Change of spectral properties of solar wind magnetic field fluctuations across different types of interplanetary shocks
Abstract
The interaction between interplanetary (IP) shocks and solar wind has been studied for the understanding of energy dissipation mechanisms and the properties of turbulence (e.g., cross helicity, residual energy, proton temperature anisotropy, magnetic compressibility, etc.) within collisionless plasmas. Compared to the study of the interaction with fast shocks, less attention has been directed to the interaction with other types of IP shocks.
We analyze all types of IP shocks (fast forward, fast reverse, slow forward and slow reverse) observed by the Wind spacecraft from 1995 to 2021. Spectral indices in the ion inertial and kinetic ranges for the upstream and downstream magnetic field fluctuations are estimated by continuous wavelet transform.
The changes of the plasma turbulence properties and the distributions of characteristic proton length scales are presented. We found that spectral indices in both inertial and kinetic ranges and the distributions of characteristic proton length scales are statistically conserved across the shocks and it implies that mechanisms associated with the energy dissipation can be unaffected by shock.
Cross helicity - the imbalance of solar wind turbulence - evolves without a significant modification as well. The dissipation of the turbulent magnetic energy in the kinetic range is discussed with respect to the magnetic field fluctuation enhancement across shock and the imbalanced propagation of the fluctuations in the up- and downstream.