ALBERT

Description: [1]  The observed γ -ray fluence distribution of Terrestrial Gamma-ray Flashes (TGFs) detected by the Fermi Gamma-ray Burst Monitor (GBM) is altered by instrumental effects. We perform corrections for deadtime, pulse pile-up and detection efficiency in a model independent manner. A sample of 106 GBM TGFs is selected to include both TGFs which triggered GBM and weaker TGFs found using an offline search. Detector deadtime and pulse pile-up lower the observed fluence of each TGF and the detection efficiency causes weaker TGFs to have a lower probability of detection than brighter TGFs. Monte Carlo simulations are performed in each case to correct for these effects. The corrected fluence distribution is well fit with a power-law of index α  = –2.20 ± 0.13. This is consistent with previous estimates using other techniques. Neither a high-fluence cut-off nor a low-fluence limit is found. The fluence distribution is also expressed in units of TGF hour –1  km –2 versus photons cm –2 per TGF.

Description: The Gamma-Ray Burst Monitor (GBM) on the Fermi Gamma-Ray Space Telescope (Fermi) detected 50 terrestrial gamma-ray flashes (TGFs) during its first 20 months of operation. The high efficiency and large area of the GBM detectors, combined with their fine timing capabilities and relatively high throughput, allow unprecedented studies of the temporal properties of TGFs. The TGF pulses are observed to have durations as brief as ∼0.05 ms, shorter than previously measured. There is a relatively narrow distribution of pulse durations; the majority of pulses have total durations between 0.10 and 0.40 ms. In some TGF events, risetimes as short as ∼0.01 ms and falltimes as short as ∼0.03 ms are observed. Three of the 50 TGFs presented here have well-separated, double peaks. Perhaps as many as 10 other TGFs show evidence, to varying degrees, of overlapping peaks. Weak emission is seen at the leading or trailing edges of some events. Five of the 50 TGFs are considerably longer than usual; these are believed to be caused by incident electrons transported from a TGF at the geomagnetic conjugate point. TGF temporal properties can be used to discriminate between models of the origin of TGFs and also provide some basic physical properties of the TGF process.

Description: Terrestrial Gamma-ray Flashes (TGFs) are brief pulses of energetic radiation observed in low-earth orbit. They are associated with thunderstorms and lightning and have been observed both as gamma-ray and electron flashes depending on the position of the spacecraft with respect to the source. While gamma-ray TGFs are detected as short pulses lasting less than 1 ms, most TGFs seen by the Fermi Gamma-ray Burst Monitor (GBM) with durations greater than 1 ms are, instead, the result of electrons traveling from the sources along geomagnetic field lines. We perform spectral analysis of the three brightest electron TGFs detected by GBM and discover strong 511 keV positron annihilation lines, demonstrating that these electron TGFs also contain substantial positron components. This shows that pair production occurs in conjunction with some terrestrial lightning and that most likely all TGFs are injecting electron-positron beams into the near Earth environment.

