[P-EM14] [EE] Dynamics in magnetosphere and ionosphere

[PEM14-18] The Earth’s Magnetopause: Force Balance and Topology Revealed by High Cadence Plasma Measurements

*Christopher T Russell¹, Robert J Strangeway¹, Cong Zhao¹, Brian J Anderson², Wolfgang Baumjohann³, Kenneth R Bromund⁴, James A Slavin⁵, Larry Kepko^4,6, Guan Le⁴, Werner Magnes³, Rumi Nakamura³, Roy B Torbert⁶, William R Paterson⁴, Thomas E Moore⁴, Barbara L Giles⁴, Stephen A Fuselier⁷, James L Burch⁷ (1.Earth Planetary and Space Sciences, University of California, Los Angeles, CA 90095, USA., 2.Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA, 3.Space Research Institute, Austrian Academy of Sciences, Graz, Austria, 4.NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA, 5.University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, MI 48109-2143, USA, 6.University of New Hampshire, Durham, NH 03824, USA, 7.Southwest Research Institute, Boulder, CO 80302, USA.)

Keywords:Magnetopause, Reconnection, Topology

The magnetopause is strongly influenced by properties of the flowing plasma that it deflects. The Magnetospheric Multiscale Mission has enabled this interaction to be probed in intimate detail. We combine the magnetic measurements of the four spacecraft to demonstrate how the magnetic forces affect the boundary between the shocked solar wind and the Earth’s magnetic field. We compare these forces with the plasma pressure, confirming the accurate intercalibration of the plasma and magnetic forces but draw attention to the tradeoff between spatial resolution and accuracy of the gradient measurements so governed by the spacecraft separation. We use the electron distribution function to examine the topology of the magnetic field. Small pockets of low magnetic field strength, small radius of curvature magnetic field lines and high electric current mark the electron diffusion region.