Atmospheric Electron Spatial Range Extended by Thundercloud Electric Field Below the Relativistic Runaway Electron Avalanche Threshold. Issue 3 (8th February 2022)

• Record Type: Journal Article
• Authors: Diniz, G.; Wada, Y.; Ohira, Y.; Nakazawa, K.; Enoto, T.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 3(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-08
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2021JD035958
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Cosmic‐ray shower, hitting the atmosphere all the time, includes high‐energy electrons. Electric fields in thunderstorms accelerate these electrons so that they can reach farther distances with producing secondary electrons. The strong field above 0.284 MV m −1 causes the Relativistic Runaway Electron Avalanches (RREA) process with an exponential increase of electrons. Even with lower electric fields below this RREA threshold which are usually measured in thunderstorms, an increase in electrons' kinetic energy and production of secondary electrons can occur without avalanche processes, known as Modification Of Spectra (MOS) of the cosmic‐ray shower. Both phenomena are related to observed gamma ray glow, which is bremsstrahlung emission from accelerated electrons in thunderstorms. We calculate an extended range and kinetic energy of electrons below the RREA threshold using an analytical evaluation and Geant4 Monte Carlo simulations. For example, at 0.280 MV m −1 slightly below the RREA threshold, 3 MeV electrons gain 100% of their original kinetic energy through the passage of the continuous slowing down approximation (CSDA) range defined at the null electric field, which is consistent with results in previous studies as the transition to the RREA process. Even at a lower field of 0.260 MV m −1, the energy recovery by the field allows an injected 20 MeV electron beam to extend its average electron range from 73 m, in the null field configuration, to 562 m. We have performed analytical calculation and Geant4 simulations of atmospheric electron behavior for initial electron energy of 0.1–100 MeV and an electric field below 0.290 MV m −1 . Key Points: We develop calculations for e − spatial range with electric fields up to the avalanche threshold, 0.284 MV/m, related to gamma ray glow Our particle simulation shows that thunderstorm fields below avalanche level extend the range of 1–100 MeV electrons by a factor of 2–10 The calculations indicate a transition to avalanche regime with 3 MeV electron under 0.280 MV/m that extends the spatial range to infinity