SM040-0011
High-density magnetospheric He+ at the dayside magnetopause and its effect on magnetic reconnection

Tuesday, 15 December 2020
Poster
Stephen A Fuselier1, Stein Haaland2, Paul Tenfjord3, Goetz Paschmann4, Sergio Toledo-Redondo5, David Malaspina6, Myeong Joon Kim7, Karlheinz J Trattner8, Petrinec M Steven9, Barbara L Giles10, Jerry Goldstein1, James L Burch11 and Robert J Strangeway12, (1)Southwest Research Institute, San Antonio, TX, United States, (2)Birkeland Centre for Space Science, University of Bergen, Bergen, Norway, Bergen, Norway, (3)University of Bergen, Space Plasma Physics Group, Bergen, Norway, (4)Max Planck Institute for extraterrestrial Physics, Garching, Germany, (5)University of Murcia, Murcia, Spain, (6)University of Colorado, Astrophysical and Planetary Sciences Department, Boulder, CO, United States, (7)University of Texas at San Antonio, Physics and Astronomy, San Antonio, TX, United States, (8)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (9)Lockheed Martin Advanced Technology Center, Palo Alto, CA, United States, (10)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (11)Southwest Research Institute San Antonio, San Antonio, TX, United States, (12)Univ California, Los Angeles, CA, United States
Abstract:
Observations from the Magnetospheric Multiscale (MMS) mission are used to quantify the maximum effect of magnetospheric H+ and He+ on dayside magnetopause reconnection. A data set of current sheet crossings from the first two sweeps of the dayside magnetopause by the MMS spacecraft is used to identify magnetopause crossings with the highest He+ concentrations. Half of the crossings with the highest He+ are directly associated with plasmaspheric plumes at the dayside magnetopause while the other half have evidence of plasmaspheric plume material in the magnetosphere even though they are located many Earth radii from the predicted location of the plasmapause. The He+ density varies dramatically within the magnetosphere adjacent to the magnetopause, with variations of an order of magnitude on timescales as short as 10 seconds (one timestep for the HPCA composition measurement). Plasma wave observations are used to determine the total electron density and composition measurements are used to determine the mass density in the magnetosheath and magnetosphere. These mass densities are then used with the magnetic field observations to determine the theoretical reduction in the reconnection rate at the magnetopause. The presence of high-density plasmaspheric plume material at the magnetopause causes transient reductions in the reconnection rate of up to 20-30%.
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