The prolonged gamma ray enhancement and the short radiation burst events observed in thunderstorms at Tien Shan

TL;DR

This study documents prolonged gamma ray enhancements and short radiation bursts in thunderstorms at Tien Shan, revealing insights into electron acceleration, positron generation, and neutron modulation during lightning events.

Contribution

It provides detailed measurements of gamma rays and electrons near thunderstorms, identifying two distinct radiation emission types and evidence of positron production.

Findings

Prolonged gamma ray enhancements (TGE) precede negative electric field variations.

Short sub-millisecond radiation bursts occur during lightning discharges.

Indications of positron generation and neutron rate modulation during thunderstorms.

Abstract

We report the observation results of the hard radiation flashes which accompanied the lightning discharges above the mountains of Northern Tien Shan. Time series of the counting rate intensity, numerical estimations of absolute flux, and energy distribution of accelerated electrons and of (20-2000)keV gamma rays were obtained at the height of 3700m a.s.l., immediately within thunderclouds, and in closest vicinity ($<$100m) to discharge region. Two different kinds of radiation emission events are presented here: a relatively prolonged rise of gamma ray intensity with minute-scale duration (the thunderstorm ground enhancement, TGE) which has preceded a negative field variation, and a short sub-millisecond radiation burst, which accompanied a close lightning discharge in thundercloud. It was revealed also an indication to positron generation in thunderclouds at the time of gamma ray emission, as well as modulation of the neutron counting rate in Tien~Shan neutron monitor which was operating at a (1.5-2)km order distance from the region of lightning development.