Influence of the Hall Term on KH Instability and Reconnection Inside KH Vortices

The Kelvin-Helmholtz instability (KHI) in its nonlinear stage can develop small-scale filamentary field and current structures at the flank boundaries of the magnetosphere. It has been shown previously with MHD simulations that magnetic reconnection can occur inside these narrow current layers, resulting in plasma transport from the solar wind into the magnetosphere. During periods of northward IMF, this transport is sufficient to generate a cold, dense plasma sheet on time scales consistent with satellite observations. However, when the length scales of these narrow current layers approach the ion inertia scale, the MHD approximation is not valid anymore and the Hall term in the Ohm’s law must be included. We will study the influence of the Hall term on the KHI with 2-D Hall-MHD simulations and compare our results with corresponding MHD simulations. We estimate plasma transport velocities of the order of ~1.5 km/s, thus confirming the results of the MHD approximation. However, the fine structure and the growth rates differ from the MHD approximation in an interesting way.