009). This anomalous IR emission arises from the radiative de-excitation of electron vacancy defects, which, upon stress-activation, flow into the unstressed portion and recombine at the surface. This non-thermal IR emission occurs in the 8 μm to 14 μm wavelength region. Field experiments are performed by slowly stressing large boulders and monitoring the IR emission in situ with a Bruker EM27 Fourier Transform Infrared (FTIR) spectrometer. The boulders are prepared by drilling four blind holes into the rock, 50-100 cm deep, in an array roughly parallel to, and behind, the surface from where the IR emission is monitored. Any debris and water is blown out of the boreholes with compressed air, and the rock is given time to dry and relax from drilling-induced stresses. The holes are then filled with grout that expands upon curing, creating an increasing radial pressure of up to 5 × 103 t/m2. The experiments were carried out with two large granite boulders, one of about 30 t of hard (over 150 MPa) granite at the University of Arizona’s Henry "Hank" Grunstedt San Xavier Mining Laboratory, located in the copper mining district near Tucson, AZ and the other of about 7 t of weathered granite in the Sierra Nevada foothills near Oakhurst, CA. The Bruker EM27 FTIR spectrometer equipped with a 20 cm reflective telescope collects the IR emission from a safe distance at a rate of a full 4-16 µm spectrum every 30 sec. After recording baseline data, the grout was mixed with water and poured into the holes as IR emission was monitored continuously until the experiment was terminated after rock failure. The time of failure is noted whenever the first acoustic or visual cues are sensed from the boulder. The IR data shows that after a period of quiescence, pronounced non-thermal IR emission is observed within minutes of the rock failure.

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

    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 predicted global methane emissions. The large range was sensitive to: (1 the amount of methane transported through aerenchyma, (2 soil pH (± 100 Tg CH4 yr−1, and (3 redox inhibition (± 45 Tg CH4 yr−1.

  18. Experience of short term earthquake precursors with VLF–VHF electromagnetic emissions

    K. Eftaxias

    2003-01-01

    Full Text Available Electromagnetic anomalies (EMA covering a wide range of frequencies from ULF, VLF up to VHF have been observed before recent destructive earthquakes in continental Greece. We show that the features of these signals are possibly correlated with the fault model characteristics of the associated earthquake and with the degree of geotectonic heterogeneity within the focal zone. The time evolution of these electromagnetic sequences reveals striking similarities to that observed in laboratory acoustic and electromagnetic emissions during different stages of failure preparation process in rocks. If we consider that the same dynamics governs the large-scale earthquakes and the microscopic scale sample rheological structure, the results of this analysis suggest that the recorded EMA might reflect the nucleation phase of the associated impending earthquake. We focus on the rise of the statistical view of earthquakes. We find electro-magnetic fingerprints of an underlying critical mechanism. Finally, we conclude that it is useful to combine ULF and VLF-VHF field measurements in an attempt to enhance the understanding of the physics behind these observations and thus to improve the quality of earthquake prediction. Further, the identification of an EMA as a seismogenic one supports the characterization of a sequence of shocks as foreshocks at the time they occur, further helping the earthquake prediction effort.

  19. Radiative forcing by coastal anthropogenic emissions explains observed 20th century Southeast Pacific cooling

    Spak, S.; Saide, P. E.; Mena, M.; Carmichael, G. R.

    2014-12-01

    The coastal Southeast Pacific cooled by 0.25K from 1979-2006, a period when the nearby Andes warmed by 0.25K. While correlated with atmospheric teleconnections, the magnitude and causes of observed cooling and changes in regional cloud cover have not been explained quantitatively. Here we show that inadvertent cloud modification by anthropogenic emissions from Chile and Peru has increased cloud brightness and lifetime throughout the region's extensive stratocumulus, resulting in net shortwave surface climate forcing and boundary layer cooling consistent with the vertical profile of observed cooling. The extensive stratocumulus observed in the region throughout the satellite era are more widespread and brighter than pre-industrial conditions. Results underscore the need to consider potentially large local and global climatic impacts when setting air quality and greenhouse gas policies in regions with extensive warm boundary layer cloud regimes.

  20. Observation of Solar Wind Charge Exchange Emission From Exospheric Material in and Outside Earth's Magnetosheath 2008 September 25

    Snowden, S. L.; Collier, M. R.; Cravens, T.; Kuntz, K. D.; Lepri, S. T.; Robertson, I.; Tomas, L.

    2009-01-01

    A long XMM-Newton exposure is used to observe solar wind charge exchange (SWCX) emission from exospheric material in and outside Earth's magnetosheath. The light curve of the O vii (0.5-0.62 keV) band is compared with a model for the expected emission, and while the emission is faint and the light curve has considerable scatter, the correlation is significant to better than 99.9%. This result demonstrates the validity of the geocoronal SWCX emission model for predicting a contribution to astrophysical observations to a scale factor of order unity (1.5). In addition, an average value of the SWCX O vii emission from the magnetosheath over the observation of 2.6 +/- 0.5 LU is derived. The results also demonstrate the potential utility of using X-ray observations to study global phenomena of the magnetosheath which currently are only investigated using in situ measurements.

  1. Inverse modeling of NOx emissions over South Korea using CAPSS emission data and the satellite observations of NO2 vertical column densities

    Kim, N.; Kim, Y.; Morino, Y.; Kurokawa, J.; Ohara, T.

    2011-12-01

    Northeast Asia including Korea, China, and Japan is characterized by high emissions of anthropogenic air pollutants. Among the air pollutants, the emission of NOx is drastically increasing. NOx is transformed to nitric acid and nitrate by physical and chemical transformations during transportation in the air. According to Kim et al. (2011, submitted), the nitrate concentrations at Gosan, Korea increased continuously. Between 1992 and 2008, the NO3- concentration in TSP increased by 317 %, that in PM10 increased by 178 % and that in PM2.5 increased by 307 %. To explain these concentration variations, the emission inventories are essential. However, most of emission inventories are developed by the bottom-up approach, which is based on combinations of activity statistics and emission factors. In bottom-up emission inventories, there are uncertainties associated with the statistics, emission factors, temporal allocation profiles, and grid allocation factors (Kurokawa et al., 2009). To solve the problems of the bottom-up approach, inverse modeling is a powerful method. Kurokawa et al. (2011) developed a simple inversion model for the optimization of NOx emissions based on a regional CTM (CMAQ) and the satellite observations of NO2 vertical column densities. In this study, this system was applied to optimize NOx emissions over South Korea between 2001 and 2007. The Global Ozone Monitoring Experiment (GOME)/Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite observations of NO2 Vertical Column Densities and the CAPSS emission inventory data estimated by National Institute of Environmental Research, Korea (NIER, 2009) was used. References Kim, N.K, Kim, Y.P. and Kang C.H. (2011) Long-term trend of Aerosol Composition and Direct Radiative Forcing due to Aerosols over Gosan: TSP, PM10, and PM2.5 data between 1992 and 2008, submitted. Kurokawa, J. Yumimoto, K., Uno, I. and Ohara, T. (2009) Adjoint inverse modeling of NOx emissions over eastern China using satellite observations of NO2 vertical column densities, Atmospheric Environment, 43, 1878-1887. Kurokawa, J., Uno, I., and Ohara, T. (2011) Recent trends for air pollutants emissions in Asia: Update of Regional Emission Inventory in Asia (REAS), Second International Workshop on Emission Inventory in Asia, Tsukuba, Japan, March. National Institute of Environmental Research (2009) National air pollutants emission 2007. Incheon, Korea.

  2. Milagro Observations of TeV Emission from Galactic Sources in the Fermi Bright Source List

    Abdo, A A; Aune, T; Berley, D; Chen, C; Christopher, G E; DeYoung, T; Dingus, B L; Ellsworth, R W; Gonzlez, M M; Goodman, J A; Hays, E; Hoffman, C M; Huentemeyer, P H; Kolterman, B E; Linnemann, J T; McEnery, J E; Morgan, T; Mincer, A I; Nmethy, P; Pretz, J; Ryan, J M; Parkinson, P M Saz; Shoup, A; Sinnis, G; Smith, A J; Vasileiou, V; Walker, G P; Williams, D A; Yodh, G B

    2009-01-01

    We present the result of a search of Milagro sky map for spatial correlations with sources from a subset of the recent Fermi Bright Source List (BSL). The BSL consists of the 205 most significant sources detected above 100 MeV by the Fermi Large Area Telescope. We select sources based on their categorization in the BSL, taking all confirmed or possible Galactic sources in the field of view of Milagro. Of the 34 Fermi sources selected, 14 are observed by Milagro at a significance of 3 standard deviations or more. We conduct this search with a new analysis which employs newly-optimized gamma-hadron separation and utilizes the full 8-year Milagro dataset. Milagro is sensitive to gamma rays above 1 TeV and these results extend the observation of these sources far above the Fermi energy band. With the new analysis and additional data, TeV emission is definitively observed associated with the Fermi pulsar J2229.0+6114, in the the Boomerang Pulsar Wind Nebula (PWN). Furthermore, an extended region of TeV emission is...

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

    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...

