Nonlinear Evolution of the Magnetohydrodynamic Kelvin-Helmholtz Instability

Simulation of the magnetohydrodynamic Kelvin-Helmholtz instability in a compressible plasma shows that a super-Alfv\'enic shear flow parallel to the magnetic field develops into small eddies, which strongly compress, twist, and hence amplify the magnetic field, and that a sub-fast (magnetosonic) shear flow transverse to the magnetic field evolves into a fast shock. The anomalous viscosity due to the instability is important in understanding a viscous drag at the solar-wind-magnetosphere interface.