Evolution of Kelvin-Helmholtz Instability
Time evolution of the Kelvin-Helmholtz instability (KHI) at the dawnside magnetospheric flank. The colour code shows plasma density, where the higher density (orange) is in the magnetosheath and lower density (purple) is in the magnetospheric side. The Black arrows are the plasma velocity vectors and the black lines are the magnetic field lines projected into shear flow plane. When the Kelvin-Helmholtz wave passes by the Cluster spacecraft it generates quasi-periodic variations in the density, temperature, total pressure and normal component of the magnetic field. The initial configuration for the simulation is such that the magnetic fields are anti-parallel across the magnetopause in the shear flow plane. In this geometry the KHI can generate reconnection in two different regions within the vortex:
A) reconnection occurs first in a current layer separating the anti-parallel magnetospheric and magnetosheath fields
B) later the reconnection develops in a magnetospheric current layer generated by twisting of the magnetospheric field due to the KHI.