Presents a parallel computational model to simulate plasmas in the radiation-magnetohydrodynamics (R-MHD) framework. The solution of the radiation field usually dominates the R-MHD computation. The authors solve the linear Boltzmann equation for the radiation field intensity, using the deterministic S/sub N/ discrete ordinates method. Choosing an energy-domain decomposition the authors have implemented the S/sub N/ method on a parallel processor, the Intel iPSC/860, and the speedups are very favorable. Increasing almost linearly with the number of processors, the speedup reaches 14 on 16 processors. A comparison of timing measurements between a single processor CRAY Y-MP and a 16 processor iPSC/860 implementation strongly favors parallelism by a factor of 3.7.<<ETX>>