Dissipation Model for Solar Wind Turbulence by Kinetic Alfvén Waves at Electron Scales

Abstract:

Recent observations of solar wind fluctuations have focused research on how the turbulent energy is dissipated and ultimately converted to heat. To reveal the physical mechanism of the dissipation process in solar wind turbulence, we develop a model which describes magnetic energy spectra at electron scales. Our model combines the energy transport process from large to small scales and collisionless damping processes, which extract energy from the magnetic fluctuations in the kinetic regime. We assume wave-particle interactions to be the main damping process. The damping is described through the imaginary part of the kinetic Alfvén wave frequency, which we obtain from linear Vlasov theory.

We show that damping by kinetic Alfvén waves can explain the spectral shape in the dissipation range and might be the dominant dissipation process at least for the given plasma conditions. The dissipation model reveals the independence of the dissipation scale from the energy cascade rate for small plasma beta, which is a remarkable difference to hydrodynamic turbulence. A statistical study of modeled energy spectra confirms this result by showing a high corrleation between the dissipation length and the electron Larmor radius. Our dissipation model provides the possibility to investigate the influence of different damping processes and varying plasma conditions on the dissipation range.