Two-dimensional MHD simulation of isothermal plasma armatures

The authors report results on the use of a two-dimensional resistive MHD code to simulate the internal dynamics in a railgun plasma armature, starting from a slightly perturbed equilibrium initial state. The plasma temperature, conductivity, and ionization fractions are treated as uniform in space and constant in time. The rear of the plasma is in contact with a low-pressure nonconducting gas. A finite-difference, explicit, Eulerian, flux-corrected transport code is used to advance all quantities in time. The computation grid has 200 cells parallel to the rails, and 20 across the rails. The results show the growth and subsequent shedding of the plasma mass toward the nonconducting region at the rear. The mass lost is not replenished and the armature becomes shorter, with steeper pressure and magnetic field profiles. The bulk of the profiles is not thoroughly disrupted, but behaves rather sturdily and seems to maintain a shape fairly close to the equilibrium profiles