Numerical solutions of planar and spherical magnetohydrodynamic blast waves

The effect of a uniform magnetic field on the expansion of an isothermal high-pressure sphere of plasma (fireball) into a fully ionized atmosphere is investigated. The ideal magnetohydrodynamic (MHD) equations in Lagrangian coordinates are integrated numerically using the von Neumann-Richtmyer method of artificial viscosity. Numerical solutions are obtained to the unsteady two-dimensional spherical blast wave model and to the simpler planar one-dimensional model. For large magnetic fields, both a fast and a slow MHD shock wave propagate ahead of the fireball which is deformed into an elliptic shape with major axis in the direction of the uniform magnetic field.