  4. Determining The Galactic Halo's Emission Measure from UV and X-ray Observations

    Lei, Shijun; Henley, David B

    2009-01-01

    We analyze a pair of Suzaku shadowing observations in order to determine the X-ray spectrum of the Galaxy's gaseous halo. We simultaneously fit the spectra with models having halo, local, and extragalactic components. The intrinsic intensities of the halo OVII triplet and OVIII Lyman alpha emission lines are 9.98^{+1.10}_{-1.99} LU (line unit; photons cm^-2 s^-1 Sr^-1) and 2.66^{+0.37}_{-0.30} LU, respectively. Meanwhile, FUSE OVI observations for the same directions and SPEAR CIV observations for a nearby direction indicate the existence of hot halo gas at temperatures of ~10^{5.0} K to ~10^{6.0} K. This collection of data implies that the hot gas in the Galactic halo is not isothermal, but its temperature spans a relatively wide range from ~10^{5.0} K to ~10^{7.0} K. We therefore construct a differential emission measure (DEM) model for the halo's hot gas, consisting of two components. In each, dEM/dlog T is assumed to follow a power-law function of the temperature and the gas is assumed to be in collisiona...

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

    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.

  6. EMISSION HEIGHT AND TEMPERATURE DISTRIBUTION OF WHITE-LIGHT EMISSION OBSERVED BY HINODE/SOT FROM THE 2012 JANUARY 27 X-CLASS SOLAR FLARE

    White-light emissions were observed from an X1.7 class solar flare on 2012 January 27, using three continuum bands (red, green, and blue) of the Solar Optical Telescope on board the Hinode satellite. This event occurred near the solar limb, and so differences in the locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower heights in the solar atmosphere. The temperature distribution was also calculated from the white-light data, and we found the lower-layer emission to have a higher temperature. This indicates that high-energy particles penetrated down to near the photosphere, and deposited heat into the ambient lower layers of the atmosphere

  7. EVE-RHESSI Observations of Thermal and Nonthermal Solar Flare Emission

    McTiernan, James; Caspi, A.; Warren, H.

    2013-07-01

    Solar flares accelerate electrons up to hundreds of MeV and heat plasma to tens of MK. In large (GOES M- and X-class) flares, in addition to the 10-25 MK plasma thought to be the result of chromospheric evaporation, even hotter plasma (up to 50 MK) may be directly heated in the corona. While observations of hard X-ray bremmstrahlung directly probe the nonthermal electron population, for large flares the spectra below 20-30 keV are typically dominated by thermal emission. The low energy extent of the nonthermal spectrum can be only loosely quantified by hard X-ray spectrometers, resulting in significant implications for calculating flare energy budgets and for constraining possible acceleration mechanisms. A precise characterization of the thermal emission is imperative. Extreme ultraviolet observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO), combined with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), currently offer the most comprehensive view of the flare temperature distribution. EVE observes EUV emission lines with peak formation temperatures of 2-20 MK, while RHESSI observes the X-ray bremsstrahlung of hot, 10-50 MK plasma; combined, the two instruments cover the full range of flare plasma temperatures. In this work, we handle the EVE-RHESSI data for a few large flares in three steps; first we calculate differential emission measures (DEMs) using EVE and RHESSI independently for purposes of cross-calibration. Second, we create combined EVE-RHESSI DEMs, fixing the nonthermal spectral parameters to those found using a RHESSI-only spectral fit. The final step is to unconstrain the nonthermal parameters (in particular, the low-energy cutoff of the spectrum) and let them be fit in the same process as the EVE-RHESSI DEM, to obtain a fully self-consistent thermal plus nonthermal model. This research is supported by NASA Heliophysics Guest Investigator Grant NNX12AH48G.

  8. Near-Infrared Observations of Molecular Hydrogen Emission in Planetary Nebulae

    Likkel, Lauren; Kindt, Anna; Dinerstein, Harriet L.; Lester, Dan F.

    We are investigating the excitation mechanism of the near-infrared emission from vibrationally-excited H2 in planetary nebulae by means of long-slit spectroscopy. We present K-band spectroscopic observations of J 900, IC 5117, and Vy 2-2 obtained at McDonald Observatory. In these objects, the intensity ratios of the H2 lines suggest that either shock excitation is the dominant excitation mechanism, or that high densities have modified the emergent spectrum of a UV-illuminated region.

  9. SMA Observations of the Extended CO(6-5) Emission in the Starburst Galaxy NGC253

    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...

  10. The use of stereoscopic satellite observation in the determination of the emissivity of cirrus

    Szejwach, G.; Sletten, T. N.; Hasler, A. F.

    1982-01-01

    The feasibility of determining cirrus 'emissivity' from combined stereoscopic and infrared satellite observations in conjunction with radiosounding data is investigated for a particular case study. Simultaneous visible images obtained during SESAME-1979 from two geosynchronous GOES meteorological satellites were processed on the NASA Goddard interactive system (AOIPS) and were used to determine the stereo cloud top height Z sub C as described by Hasler (1981). Iso-contours of radiances were outlined on the corresponding infrared image. Total brightness temperature T sub B and ground surface brightness temperature T sub S were inferred from the radiances. The special SESAME network of radiosoundings was used to determine the cloud top temperature T sub CLD at the level defined by Z sub C. The 'effective cirrus emissivity' NE where N is the fractional cirrus cloudiness and E is the emissivity in a GOES infrared picture element of about 10 km x 10 km is then computed from T sub B, T sub S and T sub CLD.

  11. Evaluation of a plot-scale methane emission model using eddy covariance observations and footprint modelling

    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.

  12. Correcting atmospheric effects in thermal ground observations for hyperspectral emissivity estimation

    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 research was to enhance current methods for estimation of hyperspectral emissivity from field measurements. In particular the research focused on the atmospheric correction of the hyperspectral data, and the estimation of emissivity and temperature. For this, radiation measurements over different vegetation types were performed using the MIDAC thermal hyperspectral radiometer. The measurements of thermal radiation were performed in 2012 during ESA`s REFLEX fieldcampaign and each consisted of rapid acquisition of 4 targets: a hot and cold black-body (with predefined temperature), a gold plate and the vegetation-component of interest (vegetation/soil). The high spectral resolution of the measurement (at 0.5 cm-1 resolution) enables the characterization of individual gaseous absorption features and consequently allows for the atmospheric correction. Atmospheric correction of the 4 measurements was performed by creating a simple atmospheric correction model on basis of MODTRAN simulations. These MODTRAN outputs were converted to band resolutions using the spectral sensitivity of the MIDAC instrument. This approach enabled the estimation of different gas concentrations, such as C02 and H20, and at the same time atmospherically correct the raw measurements. Afterwards the data of the vegetation-component and gold plate (Infragold standard) were calibrated against the measurements of the hot/cold black bodies. Using the measurement of the gold plate the measured radiation from the vegetation-component was corrected for incoming radiation. Afterwards the temperature and emissivity of the vegetation-component was determined by fitting the atmospherically corrected data against the Planck curve. The success of the methodology was tested against measurements performed simultaneously with the MIDAC acquisitions. The atmospheric correction approach was tested by comparing the retrieved gaseous concentrations with LICOR 7500 measurements of these constituents. The TES estimations were evaluated by comparing the retrieved temperature with measurements of the vegetation-component skin temperature. Preliminary results show that the atmospheric is able to retrieve similar gaseous concentrations as measured from the flux towers. Unfortunately the atmospheric correction of the radiances is troubled by a mismatch of sensor sensitivity of the actual MIDAC instrument and the one used in the sensor simulator. This causes that specific absorption features are not fully corrected for. As a consequence the temperature retrieved using the TES step of the approach provides higher uncertainties in comparison with the skin temperature measurements. At present we investigate the improvement of the sensor sensitivity in the simulator and will present the findings in the presentation.

  13. Mobile Laboratory Observations of Methane Emissions in the Barnett Shale Region.

    Yacovitch, Tara I; Herndon, Scott C; Pétron, Gabrielle; Kofler, Jonathan; Lyon, David; Zahniser, Mark S; Kolb, Charles E

    2015-07-01

    Results of mobile ground-based atmospheric measurements conducted during the Barnett Shale Coordinated Campaign in spring and fall of 2013 are presented. Methane and ethane are continuously measured downwind of facilities such as natural gas processing plants, compressor stations, and production well pads. Gaussian dispersion simulations of these methane plumes, using an iterative forward plume dispersion algorithm, are used to estimate both the source location and the emission magnitude. The distribution of emitters is peaked in the 0-5 kg/h range, with a significant tail. The ethane/methane molar enhancement ratio for this same distribution is investigated, showing a peak at ∼1.5% and a broad distribution between ∼4% and ∼17%. The regional distributions of source emissions and ethane/methane enhancement ratios are examined: the largest methane emissions appear between Fort Worth and Dallas, while the highest ethane/methane enhancement ratios occur for plumes observed in the northwestern potion of the region. Individual facilities, focusing on large emitters, are further analyzed by constraining the source location. PMID:25751617

  14. Interannual and Seasonal Variability of Biomass Burning Emissions Constrained by Satellite Observations

    Duncan, Bryan N.; Martin, Randall V.; Staudt, Amanda C.; Yevich, Rosemarie; Logan, Jennifer A.

    2003-01-01

    We present a methodology for estimating the seasonal and interannual variation of biomass burning designed for use in global chemical transport models. The average seasonal variation is estimated from 4 years of fire-count data from the Along Track Scanning Radiometer (ATSR) and 1-2 years of similar data from the Advanced Very High Resolution Radiometer (AVHRR) World Fire Atlases. We use the Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data product as a surrogate to estimate interannual variability in biomass burning for six regions: Southeast Asia, Indonesia and Malaysia, Brazil, Central America and Mexico, Canada and Alaska, and Asiatic Russia. The AI data set is available from 1979 to the present with an interruption in satellite observations from mid-1993 to mid-1996; this data gap is filled where possible with estimates of area burned from the literature for different regions. Between August 1996 and July 2000, the ATSR fire-counts are used to provide specific locations of emissions and a record of interannual variability throughout the world. We use our methodology to estimate mean seasonal and interannual variations for emissions of carbon monoxide from biomass burning, and we find that no trend is apparent in these emissions over the last two decades, but that there is significant interannual variability.