Description: A cornerstone of Einstein's special relativity is Lorentz invariance-the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, l(Planck) approximately 1.62 x 10(-33) cm or E(Planck) = M(Planck)c(2) approximately 1.22 x 10(19) GeV), at which quantum effects are expected to strongly affect the nature of space-time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in gamma-ray burst (GRB) light-curves. Here we report the detection of emission up to approximately 31 GeV from the distant and short GRB 090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2E(Planck) on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of l(Planck)/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space-time on a very small scale linearly alters the speed of light.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Abdo, A A -- Ackermann, M -- Ajello, M -- Asano, K -- Atwood, W B -- Axelsson, M -- Baldini, L -- Ballet, J -- Barbiellini, G -- Baring, M G -- Bastieri, D -- Bechtol, K -- Bellazzini, R -- Berenji, B -- Bhat, P N -- Bissaldi, E -- Bloom, E D -- Bonamente, E -- Bonnell, J -- Borgland, A W -- Bouvier, A -- Bregeon, J -- Brez, A -- Briggs, M S -- Brigida, M -- Bruel, P -- Burgess, J M -- Burnett, T H -- Caliandro, G A -- Cameron, R A -- Caraveo, P A -- Casandjian, J M -- Cecchi, C -- Celik, O -- Chaplin, V -- Charles, E -- Cheung, C C -- Chiang, J -- Ciprini, S -- Claus, R -- Cohen-Tanugi, J -- Cominsky, L R -- Connaughton, V -- Conrad, J -- Cutini, S -- 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 -- Farnier, C -- Favuzzi, C -- Fegan, S J -- Finke, J -- Fishman, G -- Focke, W B -- Foschini, L -- Fukazawa, Y -- Funk, S -- Fusco, P -- Gargano, F -- Gasparrini, D -- Gehrels, N -- Germani, S -- Gibby, L -- Giebels, B -- Giglietto, N -- Giordano, F -- Glanzman, T -- Godfrey, G -- Granot, J -- Greiner, J -- Grenier, I A -- Grondin, M-H -- Grove, J E -- Grupe, D -- Guillemot, L -- Guiriec, S -- Hanabata, Y -- Harding, A K -- Hayashida, M -- Hays, E -- Hoversten, E A -- Hughes, R E -- Johannesson, G -- Johnson, A S -- Johnson, R P -- Johnson, W N -- Kamae, T -- Katagiri, H -- Kataoka, J -- Kawai, N -- Kerr, M -- Kippen, R M -- Knodlseder, J -- Kocevski, D -- Kouveliotou, C -- Kuehn, F -- Kuss, M -- Lande, J -- Latronico, L -- Lemoine-Goumard, M -- Longo, F -- Loparco, F -- Lott, B -- Lovellette, M N -- Lubrano, P -- Madejski, G M -- Makeev, A -- Mazziotta, M N -- McBreen, S -- McEnery, J E -- McGlynn, S -- Meszaros, P -- Meurer, C -- Michelson, P F -- Mitthumsiri, W -- Mizuno, T -- Moiseev, A A -- Monte, C -- Monzani, M E -- Moretti, E -- Morselli, A -- Moskalenko, I V -- Murgia, S -- Nakamori, T -- Nolan, P L -- Norris, J P -- Nuss, E -- Ohno, M -- Ohsugi, T -- Omodei, N -- Orlando, E -- Ormes, J F -- Ozaki, M -- Paciesas, W S -- Paneque, D -- Panetta, J H -- Parent, D -- Pelassa, V -- Pepe, M -- Pesce-Rollins, M -- Petrosian, V -- Piron, F -- Porter, T A -- Preece, R -- Raino, S -- Ramirez-Ruiz, E -- Rando, R -- Razzano, M -- Razzaque, S -- Reimer, A -- Reimer, O -- Reposeur, T -- 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 -- Sgro, C -- Siskind, E J -- Smith, D A -- Smith, P D -- Spandre, G -- Spinelli, P -- Stamatikos, M -- Stecker, F W -- Strickman, M S -- Suson, D J -- Tajima, H -- Takahashi, H -- Takahashi, T -- Tanaka, T -- Thayer, J B -- Thayer, J G -- Thompson, D J -- Tibaldo, L -- Toma, K -- Torres, D F -- Tosti, G -- Troja, E -- Uchiyama, Y -- Uehara, T -- Usher, T L -- van der Horst, A J -- Vasileiou, V -- Vilchez, N -- Vitale, V -- von Kienlin, A -- Waite, A P -- Wang, P -- Wilson-Hodge, C -- Winer, B L -- Wood, K S -- Wu, X F -- Yamazaki, R -- Ylinen, T -- Ziegler, M -- England -- Nature. 2009 Nov 19;462(7271):331-4. doi: 10.1038/nature08574. Epub 2009 Oct 28.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Science Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19865083" target="_blank"〉PubMed〈/a〉

Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fermi LAT and Fermi GBM Collaborations -- 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 -- Johannesson, 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 -- Knodlseder, 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 -- Meszaros, 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 -- Raino, 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 -- Sgro, 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 -- New York, N.Y. -- Science. 2009 Mar 27;323(5922):1688-93. doi: 10.1126/science.1169101. Epub 2009 Feb 19.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19228997" target="_blank"〉PubMed〈/a〉

