Whistler Wave Turbulence in Solar Wind Plasma

TL;DR

This study uses 3D fluid simulations to explore how whistler waves influence turbulence in solar wind plasma, revealing different behaviors at scales above and below the electron inertial length.

Contribution

The paper provides the first detailed nonlinear 3D simulations showing the distinct evolution of whistler wave turbulence across different scales in solar wind plasma.

Findings

Large scale whistler modes have stronger dispersive effects but do not alter the Kolmogorov-like spectrum.

Small scale turbulence exhibits a hydrodynamic-like $k^{-5/3}$ spectrum.

Equipartition between wave velocity and magnetic fields quantifies whistler wave influence.

Abstract

Whistler waves are present in solar wind plasma. These waves possess characteristic turbulent fluctuations that are characterized typically by the frequency and length scales that are respectively bigger than ion gyro frequency and smaller than ion gyro radius. The electron inertial length is an intrinsic length scale in whistler wave turbulence that distinguishably divides the high frequency solar wind turbulent spectra into scales smaller and bigger than the electron inertial length. We present nonlinear three dimensional, time dependent, fluid simulations of whistler wave turbulence to investigate their role in solar wind plasma. Our simulations find that the dispersive whistler modes evolve entirely differently in the two regimes. While the dispersive whistler wave effects are stronger in the large scale regime, they do not influence the spectral cascades which are describable by a Kolmogorov-like $k^{-7/3}$ spectrum. By contrast, the small scale turbulent fluctuations exhibit a Navier-Stokes like evolution where characteristic turbulent eddies exhibit a typical $k^{-5/3}$ hydrodynamic turbulent spectrum. By virtue of equipartition between the wave velocity and magnetic fields, we quantify the role of whistler waves in the solar wind plasma fluctuations.