Plasma flow equilibria in 2D cylindrically symmetric expanding magnetic field

Abstract

A steady-state plasma flow exiting through an expanding magnetic field is studied by means of 2D particle in cell numerical simulations. The effects of change in the localized plasma source region dimension and the associated plasma transit length in an upstream, uniform-magnetic-field region were examined, simulating cases with different axial lengths of the dielectric plasma source region, distinct from the location of physical expansion. Axial potential profiles at various radial locations show development of a stepwise axial potential drop, producing plasma (ion) acceleration in the corresponding regions. For a narrow source region with a long pre-expansion flow region, nonmonotonic potential variation is recovered where ion phase-space scatters show the trapped region and signatures of chaotic ion trajectories and possible pre-expansion ion heating. Considering a relevance of the studied flow equilibria to the thrust generation schemes for space propulsion, a formal estimate of thrust values associated with the plasma outflow is also done for the cases simulated.