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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

    International Nuclear Information System (INIS)

    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. World map of ELF/VLF emissions as observed by a low-orbiting satellite

    International Nuclear Information System (INIS)

    Statistical studies were performed of the intensities of the ELF/VLF emissions observed by the low-orbiting satellite AUREOL-3. Data were obtained from filterbanks and the frequency range of observations extends from a few tens of Hz up to 15 kHz. The most important phenomena observed are ELF hiss and VLF hiss. Electric and magnetic components are used. Thus, representation of the waves intensities in geographical coordinates was made at different frequencies. The relative ability of natural waves (whistler, hiss) and man-made waves, such as powerful VLF transmitters or powerline harmonic radiations (PLHR), to precipitate particles in the slot region, is studied. Using geomagnetical representation, it is shown that ELF hiss is maximum between 06 and 20 Magnetic Local Time and in the invariant latitude range 500-700 as usual, but geographic representation indicates that the waves are intensified at the longitudes of VLF transmitters and near the South Atlantic Anomaly (SAA). The SAA plays a dominant role in the localization of the strongest ELF hiss. Weakest intensities are observed to the east of the SAA. As to the VLF hiss, the maximum intensity is related to regions of enhanced thunderstorm activity, and may be influenced by powerline harmonic radiations (PLHR) over USA. Comparisons with past work, experimental as well as theoretical, are made

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

    Directory of Open Access Journals (Sweden)

    B. Singh

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

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

    Indian Academy of Sciences (India)

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

    2007-12-01

    During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at the low latitude ground station Gulmarg (geomagnetic latitude 24°26?N; geomagnetic longitude 147° 09?E, L = 1.28) during moderate magnetic storm activity ( $K^{?}_{P}} = 32$, $K_P$ 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

    Indian Academy of Sciences (India)

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

    2009-06-01

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

  6. Auroral pulsations and accompanying VLF emissions

    Directory of Open Access Journals (Sweden)

    V. R. Tagirov

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

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

  7. VLF emissions from ionospheric/magnetospheric plasma

    Indian Academy of Sciences (India)

    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. Digital spectra of artificially stimulated vlf emissions

    International Nuclear Information System (INIS)

    New features of artificially stimulated VLF emissions from the magnetosphere have been discovered by using high resolution digital spectra analysis techniques. Several hundred emissions triggered by three VLF transmitters have been examined. The stimulated emissions initially grow at the frequency of the triggering signal. The NAA-triggered emissions remain at the triggering frequency until the transmitted pulse terminates; Siple and Omega emissions may show the same behavior or may break away prior to termination. The emissions always initially rise above the frequency of the triggering signal; this rise is independent of the final slope of the emissions. Where the rise occurs at the termination of the triggering signal it is usually very repeatable from event to event. Following the initial rise the frequency may often level off several hundred Hz above the triggering signal, forming a short (40-100 ms) plateau that precedes the final rising or falling phase. The bandwidth of the emission, prior to where it breaks away from the triggering signal, may be the minimum measurable (approximately 27 Hz) with the given time resolution (approximately 30 ms), indicating that the emission is practically monochromatic. The emissions characteristically show exponential growth in time with rates that vary from 25 to 250 dB/s. These observations are in good agreement with a theory that attributes the emissions to an interaction between the triggering signal and counter-streaming gyro-resonant electrons. The analysis method employed in these studies is based upon the fast Fourier transform and economically produces detailed spectra with resolutions in time and frequency of approximately 30 ms and 50 Hz, respectively. (Diss. Abstr. Int., B)

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

    Czech Academy of Sciences Publication Activity Database

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

    2013-01-01

    Ro?. 118, ?. 7 (2013), s. 4523-4533. ISSN 2169-9380 R&D Projects: GA ?R(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

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

    Czech Academy of Sciences Publication Activity Database

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

    2015-01-01

    Ro?. 42, ?. 15 (2015), s. 6137-6145. ISSN 0094-8276 R&D Projects: GA ?R(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

  11. Statistics of VLF/ELF emissions at subauroral latitudes in Athabasca, Canada and their correspondence to the Van Allen Probes observations.

    Science.gov (United States)

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

    2014-12-01

    Using a high-sampling rate (100 kHz) loop antenna installed at subauroral latitudes in Athabasca (ATH), Canada (54.7N, 246.7E, L=4) we have been able to continuously monitor VLF/ELF emissions since September 2012. Several types of VLF/ELF emissions were observed, including chorus, hiss and quasi-periodic emissions. We report statistics of VLF/ELF emissions using a one-year data set from November 1, 2012 until October 31, 2013. Using 10 minute and 24 hour spectra, we selected clearly defined emissions with a minimum intensity of 2.10-5 pT2/Hz and recorded their starting time, duration, frequency range and spectral characteristics. This data set allowed us to calculate their occurrence rate as a function of AE, Dst and other geomagnetic parameters. We found similar occurrence rates on the ground in all cases, showing a peak around 07 MLT (7-10%) and a minimum from 18 to 02 MLT (1-3%), in agreement with previous satellite measurements at the geomagnetic equator. However, occurrence rates on the ground can be 8 times lower than those observed at the equator. This could be caused by the ionosphere preventing some frequencies to go all the way through, but could also suggest an interference in the propagation process between the generation region in the geomagnetic equator and the ground. To investigate this, we compared this data set of VLF/ELF emissions with the observations made by the Van Allen Probes near the equatorial plane. We found 77 conjugate events for which the footprints of either the Van Allen Probes A or B (or both) were within 1000 km of ATH. Using the L2 magnetic field data from the EMFISIS instrument (CDF files available at https://emfisis.physics.uiowa.edu/), we were able to determine that the satellites observed VLF/ELF emissions for at least 54 of those events, suggesting that the spatial extent of the emissions is large. Within these events, we found 8 cases showing similar frequency and spectral features on the ground and on the satellite(s). We report the preliminary conclusions from our analysis of these events.

  12. Early VLF perturbations observed in association with elves

    OpenAIRE

    Á. 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 ...

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

    OpenAIRE

    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...

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

    Science.gov (United States)

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

    2015-12-01

    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.

  15. Frequency-time behavior of artificially stimulated vlf emissions

    International Nuclear Information System (INIS)

    Artificially stimulated VLF emissions (ASE's) are emissions triggered in the magnetosphere by the whistler mode signals from VLF transmitters. These emissions may be separated into two classes, rising and falling, depending on whether the final value of df/dt is positive or negative. Several hundred ASE's triggered by three transmitters have been analyzed using the fast Fourier transform with a filter spacing of 25 Hz and an effective filter width of about 45 Hz. The study was limited to the initial frequency-time behavior of ASE's. Averages taken over many events reveal that both rising and falling tones show the same initial behavior. The emissions begin at the frequency of the triggering signal. Both tones initially rise in frequency, falling tones reversing slope at a point 25--300 Hz above the triggering signal. The slope of rising tones, particularly those triggered by NAA, often abruptly levels off in this same frequency range; as a result, a short (approximately 40 ms) plateau is formed that precedes the final rising phase. The initial frequency offset commonly observed in individual events appears to result from the frequent coincidence with this plateau of a peak in amplitude. Emissions stimulated by all three transmitters show essentially the same features; this finding indicates that their frequency behavior does not depend strongly on transmitter power. The process appears to be asymmetric in frequency; no evidence of initial growth below the triggering frequency has been found. (U.S.)

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

    OpenAIRE

    M. Y. Boudjada; Schwingenschuh, K.; Biernat, H. K.; Berthelier, J.J.; Blecki, J.; Parrot, M.; Stachel, M.; Ö. Aydogar; Stangl, G.; Weingrill, J.

    2008-01-01

    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 s...

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

    Directory of Open Access Journals (Sweden)

    D. L. Pasmanik

    2004-12-01

    Full Text Available We present the results of a case study of quasi-periodic (QP ELF/VLF hiss emissions detected on board the Freja and Magion 5 satellites. Detailed analysis of available QP events revealed certain specific features of their dynamic spectra, which have not been reported earlier. In particular, we found an event with an increase in the frequency drift rate during the generation of a single element of QP emission, and an event with alteration of QP elements having different frequency drift rates. Another event demonstrates the possible relationship between QP hiss emissions and discrete VLF emissions. Properties of QP events are compared with parameters of energetic electrons and cold plasma, and other available data.

    Possible scenarios for the formation of these emissions are discussed on the basis of self-consistent simulations of the cyclotron instability, employing the information obtained experimentally. It is shown that the generation regime of self-sustained pulsations can explain consistently our data set. We show that our numerical model is capable of explaining the mentioned specific features of the dynamic spectrum of QP emissions. Comparison of the modeling results with experimental data yields an estimate for the parameters not measured directly.

    Key words. Magnetospheric physics (plasma waves and instabilities; energetic particles, precipitating; energetic particles, trapped

  18. Magnetosphere VLF observation by satellite ISIS

    International Nuclear Information System (INIS)

    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.)

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

    Directory of Open Access Journals (Sweden)

    M. Y. Boudjada

    2008-11-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-12-15

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

  1. The theory and simulation of falling frequency VLF emissions

    Science.gov (United States)

    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 ?1 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

    Directory of Open Access Journals (Sweden)

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

    CERN Document Server

    Kachakhidze, Manana

    2013-01-01

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

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

    DEFF Research Database (Denmark)

    NaitAmor, S.; AlAbdoadaim, M. A.; Cohen, M. B.; 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 (42.94°N, 0.14°E) and at Centre de Recherches Atmospheriques (CRA) in southwestern France (43.13°N, 0.37°E). The cameras observations are compared to collected VLF AWESOME data. We consider early VLF perturbations observed on 12-13, 17...

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

    DEFF Research Database (Denmark)

    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...

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

    Directory of Open Access Journals (Sweden)

    D. Nunn

    2005-12-01

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

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

    Science.gov (United States)

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

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

    Science.gov (United States)

    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.

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

    DEFF Research Database (Denmark)

    NaitAmor, S.; AlAbdoadaim, M. A.

    2010-01-01

    Two Very Low Frequency (VLF) AWESOME remote sensing systems located at Algiers, Algeria (36.45°N, 3.28°E) and Sebha, Libya (27.02°N, 14.26°E) monitor VLF signal perturbations for evidence of ionospheric disturbances. During the EuroSprite-2007 campaign a number of Transient Luminous Events (TLEs) were captured over the Mediterranean Sea by cameras at Pic du Midi (42.94°N, 0.14°E) and at Centre de Recherches Atmospheriques (CRA) in southwestern France (43.13°N, 0.37°E). The cameras observations are compared to collected VLF AWESOME data. We consider early VLF perturbations observed on 12-13, 17-18 October and 17-18 December, 2007. The data from the two VLF receivers confirm the association between TLEs and early VLF signal perturbations with the perturbations amplitudes dependent on the observation configuration i.e. whether the TLE is near the receiver, near the transmitter, or far from both and the scattering process. The results also reveal that the early VLF perturbations can occur in the absence of a TLE.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  13. VLF transmission experiments in space

    Science.gov (United States)

    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.

  14. Statistical investigation of the VLF quasi-periodic emissions measured by the DEMETER spacecraft.

    Czech Academy of Sciences Publication Activity Database

    Hayosh, Mykhaylo; N?mec, F.; Santolík, Ond?ej; Pasmanik, D. L.; Parrot, M.

    EGU, 2013. EGU2013-8852. ISSN 1607-7962. [EGU General Assembly 2013. 07.04.2013-12.04.2013, Vienna] Institutional support: RVO:68378289 Keywords : VLF quasi-periodic emissions Subject RIV: DG - Athmosphere Sciences, Meteorology http://meetingorganizer.copernicus.org/EGU2013/EGU2013-8852.pdf

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

    Czech Academy of Sciences Publication Activity Database

    Demekhov, A.; Taubenschuss, U.; Santolík, Ond?ej

    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#

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

    International Nuclear Information System (INIS)

    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

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    Two Very Low Frequency (VLF) AWESOME remote sensing systems located at Algiers, Algeria (36.45°N, 3.28°E) and Sebha, Libya (27.02°N, 14.26°E) monitor VLF signal perturbations for evidence of ionospheric disturbances. During the EuroSprite-2007 campaign a number of Transient Luminous Events (TLEs) were captured over the Mediterranean Sea by cameras at Pic du Midi (42.94°N, 0.14°E) and at Centre de Recherches Atmospheriques (CRA) in southwestern France (43.13°N, 0.37°E). The cameras observations a...

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

    OpenAIRE

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

    2010-01-01

    Two Very Low Frequency (VLF) AWESOME remote sensing systems located at Algiers, Algeria (36.45°N, 3.28°E) and Sebha, Libya (27.02°N, 14.26°E) monitor VLF signal perturbations for evidence of ionospheric disturbances. During the EuroSprite-2007 campaign a number of Transient Luminous Events (TLEs) were captured over the Mediterranean Sea by cameras at Pic du Midi (42.94°N, 0.14°E) and at Centre de Recherches Atmosphériques (CRA) in southwestern France (43.13°N, 0.37°E). The cameras observation...

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

    OpenAIRE

    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...

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

    Directory of Open Access Journals (Sweden)

    A. Rozhnoi

    2014-04-01

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

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

    OpenAIRE

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

    2004-01-01

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

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

    Directory of Open Access Journals (Sweden)

    M. Platino

    2004-07-01

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

  3. Shipborne LF-VLF oceanic lightning observations and modeling

    Science.gov (United States)

    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.

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

    CERN Document Server

    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...

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

    Czech Academy of Sciences Publication Activity Database

    Hayosh, Mykhaylo; N?mec, F.; Santolík, Ond?ej; Parrot, M.

    2014-01-01

    Ro?. 119, ?. 10 (2014), s. 8063-8072. ISSN 2169-9380 R&D Projects: GA ?R(CZ) GAP209/11/2280; GA MŠk LH12231 Grant ostatní: Rada Programu interní podpory projekt? mezinárodní spolupráce AV ?R 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

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    Pasmanik, Dmitry; Hayosh, Mykhaylo; Demekhov, Andrei; Santolík, Ond?ej; Nemec, František; Parrot, Michel

    2015-04-01

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

  8. Radiation belt precipitation due to man-made VLF transmissions. Satellite observations

    International Nuclear Information System (INIS)

    Complete text of publication follows. In the more than four decades since the discovery of the Earth's Van Allen radiation belts, it has proven difficult to confirm the principal source and loss mechanisms that control radiation belt particles. It has been recognized for some time that the loss of radiation belt electrons in the inner belt beyond L?1.5 is dominated by pitch angle scattering in wave-particle interactions with whistler mode waves, although there has been uncertainty as to the relative importance of different wave types. Relatively recent theoretical calculations have led to the rather surprising conclusion that manmade VLF transmissions may dominate losses in the inner radiation belts. This finding has sparked considerable interest, suggesting practical human control of the radiation belts to protect Earth-orbiting systems from natural and nuclear injections of high energy electrons, generally known as Radiation Belt Remediation (RBR). While strong correlations between drift-loss cone enhancements and transmitter locations have been shown previously, particle enhancements have yet to be tied directly to VLF wave observations. The occurrence frequency of drift loss cone enhancements above transmitters has also previously been unknown. In this paper we combine wave and particle observations from the DEMETER satellite with ground based VLF recordings to examine the significance of the transmitter NWC on the inner radiation belt. Enhancements of drift-loss cone electron fluxes are observed eastward of the transmitter location, with cyclotron resonance taking place on the field line near the VLF transmitter location, followed by the eastward drift of electrons towards the South Atlantic Anomaly. Transmitters located under a nighttime ionosphere are favoured, due to the lower ionospheric absorption. 95% of orbital passes which met these conditions showed evidence of an interaction. A positive correlation exists between transmitter operation and the presence of such enhancements. Typical transmissions cause a ?400-fold increase in 300 keV drift-loss cone electrons. These observations provide conclusive evidence linking drift-loss cone electron flux enhancements and transmitter operation. Numerical magnitudes and occurrence rates experimentally detected here should allow a validation of models for wave and particle dynamics in the radiation belts.

  9. Long-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations

    Science.gov (United States)

    Neal, Jason J.; Rodger, Craig J.; Clilverd, Mark A.; Thomson, Neil R.; Raita, Tero; Ulich, Thomas

    2015-03-01

    We analyze observations of subionospherically propagating very low frequency (VLF) radio waves to determine outer radiation belt energetic electron precipitation (EEP) flux magnitudes. The radio wave receiver in Sodankylä, Finland (Sodankylä Geophysical Observatory) observes signals from the transmitter with call sign NAA (Cutler, Maine). The receiver is part of the Antarctic-Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK). We use a near-continuous data set spanning November 2004 until December 2013 to determine the long time period EEP variations. We determine quiet day curves over the entire period and use these to identify propagation disturbances caused by EEP. Long Wave Propagation Code radio wave propagation modeling is used to estimate the precipitating electron flux magnitudes from the observed amplitude disturbances, allowing for solar cycle changes in the ambient D region and dynamic variations in the EEP energy spectra. Our method performs well during the summer months when the daylit ionosphere is most stable but fails during the winter. From the summer observations, we have obtained 693 days worth of hourly EEP flux magnitudes over the 2004-2013 period. These AARDDVARK-based fluxes agree well with independent satellite precipitation measurements during high-intensity events. However, our method of EEP detection is 10-50 times more sensitive to low flux levels than the satellite measurements. Our EEP variations also show good agreement with the variation in lower band chorus wave powers, providing some confidence that chorus is the primary driver for the outer belt precipitation we are monitoring.

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

    Directory of Open Access Journals (Sweden)

    Norbayah Yusop

    2014-03-01

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

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

    Science.gov (United States)

    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.

  12. Whistler-triggered emissions observed by ISIS satellites

    Science.gov (United States)

    Nakamura, Y.; Ondoh, T.

    1989-01-01

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

  13. Whistler-triggered emissions observed by ISIS satellites

    International Nuclear Information System (INIS)

    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. Assessing global lightning activity with ELF/VLF observations, Schumann resonances and ionospheric potential

    International Nuclear Information System (INIS)

    Complete text of publication follows. Global lightning activity is estimated from globally spaced ELF/VLF receivers and used to investigate the dynamics of the global atmospheric electric circuit. ELF/VLF radiation generated by lightning is known to propagate long distances in the Earth ionosphere waveguide, but propagation effects resulting from diurnal ionospheric variations often dominate received amplitudes at a fixed station. Day/night propagation effects thus make meaningful comparison and summation of activity across multiple stations difficult. Exact inversion of the propagation channel is possible only with knowledge of the location of each lightning impulse, a feat unattainable even with current detection networks. In a novel approach, propagation effects are accounted for using established monthly averages of lightning location provided by the Lightning Image Sensor (LIS) and applying known frequency specific attenuation parameters for daytime/nighttime ELF/VLF propagation. The method allows for quantification of daily lightning activity on a global scale using a small number of receiver sites. Obtained curves of daily lightning activity are compared to measurements of atmospheric electric field at mid and polar latitudes and also to lightning activity estimates based on Schumann resonances. For Schumann resonances we utilize a method of field decomposition that separates propagating and standing modes. It is found that in most examined cases daily global lightning activity and the atmospheric electric field are poorly correlated.

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

    Czech Academy of Sciences Publication Activity Database

    N?mec, František; Santolík, Ond?ej; Parrot, M.

    Vol. 2. Praha : MATFYZPRESS, Praha, 2008 - (Šafranková, J.; Pavl?, 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 ?R 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

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

    Czech Academy of Sciences Publication Activity Database

    Píša, David; N?mec, F.; Santolík, Ond?ej; Parrot, M.; Rycroft, M.

    2013-01-01

    Ro?. 118, ?. 8 (2013), s. 5286-5295. ISSN 2169-9380 R&D Projects: GA ?R(CZ) GAP209/11/2280; GA ?R GA205/09/1253 Grant ostatní: European Community Seventh Framework Programme (FP7/2007-2013),(XE) 262005; AV ?R(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

  17. VLF Technique and Science in India

    International Nuclear Information System (INIS)

    Since IGY period (1957-58), natural and artificially produced Very Low Frequency (VLF) electromagnetic radiations are being recorded at large number of ground stations and on board satellites to study various wave-plasma interactive phenomena. The terrestrial propagation of these VLF radio waves are primarily enabled through the earth ionosphere wave guide (EIWG) system to long horizontal distances around the globe and ducted along the geomagnetic field lines into the conjugate hemisphere through the ionosphere-plasmasphere-magnetosphere routes. The time frequency spectra indicate presence of dispersion and various cut-off frequencies providing several types of received signals like whistlers, chorus, tweeks, hiss, hisslers etc., which can be heard on an earphone with distinguishing audio structures. While the VLF technique has been a very effective tool for studying middle and high latitude phenomena, the importance of various anomalous characteristics over the Indian low latitude stations provide potentially new challenges for their scientific interpretation and modelling. The ducted and non-ducted propagation, low latitude TRIMPI/TLE effects, D-region ionisation perturbations due to solar and stellar x- and ? ray emissions and detecting precursors of seismic activities are a few problems which will gain from low latitude studies. Since the conjugate points of Indian stations lie over the Indian oceanic region, the VLF propagation effects would be relatively noise free to observe rare and new phenomena requiring better SNR to detect such changes. The VLF signals emanating from the active seismic zones would require high sensitivity of the system and suitable network of transmitting and receiving stations. Results obtained on whistlers and related studies from a number of Indian stations covering geomagnetic latitude range between 13-24 deg. N are mentioned and reviewed in the background of theoretical understanding of the lightning return stroke signal elements, VLF propagation through cold plasma, ionospheric wave guide mode, electron precipitation due to cyclotron resonance and production of ionisation in the D-region due to solar/stellar UV/X/?-rays. Further use of the VLF technique in terms of improving both observational data for real time monitoring/modelling of geophysical phenomena and exploring space weather conditions are considered as part of a future Indian programme.

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

    Science.gov (United States)

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

    2014-12-01

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

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

    Directory of Open Access Journals (Sweden)

    H. Höller

    2009-03-01

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

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

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

    Directory of Open Access Journals (Sweden)

    H. Höller

    2009-10-01

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

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

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

    DEFF Research Database (Denmark)

    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...

  2. Hiss emissions during quiet and disturbed periods

    Indian Academy of Sciences (India)

    D K Singh; R P Singh

    2002-10-01

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

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  6. Characteristics of VLF atmospherics near the resonance frequency of the Earth-ionosphere waveguide 1.6–2.3 kHz by observations in the auroral region

    OpenAIRE

    Manninen, J.; Turunen, T.; A. P. Nickolaenko; E. E. Titova; A. A. Ostapenko; Raita, T.

    2010-01-01

    Recordings of ELF-VLF waves with the right-hand (RH) and the left-hand (LH) circular polarization were made in Northern Finland. Analysis showed a difference between the RH and LH polarized waves. A pronounced maximum of the wave amplitude was observed at the first critical frequency of the Earth-ionosphere waveguide (the first transverse resonance) around 1.6–2.3 kHz. The wave had the circular LH polarization at this maximum. To interpret observations, we computed the characteristics of the ...

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

    Directory of Open Access Journals (Sweden)

    A. A. Lubchich

    2006-10-01

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

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

    Science.gov (United States)

    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 Pu’er 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.

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

    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 Pyrénées 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 Météorage 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.

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

    DEFF Research Database (Denmark)

    Greenberg, E.; Price, C.

