GAMMA-RAY EMISSION PRODUCED BY A RELATIVISTIC BEAM OF RUNAWAY ELECTRONS ACCELERATED BY QUASI-ELECTROSTATIC THUNDERCLOUD FIELDS

In an experiment described by Fishman et al. [1994], high energy photo ns of atmospheric origin were detected by the Burst and Transient Sour ce Experiment (BATSE) detectors, located on the Compton Gamma Ray Obse rvatory (CGRO). In this paper we assess the possibility that the burst s may be bremsstrahlung produced by relativistic (>1 MeV) runaway elec tron beams accelerated in an avalanche process by quasi-electrostatic thundercloud fields. We consider the height-dependent density profile of the relativistic electrons specified as a function of time in the c ontext of a previously reported runaway model [Bell et al., 1995]. The electron beam is modeled as a vertical cylinder with radius 10 km, an d numerical estimates are provided of gamma-ray fluxes which would be observed at the satellite. The predicted fluxes at the satellite altit ude and at horizontal distances of up to 500 km from the source are fo und to be comparable to the experimental data.