Heating of magnetized plasmas by a large-amplitude low-frequency electric field

Plasma electron and ion heating due to a large-amplitude oscillating electric field E 0 applied normal to a steady magnetic field B 0 has been followed in detail, by one-dimensional computer simulations. The large oscillating drift velocity (E 0/B 0 > ν e ) at low frequency (ωci ≪ ω0 ≃ ωpi ≪ ωce ) sets up instabilities due to the periodic electron E / B drift through the ions, which then cause rapid heating. For waves propagating across B0(k · B̂ 0 = k ‖ = 0), the instability is a Buneman-type upper-hybrid two-stream instability. Electron perpendicular thermal velocity is increased to ∼E0/B0 with little ion heating. For obliquely propagating waves (k ‖ ≠ 0), there is an additional instability, the modified two-stream instability. For small k ‖ [roughly, k ‖/k ≲ (m e / m i )(1/2)], the upper-hybrid instability dominates and the heating is similar to the k ‖ = 0 case but with a small amount of electron parallel heating. As k ‖ increases, however, the modified two-stream instability becomes dominant. Electron parallel thermal velocity is increased to ≃ (E 0/B 0)(k /k ‖). Strong ion (perpendicular) heating also occurs with the ion thermal velocity at wave saturation near (E 0/ B 0)(me / mi )(3/4)(k /k‖)(3/2). Comparison with similar work for B 0 = 0 shows that addition of B 0 is best for ion heating, improving KTi by (mi /me)(1/2). Possible applications of these results to laboratory experiments are also discussed.