A Model for Dissipation of Solar Wind Magnetic Turbulence by Kinetic Alfvén Waves at Electron Scales: Comparison with Observations

Abstract

In hydrodynamic turbulence, it is well established that the length of the dissipation scale depends on the energy cascade rate, i.e., the larger the energy input rate per unit mass, the more the turbulent fluctuations need to be driven to increasingly smaller scales to dissipate the larger energy flux. Observations of magnetic spectral energy densities indicate that this intuitive picture is not valid in solar wind turbulence. Dissipation seems to set in at the same length scale for different solar wind conditions independently of the energy flux. To investigate this difference in more detail, we present an analytic dissipation model for solar wind turbulence at electron scales, which we compare with observed spectral densities. Our model combines the energy transport from large to small scales and collisionless damping, which removes energy from the magnetic fluctuations in the kinetic regime. We assume wave-particle interactions of kinetic Alfvén waves (KAW) to be the main damping process. Wave frequencies and damping rates of KAW are obtained from the hot plasma dispersion relation. Our model assumes a critically balanced turbulence, where larger energy cascade rates excite larger parallel wavenumbers for a certain perpendicular wavenumber. If the dissipation is additionally wave driven such that the dissipation rate is proportional to the parallel wavenumber - as with KAW - then an increase of the energy cascade rate is counter-balanced by an increased dissipation rate for the same perpendicular wavenumber leading to a dissipation length independent of the energy cascade rate.

References in corpus (6)

• Anisotropic scaling of magnetohydrodynamic turbulence
• Small Scale Energy Cascade of the Solar Wind Turbulence
• Solar wind turbulent spectrum at plasma kinetic scales
• Whistler mode waves and the electron heat flux in the solar wind: Cluster observations
• Radial Dependence of the Frequency Break Between Fluid and Kinetic Scales in the Solar Wind Fluctuations
• Forward Modeling of Reduced Power Spectra From Three-Dimensional k-Space

Cited by in corpus (3)

• Anisotropies of the magnetic field fluctuations at kinetic scales in the solar wind : Cluster observations
• Spectrum of kinetic plasma turbulence at 0.3-0.9 astronomical units from the Sun
• Magnetic field turbulence in the solar wind at sub-ion scales: in situ observations and numerical simulations