LAUSR

The electrostatic dispersion relation for an unbounded homogeneous plasma in the presence of unmagnetized ions, magnetized electrons, and an applied magnetic field has been solved numerically in the near-plume of a magnetically shielded Hall thruster. The plasma conditions have been obtained by 2D (r-z) multifluid-particle-in-cell simulations. We find growth of the modified two-stream instability in most regions of the domain, with the fastest growth approaching the fluid-limit ω L H/2, radially away from the channel centerline downstream of the front magnetic poles where ω p e / ω c e ∼ 1. In this region, the relative drift between magnetized electrons and beam ions perpendicular to the magnetic field is u ≳ 3 u T i, while that between the counterstreaming beam and cathode ions is ≳4 u T i. The latter suggests that the ion–ion cross field lower hybrid instability may also be active here. The presence of these instabilities can lead to anomalous heating of ions enhancing the average energy with which they impact nearby surfaces.