Production mechanisms of leptons, photons, and hadrons and their possible feedback close to lightning leaders

Abstract

It has been discussed that lightning flashes emit high‐energy electrons, positrons, photons, and neutrons with single energies of several tens of MeV. In the first part of this paper we study the absorption of neutron beams in the atmosphere. We initiate neutron beams of initial energies of 350 keV, 10 MeV, and 20 MeV at source altitudes of 4 km and 16 km upward and downward and see that in all these cases neutrons reach ground altitudes and that the cross‐section areas extend to several km2. We estimate that for terrestrial gamma‐ray flashes approximately between 10 and 2000 neutrons per ms and m2 are possibly detectable at ground, at 6 km, or at 500 km altitude. In the second part of the paper we discuss a feedback model involving the generation and motion of electrons, positrons, neutrons, protons, and photons close to the vicinity of lightning leaders. In contrast to other feedback models, we do not consider large‐scale thundercloud fields but enhanced fields of lightning leaders. We launch different photon and electron beams upward at 4 km altitude. We present the spatial and energy distribution of leptons, hadrons, and photons after different times and see that leptons, hadrons, and photons with energies of at least 40 MeV are produced. Because of their high rest mass hadrons are measurable on a longer time scale than leptons and photons. The feedback mechanism together with the field enhancement by lightning leaders yields particle energies even above 40 MeV measurable at satellite altitudes.

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

“…Various measurements have shown that electric fields in streamer discharges can reach field strengths of up to ≈10 E k (Kim et al, 2004; Pancheshnyi et al, 2000; Spyrou & Manassis, 1989) consistent with results of streamer simulations and analytic estimates (Chanrion & Neubert, 2008; Köhn et al, 2018; Liu & Pasko, 2004; Moss et al, 2006; Naidis, 2009; Qin & Pasko, 2014; Tholin & Bourdon, 2013). In the vicinity of lightning leader tips, calculations have shown that the enhanced electric field can exceed several times the breakdown field (Köhn, Diniz, Harakeh, 2017; Köhn & Ebert, 2015). …”

“…One is that seed electrons from cosmic ray ionization of the atmosphere are born with energies in the runaway regime and are further accelerated by the ambient electric field in a cloud, forming a relativistic runaway electron avalanche (RREA; Babich et al, 2012; Dwyer, 2003; Gurevich et al, 1992; Gurevich & Karashtin, 2013; Wilson, 1925) including the feedback mechanism where high‐energy electrons produce high‐energy gamma rays through the bremsstrahlung process which subsequently produces secondary electrons and positrons through photoionization, Compton scattering, or pair production (Dwyer, 2003, 2007; Kutsyk et al, 2011; Skeltved et al, 2014). The other is that thermal (cold) electrons are accelerated into the runaway regime in the high, but very localized, field of streamer tips as well as by the enhanced electric fields in the vicinity of lightning leader tips (Babich et al, 2015; Celestin & Pasko, 2011; Chanrion & Neubert, 2008; Köhn et al, 2014; Köhn & Ebert, 2015; Köhn, Diniz, Harakeh, 2017) and subsequently turn into relativistic RREAs (Carlson et al, 2010, 2006; Köhn, Diniz, Harakeh, 2017; Moss et al, 2006). In the following we explore the streamer mechanism.…”

Modeling Neutron Emissions in High Energy Atmospheric Phenomena

“…They diffuse isotropically while losing energy through collisions. Their attenuation length is ∼685 m (Köhn et al, ). This concept is consistent with the simulated distribution of photons and neutrons in space, time, and energy.…”

Evaluation of Monte Carlo tools for high-energy atmospheric physics II: relativistic runaway electron avalanches

“…The effective value of E c may be significantly lower, as electrons could overcome the friction barrier due to their intrinsic random interactions (Lehtinen et al, 1999;Li et al, 2009;Liu et al, 2016;Chanrion et al, 2016). Cold runaway could happen in the streamer phase (Moss et al, 2006;Li et al, 2009;Chanrion and Neubert, 2010) or leader phase (Celestin and Pasko, 2011;Celestin et al, 2012;Chanrion et al, 2014;Köhn et al, 2014Köhn et al, , 2017Köhn and Ebert, 2015) of a transient discharge, explaining the high-energy electron seeding that will evolve to RREAs and produce γ rays by bremsstrahlung emission from the accelerated electrons. The cold runaway mechanism may be further investigated with laboratory experiments, in high-voltage and pulsed plasma technology, and may be linked to the not fully understood X-ray emissions that have been observed during nanosecond pulsed discharge and the formation of long sparks Shao et al, 2011;Kochkin et al, 2016, and references therein), with different possible production mechanisms that were proposed and tested using analytical modelling (Cooray et al, 2009) and computer simulations (Ihaddadene and Celestin, 2015;Luque, 2017;Lehtinen and Østgaard, 2018).…”