The relativistic feedback discharge model of terrestrial gamma ray flashes

Abstract

.[1] As thunderclouds charge, the large-scale fields may approach the relativistic feedback threshold, above which the production of relativistic runaway electron avalanches becomes self-sustaining through the generation of backward propagating runaway positrons and backscattered X-rays. Positive intracloud (IC) lightning may force the large-scale electric fields inside thunderclouds above the relativistic feedback threshold, causing the number of runaway electrons, and the resulting X-ray and gamma ray emission, to grow exponentially, producing very large fluxes of energetic radiation. As the flux of runaway electrons increases, ionization eventually causes the electric field to discharge, bringing the field below the relativistic feedback threshold again and reducing the flux of runaway electrons. These processes are investigated with a new model that includes the production, propagation, diffusion, and avalanche multiplication of runaway electrons; the production and propagation of X-rays and gamma rays; and the production, propagation, and annihilation of runaway positrons. In this model, referred to as the relativistic feedback discharge model, the large-scale electric fields are calculated self-consistently from the charge motion of the drifting low-energy electrons and ions, produced from the ionization of air by the runaway electrons, including two-and three-body attachment and recombination. Simulation results show that when relativistic feedback is considered, bright gamma ray flashes are a natural consequence of upward +IC lightning propagating in large-scale thundercloud fields. Furthermore, these flashes have the same time structures, including both single and multiple pulses, intensities, angular distributions, current moments, and energy spectra as terrestrial gamma ray flashes, and produce large current moments that should be observable in radio waves.

High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena

“…The increase in conductivity resulting from the ionization caused by the runaway electrons then partially discharges the electric field causing the feedback factor to drop below 1 again. Calculations show that the number of runaway electrons generated and the duration of the event is consistent with TGFs (Dwyer 2008(Dwyer , 2012.…”

“…Specific TGF models can broadly be divided into the following three categories: upper atmospheric discharges (UADs), i.e., high altitude runaway electron avalanches acting on cosmic-rays, either at sprite altitudes (e.g., Roussel-Dupré and Gurevich 1996;Babich et al 2001bBabich et al , 2008bBabich et al , 2011bInan 2005) or immediately above the thunderclouds (e.g., Babich et al 2004cBabich et al , 2007dBabich et al , 2008cBabich et al , 2008dBabich et al , 2009a; lightning emission models (e.g., Moss et al 2006;Dwyer 2008;Carlson et al 2009aCarlson et al , 2010a; and relativistic feedback models (e.g., Dwyer 2003Dwyer , 2008Dwyer , 2012.…”

Relativistic electron avalanches as a thunderstorm discharge competing with lightning

“…To explain the brightness of TGFs, Dwyer 14,16,17 proposed the relativistic feedback mechanism. The relativistic feedback process builds on the RREA process by including the physics of backscattered gamma rays and positrons from gamma-ray pair production, both of which propagate to the start of the avalanche region and generate new avalanches, producing an exponential growth in the number of avalanches.…”

Modeling of a New Electron Acceleration Mechanism Ahead of Streamers

“…The model is fully described by Dwyer (2007Dwyer ( , 2012. The model is fully described by Dwyer (2007Dwyer ( , 2012.…”