Ionosphere and Upper Atmosphere
Runaway breakdown and electrical discharges in thunderstorms
Article first published online: 24 DEC 2010
Copyright 2010 by the American Geophysical Union.
Journal of Geophysical Research: Space Physics (1978–2012)
Volume 115, Issue A12, December 2010
How to Cite
2010), Runaway breakdown and electrical discharges in thunderstorms, J. Geophys. Res., 115, A00E60, doi:10.1029/2009JA014818., and (
- Issue published online: 24 DEC 2010
- Article first published online: 24 DEC 2010
- Manuscript Accepted: 22 SEP 2010
- Manuscript Revised: 2 AUG 2010
- Manuscript Received: 22 AUG 2009
- runaway electrons;
- γ-ray flashes
 This review considers the precise role played by runaway breakdown (RB) in the initiation and development of lightning discharges. RB remains a fundamental research topic under intense investigation. The question of how lightning is initiated and subsequently evolves in the thunderstorm environment rests in part on a fundamental understanding of RB and cosmic rays and the potential coupling to thermal runaway (as a seed to RB) and conventional breakdown (as a source of thermal runaways). In this paper, we describe the basic mechanism of RB and the conditions required to initiate an observable avalanche. Feedback processes that fundamentally enhance RB are discussed, as are both conventional breakdown and thermal runaway. Observations that provide clear evidence for the presence of energetic particles in thunderstorms/lightning include γ-ray and X-ray flux intensifications over thunderstorms, γ-ray and X-ray bursts in conjunction with stepped leaders, terrestrial γ-ray flashes, and neutron production by lightning. Intense radio impulses termed narrow bipolar pulses (or NBPs) provide indirect evidence for RB particularly when measured in association with cosmic ray showers. Our present understanding of these phenomena and their enduring enigmatic character are touched upon briefly.