On the Generation and Dissipation of Magnetic Energy During a Shear-Flow Driven Instability in Space Plasmas

Abstract

A well-known shear flow-driven instability, namely the Kelvin‐Helmholtz instability (KHI), establishes important changes in the macroscopic dynamics of some space magnetized plasmas such as the solar corona, astrophysical jets and the Earth's magnetopause. We use two-dimensional resistive magnetohydrodynamic (MHD) simulations to investigate the generation and dissipation of magnetic energy during KHI in a compressible plasma with an initial uniform magnetic field parallel to the direction of streaming flow. Regardless of the resistivity value, the results show that, up to a specific time, amplification of magnetic energy, in particular in the linear and early nonlinear phases of KHI happens by the flow's work on the magnetic field. This work is mainly efficient on the boundaries of growing vortices of KHI. As the KHI proceeds into the fully nonlinear (turbulent) phase, magnetic energy dissipation via Ohmic heating becomes significant, and eventually balances the flow's work, so the magnetic energy becomes saturated. We also found that increasing the plasma resistivity weakens the mechanism of generating magnetic energy, and may even be completely suppressed in a highly collisional fluid.