Numerical Modeling of Alfven Waves and Quasistatic Field Structures in the Plasma Sheet Boundary Layer

A nonlinear, two-fluid MHD model in dipole geometry has been used to investigate electromagnetic field fluctuations, both Alfvén wave phenomena as well as quasistatic field structures, on magnetic field lines threading the plasma sheet boundary layer. Results of modeling Cluster satellite observations of electromagnetic field fluctuations occurring at the plasma sheet-polar cap interface will be presented. These results include a minimum variance analysis of the Cluster fields to fit the event to the modeling domain. To drive the simulation, we interpret the Cluster event as the interaction of large-scale downward current channels with the ionosphere. A comparison of simulation results with the Cluster observations suggest that observed small scale structure develops as a consequence of a scale-dependent interaction with the ionosphere and lower magnetosphere.