On the Explosion of a Supernova Into the Interstellar Magnetic Field. II.

The problem of the earlier stages of the explosion of a supernova into the interstellar medium with a uniform magnetic field was discussed in Paper I. In this paper the limit in which the magnetic field is weak is investigated This limit corresponds to the Alfv6n speed in the interstellar magnetic field being small compared to the expansion velocity of the supernova debris The magnetohydrodynamic flow produced by the supernova is calculated to second order in the field strength It is found that the expansion procedure breaks down near the supernova-debris interface, where a boundary region occurs in which the magnetic field is large, no matter how small its interstellar value. The physical quantities at the debris are evaluated It is suggested that this large field may be subject to a Rayleigh-Taylor instability and burst through the supernova-debris interface, producing a filamentary structure with large magnetic fields such as is observed in the Crab Nebula. Other comparisons with the Crab Nebula are made.