Description: Gamma-ray burst (GRB) 130427A is one of the most energetic GRBs ever observed. The initial pulse up to 2.5 seconds is possibly the brightest well-isolated pulse observed to date. A fine time resolution spectral analysis shows power-law decays of the peak energy from the onset of the pulse, consistent with models of internal synchrotron shock pulses. However, a strongly correlated power-law behavior is observed between the luminosity and the spectral peak energy that is inconsistent with curvature effects arising in the relativistic outflow. It is difficult for any of the existing models to account for all of the observed spectral and temporal behaviors simultaneously.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Preece, R -- Burgess, J Michael -- von Kienlin, A -- Bhat, P N -- Briggs, M S -- Byrne, D -- Chaplin, V -- Cleveland, W -- Collazzi, A C -- Connaughton, V -- Diekmann, A -- Fitzpatrick, G -- Foley, S -- Gibby, M -- Giles, M -- Goldstein, A -- Greiner, J -- Gruber, D -- Jenke, P -- Kippen, R M -- Kouveliotou, C -- McBreen, S -- Meegan, C -- Paciesas, W S -- Pelassa, V -- Tierney, D -- van der Horst, A J -- Wilson-Hodge, C -- Xiong, S -- Younes, G -- Yu, H-F -- Ackermann, M -- Ajello, M -- Axelsson, M -- Baldini, L -- Barbiellini, G -- Baring, M G -- Bastieri, D -- Bellazzini, R -- Bissaldi, E -- Bonamente, E -- Bregeon, J -- Brigida, M -- Bruel, P -- Buehler, R -- Buson, S -- Caliandro, G A -- Cameron, R A -- Caraveo, P A -- Cecchi, C -- Charles, E -- Chekhtman, A -- Chiang, J -- Chiaro, G -- Ciprini, S -- Claus, R -- Cohen-Tanugi, J -- Cominsky, L R -- Conrad, J -- D'Ammando, F -- de Angelis, A -- de Palma, F -- Dermer, C D -- Desiante, R -- Digel, S W -- Di Venere, L -- Drell, P S -- Drlica-Wagner, A -- Favuzzi, C -- Franckowiak, A -- Fukazawa, Y -- Fusco, P -- Gargano, F -- Gehrels, N -- Germani, S -- Giglietto, N -- Giordano, F -- Giroletti, M -- Godfrey, G -- Granot, J -- Grenier, I A -- Guiriec, S -- Hadasch, D -- Hanabata, Y -- Harding, A K -- Hayashida, M -- Iyyani, S -- Jogler, T -- Johannesson, G -- Kawano, T -- Knodlseder, J -- Kocevski, D -- Kuss, M -- Lande, J -- Larsson, J -- Larsson, S -- Latronico, L -- Longo, F -- Loparco, F -- Lovellette, M N -- Lubrano, P -- Mayer, M -- Mazziotta, M N -- Michelson, P F -- Mizuno, T -- Monzani, M E -- Moretti, E -- Morselli, A -- Murgia, S -- Nemmen, R -- Nuss, E -- Nymark, T -- Ohno, M -- Ohsugi, T -- Okumura, A -- Omodei, N -- Orienti, M -- Paneque, D -- Perkins, J S -- Pesce-Rollins, M -- Piron, F -- Pivato, G -- Porter, T A -- Racusin, J L -- Raino, S -- Rando, R -- Razzano, M -- Razzaque, S -- Reimer, A -- Reimer, O -- Ritz, S -- Roth, M -- Ryde, F -- Sartori, A -- Scargle, J D -- Schulz, A -- Sgro, C -- Siskind, E J -- Spandre, G -- Spinelli, P -- Suson, D J -- Tajima, H -- Takahashi, H -- Thayer, J G -- Thayer, J B -- Tibaldo, L -- Tinivella, M -- Torres, D F -- Tosti, G -- Troja, E -- Usher, T L -- Vandenbroucke, J -- Vasileiou, V -- Vianello, G -- Vitale, V -- Werner, M -- Winer, B L -- Wood, K S -- Zhu, S -- New York, N.Y. -- Science. 2014 Jan 3;343(6166):51-4. doi: 10.1126/science.1242302. Epub 2013 Nov 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24263132" target="_blank"〉PubMed〈/a〉