    2009-01-01

    During the summer of 2005, transient luminous events were optically imaged from the French Pyrénées 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 Météorage 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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. Characteristics of VLF atmospherics near the resonance frequency of the Earth-ionosphere waveguide 1.6–2.3 kHz by observations in the auroral region

    Directory of Open Access Journals (Sweden)

    J. Manninen

    2010-01-01

    Full Text Available Recordings of ELF-VLF waves with the right-hand (RH and the left-hand (LH circular polarization were made in Northern Finland. Analysis showed a difference between the RH and LH polarized waves. A pronounced maximum of the wave amplitude was observed at the first critical frequency of the Earth-ionosphere waveguide (the first transverse resonance around 1.6–2.3 kHz. The wave had the circular LH polarization at this maximum. To interpret observations, we computed the characteristics of the waveguide modes by using the full wave solution in the night model of the ionosphere. Computations show that the spectral maximum at the first transverse resonance frequency arises from a small absorption of the LH polarized radio wave in the magnetized ionosphere plasma, forming the upper boundary of the Earth-ionosphere waveguide.

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

    Directory of Open Access Journals (Sweden)

    Pier Francesco Biagi

    2012-04-01

    Full Text Available

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

     

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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

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

    Indian Academy of Sciences (India)

    A K Singh; S B Singh; R P Singh

    2005-12-01

    A new type of discrete VLF emissions recorded at the low-latitude ground station Varanasi (geomag. lat. $14^{\\circ}55'$ N, geomag. long. 154°E; $L = 1.07$) 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.

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

    Directory of Open Access Journals (Sweden)

    A. Rozhnoi

    2010-03-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-08-01

    We investigate a non-typical very low frequency (VLF) 1-4 kHz hiss representing a sequence of separated noise bursts with a strange "mushroom-like" shape in the frequency-time domain, each one lasting several minutes. These strange afternoon VLF emissions were recorded at Kannuslehto (KAN, ϕ = 67.74° N, ? = 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.

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

    Science.gov (United States)

    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.

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

    OpenAIRE

    ?nan, Umran Sava?; 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...

  4. VLF-EM surveys at Chalk River, Ontario

    International Nuclear Information System (INIS)

    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

  5. VLF wave intensity in the plasmasphere due to tropospheric lightning

    Science.gov (United States)

    Colman, J. J.; Starks, M. J.

    2013-07-01

    climatology of VLF (very low frequency) wave intensity from lightning in the plasmasphere is constructed. Starting from Optical Transient Detector/Lightning Imaging Sensor (OTD/LIS) lightning data representing 1995-2005, a climatology of strikes is assembled with 1° × 1° latitude-longitude spatial resolution, averaged into 2 h bins for each month of the year. Assuming a linear relationship between optical flash rate and VLF power flux, and that the VLF amplitude drops off as one over distance, a proxy for VLF power is developed. A typical lightning spectrum is applied and the values are scaled by appropriate transionospheric absorptions for each time and place. These values are mapped along geomagnetic field lines in order to compare them to E-field spectral densities measured by the DEMETER satellite between 2005 and 2009. An overview of the DEMETER survey mode data is presented which leads to the best scaling of the lightning VLF climatology in LEO (low earth orbit). The resulting data set represents a monthly, 2-hour, solar minimum climatology of VLF wave intensity from lightning in LEO. Finally, the E-field spectral densities are converted to Poynting flux, mapped to the plasmasphere, and converted to B-field spectral densities. Good overall agreement is found with previous observations and estimates. This new climatology is expected to have a significant impact on calculations of pitch-angle diffusion for relativistic electrons in the inner radiation belt.

  6. Anomalies Observed in VLF and LF Radio Signals on the Occasion of the Western Turkey Earthquake (Mw = 5.7) on May 19, 2011

    OpenAIRE

    Pier Francesco Biagi; Flavia Righetti; Tommaso Maggipinto; Luigi Schiavulli; Teresa Ligonzo; Anita Ermini; Iren Adelina Moldovan; Adrian Septimiu Moldovan; Hugo Gonçalves Silva; Mourad Bezzeghoud; Michael E. Contadakis; Dimitrios N. Arabelos; Thomas D. Xenos; Aydin Buyuksarac

    2012-01-01

    VLF radio signals lie in the 10 - 60 kHz frequency band. These radio signals are used for worldwide navigation support, time signals and for military purposes. They are propagated in the earth-ionosphere wave-guide mode along great circle propagation paths. So, their propaga-tion is strongly affected by the ionosphere conditions. LF signals lie in 150 - 300 kHz frequency band. They are used for long way broadcasting by the few (this type of broadcasting is going into disuse) transmitters loca...

  7. Optimizing an ELF/VLF Phased Array at HAARP

    Science.gov (United States)

    Fujimaru, S.; Moore, R. C.

    2013-12-01

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

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

    Science.gov (United States)

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

    2013-10-01

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

  9. Three-dimensional modelling of VLF data

    OpenAIRE

    Beamish, David

    1998-01-01

    The VLF technique is being increasingly applied to environmental and hydrogeological problems with a growing requirement for quantitative interpretation. One of the main difficulties with the VLF method stems from the directional polarisation of the transmitted field. To clarify VLF data interpretation when subsurface targets are complex and three dimensional, a modelling study was undertaken at VLF frequencies. A main concern is the interpretation of target strike directions when the transmi...

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

    Science.gov (United States)

    Lefeuvre, F.; Marshall, R.; PinçOn, 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.

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

    Science.gov (United States)

    Moore, R. C.; Fujimaru, S.

    2012-12-01

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

  12. Can the Nanoflare Model Reproduce Observed Emissions?

    Science.gov (United States)

    Mulu-Moore, Fana M.; Winebarger, Amy R.; Warren, Harry P.

    2011-01-01

    All theories that attempt to explain the high temperatures observed in the solar corona are based on short bursts of energy release. The intensities and velocities measured in the core of an active, however, can be steady over many hours of observation. One heating scenario that has been proposed to reconcile such observations with models is the "long nanoflare storm," where short duration heating events occur infrequently on many sub-resolutions strands. In this Letter, we examine the emission measure distribution predicted for such a heating scenario by modeling an arcade of strands in an active region core. Comparisons of the computed emission measure distributions with recent observations indicate that that the long nanoflare storm scenario implies much 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.

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

    Indian Academy of Sciences (India)

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

    2003-10-01

    Recently, we have succeeded in recording VLF emissions at the Indian Antarctic station, Maitri (geom. lat. $62^{\\circ}$S, geom. long. 57.23°E, $L =4.5$) using a T-type antenna, pre/main ampli?ers 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 ?rst time. The generation and propagation mechanism of these emissions are discussed brie?y.

  14. Terrestrial VLF transmitter injection into the magnetosphere

    OpenAIRE

    Ä°nan, Umran SavaÅŸ; 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...

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

    OpenAIRE

    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

  16. Constraining CO emission estimates using atmospheric observations

    Science.gov (United States)

    Hooghiemstra, P. B.

    2012-06-01

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

  17. Effects of mass density enhancements on VLF transmitter signals

    Science.gov (United States)

    Boudjada, Mohammed Y.; Lammer, Helmut; Al-Haddad, Eimad; Leitzinger, Martin; Krauss, Sandro

    2015-04-01

    We study the variation of the electric field measurements recorded by DEMETER micro-satellite above specific very low frequency (VLF) transmitters. The investigated period starts from August 2004 to December 2010. The VLF signals are combined with the mass density measurements recorded, in the same time interval, by GRACE and CHAMP satellites. Particular enhancements of the mass densities were observed at polar and sub-polar regions by both satellites. Those mass density enhancements are found to propagate from the northern or southern hemisphere to the equator region. We attempt in this study to analyse the VLF signal variations in the time interval where the mass density enhancements are recorded. Such disturbances of the atmosphere can probably affect the Earth's ionosphere. The VLF signal may be attenuated and then not detected by DEMETER. We find that it is the case at some specific occasions. Nevertheless we show that several parameters have to be taken into consideration: (a) the origin of the mass density enhancement in the polar region (e.g. solar particles), (b) its phase speed from the pole to the equator and (c) the satellite (CHAMP, DEMETER, GRACE) local time.

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

    Czech Academy of Sciences Publication Activity Database

    Hayosh, Mykhaylo; Santolík, O.; Parrot, M.; N?mec, F.

    Pa?íž : 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

  19. Rocket experiment on spontaneously and artificially stimulated VLF plasma waves in the ionosphere

    International Nuclear Information System (INIS)

    In situ active experiments on the nonlinear wave-wave and wave-particle interactions in the ionospheric plasma were performed by a Japanese sounding rocket K-9M-41. Both spontaneously and artificially stimulated plasma waves in the VLF range were observed. When a large amplitude electron plasma wave was transmitted from the rocket, parametrically excited ion acoustic waves were observed in addition to natural emissions such as whistlers, LHR emissions, and hisslike emissions. It was also found that 'risers' were triggered by the LHR emissions, which seem to be very similar to a phenomenon of the so-called ASE (artificially stimulated emissions). When a slow electron beam with energy lower than 3 eV was ejected from the rocket, a new type of periodic U-shaped discrete emission was observed which was excited through a wave-particle interaction. The frequency of these emissions is lower than the LHR frequency and decreases as the beam energy is increased. Spectrograms of the observed plasma are presented, and some are analyzed theoretically. (auth)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

  2. Observations of Diffuse Ultraviolet Emission from Draco

    CERN Document Server

    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 ...

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

    International Nuclear Information System (INIS)

    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.

  4. Two-dimensional, regularised inversion of VLF data

    OpenAIRE

    Beamish, David

    1994-01-01

    Very low frequency electromagnetic (EM) methods using VLF transmitters have found many applications in subsurface geophysical investigations. Surface measurements involving both the vertical component of the magnetic field (VLF-EM or VLF-Z) and of the apparent resistivity (VLF-R) are increasingly common. Although extensive VLF data sets have been successfully used for mapping purposes, modelling and interpretation techniques which asess the third (i.e. depth) dimension appear limited. Giv...

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

    Science.gov (United States)

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

    2013-11-01

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

  6. Airborne observations of the infrared emission bands

    International Nuclear Information System (INIS)

    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

  7. Conditions of Observation of Whistler Emissions in Space

    OpenAIRE

    Krafft, C.; Lundin, R.; Matthieussent, G.

    1995-01-01

    The peculiarities of whistler wave fields spontaneously radiated by electron beams artificially injected into the Earth's ionosphere are discussed. The conditions of registration of the whistler wave packets by a remote on board VLF receiver have been analyzed ; they depend on mutual disposition of the electron gun and the VLF receiver as well as on the pitch angle of the injected electrons. It is shown that the internal frequency width of the whistler signal, connected with the ray represent...

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

    Directory of Open Access Journals (Sweden)

    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.

  9. Experimental evidence of the simultaneous occurrence of VLF chorus on the ground in the global azimuthal scale – from pre-midnight to the late morning

    Directory of Open Access Journals (Sweden)

    T. Turunen

    2012-04-01

    Full Text Available Night-time VLF (very low frequency chorus bursts lasting about one hour have been recorded at Finnish temporal station Kannuslehto (CGM: 64.2°; 107.9°, L = 5.3 during two VLF campaigns (on 25 February–4 March 2008 and 27 March–17 April 2011. The chorus bursts were associated with substorm development. They were accompanied by riometer absorption enhancements, which occurred simultaneously within as large longitude areas as from pre-midnight (Sodankylä, ~22:00 MLT to the late morning (Tixie, ~03:00 MLT and Gakona, ~08:00 MLT longitudes. It was found that the pre-midnight chorus observed on the ground occurred simultaneously with VLF chorus emissions recorded in the late morning on the low-altitude DEMETER satellite crossing the similar geomagnetic latitudes on the opposite local time sector. For the first time some evidence of simultaneous chorus burst generation in the global longitudinal scale was found (from pre-midnight to the late morning by using direct comparison with satellite data as well as using non-direct indicator–azimuthally extended riometer absorption enhancements.

  10. Plasma heating near a VLF antenna

    International Nuclear Information System (INIS)

    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)

  11. Summary on JIKIKEN observation

    International Nuclear Information System (INIS)

    JIKIKEN (EXOS-B) was successfully launched on Sept. 16, 1978 into an orbit with initial apogee of 30,056 km and perigee of 227 km, with an inclination -31.10. This orbit is suitable for the investigation of the wave-particle interaction process in the plasmasphere and the magnetosphere near the plasmapause. An analog data transmission system is used and the fine structure of the dynamic spectrum in a frequency range from 10 kHz to 3 MHz has been obtained, as well as the wide band spectrum from several 100 Hz to 10 kHz. the important wave phenomena observed by the current observations of JIKIKEN are: i) Auroral (Earth) kilometric radio waves; ii) Upper hybrid mode emissions; iii) (n + 1/2)f sub(c) emissions; iv) Principal phenomena of the VLF frequency range such as, whistlers, chorus, and hiss; v) Pure tone emissions in the VLF range; vi) Artificially stimulated plasma waves and observation of plasma parameters; vii) Planetary radio waves; viii) Solar type III outbursts. As a preliminary approach to verifying the wave particle interaction processes, investigations of the energy spectra have also been made for the UHR mode plasma wave and pure tone emission in the ELF and VLF ranges. Very long duration UHR resonance was triggered by a 500 ?sec pulse in the stimulated plasma wave experiment. The resonance persists for up to 125 msec even in the VLF range (below 30 kHz) and the electron cyclotron resonances are stimulated in very high harmonics number n, sometimes to a maximum of n = 20. Using these resonance frequencies, the plasmapause electron density distributions are obtained. The injection of an electron beam from the spacecraft generates stimulated electrostatic waves and also results in turbulent heating of the surrounding plasma. Bursts of energetic particles of keV energies are frequently encountered outside the plasmapause. (author)

  12. Cassini CIRS Observations of Iapetus' Thermal Emission

    Science.gov (United States)

    Spencer, J. R.; Pearl, J. C.; Segura, M.

    2005-01-01

    Cassini s Composite Infrared Spectrometer (CIRS, [1]) mapped Iapetus thermal emission from 7 to approx.300 microns during the spacecraft s December 31st 2004 flyby of the satellite. Short-wavelength spectra were obtained with the CIRS "FP3" (10 - 17 micron) and "FP4" (7 - 10 micron) detector arrays, each consisting of 1 x 10 pixels with a spatial resolution of 0.29 milliradians, while longer wavelength observations used the "FP1" detector, with a single-aperture detector with 4 milliradian diameter. The detectors are scanned across the target to build up an image cube with two spatial dimensions and one spectral dimension. CIRS daytime observations covered the dark terrain of Cassini Regio, except for high northern latitudes which were occupied by bright terrain, while nighttime observations covered a mixture of bright and dark terrain. The 120,000 km flyby distance provided a maximum spatial resolution of 35 km in the FP3 and FP4 detectors, and 500 km in the FP1 detector.

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

    Science.gov (United States)

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

    2013-04-01

    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.

  14. 100 Days of ELF/VLF Generation via HF Heating with HAARP (Invited)

    Science.gov (United States)

    Cohen, M.; Golkowski, M.

    2013-12-01

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

  15. New Observations of UV Emissions from Europa

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

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

  18. Lightning and radar observations of hurricane Rita landfall

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Orlando, Elena

    2016-01-01

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

  1. Prompt Emission Observations of Swift BAT Bursts

    Science.gov (United States)

    Barthelmy, Scott

    2009-01-01

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

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

    Directory of Open Access Journals (Sweden)

    B. Lundin

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

  3. Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

    Science.gov (United States)

    Knudsen, D. L.; Kabirzadeh, R.; Burchill, J. K.; Pfaff, Robert F.; Wallis, D. D.; Bounds, S. R.; Clemmons, J. H.; Pincon, J.-L.

    2012-01-01

    The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes.

  4. Showa Station and Iceland conjugate-point observations

    International Nuclear Information System (INIS)

    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.)

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

    International Nuclear Information System (INIS)

    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

  6. ELF and VLF radiation from the polar electrojet antenna

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Airborne Observations of Ammonia Emissions from North Carolina Swine Facilities

    Science.gov (United States)

    Nowak, J. B.; Neuman, J. A.; Liao, J.; Welti, A.; Middlebrook, A. M.; McKeen, S. A.; Trainer, M.; Parrish, D. D.

    2013-12-01

    Ammonia (NH3) is the dominant gas-phase base in the troposphere. As a consequence, NH3 abundance influences particle formation and composition. Anthropogenic emissions of NH3 can react with sulfuric acid (H2SO4) and nitric acid (HNO3), photochemical oxidation products of sulfur dioxide (SO2) and nitrogen oxides (NOx (NO + NO2)), to form ammoniated particles that typically account for half or more of measured PM2.5 mass in the Eastern US. NH3 emissions are predominantly from agricultural sources, primarily livestock animal waste and crop fertilization. Accurate NH3 emissions estimates from these sources are necessary for developing effective particle control strategies. Swine facilities in North Carolina are one of the largest source of NH3 emissions in the Southeastern US. Airborne measurements of NH3 and particulate ammonium (NH4+) made aboard the NOAA WP-3D aircraft as part of the recent 2013 SENEX field campaign are used to quantify NH3 emissions from North Carolina swine facilities. The observed NH3 emissions are compared to swine facility emissions estimates from current emissions inventories. In addition, the NH3 emissions from swine facilities are placed in the broader context of NH3 sources through comparison to recent emissions observations from dairy facilities in California. The July 10 SENEX WP-3D flight track colored and sized by observed NH3 mixing ratios.

  8. Observational constraints on biogenic VOC emission model estimates (Invited)

    Science.gov (United States)

    Guenther, A. B.

    2013-12-01

    Chemistry and transport models require accurate estimates of biogenic volatile organic compound (BVOC) emissions in order to simulate the atmospheric constituents controlling air quality and climate, such as ozone and particles, and so the uncertainties associated with BVOC estimates may be limiting the development of effective air quality and climate management strategies. BVOC emission models include driving variables and algorithms that span scales from the leaf level to entire landscapes. While considerable effort has been made to improve BVOC emission models in the past decades, there have been relatively few attempts to quantify the uncertainties associated with these estimates or to rigorously assess emission modeling approaches. This presentation will summarize the availability of observations that can be used to constrain BVOC emission models including flux measurements (leaf enclosure, above canopy tower, and aircraft platforms) and ambient concentrations of BVOC and their products. Results from studies targeting specific BVOC emission processes (e.g., the response of isoprene emission to drought and the response of monoterpene emissions to bark beetle attack) will be shown and the application of these observations for BVOC model evaluation will be discussed. In addition, the results from multi-scale BVOC emission studies (leaf enclosure, whole canopy flux tower, regional aircraft eddy covariance) will be presented and a approach for incorporating these observations into a community model testbed will be described and used to evaluate regional BVOC emission models.

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

    Mijling, B.; van der A, R.

    2013-12-01

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

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    G. Stangl

    2011-04-01

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

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

    Science.gov (United States)

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

    2010-05-01

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

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

    Science.gov (United States)

    Cohen, M. B.; Go?kowski, M.

    2013-10-01

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

  15. Study of Ionospheric Perturbations in D-Layer Using Awesome VLF Receiver Data at Tashkent Station

    Science.gov (United States)

    Ahmedov, Bobomurat

    2012-07-01

    One VLF receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University and are operating in Tashkent, under the International Heliophysical Year (IHY). The results obtained at Tashkent IHY station are applied to earthquake electromagnetic precursors, lightning, and solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters connected with evolution of strongly magnetized neutron stars believed as magnetars. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Few Solar flare events are observed during February in 2010-2011 years and the analysis showed that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is explained. Assuming that earthquakes (EQs) can be preceded by the electromagnetic signals in the VLF bands detectable from ground-based measurements we have studied VLF amplitude anomalies related to the earthquakes occurred in 2009-2010 years with magnitude more than 5 on the path way from the VLF transmitters to the Tashkent station. For analysing narrowband data we have used the Nighttime Fluctuation (NF) method paying attention to the data obtained during the local nighttime (18:00 LT-06:00 LT). The amplitude data are analysed only for the reason that perturbations are identified more clearly in the amplitude data than in phase data. The mean nighttime amplitude (or trend) and normalized trend are found to increase significantly before the EQ with the same tendency as the NF and normalized NF. The obtained results have revealed a fine agreement with VLF amplitude anomalies observed in Tashkent VLF station during the strong earthquakes occurred on the path way from the transmitters to the receiver. Some of the initial results obtained from the preliminary analysis are presented to show the probing potentiality of VLF waves in ionosphere studies.

  16. Egret observations of the extragalactic gamma-ray emission

    DEFF Research Database (Denmark)

    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 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...... most likely explanation for the origin of this extragalactic high-energy gamma-ray emission is that it arises primarily from unresolved gamma-ray-emitting blazars....

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

    OpenAIRE

    Smida, R.; Werner, F; 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.

    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\\times1...

  18. On the altitude of the ELF/VLF source region generated during “beat-wave” HF heating experiments

    Science.gov (United States)

    Moore, R. C.; Fujimaru, S.; Cohen, M.; Go?kowski, M.; McCarrick, M. J.

    2012-09-01

    Modulated high frequency (HF, 3-10 MHz) heating of the ionosphere in the presence of the auroral electrojet currents is an effective method for generating extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) radio waves. The amplitudes of ELF/VLF waves generated in this manner depend sensitively on the auroral electrojet current strength, which varies with time. In an effort to improve the reliability of ELF/VLF wave generation by ionospheric heating, recent experiments at the High-frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska, have focused on methods that are independent of the strength of the auroral electrojet currents. One such potential method is so-called “beat-wave” ELF/VLF generation. Recent experimental observations have been presented to suggest that in the absence of a significant D-region ionosphere (˜60-100 km altitude), an ELF/VLF source region can be created within the F-region ionosphere (˜150-250 km altitude). In this paper, we use a time-of-arrival analysis technique to provide direct experimental evidence that the beat-wave source region is located in the D-region ionosphere, and possibly the lower E-region ionosphere (˜100-120 km altitude), even when ionospheric diagnostics indicate a very weak D-layer. These results have a tremendous impact on the interpretation of recent experimental observations.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2012-01-01

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

  2. Observations and modelling of pulsed radio emission from CU Virginis

    CERN Document Server

    Lo, K K; Hobbs, G; Murphy, T; Gaensler, B M; Melrose, D; Ravi, V; Manchester, R M; Keith, M J

    2012-01-01

    We present 13 cm and 20 cm radio observations of the magnetic chemically peculiar star CU Virginis taken with the Australia Telescope Compact Array. We detect two circularly polarised radio pulses every rotation period which confirm previous detections. In the first pulse, the lower frequency emission arrives before the higher frequency emission and the ordering reverses in the second pulse. In order to explain the frequency dependence of the time between the two pulses, we construct a geometric model of the magnetosphere of CU Virginis, and consider various emission angles relative to the magnetic field lines. A simple electron cyclotron maser emission model, in which the emission is perpendicular to the magnetic field lines, is not consistent with our data. A model in which the emission is refracted through cold plasma in the magnetosphere is shown to have the correct pulse arrival time frequency dependence.

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

    CERN Document Server

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

    2013-01-01

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

  4. Dust Obscuration and Observable Emission of Active Galactic Nuclei

    Science.gov (United States)

    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.

  5. Spatial observations of dust emission in NGC 7027

    International Nuclear Information System (INIS)

    NGC 7027 was mapped in each of five spectral bands between 8.7 and 23 ?m with a spatial resolution of 3.5 arcsec. Two new scientific results are presented: (1) Analysis of the observations shows that the dust in NGC 7027 contains two spatially distinct components, one of which is associated with and links the unidentified emission features at 8.6 and 11.3 ?m; the second component may be graphite. (2) High-quality observations indicate that thermal emission by dust in NGC 7027 is spatially coextensive with emission by ionized hydrogen over a broad spectral range in the midinfrared (approx.8--28 ?m). No significant emission above the approx.1% level was found outside the region of ionized hydrogen in any spectral band observed. The intensity distribution of the observed infrared emission was successfully modeled by emission from within the walls of a hollow cylinder, similar to the model for 5-GHz radio emission proposed by Scott [Mon. Not. R. Astron. Soc. 161, 35P (1973)

  6. Evaluating China's black carbon emissions using surface observations: sensitivity to observation representativeness and transport model error

    Science.gov (United States)

    Wang, Y.; Wang, X.; Hao, J.; Kondo, Y.; Irwin, M.; Munger, J. W.; Zhao, Y.

