Stabilization of linear ion beam right‐hand polarized instabilities by nonlinear Alfvén/ion‐cyclotron waves

Abstract

[1] It is shown that ion-beam plasma electromagnetic right-hand polarized instabilities can be stabilized by nonlinear left-hand polarized waves. This phenomenon constitutes a nonlinear saturation mechanism for right-hand polarized instabilities. Complete stabilization occurs for left-hand wave amplitudes above a threshold value. The saturation mechanism takes place within a large range of pump wave frequencies and plasma temperatures.

Behavior of linear beam-plasma instabilities in the presence of finite amplitude circularly polarized waves

“…1b, A = 0.81 and the gap between -F and -b has disappeared showing, thereby, complete stabilization of the linear r-instability. Thus, the threshold amplitude is now A t = 0.81, instead of A t = 0.16 for U = 2 as expected, A t increases with increasing U [1].…”

“…2b, we have taken A t = 0.7, and the instability is completely stabilized. Thus, as the L-wave frequency increases, the threshold A t -value decreases [1]. In general, for fixed U , the instability threshold continues to decrease as the L-wave frequency approaches the proton gyrofrequency.…”

“…It has been shown that left-hand polarized waves can stabilize linear right-handed instabilities [1]. It has also been shown that for beam velocities capable of destabilizing left-handed waves, left-hand polarized large amplitude waves can also stabilize these waves.…”

“…1a we illustrate the situation for U = 2.3 and A = 0. The gap between the two curves denoted by -F and -b corresponds to the linear r-instability [1]. The lines denoted by -F and -b are lower R sideband waves propagating in the direction of the external magnetic field [1].…”

“…Proton beams observed in the solar wind display large drift velocities which can be larger than the necessary velocity to generate a linear beam-plasma instability [18]. In [1], it was found that the behavior of linear electromagnetic right-handed polarized instabilities (rinstabilities) in a beam-plasma system can be affected by the presence of a finite amplitude left-handed polarized wave (L-wave). It was also shown that r-instabilities can be stabilized by L-waves in a linearly unstable proton beam-plasma system.…”