Electron and Ion Populations in the Magnetopause Boundary Layers: Results from Kinetic Simulations

We focus on the origins and evolution of the plasma populations observed in the magnetopause boundary layers. Our approach is to use Particle In Cell (PIC) simulations that are initialized from global MHD states of the magnetosphere. The implicit PIC code we employ allows us to simulate large sub-domains of the global simulations. Within a sub-domain we use fields and plasma moments from the global simulations to set the initial and boundary conditions of the PIC code. For southward interplanetary field conditions, three-dimensional plots of the perpendicular slippage indicate that reconnection occurs over most of the equatorial dayside magnetopause. However, the simulations reveal that the reconnection region has a much more filamentary structure than the X-line expected from the extrapolation of 2D models and that multiscale structures thread the reconnection outflow. In particular, the simulations indicate the formation of multiple layers of electrons with significant field-aligned velocities within the main magnetopause current layer. We use velocity distribution functions at different locations in the reconnection outflow to characterize the origin and evolution of the electron and ion populations of the magnetosheath and magnetospheric boundary.