    2012-12-01

    Atmospheric measurements of BC concentrations at representative locations provide invaluable independent datasets to evaluate bottom-up BC emissions, particularly when used in conjunction with chemical transport models. A few studies have evaluated China's BC emission inventory using surface observations, but their 'top-down' estimates of Chinese BC emissions vary greatly. This study examines the sensitivity of 'top-down' quantification of Chinese BC emissions to the choice of observational data and to transport model errors associated with grid resolution, wet deposition, and transport. Using hourly measurements of BC obtained with optical methods at two rural sites in China (Miyun and Chongming), we performed a detailed analysis of the model-observation comparison to filter out those observations not representative of regional emissions or heavily influenced by the model's transport errors instead of by emissions. The observed BC to CO correlation and its variation with precipitation were used to evaluate the model's wet deposition process and to quantify the wet deposition bias on BC emission estimate. By comparing top-down BC emission estimate derived from carefully-selected hourly observations with that from mere monthly-mean observations, we provided the error estimate for top-down emissions due to observation representativeness and model error. After better quantifying these errors, we evaluated China's bottom-up BC inventory of Zhang et al. [2009] by region and found that this inventory underestimated BC emissions from Center China, North China Plain and Yangtze River Delta region while overestimated emissions from Northeast China and Center South China. Our top-down estimate of BC emissions over China as a whole is 20%-40% higher than the bottom-up inventory.

  7. A tiered observational system for anthropogenic methane emissions

    Science.gov (United States)

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

    2014-12-01

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

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

    International Nuclear Information System (INIS)

    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)

  9. Observations of gamma-ray emission in solar flares

    International Nuclear Information System (INIS)

    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.)

  10. Upper Limits on O VI Emission from Voyager Observations

    Indian Academy of Sciences (India)

    Jayant Murthy

    2002-03-01

    We have examined 426 Voyager fields distributed across the sky for O VI ( 1032/1038 Ã…) 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.

  11. Egret observations of the extragalactic gamma-ray emission

    DEFF Research Database (Denmark)

    Sreekumar, P.; Bertsch, D.L.

    1998-01-01

    The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions with 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 analysis indicates that the extragalactic emission is well described by a power-law photon spectrum with an index of -(2.10 +/- 0.03) in the 30 MeV to 100 GeV energy range. No large-scale spatial anisotropy or changes in the energy spectrum are observed in the deduced extragalactic emission. The most likely explanation for the origin of this extragalactic high-energy gamma-ray emission is that it arises primarily from unresolved gamma-ray-emitting blazars.

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

    Czech Academy of Sciences Publication Activity Database

    Parrot, M.; N?mec, F.; Santolík, Ond?ej

    2014-01-01

    Ro?. 119, ?. 7 (2014), s. 5744-5754. ISSN 2169-9380 R&D Projects: GA ?R 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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    G. Dufour

    2009-03-01

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

  17. Studies of VLF radio waves for sudden ionospheric disturbances (SID) in Kashmir region

    International Nuclear Information System (INIS)

    It is recognized that the ionosphere may be sensitive to seismic effects, and the detection of ionospheric perturbations associated with seismicity would be useful for short term prediction of seismic events. To observe this effect, Indian Centre for Space Physics has installed an antenna and receiver system at Kashmir University to monitor the variation of the VLF signal transmitted from VTX. We present the preliminary results from this station.

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

    OpenAIRE

    ?nan, Umran Sava?; 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 ...

  19. Synoptic observations of Jupiter's radio emissions: average statistical properties observed by voyager

    International Nuclear Information System (INIS)

    Observations of Jupiter's low-frequency radio emission collected over one-month intervals before and after each Voyager encounter have been analyzed to provide a synoptic view of the average statistical properties of the emissions. Compilations of occurrence probability, average power flux density, and average sense of circular polarization are presented as a function of central meridian longitude, phase of Io, and frequency. The results are compared with ground-based observations. The necessary geometrical conditions and preferred polarization sense for Io-related decametric emission observed by Voyager from above both the dayside and nightside hemispheres are found to be essentially the same as those observed in earth-based studies. On the other hand, there is a clear local time dependence in the Io-dependent decametric emission. The emission is prevalent at longitudes >2000 when observed from over the dayside hemisphere but is dominant at longitudes >2000 when observed from over the postmidnight sector. Decametric emission, which comprises the dynamic spectral lesser arcs near 10 MHz, displays a distinct, bimodal polarization pattern that is predominantly in the left-hand sense at longitudes below 1500 and in the right-hand sense at longitudes above 1500. The central meridian longitude distributions of occurrence probability and average flux density at hectometric wavelengths appear to depend significantly on both the observer's latitude and local time. Io appears to have an influence on average flux density of the emission down to below 2 MHz. The average power flux density sectrum of Jupiter's emission has a broad peak near 9 MHz. Intergration of the average spectrum over all frequencies and all longitudes gives a total radiated power for an equivalent isotropic source of 4 x 1011 W

  20. The Terminator Time in subionospheric VLF/LF diurnal variation as recorded by the Romanian VLF/LF radio monitoring system related to earthquake occurrence and volcano erruptions

    Science.gov (United States)

    Moldovan, I. A.; Moldovan, A. S.; Biagi, P. F.; Ionescu, C.; Schwingenschuh, K.; Boudjada, M. Y.

    2012-04-01

    The Romanian VLF/LF monitoring system consisting in a radio receiver and the infrastructure that is necessary to record and transmit the collected data is part of the European international network named INFREP. Information on electromagnetic fields' intensities created by transmitters at a receiving site are indicating the quality of the propagation along the paths between the receivers and transmitters. Studying the ionosphere's influences on the electromagnetic waves' propagation along a certain path is a method to put into evidence possible modifications of its lower structure and composition as earthquakes' precursors. The VLF/LF receiver installed in Romania was put into operation in February 2009 and has already 3 years of testing, functioning and proving its utility in the forecast of some earthquakes or volcanic eruptions. Simultaneously we monitor, in the same site with the VLF/LF receiver, the vertical atmospheric electric field and different other meteorological parameters as: temperature, pressure or rainfall. The global magnetic conditions are emphasized with the help of Daily Geomagnetic Index Kp. At a basic level, the adopted analysis consists in a simple statistical evaluation of the signals by comparing the instantaneous values to the trend of the signal. In this paper we pay attention to the terminator times in subionospheric VLF/LF diurnal variation, which are defined as the times of minimum in amplitude (or phase) around sunrise and sunset. These terminator times are found to shift significantly just around the earthquake. In the case of Kobe earthquake, there were found significant shifts in both morning and evening terminator times and these authors interpreted the shift in terminator time in terms of the lowering of lower ionosphere by using the full-wave mode theory. A LabVIEW application which accesses the VLF/LF receiver through internet was developed. 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 appends daily files into monthly and anual 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. This type of representation, highlights the modification of the terminator time versus the length of the solar-day, improves the user's capability to detect possible propagation anomalies due to ionosphere conditions and allows a quick visual inspection of unexpected behaviors of transmission channels at different frequencies and paths. A very special result, was observed on the recordings made on the propagation path to Iceland (NRK, 37.5kHz). Recordings are made once a minute, for a period of 303 days. Icelandic channel propagation anomalies present in the range of 40-90 days are considered to be precursory phenomena associated with Eyjafjallajokull - Iceland, volcanic eruption occurred in April-May 2010.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  3. Observations of H? emission profiles in Aditya tokamak

    International Nuclear Information System (INIS)

    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 shot–to–shot 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)

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

    CERN Document Server

    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...

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

    Science.gov (United States)

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

    2014-05-01

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

  6. Biogenic nonmethane hydrocarbon emissions estimated from tethered balloon observations

    Science.gov (United States)

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

    1994-01-01

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

  7. VHE emission from extragalactic sources: open issues from MWL observations

    International Nuclear Information System (INIS)

    The Cherenkov telescopes observations together with Fermi/LAT survey and multi-wavelength (MWL) simultaneous coverage are posing new challenges to the description of extreme sources, such as BL Lacs, flat spectrum radio quasars (FSRQs), and radiogalaxies. We will review some of these new results threatening the conventional emission models. Among them: the difficulties of the usual description with single-zone SSC models of the SED of BL Lacs objects, when simultaneous very-high energy (VHE) and MWL observations are taken into account; the constraints on the location of the gamma-ray emission region as revealed by the MAGIC observations of the FSRQ PKS 1222+21; the firm VHE detection of somewhat unexpected sources such as the radiogalaxy IC 310 in the Perseus cluster of galaxies. We will also consider the interplay between intrinsic emission models and the interaction of gamma-rays with the extragalactic background light and intergalactic magnetic fields. These issues will be tackled in the framework of the results of MWL observations led by the MAGIC Cherenkov telescopes system

  8. Cold plasma diagnostics using satellite measurements of VLF signals from ground transmitters

    Science.gov (United States)

    Inan, U. S.; Bell, T. F.; Anderson, R. R.

    1977-01-01

    A diagnostic technique to obtain the cold-plasma density profile in the magnetosphere is introduced. This method uses satellite measurements of group delay and pulse duration of VLF signals from ground transmitters in conjunction with a detailed ray-tracing analysis. An iterative method is involved which starts with an approximate density profile, computes the ray paths for that profile, and then compares the properties of the rays that reach the satellite location with the actual satellite measurements. The density profile is then modified to account for any discrepancies between the two results. The same process is repeated with the new profile until one has reasonable agreement between the data and ray-tracing results. This method is applied to the case of an Imp 6 pass, where strong signals from the Siple VLF transmitter were observed for over 25 min. Good agreement is found between the results of the proposed technique and the well-known ground whistler techniques of cold-plasma diagnostics. The results also serve to illustrate the wide diversity of propagation paths from ground transmitters to high-altitude satellites during VLF wave-injection experiments.

  9. Deep 1.4-GHz observations of diffuse polarized emission

    CERN Document Server

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

    2006-01-01

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

  10. Polar cap optical emissions observed from the ISIS2 satellite

    International Nuclear Information System (INIS)

    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)

  11. GALEX OBSERVATIONS OF DIFFUSE ULTRAVIOLET EMISSION FROM DRACO

    International Nuclear Information System (INIS)

    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 ?m 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.

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

    Czech Academy of Sciences Publication Activity Database

    Parrot, M.; Berthelier, J. J.; Blecki, J.; Brochot, J. Y.; Hobara, Y.; Lagoutte, D.; Lebreton, J. P.; N?mec, F.; Onishi, T.; Pincon, J. L.; Píša, David; Santolík, Ond?ej; Sauvaud, J. A.; Slominska, E.

    2015-01-01

    Ro?. 36, ?. 3 (2015), s. 483-511. ISSN 0169-3298 R&D Projects: GA ?R(CZ) GA14-31899S; GA MŠk LH12231 Grant ostatní: Rada Programu interní podpory projekt? mezinárodní spolupráce AV ?R(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

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

    CERN Document Server

    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.

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

    CERN Document Server

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

    2001-01-01

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

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

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

    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.; Krömer 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.

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

    Science.gov (United States)

    Šmída, R.; Baur, S.; Bertaina, M.; Blümer, J.; Chiavassa, A.; Engel, R.; Haungs, A.; Huege, T.; Kampert, K.-H.; Klages, H.; Kleifges, M.; Krömer, 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.

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

    Directory of Open Access Journals (Sweden)

    Wilczy?ski 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 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.

  19. Deep 1.4-GHz observations of diffuse polarized emission

    OpenAIRE

    Carretti, E.; Poppi, S.; Reich, W.; Reich, P.; Fuerst, E.; Bernardi, G.; Cortiglioni, S.; Sbarra, C.(INFN Sezione di Bologna; Dipartimento di Fisica, Università di Bologna, Bologna, Italy)

    2005-01-01

    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...

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

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

    2015-11-01

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

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

    CERN Document Server

    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...

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

    Science.gov (United States)

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

    2015-12-31

    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

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

    Directory of Open Access Journals (Sweden)

    K. Yumimoto

    2008-06-01

    Full Text Available A four-dimensional variational (4D-Var data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4 is applied to an adjoint inversion of a heavy dust event over eastern Asia during 20 March–4 April 2007. The vertical profiles of the dust extinction coefficients derived from NIES Lidar network are directly assimilated, with validation using observation data. Two experiments assess impacts of observation site selection: Experiment A uses five Japanese observation sites located downwind of dust source regions; Experiment B uses these and two other sites near source regions. Assimilation improves the modeled dust extinction coefficients. Experiment A and Experiment B assimilation results are mutually consistent, indicating that observations of Experiment A distributed over Japan can provide comprehensive information related to dust emission inversion. Time series data of dust AOT calculated using modeled and Lidar dust extinction coefficients improve the model results. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square differences of dust AOT by 35–40%. However, at Beijing and Tsukuba, the RMS differences degrade because of fewer observations during the heavy dust event. Vertical profiles of the dust layer observed by CALIPSO are compared with assimilation results. The dense dust layer was trapped at potential temperatures (? of 280–300 K and was higher toward the north; the model reproduces those characteristics well. Latitudinal distributions of modeled dust AOT along the CALIPSO orbit paths agree well with those of CALIPSO dust AOT, OMI AI, and MODIS coarse-mode AOT, capturing the latitude at which AOTs and AI have high values. Assimilation results show increased dust emissions over the Gobi Desert and Mongolia; especially for 29–30 March, emission flux is about 10 times greater. Strong dust uplift fluxes over the Gobi Desert and Mongolia cause the heavy dust event. Total optimized dust emissions are 57.9 Tg (Experiment A; 57.8% larger than before assimilation and 56.3 Tg (Experiment B; 53.4% larger.

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

    Science.gov (United States)

    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.

  6. Fermi Observations of ?-Ray Emission from the Moon

    Science.gov (United States)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwoo, W. B.; Baldini, L.; 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.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hays, E.; Hill, A. B.; Horan, D.; Hou, X.; Hughes, R. E.; Iafrate, G.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Poon, H.; Porter, T. A.; Prokhorov, D.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reposeur, T.; Rochester, L. S.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D. A.; Sbarra, C.; Schalk, T. L.; Sgrò, C.; Share, G. H.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Stawarz, ?.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, D. L.; Wood, K. S.; Yang, Z.; Zimmer, S.

    2012-10-01

    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 cosmic-ray (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(>100\\ MeV) =(1.04+/- 0.01\\,{[statistical\\ error]}+/- 0.1\\,{[systematic\\ error]})\\times 10^{-6} cm-2 s-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(>100 MeV) ? 5 × 10-7 cm-2 s-1, when solar activity was relatively high. The higher ?-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 ?-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 ?-ray sources. Analysis of the lunar and solar emission may thus be important for studies of weak and transient sources near the ecliptic.

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

    Science.gov (United States)

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

    2012-01-01

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

  8. Observations of microwave continuum emission from air shower plasmas

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  10. Normal development of the fruitfly Drosophila in VLF magnetic fields

    International Nuclear Information System (INIS)

    Attempts to substantiate irreversible actions of a variety of magnetic fields on the fruitfly, Drosophila melanogaster, have been successful and unsuccessful in about equal numbers. The most conspicuous mutagenic effects apparently induced by pulsed HF-fields failed to appear under continuous electromagnetic irradiation. This seems to correlate the observed damage with the VLF-components of the pulsed fields. The present investigation is motivated by the occurence of these components both in the atmosphere and in the vicinity of electrical appliances. A strain of normally viable wild type males and subnormally viable Attached-X y w females was used in which the yield and the sex ratio of the progeny indicate, respectively, the extent of developmental damage and of sex-linked recessive lethal mutation induced by the exposure to detrimental conditions. Evaluation of 73,800 flies from subsequent generations of a control group and two test groups raised in steady, or rotating, homogeneous 9.6 kHz magnetic fields of about 2.5 G did not reveal any developmental or hereditar load in the test groups. (orig.)

  11. On the numerical modelling of VLF chorus dynamical spectra

    Directory of Open Access Journals (Sweden)

    D. Nunn

    2009-06-01

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

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

    International Nuclear Information System (INIS)

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

  13. Modeling Atmospheric Emission for CMB Ground-based Observations

    Science.gov (United States)

    Errard, J.; Ade, P. A. R.; Akiba, Y.; Arnold, K.; Atlas, M.; Baccigalupi, C.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Cukierman, A.; Delabrouille, J.; Dobbs, M.; Ducout, A.; Elleflot, T.; Fabbian, G.; Feng, C.; Feeney, S.; Gilbert, A.; Goeckner-Wald, N.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Hill, C.; Holzapfel, W. L.; Hori, Y.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A. H.; Jeong, O.; Katayama, N.; Kaufman, J.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Leon, D.; Linder, E.; Matsuda, F.; Matsumura, T.; Miller, N. J.; Myers, M. J.; Navaroli, M.; Nishino, H.; Okamura, T.; Paar, H.; Peloton, J.; Poletti, D.; Puglisi, G.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Rotermund, K. M.; Schenck, D. E.; Sherwin, B. D.; Siritanasak, P.; Smecher, G.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Tajima, O.; Takakura, S.; Tikhomirov, A.; Tomaru, T.; Whitehorn, N.; Wilson, B.; Yadav, A.; Zahn, O.

    2015-08-01

    Atmosphere is one of the most important noise sources for ground-based cosmic microwave background (CMB) experiments. By increasing optical loading on the detectors, it amplifies their effective noise, while its fluctuations introduce spatial and temporal correlations between detected signals. We present a physically motivated 3D-model of the atmosphere total intensity emission in the millimeter and sub-millimeter wavelengths. We derive a new analytical estimate for the correlation between detectors time-ordered data as a function of the instrument and survey design, as well as several atmospheric parameters such as wind, relative humidity, temperature and turbulence characteristics. Using an original numerical computation, we examine the effect of each physical parameter on the correlations in the time series of a given experiment. We then use a parametric-likelihood approach to validate the modeling and estimate atmosphere parameters from the polarbear-i project first season data set. We derive a new 1.0% upper limit on the linear polarization fraction of atmospheric emission. We also compare our results to previous studies and weather station measurements. The proposed model can be used for realistic simulations of future ground-based CMB observations.

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

    Science.gov (United States)

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

    2016-02-01

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

  15. Observations of Microwave Continuum Emission from Air Shower Plasmas

    CERN Document Server

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

    2007-01-01

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

  16. Role of the plasmapause in dictating the ground accessibility of ELF/VLF chorus

    OpenAIRE

    Golden, D.I.; Spasojevic, M.; Foust, F.R.; Lehtinen, N.G.; Meredith, Nigel P.; U. S. Inan

    2010-01-01

    This study explores the manner in which the plasmapause is responsible for dictating which magnetospheric source regions of ELF/VLF chorus are able to propagate to and be received by midlatitude stations on the ground. First, we explore the effects of plasmapause extent on ground?based observations of chorus via a 3 month study of ground?based measurements of chorus at Palmer Station, Antarctica (L = 2.4, 50°S geomagnetic latitude), and data on the plasmapause extent from the IMAGE EUV instru...

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

    Science.gov (United States)

    Menietti, J. D.

    2003-01-01

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

  18. Source location of chorus emissions observed by Cluster

    Directory of Open Access Journals (Sweden)

    M. Parrot

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

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2014-11-01

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

  1. Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

    Science.gov (United States)

    Tatsuta, K.; Hobara, Y.; Pal, S.; Balikhin, M.

    2015-11-01

    We investigate quantitatively the effect of geomagnetic storms on the sub-ionospheric VLF/LF (Very Low Frequency/Low Frequency) propagations for different latitudes based on 2-year nighttime data from Japanese VLF/LF observation network. Three statistical parameters such as average signal amplitude, variability of the signal amplitude, and nighttime fluctuation were calculated daily for 2 years for 16-21 independent VLF/LF transmitter-receiver propagation paths consisting of three transmitters and seven receiving stations. These propagation paths are suitable to simultaneously study high-latitude, low-mid-latitude and mid-latitude D/E-region ionospheric properties. We found that these three statistical parameters indicate significant anomalies exceeding at least 2 times of their standard deviation from the mean value during the geomagnetic storm time period in the high-latitude paths with an occurrence rate of anomaly between 40 and 50 % presumably due to the auroral energetic electron precipitation. The mid-latitude and low-mid-latitude paths have a smaller influence from the geomagnetic activity because of a lower occurrence rate of anomalies even during the geomagnetically active time period (from 20 to 30 %). The anomalies except geomagnetic storm periods may be caused by atmospheric and/or lithospheric origins. The statistical occurrence rates of ionospheric anomalies for different latitudinal paths during geomagnetic storm and non-storm time periods are basic and important information not only to identify the space weather effects toward the lower ionosphere depending on the latitudes but also to separate various external physical causes of lower ionospheric disturbances.

  2. Aperture synthesis observations of solar and stellar radio emission

    International Nuclear Information System (INIS)

    The work presented in this thesis relied upon the radio astronomical instrument, The Very Large Array. The thesis is divided into three major sections. In the first the author applied maximum entropy-type image reconstruction techniques, using both single dish and iterferometer data, to generate full disk images of the Sun at a wavelength ? ? 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

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

    Science.gov (United States)

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

    2014-05-01

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

  4. Plasma waves observed by the IRM and UKS spacecraft during the AMPTE solar wind lithium releases - Overview

    Science.gov (United States)

    Haeusler, B.; Woolliscroft, L. J.; Anderson, R. R.; Gurnett, D. A.; Holzworth, R. H.

    1986-01-01

    The wave measurements from the Ion Release Module and the United Kingdom Satellite in the diamagnetic cavity, the transition region, and the upstream region are examined. Solar wind conditions during the releases on September 11 and 20, 1984 are described. The quasi-static electric field, wideband, high-frequency waves, and medium and VLF waves observations are analyzed. The data reveal that extremely low levels of wave activity are observed in the boundary between the diamagnetic cavity and external magnetic field, medium and VLF waves in the ion acoustic electrostatic cyclotron harmonic modes are detected in the transition region from the diamagnetic cavity to the solar wind, and decay in the magnetic field strength and density, and an increase in the quasi-static electric field is seen in the upstream edge of the transition region. The emissions observed are related to the different phases of the Li cloud development and different spatial regimes of the Li plasma-solar wind interaction.

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

    Directory of Open Access Journals (Sweden)

    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 2? (?: standard deviation several days before the earthquake and the nighttime fluctuation exceeds the corresponding 2? 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 2? line, and the nighttime fluctuation shows a less significant broad enhancement before the EQ.

