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

Abstract:

We develop a dissipation model for solar wind turbulence at electron scales. The aim of our study is to describe observed magnetic energy spectra with a simple model to investigate the physical mechanisms of dissipation in the solar wind. The 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. As damping rate, we use the imaginary part of the kinetic Alfvén wave frequency derived from an appropriate dispersion relation. We find that damping by kinetic Alfvén waves can explain observed spectral shapes in the dissipation range and leads to a quasi exponential decay. Our dissipation model exhibits an independence of the dissipation scale from the energy cascade rate, which is a remarkable difference compared to hydrodynamic turbulence. The dissipation model provides the possibility to investigate the influence of varying solar wind parameters and possibly different damping mechanisms on the dissipation range. A statistical study of modeled energy spectra shows a high correlation between the dissipation length and the electron Larmor radius.