I’m a non-scientist, so this is probably partially understood, somewhat accurate, and certainly dated:
Here is a well-done video from the Sprites Project at the University of Alaska:
During what is normally a cloud to ground lightning strike during a thunderstorm, there is occasionally a discharge of energy above the cloud, high up in the atmosphere. These phenomenae are called blue jets, red sprites, and elves. They are faint, require a dark background against which to view them, and also require that you be far enough away to see the storm from a distance (preferably from aircraft or a mountain overlooking a plain).
“Sprites are highly structured discharges lasting 5 to 100 ms and extending from 40 to 85 km altitude which result from intense electric fields following a major redistribution of electric charge in the troposphere — usually a positive cloud-to-ground return stroke.”
The Runaway Breakdown thesis here’s a quote from wikipedia by Nikolai Lehtinen:
“In the upper atmosphere, cosmic rays striking air molecules within thunderstorms can supply the relativistic electrons which trigger a breakdown in “runaway” mode. The breakdown region is a conductive plasma many tens of meters long, and it can supply the “seed” which triggers a lightning flash.”
An interesting possibility…