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

    CERN Document Server

    Pal, Sujay

    2015-01-01

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

  7. Reconciling reported and unreported HFC emissions with atmospheric observations.

    Science.gov (United States)

    Lunt, Mark F; Rigby, Matthew; Ganesan, Anita L; Manning, Alistair J; Prinn, Ronald G; O'Doherty, Simon; Mühle, Jens; Harth, Christina M; Salameh, Peter K; Arnold, Tim; Weiss, Ray F; Saito, Takuya; Yokouchi, Yoko; Krummel, Paul B; Steele, L Paul; Fraser, Paul J; Li, Shanlan; Park, Sunyoung; Reimann, Stefan; Vollmer, Martin K; Lunder, Chris; Hermansen, Ove; Schmidbauer, Norbert; Maione, Michela; Arduini, Jgor; Young, Dickon; Simmonds, Peter G

    2015-05-12

    We infer global and regional emissions of five of the most abundant hydrofluorocarbons (HFCs) using atmospheric measurements from the Advanced Global Atmospheric Gases Experiment and the National Institute for Environmental Studies, Japan, networks. We find that the total CO2-equivalent emissions of the five HFCs from countries that are required to provide detailed, annual reports to the United Nations Framework Convention on Climate Change (UNFCCC) increased from 198 (175-221) Tg-CO2-eq ? y(-1) in 2007 to 275 (246-304) Tg-CO2-eq ? y(-1) in 2012. These global warming potential-weighted aggregated emissions agree well with those reported to the UNFCCC throughout this period and indicate that the gap between reported emissions and global HFC emissions derived from atmospheric trends is almost entirely due to emissions from nonreporting countries. However, our measurement-based estimates of individual HFC species suggest that emissions, from reporting countries, of the most abundant HFC, HFC-134a, were only 79% (63-95%) of the UNFCCC inventory total, while other HFC emissions were significantly greater than the reported values. These results suggest that there are inaccuracies in the reporting methods for individual HFCs, which appear to cancel when aggregated together. PMID:25918401

  8. Inversion of airborne tensor VLF data using integral equations

    Science.gov (United States)

    Kamm, Jochen; Pedersen, Laust B.

    2014-08-01

    The Geological Survey of Sweden has been collecting airborne tensor very low frequency data (VLF) over several decades, covering large parts of the country. The data has been an invaluable source of information for identifying conductive structures that can among other things be related to water-filled fault zones, wet sediments that fill valleys or ore mineralizations. Because the method only uses two differently polarized plane waves of very similar frequency, vertical resolution is low and interpretation is in most cases limited to maps that are directly derived from the data. Occasionally, 2-D inversion is carried out along selected profiles. In this paper, we present for the first time a 3-D inversion for tensor VLF data in order to further increase the usefulness of the data set. The inversion is performed using a non-linear conjugate gradient scheme (Polak-Ribière) with an inexact line-search. The gradient is obtained by an algebraic adjoint method that requires one additional forward calculation involving the adjoint system matrix. The forward modelling is based on integral equations with an analytic formulation of the half-space Green's tensor. It avoids typically required Hankel transforms and is particularly amenable to singularity removal prior to the numerical integration over the volume elements. The system is solved iteratively, thus avoiding construction and storage of the dense system matrix. By using fast 3-D Fourier transforms on nested grids, subsequently farther away interactions are represented with less detail and therefore with less computational effort, enabling us to bridge the gap between the relatively short wavelengths of the fields (tens of metres) and the large model dimensions (several square kilometres). We find that the approximation of the fields can be off by several per cent, yet the transfer functions in the air are practically unaffected. We verify our code using synthetic calculations from well-established 2-D methods, and trade modelling accuracy off against computational effort in order to keep the inversion feasible in both respects. Our compromise is to limit the permissible resistivity to not fall below 100 ?m to maintain computational domains as large as 10 × 10 km2 and computation times on the order of a few hours on standard PCs. We investigate the effect of possible local violations of these limits. Even though the conductivity magnitude can then not be recovered correctly, we do not observe any structural artefacts related to this in our tests. We invert a data set from northern Sweden, where we find an excellent agreement of known geological features, such as contacts or fault zones, with elongated conductive structures, while high resistivity is encountered in probably less disturbed geology, often related to topographic highs, which have survived predominantly glacial erosion processes. As expected from synthetic studies, the resolution is laterally high, but vertically limited down to the top of conductive structures.

  9. Effect of solar flares flux on the propagation and modal composition of VLF signal in the lower ionosphere

    Science.gov (United States)

    Bouderba, Yasmina; Nait Amor, Samir; Tribeche, Mouloud

    2015-04-01

    The VLF radio waves propagating in the Earth-Ionosphere waveguide are sensitive to the ionospheric disturbances due to X rays solar flux. In order to understand the VLF signal response to the solar flares, the LWPC code is used to simulate the signal perturbation parameters (amplitude and phase) at fixed solar zenith angle. In this work, we used the NRK-Algiers signal data and the study was done for different flares classes. The results show that the perturbed parameters increase with the increasing solar flares flux. This increases is due to the growth of the electron density resulting from the changes of the Wait's parameters. However, the behavior of the perturbation parameters as function of distance shows different forms of signal perturbations. It was also observed that the null points move towards the transmitter location when the flare flux increases which is related to the modal composition of the propagating signal. Effectively, for a given mode, the plot of the attenuation coefficient as function of the flare flux shows a decreases when the flux increases which is more significant for high modes. Thus, the solar flares effect is to amplify the VLF signal by reducing the attenuation coefficient.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-03-15

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

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

    Science.gov (United States)

    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.

  12. The south America VLF NETwork (SAVNET): Development, installation status, first results

    Scientific Electronic Library Online (English)

    J. P., Raulin; P., Correia de Matos David; R., Hadano; A. C. V., Saraiva; E., Correia; P., Kaufmann.

    2009-09-01

    Full Text Available Se presenta la red South America VLF Networks (SAVNET) que es una nueva instalación de observación en frecuencias muy bajas. SAVNET se instaló recientemente en diversas localidades en América LAtina (Brasil, Perú y Argentina) Consiste en una red de siete receptores cuyo principal objetivo científico [...] es monitorear la actividad solar en escalas temporales cortas (minutos/horas) y extensas (años). Otros objetivos incluyen una mejor comprensión de la estructura espacial de la anomalía Magnética del Atlántico sur, el estudio de fenómenos atmosféricos y la búsqueda sistemática de efectos sismico-electromágneticos genuinos. Abstract in english The South America VLF Network, a new observing facility at Very Low Frequencies is presented. It has been recently installed at different locations in Latin America (in Brazil, Peru and Argentina). It consists of a network of seven Very Low Frequency tracking receivers with the main scientific objec [...] tive of monitoring the solar activity on short (minutes to hours) and long (years) time scales. Other objectives include a better understanding of the spatial structure of the South Atlantic Magnetic Anomaly, the study of atmospheric phenomena and the search for genuine seismic-electromagnetic effects.

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

    Science.gov (United States)

    Raulin, J.

    2013-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Barbusse, St.

    2001-05-01

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

  15. A generation mechanism for chorus emission

    Directory of Open Access Journals (Sweden)

    V. Y. Trakhtengerts

    Full Text Available A chorus generation mechanism is discussed, which is based on interrelation of ELF/VLF noise-like and discrete emissions under the cyclotron wave-particle interactions. A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause. This process is accompanied by a step-like deformation of the energetic electron distribution function in the velocity space, which is situated at the boundary between resonant and nonresonant particles. The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator (BWO regime of wave generation, when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap, in the form of a succession of discrete signals with growing frequency inside each element. The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission, when the strong wavelet starts from the equatorial plane. The comparison is given of the model developed using some satellite and ground-based data. In particular, the appearance of separate groups of chorus signals with a duration 2-10 s can be connected with the preliminary stage of the step formation. BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements.

    Key words. Magnetospheric physics (Energetic particles · trapped. Space plasma physics (wave-particle interactions; waves and instabilities

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

    Directory of Open Access Journals (Sweden)

    S. Palit

    2013-09-01

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

  17. Fast emission estimates in China and South Africa constrained by satellite observations

    Science.gov (United States)

    Mijling, Bas; van der A, Ronald

    2013-04-01

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

  18. Detection of karst structures using airborne EM and VLF

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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

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

    OpenAIRE

    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...

  1. A generation mechanism of chorus emissions using BWO theory

    International Nuclear Information System (INIS)

    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.

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

    OpenAIRE

    Hamaguchi, Kenji; team, the Suzaku Eta Carinae; team, the Carinae D-1

    2007-01-01

    A number of giant HII regions are associated with soft diffuse X-ray emission. Among these, the Carina nebula possesses the brightest soft diffuse emission. The required plasma temperature and thermal energy can be produced by collisions or termination of fast winds from main-sequence or embedded young O stars, but the extended emission is often observed from regions apart from massive stellar clusters. The origin of the X-ray emission is unknown. The XIS CCD camera onboar...

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

    International Nuclear Information System (INIS)

    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

  4. Phosphorus Emissions from Fish Farms : Observed and Predicted Effects

    OpenAIRE

    Johansson, Torbjörn

    2001-01-01

    During the last decades, fish farming has been a rapidly increasing industry in many European and North American countries. Sweden has a large potential for aquaculture, but there is also a strong concern about the effects on the environment that an increased aquaculture production may cause. This thesis focuses on the eutrophication effects of fish farming in lakes and in coastal areas of the Baltic Sea. Possible eutrophication effects related to marine fish farm emissions were found in smal...

  5. Observations on some thermoluminescence emission centres in geological quartz

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. Geothermal evolution of an intruded dike in the rift zone of Kilauea volcano, Hawaii from VLF and self-potential measurements

    Science.gov (United States)

    Davis, Paul M.

    2015-09-01

    Self-potential (SP) and VLF measurements were made in 1973, 1975, 1995, 1997 and 2012 across a basaltic dike that intruded into the Koae fault zone of Kilauea volcano, Hawaii in May 1973. The SP anomaly remained strong throughout. In 2012 it was at about 60% of the strength it had in 1973. In contrast, the VLF anomaly, though diminished, was still observable in 1995/1997, but by 2012 it had disappeared. A hydrothermal dike model, with parameters calibrated by modeling the solidification of Kilauea Iki lava lake, is used to calculate temperatures and conductivity variation. Following Jaeger's (1957) method, we find that the time in years for a dike of width W (m) to solidify is 0.0075W2. Thus, a 1 m dike solidifies within the first few days, and after 39 years is only tens of degrees above ambient. Given the orders of magnitude difference between the conductivities of wet and dry basalt, we infer, that after solidification, the VLF anomalies were caused by induction in a localized veil of wet, hot basalt enveloping the dike, that was generated initially by condensation of steam, and subsequently by condensation of evaporated water as temperatures reduced. The conductivity anomaly persisted until the mid-nineties. By 2012, temperatures and condensation were too small for a VLF signal. The persistent SP anomaly is attributed to localized fluid disruption, with evaporation mainly at the water table and in the vadose zone. Streaming potentials are associated with evaporative circulation in the vadose zone. Next to the dike a positive potential is generated by upward flow of moisture-laden air, with a smaller negative potential on its flanks from downward infiltrating rainwater. The analysis indicates that the combination of SP and VLF measurements can characterize the evolving geothermal regime of intrusions above the water table.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    P. Castellanos

    2013-08-01

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

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

    Directory of Open Access Journals (Sweden)

    G. E. Caledonia

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

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

    OpenAIRE

    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 ...

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

    OpenAIRE

    K. Yumimoto; Uno, I; Sugimoto, N; Shimizu, A.; Liu, Z.; Winker, D. M.

    2008-01-01

    A four-dimensional variational (4D-Var) data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4) is applied to an adjoint inversion of a heavy dust event over eastern Asia during 20 March–4 April 2007. The vertical profiles of the dust extinction coefficients derived from NIES Lidar network are directly assimilated, with validation using observation data. Two experiments assess impacts of observation site selection: Experiment A uses five Japanese observation sites...

  14. Observation of increases in emission from modern vehicles over time in Hong Kong using remote sensing

    International Nuclear Information System (INIS)

    In this study on-road gaseous emissions of vehicles are investigated using remote sensing measurements collected over three different periods. The results show that a high percentage of gaseous pollutants were emitted from a small percentage of vehicles. Liquified Petroleum Gas (LPG) vehicles generally have higher gaseous emissions compared to other vehicles, particularly among higher-emitting vehicles. Vehicles with high vehicle specific power (VSP) tend to have lower CO and HC emissions while petrol and LPG vehicles tend to have higher NO emissions when engine load is high. It can be observed that gaseous emission factors of petrol and LPG vehicles increase greatly within 2 years of being introduced to the vehicle fleet, suggesting that engine and catalyst performance deteriorate rapidly. It can be observed that LPG vehicles have higher levels of gaseous emissions than petrol vehicles, suggesting that proper maintenance of LPG vehicles is essential in reducing gaseous emissions from vehicles. - Highlights: ? Emissions collected in 3 different periods to examine changes in emission over time. ? LPG vehicles generally emit more gaseous pollutants compared to other vehicles. ? Large increase in emissions from modern petrol/LPG vehicles after 2 years' operation. ? CO and NO emissions of modern diesel vehicles are similar to those of older vehicles. - Remote sensing measurements show large increases in gaseous emissions from vehicles in Hong Kong after 2 years of operation, indicating that engine and catalyst performance deteriorate rapidly.

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

    OpenAIRE

    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...

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    B. Mijling

    2013-07-01

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

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

    Science.gov (United States)

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

    2013-12-01

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

  19. Observations of CO J = 3 ? 2 emission from molecular clouds

    International Nuclear Information System (INIS)

    Extensive observations in the J = 3 ? 2 transition of carbon monoxide at 345 GHz (870 ?m) have been obtained using an indium anti-monide heterodyne spectral-line receiver with the United Kingdom 3.8-m Infrared Telescope (UKIRT) at Mauna Kea. Mapping observations of up to 1/2 deg2 areas are reported towards the sources NGC 1333, 2023, 2024 and 2068. These maps, obtained with a 55-arcsec beam, reveal a number of new molecular hotspots as well as confirming the previous detection of molecular cool-spots. High-quality spectra have been obtained towards the self-absorbed sources NGC 1333 IRS-1, NGC 2071, Mon R2, AFGL 961 and DR 21. These spectra are similar to those observed in lower CO transitions, but there is a tendency for the redshifted wing to be enhanced in the J = 3 ? 2 transition. Spectral observations are also reported for L 1551/HH-29. Analysis of the variation of gas kinetic temperature around several of the mapped sources shows close agreement with the expected grain kinetic temperature, assuming these sources to be irradiated by single central stars of a spectral class similar to that estimated from other methods. The present data support the previous model (from CO J = 1 ? 0 data) for NGC 2071 and show it to be a rotating cloud. (author)

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    C. J. Rodger

    2006-12-01

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

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

  2. On the numerical modelling of VLF chorus dynamical spectra

    OpenAIRE

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

    2009-01-01

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

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

    OpenAIRE

    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...

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

    Science.gov (United States)

    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.

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

    OpenAIRE

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

    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...

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

    Science.gov (United States)

    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.

  7. Observations and predictions of EUV emission from classical novae

    International Nuclear Information System (INIS)

    Theoretical modeling of novae in outburst predicts that they should be active emitters of radiation both in the EUV and soft X-ray wavelengths twice during the outburst. The first time is very early in the outburst when only an all sky survey can detect them. This period lasts only a few hours. They again become bright EUV and soft X-ray emitters late in the outburst when the remnant object becomes very hot and is still luminous. The predictions imply both that a nova can remain very hot for months to years and that the peak temperature at this time strongly depends upon the mass of the white dwarf. It is important to observe novae at these late times because a measurement of both the flux and temperature can provide information about the mass of the white dwarf, the tun-off time scale, and the energy budget of the outburst. We review the existing observations of novae in late stages of their outburst and present some newly obtained data for GQ Mus 1983. We then provide results of new hydrodynamic simulations of novae in outburst and compare the predictions to the observations. 43 refs., 6 figs

  8. The National Emissions Inventory Significantly Overestimates NOx Emissions: Analysis of CMAQ and in situ observations from DISCOVER-AQ

    Science.gov (United States)

    Anderson, D. C.; Dickerson, R. R.; Loughner, C.

    2013-12-01

    NOx and CO not only adversely impact human health, but they, along with associated VOCs, are also important precursors for O3 formation. While ambient NOx and CO concentrations have decreased dramatically over the past 10-20 years, O3 has remained a more recalcitrant problem, particularly in the Baltimore/Washington region. Reduction of O3 production requires that emissions inventories, such as the National Emissions Inventory (NEI), accurately capture total emissions of CO and NOx while also correctly apportioning them among different sectors. Previous evaluations of the NEI paint different pictures of its accuracy, with assertions that it overestimates either one or both of CO and NOx from anywhere between 25 percent to a factor of 2. These conflicting claims warrant further investigation. In this study, measurements of NOx and CO taken aboard the NOAA P3B airplane during the 2011 DISCOVER-AQ field campaign were used to determine the NOx/CO emissions ratio at 6 locations in the Washington/Baltimore region. An average molar emissions ratio of 12.8 × 1.2 CO/NOx was found by calculating the change in CO over the change in NOx from vertical concentration profiles in the planetary boundary layer. Ratios showed little variation with location. Observed values were approximately a factor of 1.35 - 1.75 times greater than that predicted by the annual, countywide emissions ratio from the 2008 NEI. When compared to a temporalized, gridded version of the inventory processed by SMOKE, ratio observations were greater than that predicted by inventories by up to a factor of 2. Comparison of the in situ measurements and remotely sensed observations from MOPITT of CO to the Community Multiscale Air Quality (CMAQ) model agree within 10-35 percent, with the model higher on average. Measurements of NOy by two separate analytical techniques, on the other hand, show that CMAQ consistently and significantly overestimates NOy concentrations. Combined with the CO observations, this indicates that the NEI overestimates NOx emissions by approximately a factor of 2. Comparison of the temporalized NEI to continuous monitoring of NOx emissions from point sources shows that, on average, agreement between observations and the NEI were within 5 percent. In a region where the NEI estimates on-road emissions can account for 50-75 percent of total NOx, the most likely source of error in the NOx inventory is in the on-road sector. Assumptions about the lifetime and efficacy of catalytic converters in the MOVES model should be investigated as a possible source of this error.

  9. ALMA capabilities for observations of spectral line emission

    Science.gov (United States)

    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. ALMA’s 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 (Japan’s entry has brought two additional bands to ALMA’s receiver retinue) have been accepted, with performance above the already-challenging specifications. ALMA’s 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 ALMA’s potential for transforming millimeter and submillimeter astronomy.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

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

    2016-01-01

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

  12. Observations of predicted cooperative shifts in optically pumped stimulated emissions in Xe

    International Nuclear Information System (INIS)

    In a recent study Garrett showed that stimulated emissions can be suppressed and shifted under the influence of a wave-mixing interference [Phys. Rev. Lett. 70, 4059 (1993)]. We observe the predicted pressure-dependent frequency shifts in optically pumped stimulated emissions from Xe

  13. Neutron emission observed from spent thermal reactor fuel assemblies

    International Nuclear Information System (INIS)

    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

  14. Observation of radio frequency emissions from electrochemical loading experiments

    International Nuclear Information System (INIS)

    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)

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

    Science.gov (United States)

    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.

  16. Top-down estimate of China's black carbon emissions using surface observations: Sensitivity to observation representativeness and transport model error

    Science.gov (United States)

    Wang, Xuan; Wang, Yuxuan; Hao, Jiming; Kondo, Yutaka; Irwin, Martin; Munger, J. William; Zhao, Yongjing

    2013-06-01

    This study examines the sensitivity of "top-down" quantification of Chinese black carbon (BC) emissions to the temporal resolution of surface observations and to the transport model error associated with the grid resolution and wet deposition. At two rural sites (Miyun in North China Plain and Chongming in Yangtze River Delta), the model-inferred emission bias based on hourly BC observations can differ by up to 41% from that based on monthly mean observations. This difference relates to the intrinsic inability of the grid-based model in simulating high pollution plumes, which often exert a larger influence on the arithmetic mean of observations at monthly time steps. Adopting the variation of BC to carbon monoxide correlation slope with precipitation as a suitable measure to evaluate the model's wet deposition, we found that wet removal of BC in the model was too weak, due in part to the model's underestimation of large precipitation events. After filtering out the observations during high pollution plumes and large precipitation events for which the transport model error should not be translated into the emission error, the inferred emission bias changed from -11% (without filtering) to -2% (with filtering) at the Miyun site, and from -22% to +1% at the Chongming site. Using surface BC observations from three more rural sites (located in Northeast, Central, and Central South China, respectively) as constraints, our top-down estimate of total BC emissions over China was 1.80 ± 0.65 Tg/yr in 2006, 0.5% lower than the bottom-up inventory of Zhang et al. (2009) but with smaller uncertainty.

  17. Observational support for dust grain emission by electrostatic forces

    Science.gov (United States)

    Silen, Johan; Hilchenbach, Martin; Hornung, Klaus; Merouane, Sihane; Schulz, Rita

    2015-04-01

    Dust collected close to the comet 67P by the COSIMA instrument, indicates that fluffy grains up to sizes of several 100 um are lifted off the comet surface and transported to the instrument substrate several tens of kilometers away. The temperature of the surface and the detected gas densities are too low to properly explain lifting grains from the cometary surface. We investigate grain dynamics using electrostatic forces. Comet surface lighting conditions create small scale multi pole electric fields by photons. These fields create forces on both charged and neutral dust grains and may serve as "active regions". The forces acting on the grain, scale as D3 with grain size and therefore large grains are proportionally simpler to elevate, provided the mass is not increasing at the same rate. The fluffy structure of the grains seem to fulfill this requirement. The limiting factor of this mechanism is set by the tensile strength of the grains. If the electrostatic force created exceeds the tensile strength, the grain will disintegrate through Coulomb explosion. The mechanism would favor lifting large fluffy grains off the surface because they have a capability of most easily creating mobile charges which interact in a favorable manner with the multi pole fields. Because of the conglomerate nature of the grains, a splitting of a grain may trigger a Coulomb explosion setting free the bulk dust distribution of small grains detected. The measured elongated impacts also suggest that disintegration is taking place close to the spacecraft. This would also be supported by the proposed model as the space craft charging represents a small scale field anomaly where grain splitting could become enhanced. The observed grains seem to fulfill all requirements of this tentative model.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-02-01

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

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

    International Nuclear Information System (INIS)

    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 × 10–7 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. Long-term inverse modeling of Chinese CO emission from satellite observations.

    Science.gov (United States)

    Yumimoto, Keiya; Uno, Itsushi; Itahashi, Syuichi

    2014-12-01

    Carbon monoxide (CO) emissions in China in 2005-2010 were estimated by inversion, using the Green's function method from vertical CO profiles derived from MOPITT Version 5 satellite data and a tagged CO simulation, and validated with independent in situ observations from the World Data Centre for Greenhouse Gases. Modeling with a posteriori emission successfully reproduced CO outflow from the continent to the East China Sea, Sea of Japan, and Japanese islands during winter and spring, and compensated for underestimates in central and eastern China in summer. A posteriori emissions showed large seasonal variations in which December and March emissions were on average 23% larger than August emissions, consistent with other studies. Estimated Chinese CO emissions were 184.4, 173.1, 184.6, 158.4, 157.4, and 157.3 Tg/year for 2005-2010, respectively. The decrease after 2007 is partly attributed to Chinese socioeconomic conditions and improved combustion efficiency. PMID:25113428

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

    Science.gov (United States)

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

    1999-08-01

    Electron emission from the valence band of n-type Si field emitter arrays is reported. High electrostatic field at the surface of Si was achieved by reducing the radius of the emitter tip. Using oxidation sharpening, 1 ?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.

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

    OpenAIRE

    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. Radio and gamma-ray emissions from pulsars: possible observational tests

    OpenAIRE

    Qiao, G. J .; Lee, K.J.; Wang, H. G.; Xu, R. X.; Zhang, B.

    2007-01-01

    Many models for the pulsar radio and $\\gamma$-ray emissions have been developed. The tests for these models using observational data are very important. Tests for the pulsar radio emission models using frequency-altitude relation are presented in this paper. In the radio band, the mean pulse profiles evolve with observing frequencies. There are various styles of pulsar profile - frequency evolutions (which we call as "beam evolution" figure), e.g. some pulsars show that mean...

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

    OpenAIRE

    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...

