Physics of Atmospheric Electric Discharges in Gases: An Informal Introduction

TL;DR

This paper reviews the physics of electrical discharges in gases, focusing on atmospheric phenomena like lightning and upper-atmosphere discharges, highlighting key parameters and the role of electrons in these processes.

Contribution

It provides an overview of the historical development and physical principles of atmospheric gas discharges, emphasizing recent observations and the effects of altitude on discharge properties.

Findings

Electrons carry all atmospheric discharge currents.

Discharges are more easily initiated in the upper atmosphere due to larger mean free paths.

Magnetization of electrons influences conductivity in the mesosphere and above.

Abstract

A short account of the physics of electrical discharges in gases is given in view of its historical evolution and application to planetary atmospheres. As such it serves as an introduction to the articles on particular aspects of electric discharges contained in this book, in particular in the chapters on lightning and the violent discharges which in the recent two decades have been observed to take place in Earth's upper atmosphere. In addition of briefly reviewing the early history of gas discharge physics we discuss the main parameters affecting violent atmospheric discharges like collision frequency, mean free path and critical electric field strength. Any discharge current in the atmosphere is clearly carried only by electrons. Above the lower bound of the mesosphere the electrons must be considered magnetized with the conductivity becoming a tensor. Moreover, the collisional mean free path in the upper atmosphere becomes relatively large which lowers the critical electric field there and more easily enables discharges than at lower altitudes. Finally we briefly mention the relation of such discharges as sources for wave emission.