Fermi Acceleration at the Fast Shock in a Solar Flare and the Impulsive Loop-Top Hard X-Ray Source

This cartoon follows the standard development based on the 2D reconnection model (see any of many examples here in the Archive), but makes specific and interesting suggestions about particle acceleration. These ideas somewhat follow the observations in the magnetosphere, wherein the auroral particle acceleration happens on closed field lines. Here the reconnection exhaust flows excites waves in closed coronal loops, resulting in (perhaps) a coronal hard X-ray source, but also (as commonly observed) the footpoint hard X-ray sources.
In the auroral zone, by contrast, the acceleration does not happen at the "loop top" (geotail), but instead near the ionosphere, "footpoints" in the solar parlance.

      Is there a really a loop-top hard X-ray source that plays a fundamental role in flare physics? Usually not. Does the reconnection outflow create a fast shock? It is not observed. Does a stationary type II radio burst always happen? Seldom. But in principle, this paper is important since it involves a volume rather than a point, and also envisions wave-particle processes.