  5. Seasonal Variation of Methane Emissions in California's Urban and Rural Regions Using Multi-site Observations

    Science.gov (United States)

    Jeong, S.; Hsu, Y.; Andrews, A. E.; Bianco, L.; Newman, S.; Cui, X.; Bagley, J.; Graven, H. D.; Salameh, P.; Sloop, C.; LaFranchi, B.; Michelsen, H. A.; Bambha, R.; Weiss, R. F.; Keeling, R. F.; Fischer, M. L.

    2014-12-01

    California's commitment (Assembly Bill 32) to reduce total greenhouse gas (GHG) emissions to 1990 levels by 2020 requires quantification of current GHG emissions. We present seasonal variation of California's total CH4 emissions for summer 2013 - spring 2014, using data from a dozen sites covering urban and rural areas of California that include South Coast Air Basin (SoCAB), Central Valley, and San Francisco Bay Area. We apply a Bayesian inverse model to estimate CH4 emissions from discrete regions of California and source sectors by combining atmospheric measurements, upstream background, updated high-resolution prior emission maps developed for California, and predicted atmospheric transport from WRF-STILT. We quantify site-specific model-measurement uncertainties due to transport using simulated and observed meteorology, background estimated from oceanic and aircraft observations, and the prior emissions. In particular, we evaluate predicted transport variables in WRF with networks of surface and upper air observations. Preliminary inversion results during summer of 2013 suggest that state total CH4 emissions are 1.2 - 1.7 times higher than the current CARB inventory. Here, we extend and improve upon earlier analyses to provide a full seasonal cycle of CH4 emissions across all major urban and rural regions in California.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  8. Searching for meteor ELF /VLF signatures

    OpenAIRE

    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...

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

    Directory of Open Access Journals (Sweden)

    M. Zavala

    2008-08-01

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

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

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

    Directory of Open Access Journals (Sweden)

    M. Zavala

    2009-01-01

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

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

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

    Science.gov (United States)

    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.

  12. Theory of weakly nonlinear VLF interactions

    International Nuclear Information System (INIS)

    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)

  13. CARMA observations of Galactic cold cores: searching for spinning dust emission

    Science.gov (United States)

    Tibbs, C. T.; Paladini, R.; Cleary, K.; Muchovej, S. J. C.; Scaife, A. M. M.; Stevenson, M. A.; Laureijs, R. J.; Ysard, N.; Grainge, K. J. B.; Perrott, Y. C.; Rumsey, C.; Villadsen, J.

    2015-11-01

    We present the first search for spinning dust emission from a sample of 34 Galactic cold cores, performed using the CARMA interferometer. For each of our cores, we use photometric data from the Herschel Space Observatory to constrain bar{N}H, bar{T}d, bar{n}H, and bar{G}0. By computing the mass of the cores and comparing it to the Bonnor-Ebert mass, we determined that 29 of the 34 cores are gravitationally unstable and undergoing collapse. In fact, we found that six cores are associated with at least one young stellar object, suggestive of their protostellar nature. By investigating the physical conditions within each core, we can shed light on the cm emission revealed (or not) by our CARMA observations. Indeed, we find that only three of our cores have any significant detectable cm emission. Using a spinning dust model, we predict the expected level of spinning dust emission in each core and find that for all 34 cores, the predicted level of emission is larger than the observed cm emission constrained by the CARMA observations. Moreover, even in the cores for which we do detect cm emission, we cannot, at this stage, discriminate between free-free emission from young stellar objects and spinning dust emission. We emphasize that although the CARMA observations described in this analysis place important constraints on the presence of spinning dust in cold, dense environments, the source sample targeted by these observations is not statistically representative of the entire population of Galactic cores.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-05-27

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

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

    Science.gov (United States)

    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.

  16. Hydrogen line and continuum emission in young stellar objects. II - Theoretical results and observational constraints

    Science.gov (United States)

    Alonso-Costa, Jose L.; Kwan, John

    1989-01-01

    Theoretical results for H I emission from YSOs are compared with available observations. IR line and radio continuum properties have been gathered for 29 objects that include a number of T Tau stars, several emission-line stars with IR excesses, and many heavily obscured luminous YSOs. The present excitation model can account for the observed Brackett line and radio continuum fluxes of YSOs with luminosities of 20-100,000 solar luminosities. It is argued that the observed Br-alpha line and 6-cm free-free continuum emissions are best explained in terms of a core-halo structure. The small core (ranging from r less than about 30 AU for a 10,000-solar luminosity YSO to r less than about 0.2 AU for a 10-solar luminosity YSO) is responsible for generating the strong IR line fluxes, while the surrounding diffuse halo dominates the 6-cm emission.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

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

    2009-01-01

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

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    H. Cui

    2015-03-01

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

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

    CERN Document Server

    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).

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

    CERN Document Server

    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.

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

    Science.gov (United States)

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

    2012-12-01

    During the last three years the comprehensive study of ionospheric generation of the artificial signals in ULF/VLF band was carried out at SURA facility. This research was stimulated by successive HAARP experiments on detection the low frequency signals genreated due the action of the ponderomotive forces. Two experimental campaigns under different ionospheric, geomagnetic and facility operation mode conditions was undertaken every year from 2010 to 2012. Here we are summarizing the main features of the artificial ULF/VLF signals observed in vicinity the SURA site. The signals in the 2-20 Hz band were observed in the small area around the facility with the radius approximately 15 km. It was not signal detection at the 30 km distance. The maximum of the amplitude was detected in the nearest receiving point about 3 km away from the transmitting array. The amplitude increased about 3 times when the beam was inclined on16 degrees to the south so the footprint of the geomagnetic field line comes close to the point of observation. The ULF signals increased slightly when the SURA operating frequency overlaps the critical foF2 frequency. As a rule the daytime signals are smaller then nighttime one. No any correlation was observed with geomagnetic disturbances. The time delay of the ionospheric ULF signals measured by phase method was estimated as 300-400 ms. Polarization of the ULF signals has a pronounced elliptical character. Sometimes it was linear. The part of measurements in June 2012 was coincide with magnetic storm (June 16-18, Kp=6). It was observed broadening of the signal line at frequencies of 11 and 17 Hz up to 0.2 Hz at the recovery stage of the storm at June 18 (see the figure). This fact can be interpreted as the result of the signal interaction with the radiation belt protons appeared over there during the storm time. In 2012 campaigns it was firstly observed at SURA signals on frequencies of several kilohertz at nightime which could not be explained by traditional mechanism of ionospheric current modulation. Also this signals displayed unusual behavior during the magnetic storm deceasing in the amplitude. The work was supported by RFBR grants 11-02-00419, 11-02-97104 and RF Ministry of education and science by state contract 16.518.11.7066.;

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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.

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

    OpenAIRE

    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 ...

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

    Directory of Open Access Journals (Sweden)

    S. Ray

    2013-06-01

    Full Text Available On 18 January 2011, at 20:23 UTC, an earthquake of magnitude 7.2 occurred in southwestern Pakistan (latitude 28°44' N, longitude 63°56' E at a depth of 68 km. We present the results of the analysis of very low frequency (VLF radio signals, received at three stations located in India. We analyze the VLF signals around this earthquake day and look for possible precursory effects of this earthquake. For our analysis, we use four different VLF propagation paths. These propagation paths are DHO–IERC (Sitapur, VTX–Pune, VTX–ICSP (Indian Centre for Space Physics, Kolkata and NWC–IERC. We observed significant shifts of the "sunrise terminator time" (SRT for DHO–IERC and VTX–Pune paths. For DHO–IERC path, the SRT of the VLF signals shifted towards nighttime three days before the earthquake day, and in the case of VTX–Pune path it shifted towards nighttime just one day before the earthquake day. For VTX–Kolkata path, the shift of SRT is four days before the earthquake day, but here the shift is not so strong, somewhere between 2? and 3? lines. For the other two paths, namely, DHO–IERC and VTX–Pune, the terminator time shifts crossed the 3? line. We found no significant shifts of SRT for NWC–IERC propagation path. Higher deviation in the VTX–Pune path as compared to VTX–ICSP path could be due to the proximity of the former to the epicenter. Similarly, DHO–IERC path is over the epicenter while NWC–IERC path is totally away from the epicenter. This could be the reason why the effect in DHO–IERC path is stronger than that in NWC–IERC path.

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

    Science.gov (United States)

    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 <1.2) provide a more realistic simulation of seasonal methanol concentrations in midlatitudes on the basis of both the IASI and TES measurements.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    International Nuclear Information System (INIS)

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    D. Nunn

    2004-04-01

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

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

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-06-15

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

  16. Observations and interpretation of the infrared emission from supernova SN1987A

    International Nuclear Information System (INIS)

    Infrared spectrophotometric observations of SN1987A from the Kuiper Airborne Observatory are presented for the wavelength range 1.5 to 12.5 microns for five epochs at about 60, 260, 415, 615, and 777 days after the explosion. These data are combined with the ultraviolet, optical, infrared (UVOIR) measurements from ESO/CTIO and SAAO in order to characterize the continuum by three components: a photospheric contribution, free-free radiation, and the infrared emission from dust characterized by greybody radiation. Line flux measurements from the continuum substracted spectra are given, including the Brackett, Pfund, and Humphreys series of hydrogen and neutral and singly-ionized nickel and argon from the core ejecta. Carbon monoxide and silicon monoxide vibration bands are identified in the spectra. A simple analysis of the hydrogen line and free-free emission is presented. Dust radiative equilibrium calculations are performed. At 415 days, excess infrared emission, not accountable by circumstellar dust, was observed. At 615 and 777 days, this new component dominated the infrared continuum and is evidence for dust condensation in the ejecta of SN1987A. The shape of the infrared emission from newly formed dust is well characterized by the Planck curve, i.e., by a greybody, and therefore the grains which formed in the ejecta are either large or their emission arises from optically thick clumps. The radiative equilibrium temperature of the observed greybody emission indicates that the dust is in the metal-rich volume of the ejected core

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

    International Nuclear Information System (INIS)

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    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).

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

    Science.gov (United States)

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

    2013-12-01

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

  1. Turbulence of electrostatic electron cyclotron harmonic waves observed by Ogo 5.

    Science.gov (United States)

    Oya, H.

    1972-01-01

    Analysis of VLF emissions that have been observed near 3/2, 5/2, and 7/2 f sub H by Ogo 5 in the magnetosphere (f sub H is the electron cyclotron frequency) in the light of the mechanism used for the diffuse plasma resonance f sub Dn observed by Alouette 2 and Isis 1. The VLF emission is considered to be generated by nonlinear coupling mechanisms in certain portions of the observation as the f sub Dn is enhanced by its association with nonlinear wave-particle interaction of the electrostatic electron cyclotron harmonic wave, including the instability due to the nonlinear inverse Landau damping mechanism in the turbulence. The difference between the two observations is in the excitation mechanism of the turbulence; the turbulence in the plasma trough detected by Ogo 5 is due to natural origins, whereas the ionospheric topside sounder makes the plasma wave turbulence artificially by submitting strong stimulation pulses. Electron density values in the plasma trough are deduced by applying the f sub Dn-f sub N/f sub H relationship obtained from the Alouette 2 experiment as well as by applying the condition for the wave-particle nonlinear interactions. The electron density values reveal good agreement with the ion density values observed simultaneously by the highly sensitive ion mass spectrometer.

  2. Electromagnetic emissions detected in the topside ionosphere related to the human activity

    Science.gov (United States)

    Rothkaehl, H.; Parrot, M.

    2005-05-01

    The Earth ionosphere undergoes various man-made influences. The electromagnetic emissions in the topside ionosphere have been investigated ever since first satellites were located on the orbits. Despite the fact that the analysis of properties of Earth electromagnetic environment has had a long history, the topics related to the electromagnetic pollutions are still not sufficiently reported. The development of new telecommunication technologies and the increased level of electromagnetic noises from VLF to microwave frequency range in the Earth environment should focus our investigations on that problem. The RF measurements can be used to diagnose the different electron plasma waves, the local electron densities as well as the maximum F2 layer electron densities. The HF diagnostics performed on the low orbiting satellite detected the enhancement of radiation, particularly over the Euro-Asia region. Thus over the Euro-Asia area enhancements of background radiation were detected in the whole frequency band, which is connected with natural plasma radiation, and for frequencies greater than the plasma frequency at maximum F2 layer, triggered by artificial ground-based origin noises. Electromagnetic waves permanently pumped to the ionosphere by the system of broadcasting stations can disturb the nearest space environment. The observed broadband emissions are a superposition of natural plasma emissions and man-made noises. The aim of this paper is to discuss the morphological properties and origins of the observed HF and VLF wave activity generated by human activity, detected at the low orbiting satellite CORONAS- I and AUREOL-3.

  3. VLF-MT survey and geoelectrical soundings in Kaminokuni town, Hokkaido; Hokkaido Kaminokuni chiiki ni okeru denki tansa

    Energy Technology Data Exchange (ETDEWEB)

    Oshima, H.; Utsugi, M.; Nagumo, H.; Sasatani, T.; Nishida, Y. [Hokkaido University, Sapporo (Japan). Faculty of Science

    1996-03-25

    For the quantitative analysis of the seismography, observed at Kaminokuni Town and affected by the properties of sub-surface structures, covering the group of aftershocks of the 1993 Hokkaido-Nansei-Oki earthquake, the VLF-MT method and electric soundings were carried out for assessing the geological structure so as to collect basic datas. VLF-MT soundings were conducted at 37 spots, and electric soundings at 9 spots using the Schlumberger electrode arrangement. For the analysis of the structure, a primary horizontal multi-layer structure was presumed, and the direct method using the linear filter technique was applied. The obtained results were compiled, disclosing what is stated below. It was learned that the quaternary system had a run in the direction of the Amano-gawa river, and that a basin structure extending NNW-SSE with the deepest location near the shore line was found. On the other hand, although the new tertiary system was but partially analyzed, yet horizontally curved basin structures were estimated to exist in Tate, Esashi, and Oanzaigawa layers, all positioned in the upper part of the new tertiary system. 11 refs., 11 figs., 1 tab.

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

    OpenAIRE

    Shendi, El-Arabi Hendi [??????? ???? ????

    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...

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

    International Nuclear Information System (INIS)

    We present observations of the known anomalous microwave emission region, G159.6–18.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.6–18.5 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.

  6. AMI Observations of the Anomalous Microwave Emission in the Perseus Molecular Cloud

    Science.gov (United States)

    Tibbs, C. T.; Scaife, A. M. M.; Dickinson, C.; Paladini, R.; Davies, R. D.; Davis, R. J.; Grainge, K. J. B.; Watson, R. A.

    2013-05-01

    We present observations of the known anomalous microwave emission region, G159.6-18.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.6-18.5 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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Struminsky, Alexei

    2015-01-01

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

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

    Science.gov (United States)

    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.

  10. Recent developments in Fire Emission Monitoring in MACC-II using Fire Radiative Power Observations

    Science.gov (United States)

    Kaiser, Johannes W.; Andela, Niels; Heil, Angelika; Paugam, Ronan; Schultz, Martin G.; van der Werf, Guido R.; Wooster, Martin J.; Remy, Samuel

    2013-04-01

    We will present the latest developments of the Global Fire Assimilation System (GFAS), which has been implemented by the MACC-II project in order to provide accurate fire biomass burning emission estimates for the real time and retrospective Copernicus/GMES atmospheric monitoring and forecasting services. Accurate fire emissions have been shown to be a crucial input for air quality forecasts even when satellite-based atmospheric observations are being assimilated. On the other hand, comparisons of the simulated smoke plumes and atmospheric observations provide information on the accuracy of the bottom-up fire emission estimates. The emission estimates of GFAS are generally consistent with those of the GFED inventory, but they are available with 1-day temporal resoution and in real time. There are also a few small systematic differences between the emission estimates of the two inventories. The general consistency is achieved by assimilating Fire Radiative Power (FRP) observations from the MODIS instruments, and by a conversion of the daily FRP to dry matter combustion rate that depends on the fire type. Emission rates for forty smoke constituents are subsequently calculated from the dry matter combustion rate. The emisson estimates have been validated against atmospheric observations of aerosol optical depth, carbon monoxide, ozone, nitrogen dioxide and formaldehyde using the atmospheric models of MACC. The GFAS data are currently produced with resolutions of 1 day and 0.1 deg, and a time lag of seven hours. They cover the period since January 2003 and are publicly available. In the future, the inclusion of FRP products from the geostationary satellites Meteosat-9, GOES-East, and GOES-West will lead to a finer temporal resolution as well as to an improved accuracy of the daily emission estimates. Estimates of smoke injection height will also become available

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

    CERN Document Server

    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.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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)

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

    Science.gov (United States)

    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 Å line observed with the UVSP) fails to model the flux level and evolution of the O V 1371.3 Åline.

  15. Sea ice effective microwave emissivities from satellite passive microwave and infrared observations

    Science.gov (United States)

    Comiso, J. C.

    1983-01-01

    Near-simultaneous images from the temperature-humidity IR radiometer and dual-polarization scanning multichannel microwave radiometer of the Nimbus 7 satellite are used to investigate microwave sea ice emissivities on a global scale. Emissivities in several Arctic region study areas are found to be approximately constant during a nine-month pereiod covering the fall, winter and spring months, in the cases of both first-year and multiyear ice. During the onset of summer, emissivity increases of about 30 percent are observed at 37 GHz in multiyear ice. A multichannel cluster analysis over very large study areas during winter indicates considerable variability in emissivities of consolidated ice clusters at 37 GHz, and only 1/3 as much variability at 18 GHz. If the variability within each cluster is quantified and taken into account by means of multispectral analysis, data on ice thickness and surface characteristics may also be obtained.

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

    Science.gov (United States)

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

    2015-04-01

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

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

    Science.gov (United States)

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

    2011-12-01

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

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

    CERN Document Server

    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...

  19. Multiwavelength observations of GRB 110731A: GeV emission from onset to afterglow

    CERN Document Server

    ,

    2012-01-01

    We report on the multiwavelength observations of the bright, long gamma-ray burst \\GRB, by the \\Fermi and \\Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that \\GRB shares many features with bright Large Area Telescope bursts observed by \\Fermi during the first 3 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 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 transparenc...

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, W. [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109 (United States); Shen, R. F. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, Ontario M5S 3H4 (Canada); Sakamoto, T. [Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Beardmore, A. P. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); De Pasquale, M. [Mullard Space Science Laboratory, University College London, Holmbury Road, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom); Wu, X. F.; Zhang, B. [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Gorosabel, J. [Instituto de Astrofisica de Andalucia (IAA-CSIC), 18008 Granada (Spain); Urata, Y. [Institute of Astronomy, National Central University, Chung-Li 32054, Taiwan (China); Sugita, S. [EcoTopia Science Institute, Nagoya University, Furo-cho, chikusa, Nagoya 464-8603 (Japan); Pozanenko, A. [Space Research Institute (IKI), 84/32 Profsoyuznaya St., Moscow 117997 (Russian Federation); Nissinen, M. [Taurus Hill Observatory, Haerkaemaeentie 88, 79480 Kangaslampi (Finland); Sahu, D. K. [CREST, Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Im, M. [Center for the Exploration of the Origin of the Universe, Department of Physics and Astronomy, FPRD, Seoul National University, Shillim-dong, San 56-1, Kwanak-gu, Seoul (Korea, Republic of); Ukwatta, T. N. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Andreev, M. [Terskol Branch of Institute of Astronomy of RAS, Kabardino-Balkaria Republic 361605 (Russian Federation); Klunko, E., E-mail: zwk@umich.edu, E-mail: rfshen@astro.utoronto.ca, E-mail: zhang@physics.unlv.edu [Institute of Solar-Terrestrial Physics, Lermontov St., 126a, Irkutsk 664033 (Russian Federation); and others

    2012-06-01

    We present a comprehensive analysis of a bright, long-duration (T{sub 90} {approx} 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 {gamma}-ray band, with optical light curve showing correlation with {gamma}-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to {gamma}-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 ({approx}1100 s), a bright (R = 14.0) optical emission hump with very steep rise ({alpha} {approx} 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 (R{sub GRB} {approx} 3 Multiplication-Sign 10{sup 13} cm), initial Lorentz factor of the outflow ({Gamma}{sub 0} {approx} 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

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

    International Nuclear Information System (INIS)

    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 ?-ray band, with optical light curve showing correlation with ?-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to ?-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 (? ? 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 (?0 ? 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

  3. Reduction of black carbon aerosols in Tokyo: Comparison of real-time observations with emission estimates

    Science.gov (United States)

    Kondo, Y.; Ram, K.; Takegawa, N.; Sahu, L.; Morino, Y.; Liu, X.; Ohara, T.

    2012-07-01

    Black carbon (BC) aerosols alter the radiation budget both directly (by absorbing solar visible radiation) and indirectly (by acting as cloud condensation nuclei) and cause adverse health effects. The absorbing efficiency and direct radiative effect of BC strongly depend on its mass concentration (MBC) and type of emission source. In the present study, we report measurements of MBC at the Research Center for Advanced Science and Technology (RCAST), located at the center of the urban boundary of Tokyo, using an EC-OC analyzer from 2003 to 2005 and a filter-based Continuous Soot Monitoring System (COSMOS) during 2007-2010. The results indicate that MBC have decreased significantly from 2.6 ?g m-3 to 0.5 ?g m-3 (˜80% reduction) between 2003 and 2010. Vehicular emissions are the dominant source of BC in Tokyo, and the observed reduction in MBC is mainly attributed to the stringent regulations of particulate matter exhaust from vehicles imposed by the Japanese government. In addition, this observation is also supported from emission estimates using diurnal-weekly variations of MBC in Tokyo and explains the observed reduction to within about 20%. This is the first clear evidence of a significant reduction in BC emissions in Tokyo and shows that measures taken to reduce BC emissions from traffic sources have a strong effect on air quality in a mega-city and also reduce the climate impact of traffic emissions. We highlight the importance of long-term and reliable measurements in detecting BC trends and for the validation and regulation of emission control measures in mega-cities.

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

    International Nuclear Information System (INIS)

    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)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

    Science.gov (United States)

    Wu, Xueran; Elbern, Hendrik; Jacob, Birgit

    2015-04-01

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  10. Using Lunar Observations to Assess Terra MODIS Thermal Emissive Bands Calibration

    Science.gov (United States)

    Xiong, Xiaoxiong; Chen, Hongda

    2010-01-01

    MODIS collects data in both the reflected solar and thermal emissive regions using 36 spectral bands. The center wavelengths of these bands cover the3.7 to 14.24 micron region. In addition to using its on-board calibrators (OBC), which include a full aperture solar diffuser (SD) and a blackbody (BB), lunar observations have been scheduled on a regular basis to support both Terra and Aqua MODIS on-orbit calibration and characterization. This paper provides an overview of MODIS lunar observations and their applications for the reflective solar bands (RSB) and thermal emissive bands (TEB) with an emphasis on potential calibration improvements of MODIS band 21 at 3.96 microns. This spectral band has detectors set with low gains to enable fire detection. Methodologies are proposed and examined on the use of lunar observations for the band 21 calibration. Also presented in this paper are preliminary results derived from Terra MODIS lunar observations and remaining challenging issues.