  15. Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA

    Lewicki, J. L.; Hilley, G. E.

    2014-09-01

    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.

  16. Dust emissions of organic soils observed in the field and laboratory

    Zobeck, T. M.; Baddock, M. C.; Guo, Z.; Van Pelt, R.; Acosta-Martinez, V.; Tatarko, J.

    2011-12-01

    According to the U.S. Soil Taxonomy, Histosols (also known as organic soils) are soils that are dominated by organic matter (>20% organic matter) in half or more of the upper 80 cm. These soils, when intensively cropped, are subject to wind erosion resulting in loss in crop productivity and degradation of soil, air, and water quality. Estimating wind erosion on Histosols has been determined by USDA-Natural Resources Conservation Service as a critical need for the Wind Erosion Prediction System (WEPS) model. WEPS has been developed to simulate wind erosion on agricultural land in the US, including soils with organic soil material surfaces. However, additional field measurements are needed to calibrate and validate estimates of wind erosion of organic soils using WEPS. In this study, we used a field portable wind tunnel to generate suspended sediment (dust) from agricultural surfaces for soils with a range of organic contents. The soils were tilled and rolled to provide a consolidated, friable surface. Dust emissions and saltation were measured using an isokinetic vertical slot sampler aspirated by a regulated suction source. Suspended dust was collected on filters of the dust slot sampler and sampled at a frequency of once every six seconds in the suction duct using a GRIMM optical particle size analyzer. In addition, bulk samples of airborne dust were collected using a sampler specifically designed to collect larger dust samples. The larger dust samples were analyzed for physical, chemical, and microbiological properties. In addition, bulk samples of the soils were tested in a laboratory wind tunnel similar to the field wind tunnel and a laboratory dust generator to compare field and laboratory results. For the field wind tunnel study, there were no differences between the highest and lowest organic content soils in terms of their steady state emission rate under an added abrader flux, but the soil with the mid-range of organic matter had less emission by one third. In the laboratory wind tunnel, samples with the same ratio of erodible to non-erodible aggregates as the field soils were abraded and dust emissions were observed with the same sampling system as used in the field wind tunnel. In the dust generator, 5 gm samples < 8 mm diameter of each organic soil were rotated in a 50 cm long tube and the dust generated was observed with the GRIMM during a 20 minute run. Comparisons of the field dust emission rates with the laboratory results will be presented.

  17. The efficiency of the human observer for lesion detection and localization in emission tomography.

    Liu, Bin; Zhou, Lili; Kulkarni, Santosh; Gindi, Gene

    2009-05-01

    For the medically relevant task of joint detection and localization of a signal (lesion) in an emission computed tomographic (ECT) image, it is of interest to measure the efficiency, defined as the relative task performance of a human observer versus that of an ideal observer. Efficiency studies can be used in system optimization, improving postprocessing (e.g., reconstruction) algorithms, deriving human-emulating model observers and computer-aided detection methods. Calculation of ideal observer performance for ECT is highly computationally complex. We can, however, compute ideal observer performance exactly using a simplified 'filtered-noise' model of ECT. This model results in images whose correlation structure, due to quantum noise, background variability and regularization, is similar to that of real ECT reconstructed images. A two-alternative forced choice test is used to obtain the performance of the human observers. We compare the efficiency of our joint detection-localization task with that of a corresponding signal-known-exactly (SKE) detection task. For the joint task, efficiency is low when the search tolerance is stringent. Efficiency for the joint task rises with signal intensity but is flat for the SKE task. For both tasks, efficiency peaks at a mid-range level of regularization corresponding to a particular noise-resolution tradeoff. PMID:19351977

  18. Characteristics of severe thunderstorms studied with the aid of VLF atmospherics over North–East India

    A Guha; Trisanu Banik; Barin Kumar De; Rakesh Roy; Abhijit Choudhury

    2013-08-01

    Electromagnetic waves from lightning activity, commonly known as atmospherics or sferics serve as an effective tool for studying the lower ionosphere as well as thunderstorm activity. It is also useful for locating lightning strokes regionally and globally. In this paper, we present the analysis of the Integrated Field Intensity of Sferics (IFIS) at six discrete VLF frequencies for 30 lightning-associated overhead thunderstorms in Tripura, within the period from August 2009 to October 2010. An ingeniously developed well calibrated GPS locked software VLF receiver, located at the Department of Physics, Tripura University (23.5°N, 91.25°E), is used for the present study. Two distinct types of variations of IFIS, (i) single peak and (ii) dual peak are found characterizing each thunderstorm and their occurrence show nearly inverse character. The spectral character of IFIS rise rate, fall rate and rate of enhancement for each type is studied searching for suitable frequencies in the VLF range to forecast a thunderstorm. It is concluded that VLF sferics from 3–10 kHz are the most effective in terms nowcasting an incoming thunderstorm well before 3–4 hours of its peak occurrence, when there may not be any visual indication of the thunderstorm.

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

    A. Kolarski; D. Grubor

    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.

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

    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.

  1. Observing and modelling F-region ionospheric dynamics using the OII 7320A emission

    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, were analyzed to provide measurements of the meridional component of the ion convection velocity along the instrument line-of-sight. The DE-2 results presented demonstrate the first spaceborne use of the remote-sensing Doppler technique for measurements of ionospheric convection. The FPI meridional ion drift measurements were 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. The spaceborne interferometric technique has future utility for 2-dimensional imaging of polar ionospheric convection. Results from a simulated space-based observing platform, based on the DE-2 technique and an extension of a 7320A aeronomical model, are presented to demonstrate that a large fraction of the entire polar ionospheric convection pattern can be monitored from space during approximately 16-minute polar passes of a suitably-instrumented satellite. In the simulation, the polar-orbiting satellite's FPI system views the 7320A emission at various tangent point altitudes at +/- 45 deg and +/- 135 deg to the satellite velocity vector. By adjusting the horizon scan angle, several swaths of vectors at different horizontal spacing from the satellite can be recovered. Doppler line profiles from the (OII) 7320A emission at F-Region altitudes, made with the FPI at Sondre Stromfjord, Greenland, were analyzed to provide ion drift vectors and temperatures

  2. Photoelectron Spectroscopy of Hexachloroplatinate-Nucleobase Complexes: Nucleobase Excited State Decay Observed via Delayed Electron Emission

    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.

  3. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    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

  4. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    Sen, Ananya; Matthews, Edward M.; Hou, Gao-Lei; Wang, Xue-Bin; Dessent, Caroline E. H.

    2015-11-01

    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.

  5. Soft X-ray Observation of the Prompt Emission of GRB100418A

    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 ($E_{\\rm p}$-$E_{\\rm iso}$).

  6. Fermi Observations of high-energy gamma-ray emissions from GRB 080916C

    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.

  7. Theoretical analysis of conditions for observation of plasma oscillations in semiconductors from pulsed terahertz emission

    Reklaitis, Antanas, E-mail: reklaitis@pfi.lt [Semiconductor Physics Institute, Center for Physical Sciences and Technology, A. Goshtauto 11, Vilnius 01108 (Lithuania)

    2014-08-28

    Oscillations of electron-hole plasma generated by femtosecond optical pulse in freestanding semiconductor are studied using hydrodynamic model and Monte Carlo simulations. The conditions required for the observation of coherent plasma oscillations in THz emission from semiconductor are determined. It is shown that several conditions have to be fulfilled in order to observe coherent plasma oscillations. First, the intensity of the optical pulse must exceed some threshold value. Second, the optical absorption depth must exceed the thickness of the built-in electric field region. Third, the generation of electron-hole pairs with uniform illumination is required, i.e., the laser beam with the flattop intensity profile has to be used. It is found that the duration of the optical pulse does not play a vital role in the development of plasma oscillations.

  8. Fermi Observations of High-Energy Gamma-Ray Emission from GRB 080916C

    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 gamma-ray 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. (authors)

  9. Supermassive binary black holes - possible observational effects in the x-ray emission

    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

  10. Soft X-ray observation of the prompt emission of GRB 100418A

    Imatani, Ritsuko; Tomida, Hiroshi; Nakahira, Satoshi; Kimura, Masashi; Sakamoto, Takanori; Arimoto, Makoto; Morooka, Yoshitaka; Yonetoku, Daisuke; Kawai, Nobuyuki; Tsunemi, Hiroshi

    2015-09-01

    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 2.5? level.

  11. Observations of the 63 micron forbidden OI emission line in the Orion and Omega Nebulae

    Melnick, G.; Gull, G. E.; Harwit, M.

    1979-01-01

    Observations of 63-micron neutral oxygen emission from the Orion and Omega Nebulae are reported which were carried out from the NASA Lear Jet flying at an altitude of approximately 13.7 km. The best estimate for the 3 P 1 - 3 P 2 transition wavelength is shown to be 63.2 microns, and the detected fluxes are found to be extraordinarily high (amounting to approximately 600 suns in M42 at 0.5 kpc and to about 2900 suns in the line in M17 at 2 kpc). Attempts are made to estimate the minimum temperature and other parameters of the emitting region in Orion. It is concluded that conditions not too different from those permitted by some current models appear to provide fluxes that agree in order of magnitude with those observed.

  12. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research

    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

  13. Virtual Observatory tools and Amateur Radio Observations Supporting Scientific Analysis of Jupiter Radio Emissions

    Cecconi, B.; Hess, S. L. G.; Le Sidaner, P.; Savalle, R.; Erard, S.; Coffre, A.; Thétas, E.; André, N.; Génot, V.; Thieman, J.; Typinski, D.; Sky, J.; Higgins, C.

