Observations have been made of a new terrestrial phenomenon: brief (-millisecond), intense flashes of gamma rays, observed with space-borne detectors. These flashes must originate at altitudes in the atmosphere above at least 30 km in order to be observable by orbiting detectors aboard the Compton Gamma-Ray Observatory (CGRO). At least a dozen events have been detected over the past 2 years. The photon spectra from the events are very hard and are consistent with bremsstrahlung emission from energetic (MeV) electrons. The most likely origin of these high energy electrons, while speculative at this time, is a rare type of high altitude electrical discharge above thunderstorm regions. 3 / 9 3 0064142https://ntrs.nasa.gov/search.jsp?R=19960001309 2018-05-11T01:44:02+00:00ZWe report here the serendipedous detection of high-energy photons from the Earth's upper atmosphere, observed by the Burst and Transient Source Experiment1 (BATSE) on the CGRO.Their apparent correlation with storm systems leads us to implicate as their cause, electrical discharges from these systems to the stratosphere/ionosphere. Runaway discharges to the ionosphere had been predicted in the early literaturG3 and modeled in detail pre~iously.~ These gamma-ray events may also be related to recently recorded optical discharge phenomena above thunderstorms5 and to other cloud-to-stratosphere discharges that have been reported in the past.6-7The Compton Observatory was launched in April 199 1 to perform observations of celestial gamma-ray sources. The BATSE experiment1 is one of four experiments on the observatory. It serves as an all-sky monitor and has detected over 800 cosmic gamma-ray bursts, several hard xray transients, numerous persistent and pulsed hard x-ray sources and several thousand solar flares. In addition to these celestial sources, on m occasions BATSE has responded to gammaray flashes from the Earth, previously unreported.BATSE consists of an array of eight detector modules located at the corners of the observatory, arranged to provide maximum unobstructed sky coverage. The scintillation detectors are sensitive to photons with energies above 20 keV. It is believed that prior instrumentation and experiments were incapable of detecting this phenomenon for several reasons, or these events were overlooked as being spurious. Most detectors used in high-energy astronomy are collimated and would likely have missed these rare events andor data are not analyzed during Earth-viewing times. Also, the temporal resolution of most experiments would not have been able to respond to these very brief events and would thus have had p r signal-to-noise when sampled with coarser time resolution. The BATSE array of multiple, independent detectors viewing different directions gives us confidence in the reality of these events as opposed to some instrumental or spacecraft effect such as electronic noise. The multiple, wide-field detectors also allow a direction determination to be made for each events The observed counting rate ratios of the detec...

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The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) has triggered on 1122 cosmic gamma-ray bursts between 1991 April 19 and 1994 September 19. These events constitute the Third BATSE (3B) burst catalog. This catalog includes the events previously reported in the 2B catalog, which covered the time interval 1991 April 19 to 1993 March 9. We present tables of the burst occurrence times, locations, peak fluxes, fluences, and durations. In general, results from previous BATSE catalogs are confirmed here with greater statistical significance. The angular distribution is consistent with isotropy. The mean galactic dipole and quadrupole moments are within 0.6 cr and 0.3 a, respectively, of the values expected for isotropy. The intensity distribution is not consistent with a homogeneous distribution of burst sources, with (V/Vm,x)= 0.33 _+ 0.01. The duration distribution (T9o) exhibits bimodality, with peaks at~0.5 and --_30 s. There is no compelling evidence for burst repetition, but only weak limits can be placed on the repetition rate.

Measurements of ELF/VLF radio atmospherics (sferics) at Palmer Station, Antarctica, provide evidence of active thunderstorms near the inferred source regions of two different gamma‐ray bursts of terrestrial origin [Fishman et al., 1994]. In one case, a relatively intense sferic occurring within ±1.5 ms of the time of the gamma‐ray burst provides the first indication of a direct association of this burst with a lightning discharge. This sferic and many others launched by positive cloud‐to‐ground (CG) discharges and observed at Palmer during the periods studied exhibit ‘slow tail’ waveforms, indicative of continuing currents in the causative lightning discharges. The slow tails of these sferics are similar to those of sferics originating in positive CG discharges that are associated with sprites.