No abstract

No abstract

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...

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) has triggered on 1637 cosmic gamma-ray bursts between 1991 April 19 and 1996 August 29. These events constitute the Fourth BATSE burst catalog. The current version (4Br) has been revised from the version first circulated on CD-ROM in September 1997 (4B) to include improved locations for a subset of bursts that have been reprocessed using additional data. A significant difference from previous BATSE catalogs is the inclusion of bursts from periods when the trigger energy range differed from the nominal 50-300 keV. 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.

No abstract