    2015-10-01

    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. Amateur radio data from the RadioJOVE project is also available. 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. A preliminary study based on January-February 2014 data will also be presented

  14. Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: From Theory to Fermi Observations

    Kalapotharakos, Constantinos; Kazanas, Demosthenes

    2013-01-01

    We compute the patterns of gamma-ray emission due to curvature radiation (CR) in dissipative pulsar magnetospheres. Our ultimate goal was to reveal the macrophysical models that are able to reproduce the observed gamma-ray light-curve phenomenology recently published in the Second Fermi Pulsar Catalog. Assuming Force-Free (FF) conditions for the closed magnetic field lines, on the open field lines we use specific dissipative prescriptions for the current density and a broad range for the conductivity values that result in solutions ranging from near-vacuum to near-FF. Using these dissipative models, we generated model gamma-ray light-curves by calculating realistic trajectories and Lorentz factors of particles, under the influence of both the accelerating electric fields and CR-reaction. In addition to modeling the gamma-ray light-curves we further constrained our models using the observed dependence of the phase-lags between the radio and gamma-ray emission on the gamma-ray peak-separation, one of the multiw...

  15. Synchrotron emission in GRBs observed by Fermi: its limitations and the role of the photosphere

    Iyyani, S.; Ryde, F.; Burgess, J. M.; Pe'er, A.; Bégué, D.

    2016-02-01

    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 eight brightest, single pulsed 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 magnetization of the jet (assuming the photosphere radius is above the coasting radius). Such a behaviour challenges several dissipation mechanisms, e.g. the internal shocks. Furthermore, in all eight cases the data clearly reject a fast-cooled synchrotron spectrum (in which a significant fraction of the emitting electrons have cooled to energies below the minimum injection energy), inferring a typical electron Lorentz factor of 104-107. Such values are much higher than what is typically expected in internal shocks. Therefore, while the synchrotron scenario is not rejected by the data, the interpretation does present several limitations that need to be addressed. Finally, we point out and discuss alternative interpretations.

  16. Characterization of urban methane emissions in Boston, Massachusetts using an observational network and inverse modeling framework

    McKain, K.; Wofsy, S. C.; John, B.; Hutyra, L.; Raciti, S.; Briber, B.; Phillips, N. G.; Jackson, R. B.; Down, A.; Schaaf, C.

    2012-12-01

    There is much uncertainty about the magnitude of methane emissions from natural gas production and delivery infrastructure, yet this quantity is necessary for understanding the climate impact of natural gas as a major fuel source and for partitioning the global methane budget. Preliminary evidence suggests that leaks from urban natural gas distribution systems may release substantial quantities of methane to the atmosphere, but this source has seldom been directly investigated in the scientific literature. As a case study, we seek to describe and quantify the natural gas fraction of the total methane source in the Boston, Massachusetts metropolitan region. We describe the design of an atmospheric methane monitoring network in and around the city. Periodic measurements of atmospheric ethane are used to estimate the fractional contribution of natural gas to the total observed urban methane enhancement. A methane emission inventory is compiled from high-resolution information on biogenic methane sources, street-level methane concentrations, and the natural gas distribution infrastructure. We present preliminary results from the observational network and an inverse modeling framework.

  17. Mars atmosphere studies with the SPICAM IR emission phase function observations

    Trokhimovskiy, Alexander; Fedorova, Anna; Montmessin, Franck; Korablev, Oleg; Bertaux, Jean-Loup

    Emission Phase Function (EPF) observations is a powerful tool for characterization of atmosphere and surface. EPF sequence provides the extensive coverage of scattering angles above the targeted surface location which allow to separate the surface and aerosol scattering, study a vertical distribution of minor species and aerosol properties. SPICAM IR instrument on Mars Express mission provides continuous atmospheric observations in near IR (1-1.7 mu) in nadir and limb starting from 2004. For the first years of SPICAM operation only a very limited number of EPFs was performed. But from the mid 2013 (Ls=225, MY31) SPICAM EPF observations become rather regular. Based on the multiple-scattering radiative transfer model SHDOM, we analyze equivalent depths of carbon dioxide (1,43 mu) and water vapour (1,38 mu) absorption bands and their dependence on airmass during observation sequence to get aerosol optical depths and properties. The derived seasonal dust opacities from near IR can be used to retrieve the size distribution from comparison with simultaneous results of other instruments in different spectral ranges. Moreover, the EPF observations of water vapour band allow to access poorly known H2O vertical distribution for different season and locations.

  18. SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP ) OBSERVATIONS: GALACTIC FOREGROUND EMISSION

    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 μK upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. Further, the cleaning process requires only three power-law foregrounds outside of the mask. We find no evidence for polarized foregrounds beyond those from soft (steep-spectrum) synchrotron and thermal dust emission; in particular 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 method, updated foreground masks, and updates to point source catalogs using two different techniques. With additional years of data, we now detect 471 point sources using a five-band technique and 417 sources using a three-band CMB-free technique. In total there are 62 newly detected point sources, a 12% increase over the five-year release. Also new are tests of the Markov chain Monte Carlo 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, the behavior in total intensity of low-frequency foregrounds is complicated and not completely understood. WMAP data show a rapidly steepening spectrum from 20 to 40 GHz, which may be due to emission from spinning dust grains, steepening synchrotron, or other effects. Comparisons are made to a 1 deg 408 MHz map (Haslam et al.) and the 11 deg ARCADE 2 data (Singal et al.). We find that spinning dust or steepening synchrotron models fit the combination of WMAP and 408 MHz data equally well. ARCADE data appear inconsistent with the steepening synchrotron model and consistent with the spinning dust model, though some discrepancies remain regarding the relative strength of spinning dust emission. More high-resolution data in the 10-40 GHz range would shed much light on these issues.

  19. Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission

    Gold, B.; Odegard, N.; Weiland, J. L.; Hill, R. S.; Kogut, A.; Bennett, C. L.; Hinshaw, G.; Chen, X.; 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.

    2011-02-01

    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 μK upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. Further, the cleaning process requires only three power-law foregrounds outside of the mask. We find no evidence for polarized foregrounds beyond those from soft (steep-spectrum) synchrotron and thermal dust emission; in particular 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 method, updated foreground masks, and updates to point source catalogs using two different techniques. With additional years of data, we now detect 471 point sources using a five-band technique and 417 sources using a three-band CMB-free technique. In total there are 62 newly detected point sources, a 12% increase over the five-year release. Also new are tests of the Markov chain Monte Carlo 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, the behavior in total intensity of low-frequency foregrounds is complicated and not completely understood. WMAP data show a rapidly steepening spectrum from 20 to 40 GHz, which may be due to emission from spinning dust grains, steepening synchrotron, or other effects. Comparisons are made to a 1 deg 408 MHz map (Haslam et al.) and the 11 deg ARCADE 2 data (Singal et al.). We find that spinning dust or steepening synchrotron models fit the combination of WMAP and 408 MHz data equally well. ARCADE data appear inconsistent with the steepening synchrotron model and consistent with the spinning dust model, though some discrepancies remain regarding the relative strength of spinning dust emission. More high-resolution data in the 10-40 GHz range would shed much light on these issues. WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.

  20. FORTE observations of simultaneous VHF and optical emissions from lightning: Basic phenomenology

    Preliminary observations of simultaneous VHF and optical emissions from lightning as seen by the Fast on-Orbit Recording of Transient Events (FORTE) spacecraft are presented. VHF/optical waveform pairs are routinely collected both as individual lightning events and as sequences of events associated with cloud-to-ground (CG) and intracloud (IC) flashes. CG pulses can be distinguished from IC pulses on the basis of the properties of the VHF and optical waveforms but mostly on the basis of the associated VHF spectrograms. The VHF spectrograms are very similar to previous ground-based HF and VHF observations of lightning and show signatures associated with return strokes, stepped and dart leaders, attachment processes, and intracloud activity. For a typical IC flash, the FORTE-detected VHF is generally characterized by impulsive broadband bursts of emission, and the associated optical emissions are often highly structured. For a typical initial return stroke, the FORTE-detected VHF is generated by the stepped leader, the attachment process, and the actual return stroke. For a typical subsequent return stroke, the FORTE-detected VHF is mainly generated by dart leader processes. The detected optical signal in both return stroke cases is primarily produced by the in-cloud portion of the discharge and lags the arrival of the corresponding VHF emissions at the satellite by a mean value of 243 ?s. This delay is composed of a transit time delay (mean of 105 ?s) as the return stroke current propagates from the attachment point up into the region of in-cloud activity plus an additional delay due to the scattering of light during its traversal through the clouds. The broadening of the light pulse during its propagation through the clouds is measured and used to infer a mean of this scattering delay of about 138 ?s (41 km additional path length) for CG light. This value for the mean scattering delay is consistent with the Thomason and Krider [1982] model for light propagation through clouds. (c) 2000 American Geophysical Union

  1. The Annual Cycle of Water Vapor on Mars as Observed by the Thermal Emission Spectrometer

    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.

  2. Modeling the thermal emission from asteroid 3 Juno using ALMA observations and the KRC thermal model

    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 Junos 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. 1659, id.2851. [11] Titus, T. N. (2015) Geophysical Research Letters, 42(7), 2130-2136.

  3. Copernicus observations of Ly-alpha and Mg II emission from HR 1099 /V711 Tauri/ and UX Ari

    Weiler, E. J.

