Atmospheric Electron Spatial Range Extended by Thundercloud Electric Field Below the Relativistic Runaway Electron Avalanche Threshold

Abstract

Electric fields in thunderstorms are associated with enhanced energetic radiation emission previously detected in ground-based, airborne, and space experiments. 70 years after Wilson (1924) proposed such high-energy phenomenon in thunderstorms, Fishman et al. (1994) discovered Terrestrial Gamma ray Flashes (TGFs), which are microsecond-lasting enhanced gamma ray bursts with energy reaching tens of MeV related with lightning discharges (Briggs et al., 2010;Smith et al., 2005;Tavani et al., 2011). A wide variaty of observations of other High Energy Atmospheric Phenomena (HEAP) (Babich, 2003) demonstrate interactions between the thundercloud electric field and high-energy particles; including gamma ray glow (also called Thunderstorm Ground Enhancement, TGE and long bursts;

Ambient Conditions of Winter Thunderstorms in Japan to Reproduce Observed Gamma‐Ray Glow Energy Spectra

“…The atmospheric density inhomogeneity may generate isolated RREA regions near the source altitude although the small density variation for the considered heights. This investigation is reserved for future works following the series of studies started with Diniz et al (2022).…”

“…The strong electric field ( E S ≥ E th ) will induce an avalanche behavior in the electron population with exponential growth and, hence, there will still produce bremsstrahlung emissions as long as there is sufficiently high E S . On the other hand, weaker electric fields ( E S ≤ E th ) simply extend the finite electrons spatial range through a friction reduction (Diniz et al., 2022; Lehtinen & Østgaard, 2018), meaning that both electron and photon generation will be finite even inside the electrified region due to the lack of avalanches.…”

“…(2021). This work is the second paper of a series of studies, starting with (Diniz et al., 2022), which calculated how the electric field strength E S below RREA threshold E th extends the electron spatial range, in order to develop a general theoretical framework of the gamma‐ray glows.…”

“…Electric field strengths below the RREA threshold E th do not promote avalanche cascade but provide energy gain with the moving electrons allowing them to move farther away (Diniz et al., 2022) and to increase the gamma‐ray production. Chilingarian et al.…”

“…Electric field strengths below the RREA threshold E th do not promote avalanche cascade but provide energy gain with the moving electrons allowing them to move farther away (Diniz et al, 2022) and to increase the gammaray production. Chilingarian et al (2012) proposed the so-called Modification Of Spectra (MOS) mechanism by which such sub-avalanche electric fields (E < E th ) could generate gamma-ray glows.…”