Parallel and lower hybrid turbulence in low β plasmas driven by strong parallel currents and the resulting parallel electron and perpendicular ion energization

Abstract

In plasmas with strong field aligned currents, the most unstable mode is not always at parallel propagation, but may be at intermediate and very oblique angles. 2D particle simulations are performed in order to examine the interaction between the plasma waves at various angles and the electron and ion distributions in low β collisionless plasmas with strong electron drifts. The parallel Buneman instability is known to arise in this situation, but the simulations demonstrate that the very oblique lower hybrid (LH) waves, until recently considered unimportant, may actually play a role just as significant as the waves at parallel propagation. The LH waves are energized by a current-driven linear instability, which may be seen as the oblique limit of the Buneman or ion-acoustic instability. The simulations resolve strong LH turbulence, substantial perpendicular ion tail heating and parallel electron heating. The combined action of parallel and oblique modes results in more complete electron relaxation than may be produced by the parallel Buneman instability alone.