Description: Detectors aboard the Compton Gamma Ray Observatory have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays. These flashes must originate in the atmosphere at altitudes above at least 30 kilometers in order to escape atmospheric absorption and reach the orbiting detectors. At least a dozen such events have been detected over the past 2 years. The photon spectra from the events are very hard (peaking in the high-energy portion of the spectrum) and are consistent with bremsstrahlung emission from energetic (million-electron volt) electrons. The most likely origin of these high-energy electrons, although speculative at this time, is a rare type of high-altitude electrical discharge above thunderstorm regions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fishman, G J -- Bhat, P N -- Mallozzi, R -- Horack, J M -- Koshut, T -- Kouveliotou, C -- Pendleton, G N -- Meegan, C A -- Wilson, R B -- Paciesas, W S -- Goodman, S J -- Christian, H J -- New York, N.Y. -- Science. 1994 May 27;264(5163):1313-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17780850" target="_blank"〉PubMed〈/a〉

Description: The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ackermann, M -- Ajello, M -- Asano, K -- Atwood, W B -- Axelsson, M -- Baldini, L -- Ballet, J -- Barbiellini, G -- Baring, M G -- Bastieri, D -- Bechtol, K -- Bellazzini, R -- Bissaldi, E -- Bonamente, E -- Bregeon, J -- Brigida, M -- Bruel, P -- Buehler, R -- Burgess, J Michael -- Buson, S -- Caliandro, G A -- Cameron, R A -- Caraveo, P A -- Cecchi, C -- Chaplin, V -- Charles, E -- Chekhtman, A -- Cheung, C C -- Chiang, J -- Chiaro, G -- Ciprini, S -- Claus, R -- Cleveland, W -- Cohen-Tanugi, J -- Collazzi, A -- Cominsky, L R -- Connaughton, V -- Conrad, J -- Cutini, S -- D'Ammando, F -- de Angelis, A -- DeKlotz, M -- de Palma, F -- Dermer, C D -- Desiante, R -- Diekmann, A -- Di Venere, L -- Drell, P S -- Drlica-Wagner, A -- Favuzzi, C -- Fegan, S J -- Ferrara, E C -- Finke, J -- Fitzpatrick, G -- Focke, W B -- Franckowiak, A -- Fukazawa, Y -- Funk, S -- Fusco, P -- Gargano, F -- Gehrels, N -- Germani, S -- Gibby, M -- Giglietto, N -- Giles, M -- Giordano, F -- Giroletti, M -- Godfrey, G -- Granot, J -- Grenier, I A -- Grove, J E -- Gruber, D -- Guiriec, S -- Hadasch, D -- Hanabata, Y -- Harding, A K -- Hayashida, M -- Hays, E -- Horan, D -- Hughes, R E -- Inoue, Y -- Jogler, T -- Johannesson, G -- Johnson, W N -- Kawano, T -- Knodlseder, J -- Kocevski, D -- Kuss, M -- Lande, J -- Larsson, S -- Latronico, L -- Longo, F -- Loparco, F -- Lovellette, M N -- Lubrano, P -- Mayer, M -- Mazziotta, M N -- McEnery, J E -- Michelson, P F -- Mizuno, T -- Moiseev, A A -- Monzani, M E -- Moretti, E -- Morselli, A -- Moskalenko, I V -- Murgia, S -- Nemmen, R -- Nuss, E -- Ohno, M -- Ohsugi, T -- Okumura, A -- Omodei, N -- Orienti, M -- Paneque, D -- Pelassa, V -- Perkins, J S -- Pesce-Rollins, M -- Petrosian, V -- Piron, F -- Pivato, G -- Porter, T A -- Racusin, J L -- Raino, S -- Rando, R -- Razzano, M -- Razzaque, S -- Reimer, A -- Reimer, O -- Ritz, S -- Roth, M -- Ryde, F -- Sartori, A -- Parkinson, P M Saz -- Scargle, J D -- Schulz, A -- Sgro, C -- Siskind, E J -- Sonbas, E -- Spandre, G -- Spinelli, P -- Tajima, H -- Takahashi, H -- Thayer, J G -- Thayer, J B -- Thompson, D J -- Tibaldo, L -- Tinivella, M -- Torres, D F -- Tosti, G -- Troja, E -- Usher, T L -- Vandenbroucke, J -- Vasileiou, V -- Vianello, G -- Vitale, V -- Winer, B L -- Wood, K S -- Yamazaki, R -- Younes, G -- Yu, H-F -- Zhu, S J -- Bhat, P N -- Briggs, M S -- Byrne, D -- Foley, S -- Goldstein, A -- Jenke, P -- Kippen, R M -- Kouveliotou, C -- McBreen, S -- Meegan, C -- Paciesas, W S -- Preece, R -- Rau, A -- Tierney, D -- van der Horst, A J -- von Kienlin, A -- Wilson-Hodge, C -- Xiong, S -- Cusumano, G -- La Parola, V -- Cummings, J R -- New York, N.Y. -- Science. 2014 Jan 3;343(6166):42-7. doi: 10.1126/science.1242353. Epub 2013 Nov 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24263133" target="_blank"〉PubMed〈/a〉

