Magnetopause properties at the dusk magnetospheric flank from global magnetohydrodynamic simulations, the kinetic Vlasov equilibrium, and in situ observations − Potential implications for SMILE

Abstract

We derived the properties of the terrestrial magnetopause (MP) from two modeling approaches, one global–fluid, the other local–kinetic, and compared the results with data collected in situ by the Magnetospheric Multiscale 2 (MMS2) spacecraft. We used global magnetohydrodynamic (MHD) simulations of the Earth’s magnetosphere (publicly available from the NASA-CCMC [National Aeronautics and Space Administration–Community Coordinated Modeling Center]) and local Vlasov equilibrium models (based on kinetic models for tangential discontinuities) to extract spatial profiles of the plasma and field variables at the Earth’s MP. The global MHD simulations used initial solar wind conditions extracted from the OMNI database at the time epoch when the MMS2 observes the MP. The kinetic Vlasov model used asymptotic boundary conditions derived from the same in situ MMS measurements upstream or downstream of the MP. The global MHD simulations provide a three-dimensional image of the magnetosphere at the time when the MMS2 crosses the MP. The Vlasov model provides a one-dimensional local view of the MP derived from first principles of kinetic theory. The MMS2 experimental data also serve as a reference for comparing and validating the numerical simulations and modeling. We found that the MP transition layer formed in global MHD simulations was generally localized closer to the Earth (roughly by one Earth radius) from the position of the real MP observed by the MMS. We also found that the global MHD simulations overestimated the thickness of the MP transition by one order of magnitude for three analyzed variables: magnetic field, density, and tangential speed. The MP thickness derived from the local Vlasov equilibrium was consistent with observations for all three of these variables. The overestimation of density in the Vlasov equilibrium was reduced compared with the global MHD solutions. We discuss our results in the context of future SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) campaigns for observing the Earth’s MP.

Keywords

• magnetopause
• magnetohydrodynamic numerical simulations
• vlasov equilibrium
• magnetospheric multiscale observations