    1978-01-01

    Ultraviolet observations of two RS CVn binaries obtained with Copernicus are described. High-resolution (0.05 A) U1 observations indicate that both HR 1099 and UX Ari display broad Ly-alpha emission. The Ly-alpha emission strength from HR 1099 is variable and seems to be correlated with orbital phase, while the UX Ari results indicate no significant variation. Moderate resolution (0.51 A) V2 scans of both systems show variable Mg II h and k emission-line profiles which usually matched the velocity of the more active star in each binary. Additionally, displaced emission components were seen at velocities of up to + or - 250 km/s, indicative of high-velocity gas motions. The radial velocities of these emission features from HR 1099 are marginally correlated with orbital phase. Highly active and variable chromospheric phenomena are found to be the most consistent explanation of these results.

  4. Observation of a physical matrix effect during cold vapour generation measurement of mercury in emissions samples

    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

  5. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission

    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...

  6. Derivation of an observation-based map of North African dust emission

    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.

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

    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...

  8. observations of hot molecular gas emission from embedded low-mass protostars

    Visser, R.; Kristensen, L. E.; Bruderer, S.; van Dishoeck, E. F.; Herczeg, G. J.; Brinch, C.; Doty, S. D.; Harsono, D.; Wolfire, M. G.

    2012-01-01

    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...... characteristics 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...

  9. Polarization observations in a low synchrotron emission field at 1.4 GHz

    Bernardi, G; Cortiglioni, S; Sault, R J; Kesteven, M J; Poppi, S

    2003-01-01

    We present the first observation of the diffuse polarized synchrotron radiation of a patch ($\\sim 3^\\circ \\times 3^\\circ$) in the BOOMERanG field, one of the areas with the lowest CMB foreground emission. The work has been carried out with the Australia Telescope Compact Array at 1.4 GHz with 3.4 arcmin resolution and sensitivity of $\\sim 0.18$ mJy beam$^{-1}$. The mean polarized signal has been found to be $P_{rms} = \\sqrt{(Q_{rms}^2 + U_{rms}^2)} = 11.6 \\pm 0.6$ mK, nearly one order of magnitude below than in the Galactic Plane. Extrapolations to frequencies of interest for cosmological investigations suggest that polarized synchrotron foreground noise should allow the detection of the CMB Polarization $E$--mode already at 32 GHz and make us confident that, at 90 GHz, it is accessible with no relevant foreground contamination. Last but not least, even the $B$--mode detection for $T/S > 0.01$ is not ruled out in such a low emission patch.

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

    Riemer-Sørensen, S.; Wik, D.; Madejski, G.; Molendi, S.; Gastaldello, F.; Harrison, F. A.; Craig, W. W.; Hailey, C. J.; Boggs, S. E.; Christensen, Finn Erland; Stern, D.; Zhang, W. W.; Hornstrup, Allan

    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....

  11. Building and the analysis of two radio antennas (SSRT) in vlf zone

    Marbouti, Marjan; Khakian Ghomi, Mehdi; Salmanpour Paeen Afrakati, Mohammad Reza; Riahi, Jahad; Ghanbari, Keyvan; Moradi Khanghahi, Abolfazl; Nahavandi, Behzad

    This design is a joint project between telecommunication and astrophysics subjects carried out for the first time in Iran. In this article, we engage in building of two looped antennas (SSRT) that the first type of it is a SSRT (octagonal looped antenna) with an outer filter system of 80 cm diameter, cable thickness of 0.55 mm, inductance 38.24 MH and capacitor’s capacitance of 919 pf. The software of Spectrum lab and SSRT Robot2 were used for software section and to store the related information. While second antenna type is a SSRT (two interconnected square type loop antennas) with inner filter system in the form of two interconnected squares with beveled corners such that the number of windings for outer square are (larger) 60 rounds, while for inner square (smaller) 95 rounds. The CATIA software was used to design the antenna structure and “Protel Dxp’’ software has been used to design its circuit. A program has been designed with C# language for receiving section and processing of data. Considering the closeness of Turkey transmitter to the city of Tehran (test location), the designed SSRTs are responsible for receiving the frequency of 26.7 kHz while TBB (Bafa, Turkey) is considered the frequency producing source for it. In the continuation of project, we started to store our receiving data from SSRTs following the calibration, average taking as well as noise elimination that was produced due to different factors such as the noises caused by electrical equipment and the everyday activities of telecommunication devices. In this stage, we were observing our receiving coincidences with all SSRTs as well as the Goes satellite. Afterwards, we dealt with the analysis of solar flares, sunrise-sunset effects and electrical disturbances. Then, in a separate project, the received data secured from 8 different VLF receivers were studied and examined, by means of Mr. Loudet receiver located in France, for the years of 2010, 2011 and 2012 and we attained the interesting results in this regard. The first result is that the time difference between SRT (time of rise end across ionosphere) and the sunrise as well as the SST (time of set beginning in ionosphere) and the sunset in the geographical location of signal encounter from ionosphere during summer is more as compared to winter season. And the second result is that we could measure a height of ionosphere by means of some calculations; during this period the signal had the maximum absorption. This is called the effective annihilation height and this effective annihilation height was secured for 8 VLF receivers. The results indicated that the effective annihilation height during autumn and winter seasons is higher and more than spring and summer seasons

  12. Observing Infrared Emission Lines of Neutron-Capture Species in Planetary Nebulae: New Detections with IGRINS

    Dinerstein, Harriet L.; Sterling, N. C.; Kaplan, Kyle F.; Bautista, Manuel A.

    2015-08-01

    As the former envelopes of evolved stars, planetary nebulae (PNe) present an opportunity to study slow neutron-capture reactions (the “s-process”) during the AGB. Such studies differ from those of AGB stars in two ways. First, PNe represent the end point of self-enrichment and dredge-up in the star and most of its mass return to the ISM, enabling us to infer the nucleosynthetic yield of a specific element. Second, some s-process products are observable in PNe but difficult or impossible to observe in cool stars. These include some species with nuclear charge Z in the 30’s for which the major synthesis sites are uncertain. Optical emission lines of trans-iron species have been observed in some PNe, but are faint and can suffer from blending with lines of more abundant elements (Péquignot & Baluteau 1994, A&A, 283, 593; Sharpee et al. 2007, ApJ, 659, 1265). Observing infrared transitions from low energy states has proven to be a fruitful alternate approach. We used K-band lines of Se (Z=34) and Kr (Z=36) to study the demographics of their abundances in a large sample of Milky Way PNe (Dinerstein 2001, ApJ, 550, L223; Sterling & Dinerstein 2008, ApJ, 174, 158; Sterling, Porter, & Dinerstein 2015, submitted). An L-band emission line of Zn identified by Dinerstein & Geballe (2001, ApJ, 562, 515) and further observed by Smith, Zijlstra, & Dinerstein 2014 (MNRAS, 441, 3161), can be used as a tracer of the Fe-group, enabling determinations of the key stellar population diagnostic ratio [alpha/Fe] in PNe (see poster by Dinerstein et al., Focus Meeting 4). Using IGRINS, a high spectral resolution H and K band spectrometer (Park & Jaffe et al. 2014, Proc SPIE, 9147), we have discovered several new lines not previously reported in any astronomical object. Our detection of an H-band line of Rb (Z=37) confirms previous claims of optical Rb detections and indicates enrichment by a factor of ~4 in the PN NGC 7027 (Sterling, Dinerstein, Kaplan, & Bautista, in preparation). We also detect lines that we tentatively identify as Ge (Z=32) and Cd (Z=48). This work was supported by NSF grants AST 0708429 and 1412928.

  13. Quantifying urban/industrial emissions of greenhouse and ozone-depleting gases based on atmospheric observations

    Barnes, Diana Hart

    2000-11-01

    Background and pollution trends and cycles of fourteen trace gases over the Northeastern U.S. are inferred from continuous atmospheric observations at the Harvard Forest research station located in Petersham, Massachusetts. This site receives background `clean' air from the northwest (Canada) and `dirty' polluted air from the southwest (New York City-Washington, D.C. corridor). Mixing ratios of gases regulated by the Montreal Protocol or other policies (CO, PCE, CFC11, CFC12, CFC113, CH 3CCl3, CCl4, and Halon-1211) and of those not subject to restrictions (H2, CH4, CHCl3, TCE, N2O, and SF6) were measured over the three-year period, 1996 to 1998, every 24 minutes by a fully automated gas chromatographic instrument with electron capture detectors. Evidence for polar vortex venting is found consistently in the month of June of the background seasonal cycles. The ratio of CO and PCE enhancements borne on southwesterly winds are in excellent agreement with county-level EPA and sales-based inventories for the New York City-Washington, D.C. region. From this firm footing, we use CO and PCE as reference compounds to determine the urban/industrial source strengths for the other species. A broad historical and geographic study of emissions reveals that the international treaty has by and large been a success. Locally, despite the passing of the 1996 Montreal Protocol ban, only emissions of CFC12 and CH3CCl3 are abating. Though source strengths are waning, the sources are not spent and continued releases to the atmosphere may be expected for some years to come. For CH3CCl3, whose rate of decline is central to our understanding of atmospheric processes, we estimate that absolute concentrations may persist until around the year 2010. The long-term high frequency time series of hydrogen provided here represents the first such data set of its kind. The H2 diurnal cycle is established and explained in terms of its sources and sinks. The ratio of H2 to CO in pollution plumes is found to be a seasonal and unchanged since early automobile exhaust studies of the 1960s, despite the many restrictions placed on car emissions and fuels since that time. Based on this result, a spatial inventory of H2 emissions from fossil fuel combustion is developed at the county level for the entire Northeastern U.S.

