Structuring in the Magnetotail Plasma Sheet: Multi-point Observations and Global Simulations

Single and multi-spacecraft observations have demonstrated that the magnetotail current sheet, one of the key dynamic regions of the magnetosphere, has both spatial and temporal structure. These current sheet structures are important signatures of the magnetotail's response to the evolving solar wind and interplanetary magnetic field. In this study, we will use multi-point observations of the magnetotail and the plasma sheet from the Cluster spacecraft and high spatial resolution global magnetohydrodynamic (MHD) simulations, driven by solar wind and IMF observations from the WIND spacecraft, to examine and understand the configuration and dynamics of magnetotail current sheet structures. On October 8, 2004, Cluster, Geotail, and Double Star were all located close to the current sheet at comparable distances downtail. Cluster and Double Star sampled the plasma sheet boundary layer (PSBL) multiple times, and both observed high-speed beams at the lobeward edge of the PSBL that contained small-scale structures. Differences in these observations demonstrate the variability and scale of the observed structures. We will show that MHD simulations reproduce some of the large-scale plasma and magnetic field measurements made by the Cluster and Double Star spacecraft in the plasma sheet and can place these observations in the context of large-scale convection and magnetic reconnection. To model the similarities and differences in the properties of the observed plasma, global MHD simulations will be supplemented by large-scale kinetic (LSK) calculations in which ion trajectories are followed in the electric and magnetic fields from the global MHD simulation. This will allow us to examine the acceleration and transport processes forming the PSBL ion beams, their spatial and energy dispersion, and their possible sub- structuring. Quantitative comparisons will be made between the results of the LSK calculations and the observations.