The radio and X-ray emission from type II supernovae

The interaction of the outer parts of a supernova envelope with circumstellar matter creates a high-energy density shell. The equation of motion of the shell is deduced on the basis of the approximations that the shell is thin and that the supernova density profile is a power law in radius. It is noted that the density structure in the shell is Rayleigh-Taylor unstable and that the energy density created by the instability can be a substantial fraction of the original thermal energy density. The instability can drive turbulent motions, and these, it is thought, may amplify the magnetic field and accelerate relativistic electrons. If the efficiency of these processes is comparable to that inferred from the Cassiopeia A supernova remnant, the observed radio luminosity from SN 1980k and SN 1979 may be reproduced. Several mechanisms for the early low-frequency absorption of the radio emission are considered.