  11. Emission inventory evaluation using observations of regional atmospheric background stations of China.

    Science.gov (United States)

    An, Xingqin; Sun, Zhaobin; Lin, Weili; Jin, Min; Li, Nan

    2013-03-01

    Any accurate simulation of regional air quality by numerical models entails accurate and up-to-date emissions data for that region. The INTEX-B2006 (I06), one of the newest emission inventories recently popularly used in China and East Asia, has been assessed using the Community Multiscale Air Quality model and observations from regional atmospheric background stations of China. Comparisons of the model results with the observations for the species SO2, NO2, O3 and CO from the three regional atmospheric background stations of Shangdianzi, Longfengshan and Linan show that the model can basically capture the temporal characteristics of observations such as the monthly, seasonal and diurnal variance trends. Compared to the other three species, the simulated CO values were grossly underestimated by about two-third or one-half of the observed values, related to the uncertainty in CO emissions. Compared to the other two stations, Shangdianzi had poorer simulations, especially for SO2 and CO, which partly resulted from the site location close to local emission sources from the Beijing area; and the regional inventory used was not capable of capturing the influencing factors of strong regional sources on stations. Generally, the fact that summer gave poor simulation, especially for SO2 and O3, might partly relate to poor simulations of meteorological fields such as temperature and wind. PMID:23923427

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

    Science.gov (United States)

    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

  13. Resonant behavior observed in electron field emission from acid functionalized multiwall carbon nanotubes

    OpenAIRE

    Lyth, SM; SILVA, SRP

    2009-01-01

    Acid functionalized multiwall carbon nanotube ink was deposited onto carbon fiber fabric via dip coating. Repeatable staircaselike current-field curves were observed in the field emission data. These atypical curves are attributed to resonant tunneling through localized surface states in a quantum well structure, which arises due to the presence of the surface carboxylic functional group.

  14. Observations of correlations between nuclear, acoustic and electromagnetic emissions during palladium electrolytic saturation with deuterium

    International Nuclear Information System (INIS)

    In the course of palladium electrolytic saturation with deuterium two events were observed with a 'rigid' time correlation between nuclear, acoustic and electromagnetic emission pulses, which confirmated the relationship between processes of crack formation and low-temperature nuclear fusion predicted by the 'accelerating' model

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

    Science.gov (United States)

    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.

  16. Spicule emission profiles observed in \\ion{He}{i} 10830 \\AA

    OpenAIRE

    Nuño, B. Sánchez-Andrade; Centeno, R.; Puschmann, K. G.; Bueno, J. Trujillo; Rodríguez, J. Blanco; Kneer, F.

    2007-01-01

    Off-the-limb observations with high spatial and spectral resolution will help us understand the physical properties of spicules in the solar chromosphere Spectropolarimetric observations of spicules in the \\ion{He}{i} 10830 \\AA\\ multiplet were obtained with the Tenerife Infrared Polarimeter on the German Vacuum Tower Telescope at the Observatorio del Teide (Tenerife, Spain). The analysis shows the variation of the off-limb emission profiles as a function of the distance to t...

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

    Directory of Open Access Journals (Sweden)

    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

    International Nuclear Information System (INIS)

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

    Directory of Open Access Journals (Sweden)

    A. K. Mebust

    2013-08-01

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

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

    CERN Document Server

    Hamaguchi, Kenji

    2007-01-01

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

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

    Science.gov (United States)

    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.

  2. observations of hot molecular gas emission from embedded low-mass protostars

    DEFF Research Database (Denmark)

    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

    Aims. Young stars interact vigorously with their surroundings, as evident from the highly rotationally excited CO (up to Eu/k = 4000 K) and H2O emission (up to 600 K) detected by the Herschel Space Observatory in embedded low-mass protostars. Our aim is to construct a model that reproduces the observations quantitatively, to investigate the origin of the emission, and to use the lines as probes of the various heating mechanisms. Methods. The model consists of a spherical envelope with a power-la...

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

    OpenAIRE

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

    2011-01-01

    We report results of a Hubble Space Telescope (HST) campaign with the Advanced Camera for Surveys to observe Europa at eastern elongation, i.e. Europa's leading side, on 2008 June 29. With five consecutive HST orbits, we constrain Europa's atmospheric \\ion{O}{1} 1304 \\A and \\ion{O}{1} 1356 \\A emissions using the prism PR130L. The total emissions of both oxygen multiplets range between 132 $\\pm$ 14 and 226 $\\pm$ 14 Rayleigh. An additional systematic error with values on the s...

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

    OpenAIRE

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

    2012-01-01

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

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

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

    2014-01-01

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

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

    CERN Document Server

    Wu, Xueran; Jacob, Birgit

    2015-01-01

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

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

    CERN Document Server

    Riemer-Sørensen, S; Madejski, G; Molendi, S; Gastaldello, F; Harrison, F A; Craig, W W; Hailey, C J; Boggs, S E; Christensen, F E; Stern, D; Zhang, W W; Hornstrup, A

    2015-01-01

    Line emission from dark matter is well motivated for some candidates e.g. sterile neutrinos. We present the first search for dark matter line emission in the 3-80keV 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 3.5keV, but improves on the constraints for energies of 10-25keV.

  12. Probing the origin of VHE emission from M 87 with MWL observations in 2010

    International Nuclear Information System (INIS)

    The large majority of extragalactic very high energy (VHE; E >100 GeV) sources belongs to the class of active galactic nuclei (AGN), in particular the BL Lac sub-class. AGNs are characterized by an extremely bright and compact emission region, powered by a super-massive black hole (SMBH) and an accretion disk, and relativistic outflows (jets) detected all across the electro-magnetic spectrum. In BL Lac sources the jet axis is oriented close to the line of sight, giving rise to a relativistic boosting of the emission. In radio galaxies, on the other hand, the jet makes a larger angle to the line of sight allowing to resolve the central core and the jet in great details. The giant radio galaxy M 87 with its proximity (16 Mpc) and its very massive black hole ((3-6)x109MSun) provides a unique laboratory to investigate VHE emission in such objects and thereby probe particle acceleration to relativistic energies near SMBH and in jets. M 87 has been established as a VHE emitter since 2005. The VHE emission displays strong variability on time-scales as short as a day. It has been subject of a large joint VHE and multi-wavelength (MWL) monitoring campaign in 2008, where a rise in the 43 GHz VLBA radio emission of the innermost region (core) was found to coincide with a flaring activity at VHE. This had been interpreted as a strong indication that the VHE emission is produced in the direct vicinity of the SMBH black hole. In 2010 again a flare at VHE was detected triggering further MWL observations with the VLBA, Chandra, and other instruments. At the same time M 87 was also observed with the Fermi/LAT telescope at GeV energies and the European VLBI Network (EVN). In this contribution preliminary results from the campaign will be presented.

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

    Science.gov (United States)

    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.

  14. Simulated VLF-fields as a risk factor of thrombosis

    Science.gov (United States)

    Jacobi, E.; Richter, O.; Krüskemper, Gertrud

    1981-06-01

    VLF (Very Low Frequencies)-fields are damped electromagnetic waves of atmospheric origin (sferics). Sferics were artificially produced within a steel-built chamber; blood was drawn and platelet adhesiveness, platelet cyclic AMP and coagulation factors were measured in human volunteers placed within the chamber. Following frequency of the impulses of 10 Hz and a field strength of 400 mV/m increased platelet adhesiveness and decreased platelet cyclic AMP. Medication of the anti-platelet drugs were not effective at all, but the pretreatment of dipyridamole 75 mg combined with acetylsalicylic acid 100 mg blocked the sferics induced increment in platelet adhesiveness. Psychologically labile volunteers exhibited more marked effects of sferics upon platelet adhesiveness. Simulation of stressors upon platelets showed the same effect. The increase in platelet adhesiveness induced by all kind of stressors is not a risk factor of thrombosis in itself. Only if the vessel walls are damaged, e.g. by atherosclerotic plaques, or if the blood flow is reduced, e.g. by heart failure, then the increased platelet adhesiveness will cause thrombosis.

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

    Science.gov (United States)

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

    2014-05-01

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

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

    CERN Document Server

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

    2011-01-01

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

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

    Science.gov (United States)

    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].

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    T. Pedersen

    2008-05-01

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

  20. Atmospheric observations of carbon monoxide and fossil fuel CO2 emissions from East Asia

    DEFF Research Database (Denmark)

    Turnbull, Jocelyn C.; Tans, Pieter P.

    2011-01-01

    Flask samples from two sites in East Asia, Tae-Ahn Peninsula, Korea (TAP), and Shangdianzi, China (SDZ), were measured for trace gases including CO2, CO and fossil fuel CO2(CO(2)ff, derived from Delta(CO2)-C-14 observations). The five-year TAP record shows high CO(2)ff when local air comes from the Korean Peninsula. Most samples, however, reflect air masses from Northeastern China with lower CO(2)ff. Our small set of SDZ samples from winter 2009/2010 have strongly elevated CO(2)ff. Biospheric CO2 contributes substantially to total CO2 variability 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. Carbon monoxide (CO) correlates strongly with CO(2)ff. The SDZ and TAP far-field (China influenced) samples have CO: CO(2)ff ratios (R-CO:CO2ff) of 47 +/- 2 and 44 +/- 3 ppb/ppm respectively, consistent with recent bottom-up inventory estimates and other observational studies. Locally influenced TAP samples fall into two distinct data sets, ascribed to air sourced from South Korea and North Korea. The South Korea samples have low R-CO:CO2ff of 13 +/- 3 ppb/ppm, slightly higher than bottom-up inventories, but consistent with emission ratios for other developed nations. We compare our CO(2)ff observations with modeled CO(2)ff using the FLEXPART Lagrangian particle dispersion model convolved with a bottom-up CO(2)ff emission inventories. The modeled annual mean CO(2)ff mole fractions are consistent with our observations when the model inventory includes the reported 63% increase in Chinese emissions from 2004 to 2010, whereas a model version which holds Chinese emissions flat is unable to replicate the observations.

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

    International Nuclear Information System (INIS)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-01

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

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

    CERN Document Server

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

    2011-01-01

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

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

    CERN Document Server

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

    2013-01-01

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

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

    CERN Document Server

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

    2016-01-01

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

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

    CERN Document Server

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

    2015-01-01

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

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

    DEFF Research Database (Denmark)

    Wik, Daniel R.; Hornstrup, Allan; Molendi, S.; Madejski, G.; Harrison, F. A.; Zoglauer, A.; Grefenstette, B. W.; Gastaldello, F.; Madsen, K. K.; Westergaard, Niels Jørgen 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...

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

    CERN Document Server

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

    2007-01-01

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

  9. Improved model of isoprene emissions in Africa using OMI satellite observations of formaldehyde: implications for oxidants and particulate matter

    OpenAIRE

    E. A. Marais; Jacob, D J; Guenther, A.; Chance, K; Kurosu, T. P.; Murphy, J G; Reeves, C. E.; Pye, H. O. T.

    2014-01-01

    We use a 2005–2009 record of isoprene emissions over Africa derived from OMI satellite observations of formaldehyde (HCHO) to better understand the factors controlling isoprene emission on the scale of the continent and evaluate the impact of isoprene emissions on atmospheric composition in Africa. OMI-derived isoprene emissions show large seasonality over savannas driven by temperature and leaf area index (LAI), and much weaker seasonality over equatorial f...

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

    Directory of Open Access Journals (Sweden)

    L. Meng

    2012-07-01

    Full Text Available Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011 into the Community Land Model 4.0 (CLM4CN in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr?1 (including the soil sink and rice paddy emissions in the year 2000 were 42 Tg CH4 yr?1. Tropical wetlands contributed 201 Tg CH4 yr?1, or 78% of the global wetland flux. Northern latitude (>50 N systems contributed 12 Tg CH4 yr?1. However, sensitivity studies show a large range (150–346 Tg CH4 yr?1 in predicted global methane emissions (excluding emissions from rice paddies. The large range is 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. Evidence from sub-millimetre observations for thermal dust emission in NGC4151

    Science.gov (United States)

    Edelson, R. A.; Gear, W. K. P.; Malkan, M. A.; Robson, E. I.

    1988-01-01

    Observations of the Seyfert 1 galaxy NGC4151 using the UKT14 bolometer on the James Clerk Maxwell Telescope are reported. A 5 sigma upper limit of 200 mJy in an 11 arcsec aperture is found. Comparison with an earlier measurement at 155 microns indicates that at least half of the 155-micron flux is due to thermal dust emission. The remainder may be from a synchrotron source which becomes self-absorbed at wavelengths of less than 80 microns.

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

    Science.gov (United States)

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

    2016-01-19

    Observations of elemental mercury (Hg(0)) at sites in North America and Europe show large decreases (∼1-2% y(-1)) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (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

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

    Science.gov (United States)

    Huang, Kan; Zhang, Xingying; Lin, Yanfen

    2015-10-01

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

  14. Field Observations of Increased Isoprene Emissions Under Ozone Fumigation: Implications for Tropospheric Chemistry?

    Science.gov (United States)

    Sparks, J. P.; Greenberg, J. P.; Harley, P. C.; Guenther, A. B.

    2003-12-01

    Isoprene is the most abundant biogenic hydrocarbon released from vegetation and plays a key role in the chemistry of the lower atmosphere. Isoprene is produced and emitted by many plant species, yet the reason plants produce this seemingly wasteful carbon compound is still in debate in the plant physiology community. It has been proposed that isoprene may protect plant leaves from thermal damage or damage from oxidant exposure by stabilizing cellular and chloroplast membranes or by direct reactions between exogenous isoprene and oxidative species. As part of the Chemical Emission, Loss, Transformation and Interactions within Canopies (CELTIC) study held at Duke Forest during the summer of 2003, we used dynamic cuvette systems to fumigate leaves of sweet gum (Liquidambar styraciflua) with ozone at partial pressures ranging from 0 to 300 ppbv. During fumigations, the effluent air was monitored using infrared gas analysis, on-line proton-transfer-reaction mass spectrometry (PTR-MS) and gas chromatography to quantify changes in partial pressure of CO2, water vapor, isoprene and other volatile organics. At fumigations above 100 ppbv ozone, leaf-isoprene emission increased 20-35% compared to pre-fumigation. To our knowledge, this is the first reported observation of increased isoprene emission under ozone fumigation. Over the timescale of our measurements (several hours), isoprene emissions, once elevated, did not decrease even after fumigation levels were reduced. The increase in isoprene emission could potentially be due to upregulation of the isoprene synthase gene or simply an increase in the production (or reallocation) of subcellular isoprene precursor species. However, our measurements did not elucidate or eliminate a particular mechanism. If increases in isoprene emission in response to ozone are common among isoprene emitting species, the feedback implications for the atmosphere could be large. Both a mechanistic understanding of the upregulation process and knowledge of the distribution of the response across plant species are needed for future model parameterization.

  15. (12)CO (3-2) & (1-0) emission line observations of nearby starburst galaxy nuclei

    Science.gov (United States)

    Devereux, Nicholas; Taniguchi, Yoshiaki; Sanders, D. B.; Nakai, N.; Young, J. S.

    1994-01-01

    New measurements of the (12)CO (1-0) and (12)CO (3-2) line emission are presented for the nuclei of seven nearby starburst galaxies selected from a complete sample of 21 nearby starburst galaxies for which the nuclear star formation rates are measured to be comparable to the archetype starburst galaxies M82 and NGC 253. The new observations capitalize on the coincidence between the beam size of the 45 m Nobeyama telescope at 115 GHz and that of the 15 m James Clerk Maxwell Telescope at 345 GHz to measure the value of the (12)CO (3-2)/(1-0) emission line ratio in a 15 sec (less than or equal to 2.5 kpc) diameter region centered on the nuclear starburst. In principle, the (12)CO (3-2)/(1-0) emission line ratio provides a measure of temperature and optical depth for the (12)CO gas. The error weighted mean value of the (12)CO (3-2)/(1-0) emission line ratio measured for the seven starburst galaxy nuclei is -0.64 +/- 0.06. The (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is significantly higher than the average value measured for molecular gas in the disk of the Galaxy, implying warmer temperatures for the molecular gas in starburst galaxy nuclei. On the other hand, the (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is not as high as would be expected if the molecular gas were hot, greater than 20 K, and optically thin, tau much less than 1. The total mass of molecular gas contained within the central 1.2-2.8 kpc diameter region of the starburst galaxy nuclei ranges from 10(exp 8) to 10(exp 9) solar mass. While substantial, the molecular gas mass represents only a small percentage, approximately 9%-16%, of the dynamical mass in the same region.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    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...

  18. Characterization of kraft pulp mill particulate emissions—A summary of existing measurements and observations

    Science.gov (United States)

    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.

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

    OpenAIRE

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

    2007-01-01

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

  20. Observations of 6 - 200 {\\mu}m emission of the Ophiuchus cloud LDN 1688

    OpenAIRE

    Rawlings, M. G.; Juvela, M.; 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 isolat...

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

    Science.gov (United States)

    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.

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

    OpenAIRE

    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,...

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

    OpenAIRE

    Ä°nan, Umran SavaÅŸ; 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...

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    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...

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

    Directory of Open Access Journals (Sweden)

    S. M. Cowie

    2014-03-01

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

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

    International Nuclear Information System (INIS)

    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.)

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

    International Nuclear Information System (INIS)

    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.

  9. FUSE Observations of CO and H2 emission in Comet C/2001 A2 (LINEAR)

    Science.gov (United States)

    Feldman, P. D.; Weaver, H. A.; Burgh, E. B.

    2001-11-01

    We report observations of comet C/2001 A2 (LINEAR) with the Far Ultraviolet Spectroscopic Explorer beginning July 12.58 coinciding with a photometric increase of ~1.5 magnitudes. Spectra were obtained in the 905--1180 Å range at 0.3 Å spectral resolution using the 30'' x 30'' aperture. Several new cometary emissions were identified, particularly the (0,0) bands of the CO Birge-Hopfield systems (C-X and B-X) at 1088 and 1151 Å, respectively, O 1 (1D - 1D) at 1152 Å, and three lines of the H2 Lyman system at 1071.6, 1118.6, and 1166.8 Å, pumped by solar Lyman-? fluorescence. Also detected were O 1 multiplets at 989, 1027, and 1040 Å, and several lines of the H 1 Lyman series. The rotational envelopes of the CO bands are resolved and appear to consist of both cold and warm components, the cold component accounting for 80% of the flux and with a rotational temperature of 60 K. The warm component may be indicative of a CO2 source. Both the CO bands and the O 1 ? 1152 emission (an indicator of H2O production) decreased by a factor of two over the 7.5 hr observation. Preliminary estimates of the production rates at the beginning of the observation are Q(CO) = 4 x 1027 molecules s-1 and Q(H2O) = 3 x 1029 molecules s-1 (vectorial model). These values may be uncertain by as much as a factor of two due to uncertainties in the solar flux. No emission is detected from Ar I at 1048 and 1067 Å and He 1 at 584 Å (in second order). We derive Q(Ar) <= 6 x 1025 atoms s-1 (5? upper limit), which implies that Ar/O is more than a factor of ten less than solar. In addition to the features listed above, there are about two dozen other emissions that have not yet been definitively identified, although some appear to be from N 1, C 1, and S 1. We do not detect any emission from O 6, which may constrain models that seek to explain cometary X-ray emission as being produced by charge exchange of solar wind ions with cometary neutrals. This work is based on data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by The Johns Hopkins University. Financial support has been provided by NASA contract NAS5-32985.

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

    DEFF Research Database (Denmark)

    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...

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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 ?-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 ?-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 ?-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 ?-ray emission on the ?-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 ?-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.

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

    CERN Document Server

    Masetti, N; Palazzi, E; Amati, L; Caroli, E; 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. Comparison with previous observations indicates that the source was in its high (banana) state and displayed a soft spectrum during the INTEGRAL pointing. A (non simultaneous) broadband radio-to-gamma-rays broad-band spectral energy distribution for Ser X-1 is also presented for the first time.

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

    CERN Document Server

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

    2014-01-01

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

  16. OBSERVATION OF EXTENDED VERY HIGH ENERGY EMISSION FROM THE SUPERNOVA REMNANT IC 443 WITH VERITAS

    International Nuclear Information System (INIS)

    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 hr during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (?) before trials and 7.5? after trials in a point-source search. The emission is centered at 6h16m51s + 22030'11'' (J2000) ±0.003stat ± 0.008sys, with an intrinsic extension of 0.016 ± 0.003stat ± 0.004sys. The VHE spectrum is well fit by a power law (dN/dE = N 0 x (E/TeV)-?) with a photon index of 2.99 ± 0.38stat ± 0.3sys and an integral flux above 300 GeV of (4.63 ± 0.90stat ± 0.93sys) x 10-12 cm-2 s-1. These results are discussed in the context of existing models for gamma-ray production in IC 443.

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

    CERN Document Server

    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 ...

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

    Science.gov (United States)

    Paladini, R.

    2010-07-01

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

  19. Inclusive observables and hard gluon emission in neutrino deep inelastic scattering

    International Nuclear Information System (INIS)

    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.)

  20. Direct observation of electron emission and recombination processes by time domain measurements of charge pumping current

    International Nuclear Information System (INIS)

    To analyze the charge pumping (CP) sequence in detail, the source/drain electron current and the substrate hole current under the CP mode of transistors are simultaneously monitored in the time domain. Peaks are observed in both the electron and hole currents, which are, respectively, attributed to the electron emission from the interface defects and to the recombination with holes. The peak caused by the electron emission is found to consist of two components, strongly suggesting that the present time-domain measurement can enable us to resolve different kinds of interface defects. Investigating the correlation between the number of emitted and recombined electrons reveals that only one of the two components contributes to the CP current for the gate-pulse fall time from 6.25?×?10?4 to 1.25?×?10?2 s

  1. Rocket observation of the N II 2143 A emission in an aurora

    Science.gov (United States)

    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.

  2. Cassini and Wind Stereoscopic Observations of Jovian Non-Thermal Radio Emissions

    Science.gov (United States)

    Kaiser, Michael L.; Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.; Zarka, P.

    1999-01-01

    During two intervals in 1999, simultaneous observations of Jupiter's decametric and hectometric radio emissions were made with the Cassini radio and plasma wave instrument (RPWS) and the radio and plasma wave instrument (WAVES) on the Wind spacecraft in Earth orbit. During January, the Jovian longitude difference between the two spacecraft was about 5 deg, whereas for the August-September Earth flyby of Cassini, the angle ranged from 0 deg to about 2.5 deg. With these separations, the instantaneous widths of the walls of the hollow conical radiation beams of some of the decametric arcs were measured suggesting that the typical width is approximately 2 deg. The conical beams seem to move at Io's revolution rate rather than with Jupiter's rotation rate. Additionally, some of the non-arc emissions have very narrow and quite peculiar beamwidths.

  3. Observations and trends of emissions from gas flaring in the Persian Gulf region using OMI

    Science.gov (United States)

    He, H.; Soltanieh, M.; Dickerson, R. R.

    2014-12-01

    Gas flaring associated with oil production is common where there is no local market for natural gas (mostly methane) and emits large amount of air pollutants and greenhouse gases to the atmosphere. OMI NO2, SO2 and Aerosol Index (AI) observations from 2005 to 2013 were analyzed, and successfully characterize emissions from major flaring sources in the Persian Gulf region. The SO2/NO2 ratio can distinguish flaring regions with relatively high SO2 component, from urban and industrial areas, where domestic heating, internal combustion of motor vehicles and power generation with a relatively high NO2 component dominate. Concentrations of these gases over facilities for production and export of oil reflect the economic recession of 2008/9 and reduced oil exports due to sanctions imposed in 2012. A nearby site involved primarily in copper smelting show no such trend. These temporal trends are being analyzed to improve emissions estimates.

