Relativistic feedback mechanism in homogeneous electric fields revisited

TL;DR

This paper provides an analytical revision of the relativistic feedback mechanism in homogeneous electric fields, clarifying how positron and gamma feedback contribute to runaway electron avalanches and their role in atmospheric phenomena like TGFs.

Contribution

It introduces a kinetic model that naturally derives positron and gamma feedback mechanisms, offering a comprehensive evaluation of relativistic feedback in thundercloud electric fields.

Findings

Positron and gamma feedback mechanisms arise from RREA dynamics.

The electron avalanche multiplication factor is derived.

Conditions for self-sustainable feedback are identified.

Abstract

Recent results link relativistic runaway electron avalanches (RREA) accelerated by the electric field in thunderclouds to high-energy atmospheric phenomena such as the Terrestrial Gamma-Ray Flashes (TGF). Research shows that the mere existence of runaway electron avalanches is not sufficient to generate TGF. In an attempt to settle this issue, a model of a relativistic feedback mechanism was suggested. In this paper, an analytical kinetic revision of the relativistic feedback mechanism is provided. It was shown that positron and gamma feedback mechanisms arise naturally from dynamics equations of RREA initiated independently by positrons and gamma-quanta. Establishing both mechanisms turned out to be enough to evaluate complete relativistic feedback. The electron avalanche multiplication factor is obtained, followed by a study of the minimal conditions of self-sustainable relativistic feedback in homogeneous electric fields and a discussion of the role of this mechanism in TGF and lightning initiation problems.