Preferential Heating of Heavy Ions in Shocks

Observations show that postshock temperatures of heavy ions in supernovae collisionless shocks are approximately proportional to their masses. So far there is no convincing explanation of this dependence that would take into account the microphysics of the ion interaction with the electromagnetic fields inside the shock front. Here it is shown that perpendicular temperature increases due to the gyration of heavy ions starts inevitably upon crossing the shock front because of the global change of the magnetic field. An estimate for the downstream temperature as a function of the shock angle and magnetic compression is derived.