  14. Impact of emission controls on air quality in Beijing during APEC 2014: lidar ceilometer observations

    Tang, G.; Zhu, X.; Hu, B.; Xin, J.; Wang, L.; Münkel, C.; Mao, G.; Wang, Y.

    2015-11-01

    The implementation of emission reductions during the 2014 Asia-Pacific Economic Cooperation (APEC) summit provides a valuable opportunity to study air pollution in Beijing. From 15 October to 30 November 2014, the height of the atmospheric mixing layer and the vertical attenuated backscattering coefficient profiles were observed online using a~lidar ceilometer. Compared with fine particulate matter (PM2.5) and aerosol optical depth (AOD) data, the attenuated backscattering coefficients measured by the lidar ceilometer were strongly correlated with the PM2.5 concentration and AOD (correlation coefficients of 0.89 and 0.86, respectively). This result demonstrated the reliability of the vertical distribution of particles measured by the lidar ceilometer. By classifying different degrees of air pollution based on visibility, we found that during the transition period of air pollution, which was affected by transport of southerly flows in the mixing layer, the attenuated backscattering coefficient from 0 to 1500 m was enhanced by approximately 1.4 Mm-1 sr-1 (140 %). During the polluted period, the attenuated backscattering coefficient from 0 to 300 m suddenly increased, and the coefficient near the surface peaked (approximately 14 Mm-1 sr-1); however, the attenuated backscattering coefficient from 300 to 900 m decreased gradually, and the average value from 0 to 1500 m decreased by 0.5 Mm-1sr-1 (20 %). The height of the mixing layer gradually decreased, and the ratio of CO / SO2 gradually increased, which indicate that the polluted period was dominated by local contribution. Due to the emission reductions during APEC (DAPEC), the concentration of PM2.5 decreased by 59.2 and 58.9 % and visibility improved by 70.2 and 56.0 % compared to before (BAPEC) and after APEC (AAPEC), respectively. The contribution of regional transport in DAPEC decreased by approximately 36 and 25 %, and the local contribution decreased by approximately 48 and 54 % compared to BAPEC and AAPEC, respectively. The most effective method of controlling air pollution in the Beijing area is to reduce regional emissions during the transition period and reduce local emissions during the polluted period.

  15. XMM-Newton Observation of Fe K(alpha) Emission from a BAL QSO: Mrk 231

    Turner, T. J.; Kraemer, S. B.

    2003-01-01

    We present results from a 20 ksec XMM-Newton observation of Mrk 231. EPIC spectral data reveal strong line emission due to Fe K alpha, which has rarely been detected in this class, as BAL QSOs are very faint in the X-ray band. The line energy is consistent with an origin in neutral Fe. The width of the line is equivalent to a velocity dispersion approximately 18,000 kilometers per second and thus the line may be attributed to transmission and/or reflection from a distribution of emitting clouds. If, instead, the line originates in the accretion disk then the line strength and flat X-ray continuum support some contribution from a reflected component, although the data disfavor a model where the hard X-ray band is purely reflected X-rays. The line parameters are similar to those obtained for the Fe Ka line detected in another BAL QSO, H1413 + 117.

  16. Observations of the Quadrantid meteor shower from 2008 to 2012: orbits and emission spectra

    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.

  17. Observation of stimulated emission in an ultrashort-period nonsymmetric GaAs/AlAs superlattice

    Nonsymmetric short-period GaAs/AlAs superlattices, for which the well thickness is at least a factor of 2 larger than the barrier thickness, have been shown to exhibit a direct band gap for any well thickness. These superlattices are characterized by an enhanced intensity of the luminescence as compared to their symmetric indirect-gap counterparts with the same well width, and, thus, may be used as light-emitting devices, in particular, as low-threshold lasers in the red visible spectrum. This conjecture is supported by the observation of stimulated emission at T=80K for a GaAs/AlAs superlattice with six monolayers well and three monolayers barrier width. [copyright] 2001 American Institute of Physics

  18. Observation of extreme ultraviolet emission from hydrogen-KI plasmas produced by a hollow cathode discharge

    Mills, R.L. [BlackLight Power, Inc., Cranbury, NJ (United States)

    2001-06-01

    A high-voltage discharge of hydrogen with and without the presence of a source of potassium, potassium iodide, in the discharge was performed with a hollow cathode. It has been reported that intense extreme ultraviolet (EUV) emission was observed from atomic hydrogen and certain elements or certain ions which ionize at integer multiples of the potential energy of atomic hydrogen, 27.2 eV (Mills et al., 1999 Pacific Conference on Chemistry and Spectroscopy and the 35th ACS Western Regional Meeting, Ontario Convention Center, Ontario, CA, October 6-8, 1999; Mills et al., Int. J. Hydrogen Energy 2000;25:919; Mills, Int. J. Hydrogen Energy 2001;26:327; Mills, Lu and Onuma, Int. J. Hydrogen Energy 2001 in press; Mills et al., Int. J. Hydrogen Energy 2001;26:309; Mills et al., June ACS Meeting, 29th Northeast Regional Meeting, University of Connecticut, Storrs, CT, June 18-2 1, 2000). Two potassium ions or a potassium atom may each provide an electron ionization or transfer reaction that has a net enthalpy equal to an integer multiple of 27.2 eV. The spectral lines of atomic hydrogen were intense enough to be recorded on photographic films only when KI was present. EUV lines not assignable to potassium, iodine, or hydrogen were observed at 73.0,132.6,513.6,677.8,885.9, and 1032.9 Angstrom. The lines could be assigned to transitions of atomic hydrogen to lower-energy levels corresponding to lower-energy hydrogen atoms called hydrino atoms and the emission from the excitation of the corresponding hydride ions formed from the hydrino atoms. (author)

  19. Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems

    Designed, green infrastructures are becoming a customary feature of the urban landscape. Sustainable technologies for stormwater management, and biofilters in particular, are increasingly used to reduce stormwater runoff volumes and peaks as well as improve the water quality of runoff discharged into urban water bodies. Although a lot of research has been devoted to these technologies, their effect in terms of greenhouse gas fluxes in urban areas has not been yet investigated. We present the first study aimed at quantifying greenhouse gas fluxes between the soil of stormwater biofilters and the atmosphere. N2O, CH4, and CO2 were measured periodically over a year in two operational vegetated biofiltration cells at Monash University in Melbourne, Australia. One cell had a saturated zone at the bottom, and compost and hardwood mulch added to the sandy loam filter media. The other cell had no saturated zone and was composed of sandy loam. Similar sedges were planted in both cells. The biofilter soil was a small N2O source and a sink for CH4 for most measurement events, with occasional large emissions of both N2O and CH4 under very wet conditions. Average N2O fluxes from the cell with the saturated zone were almost five-fold greater (65.6 μg N2O–N m−2 h−1) than from the other cell (13.7 μg N2O–N m−2 h−1), with peaks up to 1100 μg N2O–N m−2 h−1. These N2O fluxes are of similar magnitude to those measured in other urban soils, but with larger peak emissions. The CH4 sink strength of the cell with the saturated zone (− 3.8 μg CH4–C m−2 h−1) was lower than the other cell (− 18.3 μg CH4–C m−2 h−1). Both cells of the biofilter appeared to take up CH4 at similar rates to other urban lawn systems; however, the biofilter cells displayed occasional large CH4 emissions following inflow events, which were not seen in other urban systems. CO2 fluxes increased with soil temperature in both cells, and in the cell without the saturated zone CO2 fluxes decreased as soil moisture increased. Other studies of CO2 fluxes from urban soils have found both similar and larger CO2 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

  20. Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems

    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

    Designed, green infrastructures are becoming a customary feature of the urban landscape. Sustainable technologies for stormwater management, and biofilters in particular, are increasingly used to reduce stormwater runoff volumes and peaks as well as improve the water quality of runoff discharged into urban water bodies. Although a lot of research has been devoted to these technologies, their effect in terms of greenhouse gas fluxes in urban areas has not been yet investigated. We present the first study aimed at quantifying greenhouse gas fluxes between the soil of stormwater biofilters and the atmosphere. N{sub 2}O, CH{sub 4}, and CO{sub 2} were measured periodically over a year in two operational vegetated biofiltration cells at Monash University in Melbourne, Australia. One cell had a saturated zone at the bottom, and compost and hardwood mulch added to the sandy loam filter media. The other cell had no saturated zone and was composed of sandy loam. Similar sedges were planted in both cells. The biofilter soil was a small N{sub 2}O source and a sink for CH{sub 4} for most measurement events, with occasional large emissions of both N{sub 2}O and CH{sub 4} under very wet conditions. Average N{sub 2}O fluxes from the cell with the saturated zone were almost five-fold greater (65.6 μg N{sub 2}O–N m{sup −2} h{sup −1}) than from the other cell (13.7 μg N{sub 2}O–N m{sup −2} h{sup −1}), with peaks up to 1100 μg N{sub 2}O–N m{sup −2} h{sup −1}. These N{sub 2}O fluxes are of similar magnitude to those measured in other urban soils, but with larger peak emissions. The CH{sub 4} sink strength of the cell with the saturated zone (− 3.8 μg CH{sub 4}–C m{sup −2} h{sup −1}) was lower than the other cell (− 18.3 μg CH{sub 4}–C m{sup −2} h{sup −1}). Both cells of the biofilter appeared to take up CH{sub 4} at similar rates to other urban lawn systems; however, the biofilter cells displayed occasional large CH{sub 4} emissions following 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.

  1. Estimation of NOx emissions from Delhi using Car MAX-DOAS observations and comparison with OMI satellite data

    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.

