Spherically symmetric magnetohydrodynamics in general relativity

Spherically symmetric spacetimes representing a perfect fluid coupled to an electromagnetic field are considered in full generality. It is shown that the Hall current is necessarily zero and that the four-current contains, in general, both a convection and a conduction term in the case of a non-null electromagnetic field, whereas it vanishes necessarily if the electromagnetic field is null. Examples illustrating the various possibilities and satisfying the dominant energy condition are provided. The problem of matching solutions of the considered type (and more general others) to the Vaidya spacetime is considered, and a result relating this possibility to the satisfaction of the dominant energy condition on a certain compact spacetime submanifold is proven. Some of the examples given are explicitly joined to Vaidya's solution, thus providing examples of stellar models. [S0556-2821(99)00114-9].