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

    Science.gov (United States)

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

    2007-01-01

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

  5. Relations between observable parameters of collisionally broadened emission lines of rotating stars: a useful plot

    International Nuclear Information System (INIS)

    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)

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

    CERN Document Server

    ,

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    L. Meng

    2011-06-01

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

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

    Science.gov (United States)

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

    2010-01-01

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

  9. Millimeter molecular line and infrared observations of dense clouds associated with small H? emission regions

    International Nuclear Information System (INIS)

    A search for new sites of ongoing star formation was made using H? emission nebulosity as a guide. The J = 1 ? 0 transition of 12C16O (115 GHz) is used as a temperature probe of the structure of these regions and thus as an indicator of the position of heating sources embedded in these molecular clouds. Of the 60 H? regions surveyed, 30 distinct areas of CO emission enhanced in one or more localized areas have been detected. Several are very strong molecular-emission sources and some appear to be quite simple in structure compared to the giant molecular cloud/HII region complexes most commonly discussed in the literature. A search for high-density cores of these new regions was made using three transitions of H2CO. The column density of the 13CO (110 GHz) isotopic species was used as a rough guide for the formaldehyde survey. Compact high-density cores were found in the six best candidates, with H2 densities estimated to be greater than 104 to 105 cm-3. At least five of the six high-density regions found in the formaldehyde survey contain embedded infrared sources. These sources were found by mapping at 2.2?. For two of the new molecular clouds, S140 and S255, sufficient data are available to assess the relative importance of various heat inputs to the clouds. Each cloud contains only one embedded source and two external stars. The gas kinetic temperature contour maps, obtained from detailed 12C16O observations, are then used to predict the dust cooling flux through far-infrared radiation and gas cooling through 12C16O radiation. The predicted far-infrared emission greatly exceeds the cooling by molecular lnes. This far-infrared flux should be observable

  10. Disturbances of the VLF/LF radio signal reception at Dobrogea Seismological Observatory due to local abnormal electric activity

    Science.gov (United States)

    Moldovan, Iren-Adelina; Toader, Victorin; Dolea, Paul; Biagi, Pier Francesco

    2015-04-01

    The National Institute for Earth Physics, as part of the INFREP initiative, has monitored radio waves emitted by 10 transmitters all over Europe in relation with seismicity in the last 5 years. In Romania a radio receiving system is located in only one site (Dobrogea Seismological Observatory) situated in Eforie Nord, in the Eastern part of Romania. The electro-magnetic field monitored both at the ground and (sub) ionospheric level, in different frequency ranges (VLF/LF) is considered to be promising for earthquake forecasting. Because the abnormal behavior of the VLF/LF recordings that could not be correlated with the tectonic activity of the seismogenic zones crossed by the radio paths, we decided to monitor other two parameters, at the receiving site: the vertical component of the atmospheric electric field, which indicates variations of electrical properties of the near-ground air (Boltek electric field mill), and the atmospheric local conditions (WS-3600 weather station). The zone is also surveyed by seismic devices (seismometers, accelerometers and infrasonic equipment) and GPS/GNSS base stations to emphasize the local tectonic conditions. We obtained in such way a multiple-parameter monitoring system that increases the confidence in observational data and decreases uncertainties regarding the accuracy of the data recorded until now. As we are exploring different parameters we have obtained some conclusions regarding the correlation of the anomalies with their possible causes. The final expectation of the monitoring system regard the chance to take a snapshot of the geophysical medium before, during and after a significant earthquake occurrence and to reveal if there was or wasn't a noticeable trace of the preparatory stage of it. This work was partially supported by a grant of the Romanian National Authority for Scientific Research, Programe for research- Space Technology and Avanced Research - STAR, project number 84/2013, and by the NUCLEU project, PN 09 30/2009.

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

    Directory of Open Access Journals (Sweden)

    M. Parrot

    2010-05-01

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

  12. Global SF6 emission estimates inferred from atmospheric observations - a test case for Kyoto reporting

    Science.gov (United States)

    Levin, I.; Naegler, T.

    2009-04-01

    Sulphur hexafluoride (SF6) is one of the strongest greenhouse gases per molecule in the atmosphere. SF6 emissions are also one of the six greenhouse gases targeted for reduction under the Kyoto Protocol. Here we present a long-term data set of globally distributed high-precision atmospheric SF6 observations which show an increase in mixing ratios from near zero in the 1970s to a global mean value of 6.3 ppt by the end of 2007. Because of its long atmospheric lifetime of around 3000 years, the accumulation of SF6 in the atmosphere is a direct measure of its global emissions: Analysis of our long-term data records implies a decrease of global SF6 sources after 1995, most likely due to emission reductions in industrialised countries. However, after 1998 the global SF6 source increases again, which is probably due to enhanced emissions from transition economies such as in China and India. Moreover, observed north-south concentration differences in SF6 suggest that emissions calculated from statistical (bottom-up) information and reported by Annex II parties to the United Nations Framework Convention on Climate Change (UNFCCC) may be too low by up to 50%. This clearly shows the importance and need for atmospheric (top-down) validation of Kyoto reporting which is only feasible with a dense world-wide observational network for greenhouse and other trace gases. Other members of the Global SF6 Trends Team: R. Heinz (1), D. Osusko (1), E. Cuevas (2), A. Engel (3), J. Ilmberger (1), R.L. Langenfelds (4), B. Neininger (5), C.v. Rohden (1), L.P. Steele (4), A. Varlagin (6), R. Weller (7), D.E. Worthy (8), S.A. Zimov (9) (1) Institut für Umweltphysik, University of Heidelberg, 69120 Heidelberg, Germany, (2) Centro de Investigación Atmosférica de Izaña, Instituto Nacional de Meteorología (INM), 38071 Santa Cruz de Tenerife, Spain, (3) Institut für Atmosphäre und Umwelt, J.W. Goethe Universität Frankfurt, 60438 Frankfurt/Main, Germany, (4) Centre for Australian Weather and Climate Research / CSIRO Marine and Atmospheric Research (CMAR), Aspendale, Victoria 3195, Australia, (5) MetAir AG, 6313 Menzingen, Switzerland, (6) Svertsov Institute for Evolutionary and Ecological Problems (IPEE), 117071 Moscow, Russia, (7) Alfred Wegener Institute for Polar and Marine Research, 27568 Bremerhaven, Germany, (8) Environment Canada, Climate Research Division / CCMR, Toronto, ON M3H 5T4, Canada, (9) Cherskii, Republic of Sakha (Yakutia), Russia

  13. Radiative forcing by coastal anthropogenic emissions explains observed 20th century Southeast Pacific cooling

    Science.gov (United States)

    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.

  14. Observation of Solar Wind Charge Exchange Emission From Exospheric Material in and Outside Earth's Magnetosheath 2008 September 25

    Science.gov (United States)

    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.

  15. Milagro Observations of TeV Emission from Galactic Sources in the Fermi Bright Source List

    CERN Document Server

    Abdo, A A; Aune, T; Berley, D; Chen, C; Christopher, G E; DeYoung, T; Dingus, B L; Ellsworth, R W; González, 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; Némethy, 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...

  16. Determining The Galactic Halo's Emission Measure from UV and X-ray Observations

    CERN Document Server

    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...

  17. EMISSION HEIGHT AND TEMPERATURE DISTRIBUTION OF WHITE-LIGHT EMISSION OBSERVED BY HINODE/SOT FROM THE 2012 JANUARY 27 X-CLASS SOLAR FLARE

    International Nuclear Information System (INIS)

    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

  18. Characteristics of severe thunderstorms studied with the aid of VLF atmospherics over North–East India

    Indian Academy of Sciences (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. Anomalously strong vertical magnetic fields from distant ELF/VLF sources

    Science.gov (United States)

    Silber, Israel; Price, Colin; Galanti, Eli; Shuval, Abraham

    2015-07-01

    There are many sources of very low frequency (VLF—3-30 kHz) and extremely low frequency (ELF—3-3000 Hz) radiation in the Earth-ionosphere waveguide (e.g., lightning and ELF/VLF communication transmitters). At distances of thousands of kilometers from these sources, the vertical component of the ELF/VLF AC magnetic fields is expected to be very weak and several orders of magnitude lower than the horizontal magnetic components. However, measurements in Israel show a relatively strong vertical magnetic component in both the ELF and VLF bands, at the same order of magnitude as the horizontal components. Our measurements suggest that the real Earth-ionosphere waveguide might often be very different from the theoretical waveguide used in model calculations. In addition, our results imply that using only the horizontal components for direction finding or the absolute magnetic field strength may result in errors, since often a significant fraction of the magnetic field energy hides in the vertical component.

  20. Near-Infrared Observations of Molecular Hydrogen Emission in Planetary Nebulae

    Science.gov (United States)

    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.

  1. Soft X-ray emission observation during magnetic reconnection in spherical tokamak merging

    International Nuclear Information System (INIS)

    Burst of bremsstrahlung soft X-ray emission was observed during spherical tokamak merging process in the University of Tokyo Spherical Tokamak (UTST) experiment. The soft X-ray signal waveform coincided well with the enhancement of the reconnection electric field and its intensity showed nearly linear dependency on the strength of the toroidal magnetic field. These results suggest that the electrons near the X point are effectively accelerated in the toroidal direction by the parallel electric field during plasma merging in the presence of the strong toroidal magnetic field. (author)

  2. EVE-RHESSI Observations of Thermal and Nonthermal Solar Flare Emission

    Science.gov (United States)

    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.

  3. A framework of field observations and spatial data for understanding dust emissions in the Mojave Desert

    Science.gov (United States)

    Ballantine, J.; Reynolds, R. L.; Chavez, P.; Bogle, R.; Clow, G.; Fulton, R.; Reheis, M.; Urban, F.; Wallace, C.; Yount, J.

    2007-12-01

    Modeling dust events at landscape to regional scales requires field observations of dust-source characteristics, mapping of source types by remote sensing, and wind fields representing the conditions that mobilize dust from the surface. A conceptual framework has been built for understanding dust-source types and their dynamics in the Mojave Desert. Observations of dust events in the Mojave indicate five general source types: 1) Sparsely vegetated surfaces that are vulnerable during periods of drought; 2) wet playas where a near-surface groundwater table generates "fluffy" (very soft sediment) conditions; 3) transitional playas where groundwater extraction has lowered the water table, and playa surface composition produces sediments that are vulnerable to erosion; 4) ephemeral flood deposits; and 5) anthropogenic sources where off-road vehicles, military training exercises, and dirt roads create a disturbed surface. Some sources are perennial and others are strongly influenced (sometimes in opposite ways) by precipitation cycles. A multi-year study of precipitation, vegetation, winds, and saltation at several plots in the Mojave National Preserve shows that blooms of annual vegetation in wet years can leave biomass that protects the surface for more than a year after the rains. Monitoring of the wet Franklin Lake Playa shows that a shallow ground-water table is associated with more vulnerable conditions for dust emission. Repeat photography of the relations between winds and dustiness at transitional Mesquite Lake Playa shows that dust is mobilized during the spring when winds are greater than about 5 m/s. Satellite images reveal dust emission from ephemeral fluvial systems, such as the Mojave River Sink, at the end of wet spring seasons. Satellite images also document dust emissions from areas of heavy military and off-road vehicle activity. Landsat imagery was used to map perennial vegetation cover for the Mojave Desert, calibrated to 250 field transects. The perennial vegetation map was used in conjunction with a Landsat-derived surface-sheltering map to identify areas vulnerable to dust emissions due to sparse vegetation. A map of playa lakes, derived from USGS 1:100,000 maps, satellite imagery, and field observations establishes the boundaries of wet, transitional, and dry playas. Wind fields generated from a regional climate model show that intense winds in vulnerable regions are associated with contemporaneous dust plumes observed from geostationary satellites during the major dust storms of January 5, 2007 and March 27, 2007. Through systematic collection of data from the scale of field plots to satellite images, a framework for the modeling of dust generation for a geographically complex and temporally dynamic region like the Mojave Desert is being created.

  4. Observation of field-induced electron emission in porous polycrystalline silicon nano-structured diode

    International Nuclear Information System (INIS)

    Field-induced electron emission properties of porous poly-silicon nano-structured (PNS) diodes were investigated as a function of anodizing conditions, including morphological analysis, various kinds of top electrode thickness and the measuring substrate temperature. Also, the vacuum packaging process was performed by the normal glass frit method. The PNS layer was formed on heavily-dope n-type Si substrate. Non-doped poly-silicon layer was grown by low-pressure chemical vapor deposition (LPCVD) to a thickness of 2mm. Subsequently, the poly-silicon layer was anodized in a mixed solution HF (50 wt%): ethanol(99.8 wt%) = 1:1 as a function of anodizing condition. After anodizing, the PNS layer was thermally oxidized for 1 hr at 900 .deg. C. Subsequently, the top electrode was deposited as a function of Au thickness using E-beam evaporator and, in order to establish ohmic contact, thermally evaporated Al was deposited on the back side of a Si substrate. The prepared PNS diode was packaged using the normal vacuum sealing method. After the vacuum sealing process, the PNS diode was mounted on the PC measurement table. When a positive bias was applied to the top electrode, the electron emission was observed, which was caused by field-induced electron emission through the top metal

  5. SMA Observations of the Extended CO(6-5) Emission in the Starburst Galaxy NGC253

    CERN Document Server

    Krips, Melanie; Peck, Alison; Sakamoto, Kazushi; Neri, Roberto; Gurwell, Mark; Petitpas, Glen; Zhao, Jun-Hui

    2016-01-01

    We present observations of the $^{12}$CO(6-5) line and 686GHz continuum emission in NGC253 with the Submillimeter Array at an angular resolution of ~4arcsec. The $^{12}$CO(6-5) emission is clearly detected along the disk and follows the distribution of the lower $^{12}$CO line transitions with little variations of the line ratios in it. A large-velocity gradient analysis suggests a two-temperature model of the molecular gas in the disk, likely dominated by a combination of low-velocity shocks and the disk wide PDRs. Only marginal $^{12}$CO(6-5) emission is detected in the vicinity of the expanding shells at the eastern and western edges of the disk. While the eastern shell contains gas even warmer (T$_{\\rm kin}$>300~K) than the hot gas component (T$_{\\rm kin}$=300K) of the disk, the western shell is surrounded by gas much cooler (T$_{\\rm kin}$=60K) than the eastern shell but somewhat hotter than the cold gas component of the disk (for similar H$_2$ and CO column densities), indicative of different (or differe...

  6. Mobile Laboratory Observations of Methane Emissions in the Barnett Shale Region.

    Science.gov (United States)

    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

  7. ?-ray emission from the Perseus cluster of galaxies observed with the MAGIC telescopes

    Science.gov (United States)

    Colin, P.; Eisenacher, D.; Hildebrand, D.; Lombardi, S.; Lindfors, E.; Paneque, D.; Partini, S.; Prada, F.; Sitarek, J.; Zandanel, F.; MAGIC Collaboration; Dauser, T.; Kadler, M.; Krauss, F.; Kataoka, J.; Pfrommer, C.; Pinzke, A.; Takahashi, Y.; Wilbert, S.; Wilms, J.

    2012-12-01

    The Perseus cluster of galaxies is a nearby cool-core cluster with an intra-clustermedium (ICM) characterized by very high central densities. The observation of the Perseus cluster with the MAGIC telescopes, during 85 h from 2009 to 2011, resulted in the discovery of 2 point-like sources at very high energy (>100 GeV, VHE) coinciding with the central radio galaxy NGC1275 and the radio galaxy IC310. The ?-ray properties of these 2 sources are presented, taking into account contemporaneous Fermi-LAT as well as multi-wavelength data. Flux variability and spectral energy distribution shapes indicate that the VHE ?-rays do not originate from large-scale interaction of the radio galaxies with ICM but more likely from the active nuclei of these two galaxies. They could be both misaligned version of BL Lac objects, the most common TeV AGN. Our results provide vital clues to understand emission mechanisms of such misaligned objects, and how they may be related to the beamed emission seen in BL Lacs. No evidence of large-scale VHE ?-ray emission from hadronic cosmic ray (CR) interactions with the ICM has been found. The flux upper limit above 1 TeV reaches the signal expected by some theoretical models, constraining the cluster CR physics. In the framework of the hadronicmodel of the radiomini-halos, this limit implies aminimal magnetic field ranging from 4-9?G for the central cluster region.

  8. The use of stereoscopic satellite observation in the determination of the emissivity of cirrus

    Science.gov (United States)

    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.

  9. Evaluation of a plot-scale methane emission model using eddy covariance observations and footprint modelling

    Directory of Open Access Journals (Sweden)

    A. Budishchev

    2014-09-01

    Full Text Available Most plot-scale methane emission models – of which many have been developed in the recent past – are validated using data collected with the closed-chamber technique. This method, however, suffers from a low spatial representativeness and a poor temporal resolution. Also, during a chamber-flux measurement the air within a chamber is separated from the ambient atmosphere, which negates the influence of wind on emissions. Additionally, some methane models are validated by upscaling fluxes based on the area-weighted averages of modelled fluxes, and by comparing those to the eddy covariance (EC flux. This technique is rather inaccurate, as the area of upscaling might be different from the EC tower footprint, therefore introducing significant mismatch. In this study, we present an approach to validate plot-scale methane models with EC observations using the footprint-weighted average method. Our results show that the fluxes obtained by the footprint-weighted average method are of the same magnitude as the EC flux. More importantly, the temporal dynamics of the EC flux on a daily timescale are also captured (r2 = 0.7. In contrast, using the area-weighted average method yielded a low (r2 = 0.14 correlation with the EC measurements. This shows that the footprint-weighted average method is preferable when validating methane emission models with EC fluxes for areas with a heterogeneous and irregular vegetation pattern.

  10. Novel Stimulated Electromagnetic Emission Observations with Artificial Airglow Using RF Excitation with HAARP

    Science.gov (United States)

    Briczinski, S. J., Jr.; Bernhardt, P. A.; Siefring, C. L.; Michell, R.; Hampton, D. L.; Watkins, B. J.; Bristow, W. A.

    2014-12-01

    High power HF radio waves interacting with the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaksa is the world's largest heating facility, producing effective radiated powers in the gigawatt range. Experiments performed at HAARP have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emissions (SEE) are of interest to the ionospheric community for its diagnostic purposes. Typical SEE experiments at HAARP have focused on characterizing the parametric decay of the electromagnetic pump wave into several different wave modes such as upper and lower hybrid, ion acoustic, ion-Bernstein and electron-Bernstein. Recent HAARP experiments have used both conventional and novel techniques to excite ionospheric disturbances at gyroharmonic frequencies. Stable layers of artificial ionization have been generated using a "twisted beam" pattern with the heating array. Compared to pencil beam techniques, these layers are long-lived and produce their own unique SEE patterns. The "downshifted mass" or DSM has shown to be a strong indicator of artificial ionization generation. Additionally, several other previously uncharacterized SEE features have been observed. These emissions are under study to be linked with other heating phenomena such as enhanced optical emissions, ion and plasma line generation, HF radar backscatter and enhanced electron acceleration.

  11. Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA

    Science.gov (United States)

    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.

  12. Dust emissions of organic soils observed in the field and laboratory

    Science.gov (United States)

    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.

  13. Observations and modeling of forward and reflected chorus waves captured by THEMIS

    Directory of Open Access Journals (Sweden)

    O. Agapitov

    2011-03-01

    Full Text Available Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms spacecraft Search Coil Magnetometer (SCM and Electric Field Instrument (EFI at ELF/VLF frequencies up to 4 kHz at L?8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar, discrete structure and rising tones, reflected waves are attenuated by a factor of 10–30 and have 10% higher frequency than concurrently-observed forward waves. Modeling of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger.

  14. Observation of gamma-ray emission from the galaxy M87 above 250 GeV with VERITAS

    OpenAIRE

    Acciari, V. A.; Beilicke, M.; Blaylock, G.; Bradbury, S. M.; J.H. Buckley; Bugaev, V.; Butt, Y.; O Celik; Cesarini, A; L. Ciupik; Cogan, P.; COLIN, P; Cui, W; Daniel, M K; Duke, C

    2008-01-01

    The multiwavelength observation of the nearby radio galaxy M87 provides a unique opportunity to study in detail processes occurring in active galactic nuclei from radio waves to TeV gamma-rays. Here we report the detection of gamma-ray emission above 250 GeV from M87 in spring 2007 with the VERITAS atmospheric Cerenkov telescope array and discuss its correlation with the X-ray emission. The gamma-ray emission is m...

  15. NuSTAR observations of the bullet cluster: constraints on inverse Compton emission

    International Nuclear Information System (INIS)

    The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Because all prior telescopes sensitive at E > 10 keV do not focus light and have degree-scale fields of view, their backgrounds are both high and difficult to characterize. The associated uncertainties result in lower sensitivity to IC emission and a greater chance of false detection. In this work, we present 266 ks NuSTAR observations of the Bullet cluster, which is detected in the energy range 3-30 keV. NuSTAR's unprecedented hard X-ray focusing capability largely eliminates confusion between diffuse IC and point sources; however, at the highest energies, the background still dominates and must be well understood. To this end, we have developed a complete background model constructed of physically inspired components constrained by extragalactic survey field observations, the specific parameters of which are derived locally from data in non-source regions of target observations. Applying the background model to the Bullet cluster data, we find that the spectrum is well—but not perfectly—described as an isothermal plasma with kT = 14.2 ± 0.2 keV. To slightly improve the fit, a second temperature component is added, which appears to account for lower temperature emission from the cool core, pushing the primary component to kT ? 15.3 keV. We see no convincing need to invoke an IC component to describe the spectrum of the Bullet cluster, and instead argue that it is dominated at all energies by emission from purely thermal gas. The conservatively derived 90% upper limit on the IC flux of 1.1 × 10–12 erg s–1 cm–2 (50-100 keV), implying a lower limit on B ? 0.2 ?G, is barely consistent with detected fluxes previously reported. In addition to discussing the possible origin of this discrepancy, we remark on the potential implications of this analysis for the prospects for detecting IC in galaxy clusters in the future.

  16. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    Science.gov (United States)

    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.

  17. Observing and modelling F-region ionospheric dynamics using the OII 7320A emission

    International Nuclear Information System (INIS)

    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

  18. AN OBSERVED CORRELATION BETWEEN THERMAL AND NON-THERMAL EMISSION IN GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Michael Burgess, J.; Preece, Robert D. [Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Ryde, Felix; Axelsson, Magnus [Department of Physics, Royal Institute of Technology (KTH), AlbaNova, SE-106 91 Stockholm (Sweden); Veres, Peter; Mészáros, Peter [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Connaughton, Valerie; Briggs, Michael; Bhat, P. N.; Pelassa, Veronique [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Pe' er, Asaf [Physics Department, University College Cork, Cork (Ireland); Iyyani, Shabnam [The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm (Sweden); Goldstein, Adam [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Byrne, David; Fitzpatrick, Gerard; Foley, Suzanne [University College Dublin, Belfield, Dublin 4 (Ireland); Kocevski, Daniel; Omodei, Nicola [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Paciesas, William S., E-mail: jmichaelburgess@gmail.com, E-mail: rob.preece@nasa.gov, E-mail: felix@particle.kth.se, E-mail: veres@gwu.edu, E-mail: npp@astro.psu.edu [Universities Space Research Association, Huntsville, AL 35805 (United States); and others

    2014-04-01

    Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal ?-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, E {sub p} and kT, of these two components are correlated via the relation E {sub p}?T {sup ?} which varies from GRB to GRB. We present an interpretation in which the value of the index ? indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.

