Energy Redistribution at Shocks: Known and Unknown (Invited)

The main process which occurs at the collisionless shock front is the redistribution of the energy of the incident ions to plasma thermalization and accelerated particles. Recent measurements at the termination bow shock, observations of supernova remnants and gamma-ray bursts reveal that much of this process is not well understood yet. Despite our understanding of the processes which occur in the nearest vicinity (terrestrial bow shock) we are still unable to predict the energy of accelerated particles or relative efficiency of electron and ion heating for the shock parameters substantially different from those in the heliosphere. We review our present knowledge of the subject and outline the basic problems.