Fast And Very Energetic

Transient energetic events, which are covered in the paper, include Terrestrial Gamma-Flashes (TGFs), several types of Transient Luminous Events (TLEs), Fast Thunderstorm Ground Enhancements (FTGEs). They emerge in the lower as well as in the upper layers of the atmosphere, up to mesospheric heights (about tens of kilometres) as transitory fluxes of electrons, gammaphotons, and neutrons and optical-rays bursts, from ultraviolet to infrared. One of the possible models explaining them includes avalanches of sub-relativistic and relativistic electrons as a key element. They might be generated as a result of fast changes of the electric fields in the atmosphere during thunderstroms (‘down-up’ model). However, one can suggest that electrons of lower energies might precipitate from Earth radiation belts into the atmosphere (‘up-down’ model respectively). Electron avalanches from below together with the electron beams coming from above can explain the whole set of phenomena with large energy release in the lower and upper atmosphere. It is possible that all of them exist on a similar timescale. We suggest that similar mechanism can explain the emergence of transient gamma-ray avalanches under the thunderclouds (FTGEs). We provide experimental arguments in support of these models, discuss several problems and further directions for experimental research.

,