An attempt to detect the effects of cosmic gamma-ray bursts in the lower ionosphere

Abstract

DETECTION of gamma-ray bursts of cosmic origin by detectors onboard Vela, OGO, IMP-6 and OSO-7 satellites^1–3 was one of the major surprises of observational astronomy recently. The bursts were observed over the energy range 7 keV to 1.5 MeV and were found to have time durations ranging from less than a second to about 80 s with integrated flux density between a few times 10⁻⁶ and 3 × 10⁻⁴ erg cm⁻² for different events. From the 20 events that have been detected so far (from data accumulated over 5 yr) it seems that these events are distributed almost isotropically on the celestial sphere and occur at frequencies of about four to five each year, at the level of sensitivity of Vela satellites. In view of the absence of definitive positive associations with well known transient phenomena^1,4 such as supernovae, galactic radio noise spikes, rapid atmospheric fluorescence increases, Cygnus X-3 radio flares or even with gravitational radiation events, continuous patrol for detecting these events through as many independent techniques as possible is very important to understand the nature of their origin.