Generation Possibility of Gamma‐Ray Glows Induced by Photonuclear Reactions

Abstract

Relativistic runaway electron avalanches (RREAs) imply a large multiplication of high‐energy electrons (∼1 MeV). Two factors are necessary for this phenomenon: a high electric field sustained over a large distance and an energetic particle to serve as a seed. The former sustains particle energies as they keep colliding and lose energy randomly; and the latter serves as a multiplication starting point that promotes avalanches. RREA is usually connected to both terrestrial gamma‐ray flashes (TGFs) and gamma‐ray glows (also known as Thunderstorm Ground Enhancement (TGE) when detected at ground level) as possible generation mechanism of both events, but the current knowledge does not provide a clear relationship between these events (TGF and TGE), beyond their possible common source mechanism, still as they have different characteristics. In particular, their timescales differ by several orders of magnitude. This work shows that chain reactions by TGF byproducts can continue for the timescale of gamma‐ray glows and even provide energetic particles as seeds for RREAs of gamma‐ray glows.

Hazards to Aircraft Crews, Passengers, and Equipment from Thunderstorm-Generated X-rays and Gamma-Rays

“…One more high-energy phenomenon has been discovered to be associated with thunderstorms. It is often referred to as "gamma-ray glows" [5,[13][14][15][16][17][18] or "thunderstorm ground enhancements" [19,20], although no single term has been agreed on yet to describe it (see, e.g., [4,[21][22][23][24][25]). Enoto et al [25] use the term "γ-ray glow" only to describe "bremsstrahlung radiation from electrons accelerated in thunderclouds".…”

“…They term the latter emission "prolonged line emission." The term "prolonged emission" can be considered as a universal one describing any flux of high-energy photons not associated with rain washout of radioactive isotopes (see, e.g., [15][16][17][18]20,21,23,25]), with a duration of about one second or longer.…”

“…Gamma-ray fluxes, described as gamma-ray glows, etc., can last from seconds to minutes, and can produce gamma-ray photons with numbers exceeding the normal background level in some spectral ranges at least by one to two decades, while situations when the intensity of the glow is of the order of 10% of the background are also described [4,5,[13][14][15][16][17][18][19][20][21]26,27]. In principle, the generation of several subsequent and/or time-overlapping glows seems to be possible (see, e.g., [20,28]).…”

“…The detection of gamma-ray glows by ground-based or roof-mounted equipment is hampered by the absorption and scattering of photons by air, although this problem is reduced if observations are made at high-altitude mountain observatories or of thunderstorms with low-altitude charge-containing regions [4,5,13,14,[17][18][19][20][21]23,[26][27][28]30,31]. However, the altitudes at which commercial jet aircraft fly and the possibility of relatively short distances between the main region of the emission of high-energy photons and the aircraft mean that the aircraft are much less protected from such radiation by the air than is the case at ground level.…”

“…However, the altitudes at which commercial jet aircraft fly and the possibility of relatively short distances between the main region of the emission of high-energy photons and the aircraft mean that the aircraft are much less protected from such radiation by the air than is the case at ground level. It should be emphasized that there are several different assumptions about the physical nature of gamma-ray glows (see, e.g., [12,15,18,20,[22][23][24]26,28,29] and bibliographies therein). According to one author, some gamma-ray glows are generated by ball lightning [22,24,28,31].…”