Sprites could be produced by an avalanche of relativists electrons (with energies higher than 1 MeV) started by cosmic radiation,. This electron beam could interact with the air molecules and to produce an X-ray radiation and secondary gamma. The theoretical studies predict that these mechanisms are accompanied by radio intense transmissions which could reach 10 to several dozens of MHz. Such emissions were not identified until now. The characterization of these emissions could allow a better understanding of these phenomena.
Sprites are massive but weak luminous flashes that appear directly above an active thunderstorm system and are coincident with cloud-to-ground or intracloud lightnings. Their spatial structures could be the following :
Sprites are predominantly red. The brightest part is located between 65 and 75 km. Below the bright red section, blue filamentary structures extend downward to as low as 40 km high. Sprites rarely appear singly, usually occurring in clusters of two, three or more.
The sprites duration is only a few milliseconds. It is necessary to have a high speed low light camera in order to image them.
Current research points to show that those sprites are correlated with large positive cloud-to-ground lightning strokes. The magnitude of sprite clusters can be compared to moderately bright auroral arc.