A nested grid refinement technique for magnetohydrodynamical flows

A grid refinement technique for high resolution magnetohydrodynamical flows is described. It is based on the use of multiple nested grids having successively higher resolution. The numerical algorithm is formulated in such a way that the advection part of the hydrodynamical equations are solved in conservative form on the whole integration domain. In particular, the divergence free constraint for the magnetic field, del . B = 0, is fulfilled during the simulation. Several numerical tests are presented demonstrating the applicability of the nested grid code to many astrophysical problems including phenomena in which steep gradients such as shocks or contact discontinuities appear.