  2. Seasonal and diurnal variation of ELF emission occurrences at 750-Hz band observed at geomagnetically conjugate stations

    Suzuki, Hiroyuki (Yamagata Univ. (Japan)); Sato, Natsuo (National Inst. of Polar Research, Tokyo (Japan))

    1987-06-01

    Statistical characteristics of emission occurrence are examined, using digital data of 750-Hz intensity records obtained at the conuugate pai of statins, Syowa Station in Antarrctica and Husafell in Iceland. The geographic local time at Syowa and Husafell is magnetic local time plus 3 hours and minur 1 hour, respectively. The following notable diurnal variations and seasonal variations were found: (1) The emissions were mostly observed during the daytime in the conjugate region. However, the magnetic local time when the emission occurrence rate reached maximum at Husafell was 2-3 hours later than that at Syowa. (2) The seasonal variations of emission occurrence showed the same tendency at the conjugate stations. The emission intensities showed a maximum during local summer and a minimum during local winter in both hemispheres. The ratio fo average emission intensity in each season to the intensity in winter is approximately 2.1-2.2 for summer, 1.7-1.9 for autumn, and 1.7 for spring. From these statistical characteristics, ELF emission intensity strongly depends on not only magnetic local time but also geographic local time and seasons, suggesting that ELF emissions observed on the ground are strongly controlled by the sunlight effects. The sunlight may affect the asymmetry of wave duct enhancement and wave propagation from the magnetosphere to the ionosphere in both hemisphers. Other effects are also discussed in this paper.

  3. Seasonal and diurnal variation of ELF emission occurrences at 750-Hz band observed at geomagnetically conjugate stations

    Statistical characteristics of emission occurrence are examined, using digital data of 750-Hz intensity records obtained at the conuugate pai of statins, Syowa Station in Antarrctica and Husafell in Iceland. The geographic local time at Syowa and Husafell is magnetic local time plus 3 hours and minur 1 hour, respectively. The following notable diurnal variations and seasonal variations were found: (1) The emissions were mostly observed during the daytime in the conjugate region. However, the magnetic local time when the emission occurrence rate reached maximum at Husafell was 2-3 hours later than that at Syowa. (2) The seasonal variations of emission occurrence showed the same tendency at the conjugate stations. The emission intensities showed a maximum during local summer and a minimum during local winter in both hemispheres. The ratio fo average emission intensity in each season to the intensity in winter is approximately 2.1-2.2 for summer, 1.7-1.9 for autumn, and 1.7 for spring. From these statistical characteristics, ELF emission intensity strongly depends on not only magnetic local time but also geographic local time and seasons, suggesting that ELF emissions observed on the ground are strongly controlled by the sunlight effects. The sunlight may affect the asymmetry of wave duct enhancement and wave propagation from the magnetosphere to the ionosphere in both hemisphers. Other effects are also discussed in this paper

  4. XMM-Newton Observations of MBM 12: More Constraints on the Solar Wind Charge Exchange and Local Bubble Emissions

    Koutroumpa, Dimitra; Smith, Randall K.; Edgar, Richard J.; Kuntz, Kip D.; Plucinsky, Paul P.; Snowden, Steven L.

    2010-01-01

    We present the first analysis of an XMM-Newton observation of the nearby molecular cloud MBM 12. We find that in the direction of MBM 12 the total O VII (0.57 keV) triplet emission is 1.8(+0.5/-0.6) photons/sq cm/s/sr (or Line Units - LU) while for the O VIII (0.65 keV) line emission we find a 3(sigma) upper limit of Newton observations. This comparison provides new constraints on the relative heliospheric and Local Bubble contributions to the local diffuse X-ray background. The heliospheric SWCX model predicts 0.82 LU for O VII, which accounts for approx. 46+/-15% of the observed value, and 0.33 LU for the O VIII line emission consistent with the XMM-Newton observed value. We discuss our results in combination with previous observations of the MBM 12 with CHANDRA and Suzaku.

  5. Observations and modeling of the dust emission from the H2-bright galaxy-wide shock in Stephan's Quintet

    Guillard, P; Cluver, M E; Appleton, P N; Forets, G Pineau des; Ogle, P

    2010-01-01

    Spitzer Space Telescope observations revealed powerful mid-infrared (mid-IR) H2 rotational line emission from the Stephan's Quintet (SQ) X-ray emitting large scale shock associated with a collision between two galaxies. Because H2 forms on dust grains, the presence of H2 is physically linked to the survival of dust, and we expect some dust emission to come from the molecular gas. To test this interpretation, IR observations and dust modeling are used to identify and characterize the thermal dust emission from the shocked molecular gas. The spatial distribution of the IR emission allows us to isolate the faint PAH and dust continuum emission associated with the molecular gas in the SQ shock. We model the spectral energy distribution (SED) of this emission, and fit it to Spitzer observations. Faint PAH and dust continuum emission are detected in the SQ shock, outside star-forming regions. The 12/24um flux ratio in the shock is remarkably close to that of the diffuse Galactic interstellar medium, leading to a Ga...

  6. Direct observation of electron emission from the grain boundaries of chemical vapour deposition diamond films by tunneling atomic force microscopy

    The emission of electrons from diamond in vacuum occurs readily as a result of the negative electron affinity of the hydrogenated surface due to features with nanoscale dimensions, which can concentrate electric fields high enough to induce electron emission from them. Electrons can be emitted as a result of an applied electric field (field emission) with possible uses in displays or cold-cathode devices. Alternatively, electrons can be emitted simply by heating the diamond in vacuum to temperatures as low as 350?C (thermionic emission), and this may find applications in solar energy generation or energy harvesting devices. Electron emission studies usually use doped polycrystalline diamond films deposited onto Si or metallic substrates by chemical vapor deposition, and these films have a rough, faceted morphology on the micron or nanometer scale. Electron emission is often improved by patterning the diamond surface into sharp points or needles, the idea being that the field lines concentrate at the points lowering the barrier for electron emission. However, there is little direct evidence that electrons are emitted from these sharp tips. The few reports in the literature that have studied the emission sites suggested that emission came from the grain boundaries and not the protruding regions. We now present direct observation of the emission sites over a large area of polycrystalline diamond using tunneling atomic force microscopy. We confirm that the emission current comes mostly from the grain boundaries, which is consistent with a model for emission in which the non-diamond phase is the source of electrons with a threshold that is determined by the surrounding hydrogenated diamond surface

  7. Ionospheric perturbations associated with two huge earthquakes in Japan, using principal component analysis for multiple subionospheric VLF/LF propagation paths

    Maria Solovieva

    2012-04-01

    Full Text Available

    The presence of ionospheric perturbations in possible association with two huge earthquakes (Noto-hanto peninsula and Niigata-chuetu-oki earthquakes in 2007 was studied on the basis of a conventional statistical study for a particular propagation path from the JJI transmitter in Miyazaki, Kyushu, to Moshiri in Hokkaido. This is based on automatic routine-based signal processing, in which the trend as the average nighttime amplitude is significantly decreased, with almost simultaneous significant enhancement in the night-time fluctuation as the night-time integration of negative fluctuation from the average. It is, however, shown that this routine-based signal analysis sometime suffers from artificial (or man-made effects. Thus, in this study, we propose an additional use of principal component analysis (PCA for simultaneous observation of a few VLF/LF propagation paths. With the application of this PCA method to multi-path data, the artificial effects can be reasonably removed, and also only the geophysical effects associated with earthquakes are detected, by focusing mainly on the third principal component. The satisfactory separation of the principal components is made possible by pre-analysis of the VLF data (extraction from the raw data of the average over a whole year. This PCA method enables us to identify the seismogenic effects in association with earthquakes with smaller magnitudes, down to M 5.5 or M 5.0.

     

  8. Airborne Ethane Observations over the Barnett and Bakken Shale Formations: Quantification of Ethane Fluxes and Attribution of Methane Emissions

    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 from the Barnett and Bakken regions were observed (1% to 10% of estimated national ethane emissions), and emissions of these magnitudes may significantly impact regional atmospheric chemistry and air quality by influencing production of tropospheric ozone.

  9. ECLAIRs: A satellite for observing the prompt optical and X-ray emission of Gamma-Ray Bursts

    Barret, Didier; Atteia, Jean-Luc; Boer, M.; Mochkovitch, F. R.; Daigne, F.; Paul, J.; Goldoni, P.; Henri, G.; Pelletier, G.; Reglero, V.; Rodrigo, J. M.; Castro-Tirado, A.; Beloborodov, A.; Poutanen, J.; Svensson, R.; Ricker, G.; Jernigan, G.; Martel, F.; Dingus, B.; Hurley, K.; Lamb, D.

    2001-05-01

    Gamma-ray bursts are the most energetic explosions observed in the Universe. Their cosmological origin as well as the discovery of their X-ray and optical afterglows has led to a standard model in which a gamma-ray burst is associated with the fast accretion of matter onto a black hole. In this model, the gamma-ray emission is produced when an ultra-relativistic energy-flow is converted into radiation. Due to the lack of observations, the origin of the prompt emission observed in gamma-rays, in X-rays and in the optical remains highly speculative. It is commonly agreed, however, that this emission hides critical information about the formation and acceleration of the relativistic wind and the emission mechanisms at work during the bursts. ECLAIRs is a microsatellite devoted to the observation of the prompt emission of gamma-ray bursts (and of the transition to the afterglow regime) at optical and X-rays wavelengths. Is this emission thermal ? Is it produced in internal or reverse shocks? What's its link with the gamma-ray emission? As many questions as ECLAIRs will answer. ECLAIRs is unique as it will observe the prompt optical and X-ray emission of about 150 bursts/year, and localize them to better than 5 arcsecond in almost real time. Furthermore ECLAIRs is proposed to operate simultaneously wit GLAST on a similar orbit. The combination of the GLAST/Gamma-Ray Burst Monitor and ECLAIRs will provide an unprecedented spectral coverage, from eV to GeV, for about 100 bursts a year. We will outline the scientific objectives of ECLAIRs and describe the science payload and the mission implementation. ECLAIRs is based on an international collaboration involving European and American theoretical and hardware groups.

