Generation possibility of gamma-ray glows induced by photo-nuclear reactions
Abstract
Relativistic runaway electron avalanches (RREAs) imply a large multiplication of high energy electrons (~ 1 MeV). Two factors are necessary for this phenomenon: enough potential and an energetic particle to serve as a seed. The former sustains particle energies as they keep colliding and lose energy randomly, this is usually the electric field role; and the latter serves as a multiplication starting point that promotes avalanches themselves. RREA is usually connected to both terrestrial gamma-ray flashes (TGFs) and gamma-ray glows as their generation mechanism but the current knowledge does not correlate these events still as they have different characteristics, in particular, their timescales differ by several orders of magnitude. A possible bridge between TGFs and gamma-ray glows may be at the well-known neutron production from photo-nuclear reactions related to TGFs; those reactions also produce unstable nuclei (13N and 15O), as the remainder, that engage into beta plus decay with a minute-long characteristic time while the decay spectrum shows MeV energy. The combination of long duration and relativistic energies makes these unstable nuclei a possible source for Gamma-ray glow since there will be an emission of high energetic positrons for minutes and those can act as RREA seeds. Monte Carlo GEANT4 simulations also demonstrate that positrons are effective RREA seeds, especially at lower energies in which they are more likely to produce avalanches than electrons due to the annihilation possibility while recent observations report enough photo-nuclear related positron flux to act as RREA. Such a process connects TGF to Gamma-ray glow and extended TGF timescale further.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMAE005..06S
- Keywords:
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- 3304 Atmospheric electricity;
- ATMOSPHERIC PROCESSES;
- 3324 Lightning;
- ATMOSPHERIC PROCESSES;
- 4301 Atmospheric;
- NATURAL HAZARDS