  19. Supermassive binary black holes - possible observational effects in the x-ray emission

    Directory of Open Access Journals (Sweden)

    Jovanović Predrag

    2014-01-01

    Full Text Available Here we discuss the possible observational effects in the X-ray emission from two relativistic accretion disks in a supermassive binary black hole system. For that purpose we developed a model and performed numerical simulations of the X-ray radiation from a relativistic accretion disk around a supermassive black hole, based on the ray-tracing method in the Kerr metric, and applied it to the case of the close binary supermassive black holes. Our results indicate that the broad Fe Kα line is a powerful tool for detecting such systems and studying their properties. The most favorable candidates for observational studies are the supermassive binary black holes in the galactic mergers during the phase when the orbital velocities of their components are very large and exceed several thousand kms -1. [Projekat Ministarstva nauke Republike Srbije, br. 176003: Gravitation and the Large Scale Structure of the Universe i br. 176001: Astrophysical Spectroscopy of Extragalactic Objects

  20. AN OBSERVED CORRELATION BETWEEN THERMAL AND NON-THERMAL EMISSION IN GAMMA-RAY BURSTS

    International Nuclear Information System (INIS)

    Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal ?-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, E p and kT, of these two components are correlated via the relation E p?T ? which varies from GRB to GRB. We present an interpretation in which the value of the index ? indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data

  1. Soft X-ray observation of the prompt emission of GRB 100418A

    Science.gov (United States)

    Imatani, Ritsuko; Tomida, Hiroshi; Nakahira, Satoshi; Kimura, Masashi; Sakamoto, Takanori; Arimoto, Makoto; Morooka, Yoshitaka; Yonetoku, Daisuke; Kawai, Nobuyuki; Tsunemi, Hiroshi

    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.

  2. Theoretical analysis of conditions for observation of plasma oscillations in semiconductors from pulsed terahertz emission

    Energy Technology Data Exchange (ETDEWEB)

    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.

  3. Fermi Observations of High-Energy Gamma-Ray Emission from GRB 080916C

    International Nuclear Information System (INIS)

    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)

  4. Fermi Observations of high-energy gamma-ray emissions from GRB 080916C

    CERN Document Server

    Abdo, A A; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, Guido; Baring, Matthew G; Bastieri, Denis; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, Elliott D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, Thompson H; Burrows, David N; Busetto, Giovanni; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, Annalisa; Charles, E; Chekhtman, A; Cheung, C.C.Teddy; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, Johann; Cominsky, Lynn R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; DeKlotz, M; Dermer, C D; De Angelis, Alessandro; de Palma, F; Digel, S W; Dingus, B L; do Couto e Silva, Eduardo; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, Justin D; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, Thomas Lynn; Godfrey, Gary L; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M H; Grove, J.Eric; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, Alice K; Hayashida, M; Hays, Elizabeth A; Hernando Morata, J A; Hoover, A; Hughes, R E; Johannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, Tsuneyoshi; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knodlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, Frederick Gabriel Ivar; Kuss, Michael; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, Pasquale; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, Sheila; McEnery, J E; McGlynn, S; Meegan, C; Miszaros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, Igor Vladimirovich; Murgia, Simona; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, Takashi; Okumura, Akira; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, Vahe; Pinchera, M; Piron, F; Porter, Troy A; Preece, R; Rainr, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, Soebur; Rea, N; Reimer, A; Reimer, O; Reposeur, Thierry; Reyes, Luis C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F W; Sanchez, D; Sander, A; Parkinson, P.M.Saz; Scargle, J D; Schalk, T L; Segal, K N; Sgro, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, Jean-Luc; Stecker, Floyd William; Steinle, H; Stephens, T E; Strickman, M S; Suson, Daniel J; Tagliaferri, G.; Tajima, Hiroyasu; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, Diego F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M; 10.1126/science.1169101

    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.

  5. Soft X-ray Observation of the Prompt Emission of GRB100418A

    CERN Document Server

    Imatani, Ritsuko; Nakahira, Satoshi; Kimura, Masashi; Sakamoto, Takanori; Arimoto, Makoto; Morooka, Yoshitaka; Yonetoku, Daisuke; Kawai, Nobuyuki; Tsunemi, Hiroshi

    2015-01-01

    We have observed the prompt emission of GRB100418A, from its beginning by the MAXI/SSC (0.7-7 keV) on board the International Space Station followed by the Swift/XRT (0.3-10 keV) observation. The light curve can be fitted by a combination of a power law component and an exponential component (decay constant is $31.6\\pm 1.6$). The X-ray spectrum is well expressed by the Band function with $E_{\\rm p}\\leq$8.3 keV. This is the brightest GRB showing a very low value of $E_{\\rm p}$. It is also consistent with the Yonetoku-relation ($E_{\\rm p}$-$L_{\\rm p}$) while it is not clear with the Amati-relation ($E_{\\rm p}$-$E_{\\rm iso}$).

  6. Fermi observations of high-energy gamma-ray emission from GRB 080916C.

    Science.gov (United States)

    Abdo, A A; Ackermann, M; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, G; Baring, M G; Bastieri, D; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, E 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, T H; Burrows, D; Busetto, G; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, A; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; Deklotz, M; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Dingus, B L; do Couto E Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, J; 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, T; Godfrey, G; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hernando Morat, J A; Hoover, A; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knödlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, F; Kuss, M; 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, P; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, S; McEnery, J E; McGlynn, S; Meegan, C; Mészáros, 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, I V; Murgia, S; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; 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, V; Pinchera, M; Piron, F; Porter, T A; Preece, R; Rainò, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, S; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Reyes, L C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Segal, K N; Sgrò, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, J-L; Stecker, F W; Steinle, H; Stephens, T E; Strickman, M S; Suson, D J; Tagliaferri, G; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D 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

    2009-03-27

    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. PMID:19228997

  7. Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: From Theory to Fermi Observations

    CERN Document Server

    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...

  8. Synchrotron emission in GRBs observed by Fermi: its limitations and the role of the photosphere

    Science.gov (United States)

    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.

  9. Virtual Observatory tools and Amateur Radio Observations Supporting Scientific Analysis of Jupiter Radio Emissions

    Science.gov (United States)

    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

  10. OBSERVATIONAL STUDY OF THE CONTINUUM AND WATER MASER EMISSION IN THE IRAS 19217+1651 REGION

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Esnard, T.; Trinidad, M. A. [Departamento de Astronomia, Universidad de Guanajuato, Apdo Postal 144, Guanajuato, GTO, Mexico CP 36000 (Mexico); Migenes, V., E-mail: tatiana@iga.cu, E-mail: trinidad@astro.ugto.mx, E-mail: vmigenes@byu.edu [Department of Physics and Astronomy, Brigham Young University, ESC-N145, Provo, UT 84602 (United States)

    2012-12-20

    We report interferometric observations of the high-mass star-forming region IRAS 19217+1651. We observed the radio continuum (1.3 cm and 3.6 cm) and water maser emission using the Very Large Array (VLA-EVLA) in transition mode (configuration A). Two radio continuum sources were detected at both wavelengths, I19217-A and I19217-B. In addition, 17 maser spots were observed distributed mainly in two groups, M1 and M2, and one isolated maser. This latter could be indicating the relative position of another continuum source which we did not detect. The results indicate that I19217-A appears to be consistent with an ultracompact H II region associated with a zero-age main-sequence B0-type star. Furthermore, the 1.3 cm continuum emission of this source suggests a cometary morphology. In addition, I19217-B appears to be an H II region consisting of at least two stars, which may be contributing to its complex structure. It was also found that the H{sub 2}O masers of the group M1 are apparently associated with the continuum source I19217-A. These are tracing motions which are not gravitationally bound according to their spatial distribution and kinematics. They also seem to be describing outflows in the direction of the elongated cometary region. On the other hand, the second maser group, M2, could be tracing the base of a jet. Finally, infrared data from Spitzer, Midcourse Space Experiment, and IRIS show that IRAS 19217+1651 is embedded inside a large open bubble, like a broken ring, which possibly has affected the morphology of the cometary H II region observed at 1.3 cm.

  11. Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission

    Science.gov (United States)

    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 ?K 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.

  12. FORTE observations of simultaneous VHF and optical emissions from lightning: Basic phenomenology

    International Nuclear Information System (INIS)

    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

  13. Building and the analysis of two radio antennas (SSRT) in vlf zone

    Science.gov (United States)

    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

  14. Hectometric and kilometric solar radio emission observed from satellites in August 1972

    International Nuclear Information System (INIS)

    Type II, III, and continuum solar radio events, as well as intense terrestrial magnetospheric radio emissions, were observed at low frequencies (10 MHz to 30 kHz) by the IMP-6 satellite during the period of high solar activity in August 1972. This review covers briefly the unique direction finding capability of the experiment, as well as a detailed chronology of the low frequency radio events, and, where possible, their association with both groundbased radio observations and solar flares. The attempted observation of solar bursts in the presence of intense magnetospheric noise may, as illustrated, lead to erroneous results in the absence of directional information. The problem of assigning an electron density scale and its influence on determining burst trajectories is reviewed. However, for the disturbed conditions existing during the period in question, it is felt that such trajectories cannot be determined accurately by this method. In conclusion, the capabilities, limitations, and observing programs of present and future satellite experiments are briefly discussed. (Auth.)

  15. The Annual Cycle of Water Vapor on Mars as Observed by the Thermal Emission Spectrometer

    Science.gov (United States)

    Smith, Michael D.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Spectra taken by the Mars Global Surveyor Thermal Emission Spectrometer (TES) have been used to monitor the latitude, longitude, and seasonal dependence of water vapor for over one full Martian year (March 1999-March 2001). A maximum in water vapor abundance is observed at high latitudes during mid-summer in both hemispheres, reaching a maximum value of approximately 100 pr-micrometer in the north and approximately 50 pr-micrometer in the south. Low water vapor abundance (water vapor. The latitudinal and seasonal dependence of the decay of the northern summer water vapor maximum implies cross-equatorial transport of water to the southern hemisphere, while there is little or no corresponding transport during the decay of the southern hemisphere summer maximum. The latitude-longitude dependence of annually-averaged water vapor (corrected for topography) has a significant positive correlation with albedo and significant negative correlations with thermal inertia and surface pressure. Comparison of TES results with those retrieved from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) experiments shows some similar features, but also many significant differences. The southern hemisphere maximum observed by TES was not observed by MAWD and the large latitudinal gradient in annually-averaged water vapor observed by MAWD does not appear in the TES results.

  16. Observations of Free-Free and Anomalous Microwave Emission from LDN 1622 with the 100 m Green Bank Telescope

    OpenAIRE

    Harper, S E; Dickinson, C.; Cleary, K.

    2015-01-01

    LDN 1622 has previously been identified as a possible strong source of dust-correlated Anomalous Microwave Emission (AME). Previous observations were limited by resolution meaning that the radio emission could not be compared with current generation high-resolution infrared data from Herschel, Spitzer or WISE. This Paper presents arcminute resolution mapping observations of LDN 1622 at 4.85 GHz and 13.7 GHz using the 100 m Robert C. Byrd Green Bank Telescope. The 4.85 GHz ma...

  17. Modeling the thermal emission from asteroid 3 Juno using ALMA observations and the KRC thermal model

    Science.gov (United States)

    Titus, Timothy N.; Li, Jian-Yang; Moullet, Arielle; Sykes, Mark V.

    2015-11-01

    Asteroid 3 Juno (hereafter referred to as Juno), discovered 1 September 1804, is the 11th largest asteroid in the Main Asteroid Belt (MAB). Containing approximately 1% of the mass in the MAB [1], Juno is the second largest S-type [2].As part of the observations acquired from Atacama Large Millimeter/submillimeter Array (ALMA) [3], 10 reconstructed images at ~60km/pixel resolution were acquired of Juno [4] that showed significant deviations from the Standard Thermal Model (STM) [5]. These deviations could be a result of surface topography, albedo variations, emissivity variations, thermal inertia variations, or any combination.The KRC thermal model [6, 7], which has been extensively used for Mars [e.g. 8, 9] and has been applied to Vesta [10] and Ceres [11], will be used to compare model thermal emission to that observed by ALMA at a wavelength of 1.33 mm [4]. The 10 images, acquired over a four hour period, captured ~55% of Juno’s 7.21 hour rotation. Variations in temperature as a function of local time will be used to constrain the source of the thermal emission deviations from the STM.This work is supported by the NASA Solar System Observations Program.References:[1] Pitjeva, E. V. (2005) Solar System Research 39(3), 176. [2] Baer, J. and S. R. Chesley (2008) Celestial Mechanics and Dynamical Astronomy, 100, 27-42. [3] Wootten A. et al. (2015) IAU General Assembly, Meeting #29, #2237199 [4] arXiv:1503.02650 [astro-ph.EP] doi: 10.1088/2041-8205/808/1/L2 [5] Lebofsky, L.A. eta al. (1986) Icarus, 68, 239-251. [6] Kieffer, H. H., et al. (1977) J. Geophys. Res., 82, 4249-4291. [7] Kieffer, Hugh H., (2013) Journal of Geophysical Research: Planets, Volume 118, Issue 3, pp. 451-470 [8] Titus, T. N., H. H. Kieffer, and P. N. Christensen (2003) Science, 299, 1048-1051. [9] Fergason, R. L. et al. (2012) Space Sci. Rev, 170, 739-773, doi:10.1007/s11214-012-9891-3. [10] Titus, T. N. et al. (2012) 43rd LPSC, held March 19-23, 2012 at The Woodlands, Texas. LPI Contribution No. 1659, id.2851. [11] Titus, T. N. (2015) Geophysical Research Letters, 42(7), 2130-2136.

  18. Polarization observations in a low synchrotron emission field at 1.4 GHz

    CERN Document Server

    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.

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

    CERN Document Server

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

    2012-01-01

    Carbon monoxide is an excellent tracer of the physical conditions of gas in molecular outflows from young stars. To understand the outflow mechanism we need to investigate the origin of the molecular emission and the structure and interaction of the outflowing molecular gas. Deriving the physical parameters of the gas will help us to trace and understand the various gas components in the flow. We observed CO(12-11) line emission at various positions along the L1157 bipolar outflow with GREAT aboard SOFIA. Comparing these new data with CO(2-1), we find basically constant line ratios along the outflow and even at the position of the source. These line ratios lead us to estimates of 10^5 to 10^6 cm^-3 for the gas density and 60 to 100 K for the gas temperature of the outflowing gas. The constrained density and temperature values indicate that we are mostly tracing a low-velocity gas component everywhere along the outflow, which is intermediate between the already known cold gas component, which gets entrained in...

  20. Observation of a physical matrix effect during cold vapour generation measurement of mercury in emissions samples

    International Nuclear Information System (INIS)

    Highlights: • A matrix effect for CV-AFS measurement of mercury in emissions samples is reported. • This results from the different efficiencies of liberation of reduced mercury. • There is a good correlation between solution density and the size of the effect. • Several methods to overcome the bias are presented and discussed. - Abstract: The observation of a physical matrix effect during the cold vapour generation–atomic fluorescence measurement of mercury in emissions samples is reported. The effect is as a result of the different efficiencies of liberation of reduced mercury from solution as the matrix of the solution under test varies. The result of this is that peak area to peak height ratios decease as matrix concentration increases, passing through a minimum, before the ratio then increases as matrix concentration further increases. In the test matrices examined – acidified potassium dichromate and sodium chloride solutions – the possible biases caused by differences between the calibration standard matrix and the test sample matrix were as large as 2.8% (relative) representing peak area to peak height ratios for calibration standards and matrix samples of 45 and 43.75, respectively. For the system considered there is a good correlation between the density of the matrix and point of optimum liberation of dissolved mercury for both matrix types. Several methods employing matrix matching and mathematical correction to overcome the bias are presented and their relative merits discussed; the most promising being the use of peak area, rather than peak height, for quantification

  1. Observed spectral energy distribution of the thermal emission from the dayside of WASP-46b

    CERN Document Server

    Chen, Guo; Wang, Hongchi; Nikolov, Nikolay; Seemann, Ulf; Henning, Thomas

    2014-01-01

    We aim to construct a spectral energy distribution (SED) for the emission from the dayside atmosphere of the hot Jupiter WASP-46b and to investigate its energy budget. We observed a secondary eclipse of WASP-46b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2m telescope. Eclipse depths of the acquired light curves were derived to infer the brightness temperatures at multibands that cover the SED peak. We report the first detection of the thermal emission from the dayside of WASP-46b in the K band at 4.2-sigma level and tentative detections in the H (2.5-sigma) and J (2.3-sigma) bands, with flux ratios of 0.253 +0.063/-0.060%, 0.194 +/- 0.078%, and 0.129 +/- 0.055%, respectively. The derived brightness temperatures (2306 +177/-187K, 2462 +245/-302K, and 2453 +198/-258K, respectively) are consistent with an isothermal temperature profile of 2386K, which is significantly higher than the dayside-averaged equilibrium temperature, indicative of very poor heat redistribution eff...

  2. Derivation of an observation-based map of North African dust emission

    Energy Technology Data Exchange (ETDEWEB)

    Evan, Amato T.; Fiedler, Stephanie; Zhao, Chun; Menut, Laurent; Schepanski, Kerstin; Flamant, C.; Doherty, Owen

    2015-03-01

    Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodélé depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Aïr and Hoggar Mountains, making this area the second most important region of emission within North Africa.

  3. Derivation of an observation-based map of North African dust emission

    Science.gov (United States)

    Evan, Amato T.; Fiedler, Stephanie; Zhao, Chun; Menut, Laurent; Schepanski, Kerstin; Flamant, Cyrille; 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.

  4. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission

    CERN Document Server

    Gold, B; Weiland, J L; Hill, R S; Kogut, A; Bennett, C L; Hinshaw, G; Dunkley, J; Halpern, M; Jarosik, N; Komatsu, E; Larson, D; Limon, M; Meyer, S S; Nolta, M R; Page, L; Smith, K M; Spergel, D N; Tucker, G S; Wollack, E; Wright, E L

    2010-01-01

    [Abridged] We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground contamination outside of the updated (KQ85y7) foreground mask. We place a 15 microKelvin upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. We find no indication in the polarization data of an extra "haze" of hard synchrotron emission from energetic electrons near the Galactic center. We provide an updated map of the cosmic microwave background (CMB) using the internal linear combination (ILC) method, updated foreground masks, and updates to point source catalogs with 62 newly detected sources. Also new are tests of the Markov chain Monte Carlo (MCMC) foreground fitting procedure against systematics in the time-stream data, and tests against the observed beam asymmetry. Within a few degrees of the Galactic plane, WMAP total intensity data show...

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

    DEFF Research Database (Denmark)

    Riemer-SØrensen, S.; Wik, D.

    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.

  6. Observing Infrared Emission Lines of Neutron-Capture Species in Planetary Nebulae: New Detections with IGRINS

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  8. Quantifying urban/industrial emissions of greenhouse and ozone-depleting gases based on atmospheric observations

    Science.gov (United States)

    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.

  9. Observation of stimulated emission in an ultrashort-period nonsymmetric GaAs/AlAs superlattice

    International Nuclear Information System (INIS)

    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

  10. Satellite observations of peroxyacetyl nitrate from the Aura Tropospheric Emission Spectrometer

    Directory of Open Access Journals (Sweden)

    V. H. Payne

    2014-06-01

    Full Text Available We present a description of the algorithm used to retrieve peroxyacetyl nitrate (PAN concentrations from the Aura Tropospheric Emission Spectrometer (TES. We describe the spectral microwindows, error analysis and the utilization of a priori and initial guess information provided by the GEOS-Chem global chemical transport model. The TES PAN retrievals contain up to one degree of freedom for signal. Estimated single-measurement uncertainties are 30 to 50%. The detection limit for a single TES measurement is dependent on the atmospheric and surface conditions as well as on the instrument noise. For observations where the cloud optical depth is less than 0.5, we find that the TES detection limit for PAN is in the region of 200 to 300 pptv. We show that PAN retrievals over the Northern Hemisphere Pacific in springtime show spatial features that are qualitatively consistent with the expected distribution of PAN in outflow of Asian pollution.

  11. Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems

    Energy Technology Data Exchange (ETDEWEB)

    Grover, Samantha P.P., E-mail: samantha.grover@monash.edu [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Cohan, Amanda, E-mail: acoh5@student.monash.edu [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Chan, Hon Sen, E-mail: hon.sen.chan@gmail.com [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Livesley, Stephen J., E-mail: sjlive@unimelb.edu.au [Department of Resource Management and Geography, The University of Melbourne, Richmond, Victoria, 3121 (Australia); Beringer, Jason, E-mail: jason.beringer@monash.edu [School of Geography and Environmental Science, Monash University, Clayton, Victoria, 3800 (Australia); Monash Water for Liveability, Monash University, Clayton, Victoria, 3800 (Australia); Daly, Edoardo, E-mail: edoardo.daly@monash.edu [Department of Civil Engineering, Monash University, Clayton, Victoria, 3800 (Australia); Monash Water for Liveability, Monash University, Clayton, Victoria, 3800 (Australia)

    2013-11-01

    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.

  12. Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems

    International Nuclear Information System (INIS)

    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

  13. 7-year temporal trend of anthropogenic SO2 emissions over China identified from GOME observations

    Science.gov (United States)

    Khokhar, M. F.; Beirle, S.; Platt, U.; Wagner, T.

    Fossil fuels such as coal and oil contain significant amounts of sulfur When burned this sulfur is generally converted to SO2 The GOME observations showed enhancements of SO2 column amounts due to anthropogenic emission sources These enhancements are identified from the regions with extensive burning of coal smelting of metal ores and heavy industrial activities such as from China Eastern USA the Arabian Peninsula Eastern Europe South Africa and particularly Norilsk Russia Also a comparison with GOME observations of anthropogenic NO2 column amounts is presented In this paper we present time series of SO2 SCDs over China We analyzed GOME data for the time period 1996-2002 Time series over the highly industrialized regions Beijing and Shanghai showed a slight increase in the SO2 SCD attributable to the increased use of coal for power generation in China Zhou 2001 Especially during the GOME-period 1996-2001 coal consumption and SO2 time series reflect similar behaviour However Richter et al 2005 calculated a significant increase in the NO2 concentrations over the industrial areas of China for the time period of 1996-2004 Additionally preliminary results of atmospheric SO2 from SCIAMACHY on board EnviSAT-1 since March 2002 instrument with broader spectral and better spatial resolution is presented The better spatial resolution will help to study and localize the impacts of SO2 emissions on a finer spatial scale References Richter A J P Burrows H Nuess C Granier and U Niemeier Increase in tropospheric nitrogen

  14. Observation of extreme ultraviolet emission from hydrogen-KI plasmas produced by a hollow cathode discharge

    Energy Technology Data Exchange (ETDEWEB)

    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)

  15. Constrain Carbonyl Sulfide Ocean flux using free tropospheric observations from Aura Tropospheric Emissions Spectrometer

    Science.gov (United States)

    Kuai, L.; Worden, J.; Campbell, J.; Kulawik, S. S.; Montzka, S. A.; Liu, J.

    2013-12-01

    We developed a retrieval algorithm for free tropospheric carbonyl sulfide (OCS) observations from space above ocean from the Tropospheric Emission Spectrometer (TES). The evaluation of the biases and uncertainties against aircraft profiles from the HIPPO campaign and data from the NOAA Mauna Loa site suggest the OCS retrievals (1) have less than 1.0 degree of freedom for signals (DOFs), (2) are sensitive in the mid-troposphere with a peak sensitivity typically between 300 to 500 hPa, (3) but have much smaller systematic errors from temperature, CO2 and H2O calibrations relative to random errors from measurement noise. Here we estimate the monthly means from TES measurements averaged over multiple years so that random errors are reduced and useful information about OCS seasonal and latitudinal variability can be derived. With this averaging, TES OCS data are found to be consistent (within the calculated uncertainties) with NOAA ground observations and HIPPO aircraft measurements. TES OCS data also captures the seasonal and latitudinal variations observed by these in situ data. This TES OCS monthly data would be useful to constrain ocean flux, understand some tropical ocean contracts (e.g., west-east contrast at Pacific), and estimate tropical ocean fluxes.

  16. Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at HAARP and EISCAT

    Science.gov (United States)

    Scales, W.; Mahmoudian, A.; Fu, H.; Bordikar, M. R.; Samimi, A.; Bernhardt, P. A.; Briczinski, S. J., Jr.; Kosch, M. J.; Senior, A.; Isham, B.

    2014-12-01

    There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Berns