  10. CHIANTI - An atomic database for emission lines. XI. EUV emission lines of Fe VII, Fe VIII and Fe IX observed by Hinode/EIS

    Young, P R; Landi, E.

    2009-01-01

    A detailed study of emission lines from Fe VII, Fe VIII and Fe IX observed by the EUV Imaging Spectrometer on board the Hinode satellite is presented. Spectra in the ranges 170-212 A and 246-292 A show strongly enhanced lines from the upper solar transition region (temperatures 5.4

  11. New radio observations of anomalous microwave emission in the HII region RCW175

    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...

  12. Solar Flare Chromospheric Line Emission: Comparison Between IBIS High-resolution Observations and Radiative Hydrodynamic Simulations

    da Costa, Fatima Rubio; Petrosian, Vahé; Dalda, Alberto Sainz; Liu, Wei

    2014-01-01

    Solar flares involve impulsive energy release, which results in enhanced radiation in a broad spectral and at a wide height range. In particular, line emission from the chromosphere (lower atmosphere) can provide critical diagnostics of plasma heating processes. Thus, a direct comparison between high-resolution spectroscopic observations and advanced numerical modeling results can be extremely valuable, but has not been attempted so far. We present in this paper such a self-consistent investigation of an M3.0 flare observed by the Dunn Solar Telescope's (DST) Interferometric Bi-dimensional Spectrometer (IBIS) on 2011 September 24 that we have modeled with the radiative hydrodynamic code RADYN (Carlsson & Stein 1992, 1997; Abbett & Hawley 1999; Allred et al. 2005). We obtained images and spectra of the flaring region with IBIS in H$\\alpha$ 6563 \\AA\\ and Ca II 8542 \\AA, and with the Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI) in X-rays. The latter was used to infer the non-thermal elect...

  13. Observations of 6 - 200 {\\mu}m emission of the Ophiuchus cloud LDN 1688

    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...

  14. On the reconstructing the coronal magnetic field from Fe XIII 10747 A emission line observations

    Kramar, M.; Lin, H.; Inhester, B.

    2009-12-01

    Magnetic fields in the solar corona are the dominant fields that determine the static and dynamic properties of this outermost region of the solar atmosphere. It is within this tenuous region that the magnetic force dominates the gas pressure. Direct measurement of the coronal magnetic field is one of the most challenging problems in observational solar astronomy. To date, one of the promising measurement methods that have been successfully demonstrated is the spectropolarimetric measurement of the Fe XIII 10747 A forbidden emission line (CEL) (Lin, Penn, Tomczyk 2000; Lin, Kuhn, Coulter 2004; Tomczyk et al. 2007) formed due to Hanle and Zeeman effects. However, because coronal measurements are integrated over line-of-site (LOS), it is impossible to derive the configuration of the coronal magnetic field from a single observation (from a single viewing direction). Recent development in vector tomography techniques based on IR forbidden CEL polarization measurements from several viewing direction (Kramar, Inhester, Solanki 2006; Kramar, Inhester 2007) has the potential to resolve the 3D coronal magnetic field structure. In this paper, we will present a study of the effects of instrumental characteristics on the results of vector tomographic inversion using simulated data. We also investigate the sensitivity of the vector tomographic inversion to different coronal magnetic field configuration.

  15. Direct Observation of Solar Coronal Magnetic Fields by Vector Tomography of the Coronal Emission Line Polarizations

    Kramar, M.; Lin, H.; Tomczyk, S.

    2016-03-01

    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.

  16. SOFIA observations of far-infrared hydroxyl emission toward classical ultracompact HII/OH maser regions

    Csengeri, T; Wyrowski, F; Requena-Torres, M A; Güsten, R; Wiesemeyer, H; Hübers, H -W; Hartogh, P; Jacobs, K

    2012-01-01

    The hydroxyl radical (OH) is found in various environments within the interstellar medium (ISM) of the Milky Way and external galaxies, mostly either in diffuse interstellar clouds or in the warm, dense environments of newly formed low-mass and high-mass stars, i.e, in the dense shells of compact and ultracompact HII regions (UCHIIRs). Until today, most studies of interstellar OH involved the molecule's radio wavelength hyperfine structure (hfs) transitions. These lines are generally not in LTE and either masing or over-cooling complicates their interpretation. In the past, observations of transitions between different rotational levels of OH, which are at far-infrared wavelengths, have suffered from limited spectral and angular resolution. Since these lines have critical densities many orders of magnitude higher than the radio wavelength ground state hfs lines and are emitted from levels with more than 100 K above the ground state, when observed in emission, they probe very dense and warm material. We probe ...

  17. Submillimeter Array Observations of 321 GHz Water Maser Emission in Cepheus A

    Patel, N A; Zhang, Q; Sridharan, T K; Ho, P T P; Torrelles, J M

    2007-01-01

    Using the Submillimeter Array (SMA) we have imaged for the first time the 321.226 GHz, 10_{29}-9_{36} ortho-H2O maser emission. This is also the first detection of this line in the Cepheus A high-mass star-forming region. The 22.235 GHz, 6_{16}-5_{23} water masers were also observed with the Very Large Array 43 days following the SMA observations. Three of the nine detected submillimeter maser spots are associated with the centimeter masers spatially as well as kinematically, while there are 36 22 GHz maser spots without corresponding submillimeter masers. In the HW2 source, both the 321 GHz and 22 GHz masers occur within the region of ~1'' which includes the disk-jet system, but the position angles of the roughly linear structures traced by the masers indicate that the 321 GHz masers are along the jet while the 22 GHz masers are perpendicular to it. We interpret the submillimeter masers in Cepheus A to be tracing significantly hotter regions (600~2000 K) than the centimeter masers.

  18. Observations of the 63 micron [O I] emission line in the Orion and Omega Nebulae

    We report the first observations of the 63 μm fine-structure transition rho4: 3P1→3P2 for neutral atomic oxygen. The measurements were obtained during a series of flights on the NASA Lear Jet at an altitude of approx.13.7 km. In the Orion Nebula (M42) our observed line strength is 8 x 10-5 W cm-2, which we estimate to be approx.0.3% of the energy radiated at all wavelengths. For the Omega Nebula (M17) the line strength is 2.4 x 10-15 W cm-2, and the fraction of the total radiated power is slightly higher. These figures refer to a 4' x 6' field of view centered on the peak far-infrared emission from each source. The uncertainty in the line strength is approx.50% and is caused by variable water-vapor absorption along the flight path of the airplane. Our estimate of the line position is 63.2 μm (+0.1, -0.2 μm). The prime uncertainty is due to the uncertain position of the [O I] emitting regions in our field of view

  19. Constraints on ship NOx emissions in Europe using GEOS-Chem and OMI satellite NO2 observations

    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.

  20. Emissions of mercury in southern Africa derived from long-term observations at Cape Point, South Africa

    E.-G. Brunke

    2012-08-01

    Full Text Available Mercury emissions in South Africa have so far been estimated only by a bottom-up approach from activities and emission factors for different processes. In this paper we derive GEM/CO (GEM being gaseous elemental mercury, Hg0, GEM/CO2, GEM/CH4, CO/CO2, CH4/CO2, and CH4/CO emission ratios from plumes observed during long-term monitoring of these species at Cape Point between March 2007 and December 2009. The average observed GEM/CO, GEM/CO2, GEM/CH4, CO/CO2, CH4/CO2, and CH4/CO emission ratios were 2.40 2.65 pg m?3 ppb?1 (n = 47, 62.7 80.2 pg m?3 ppm?1 (n = 44, 3.61 4.66 pg m?3 ppb?1 (n = 46, 35.6 25.4 ppb ppm?1 (n = 52, 20.2 15.5 ppb ppm?1 (n = 48, and 0.876 1.106 ppb ppb?1 (n = 42, respectively. The observed CO/CO2, CH4/CO2, and CH4/CO emission ratios agree within the combined uncertainties of the observations and emissions with the ratios calculated from EDGAR (version 4.2 CO2, CO, and CH4 inventories for South Africa and southern Africa (South Africa, Lesotho, Swaziland, Namibia, Botswana, Zimbabwe, and Mozambique in 2007 and 2008 (inventories for 2009 are not available yet. Total elemental mercury emission of 13.1, 15.2, and 16.1 t Hg yr?1 are estimated independently using the GEM/CO, GEM/CO2, and GEM/CH4 emission ratios and the annual mean CO, CO2, and CH4 emissions, respectively, of South Africa in 2007 and 2008. The average of these independent estimates of 14.8 t GEM yr?1 is much less than the total emission of 257 t Hg yr?1 shown by older inventories which are now considered to be wrong. Considering the uncertainties of our emission estimate, of the emission inventories, and the fact that emission of GEM represents 5078 % of all mercury emissions, our estimate is comparable to the currently cited GEM emissions in 2004 and somewhat smaller than emissions in 2006. A further increase of mercury emissions due to increasing electricity consumption will lead to a more pronounced difference. A quantitative assessment of the difference and its significance, however, will require emission inventories for the years of observations (20072009 as well as better data on the speciation of the total mercury emissions in South Africa.