Co-existence of Whistler Waves with Kinetic Alfven Wave Turbulence for the High-beta Solar Wind Plasma

TL;DR

This paper demonstrates that whistler waves can coexist with kinetic Alfven wave turbulence in high-beta solar wind plasma, significantly influencing electron distribution despite their low energy density.

Contribution

It reveals that small amplitude whistler waves can impact electron dynamics in high-beta solar wind by interacting with kinetic Alfven wave turbulence.

Findings

Whistler wave dispersion relation is identical in high and low beta plasma.

Whistler waves meet Landau resonance with electrons at velocities below thermal speed.

Small amplitude whistlers (~10^-3 of KAW energy density) significantly affect electron distribution.

Abstract

It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore in the high-beta solar wind plasma whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers can survive because the background kinetic Alfven wave turbulence creates a plateau by quasilinear diffusion in the solar wind electron distribution at small velocities. It is found that for whistler energy density of only ~10^-3 that of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers is comparable to KAW. Thus very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function.