Description: We report on the spectral analysis of individual Terrestrial Gamma-ray Flashes (TGFs) observed with the Fermi Gamma-ray Burst Monitor (GBM). The large GBM TGF sample provides 46 events suitable for individual spectral analysis: sufficiently bright, localized by ground-based radio, and with the gamma rays reaching a detector unobstructed. These TGFs exhibit diverse spectral characteristics that are hidden when using summed analysis methods. We account for the low counts in individual TGFs by using Poisson likelihood, and we also consider instrumental effects. The data are fit with models obtained from Monte Carlo simulations of the large scale Relativistic Runaway Electron Avalanche (RREA) model, including propagation through the atmosphere. Source altitudes ranging from 11.6 to 20.2 km are simulated. Two beaming geometries were considered: In one, the photons retain the intrinsic distribution from scattering (narrow), and in the other, the photons are smeared into a wider beam (wide). Several TGFs are well fit only by narrow models, while others favor wide models. Large-scale RREA models can accommodate both narrow and wide beams, with narrow beams suggest large-scale RREA in organized electric fields while wide beams may imply converging or diverging electric fields. Wide beams are also consistent with acceleration in the electric fields of lightning leaders, but the TGFs that favor narrow beam models appear inconsistent with some lightning leader models.

Description: The Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope has triggered on over 300 Terrestrial Gamma-ray Flashes (TGFs) since its launch in June 2008. With 14 detectors, GBM collects on average ~ 100 counts per triggered TGF, enabling unprecedented studies of the time profiles of TGFs. Here we present the first rigorous analysis of the temporal properties of a large sample of TGFs (278), including the distributions of the rise and fall time of the individual pulses and their durations. A variety of time profiles are observed with 19% of TGFs having multiple pulses separated in time and 31 clear cases of partially overlapping pulses. The effect of instrumental dead time and pulse pile-up on the temporal properties are also presented. As the observed gamma-ray pulse structure is representative of the electron flux at the source, TGF pulse parameters are critical to distinguish between relativistic feedback discharge and lightning leader models. We show that at least 67% of TGFs at satellite altitudes are significantly asymmetric. For the asymmetric pulses, the rise times are almost always shorter than the fall times. Those which are not are consistent with statistical fluctuations. The median rise time for asymmetric pulses is ~ 3 times shorter than for symmetric pulses while their fall times are comparable. The asymmetric shapes observed are consistent with the Relativistic Feedback Discharge (RFD) model when Compton scattering of photons between the source and Fermi isincluded and instrumental effects are taken into account.