Plasma Transport, Acceleration, and Loss in Mercury’s Magnetosphere and Comparison with Other Planetary Magnetospheres

David Schriver1, Pavel M Travnicek2, Brian J Anderson3, Maha Ashour-Abdalla4, Daniel N Baker5, Mehdi Benna6, Scott A Boardsen7, Petr Hellinger8, George C Ho9, Haje Korth10, Stamatios Mike Krimigis11, Ralph L McNutt Jr12, Jim M Raines13, Robert L Richard1, James A Slavin14, Richard D Starr15, Sean C Solomon16 and Thomas Zurbuchen14, (1)University of California Los Angeles, Department of Physics and Astronomy, Los Angeles, CA, United States, (2)University of California Berkeley, Space Sciences Laboratory, Berkeley, CA, United States, (3)Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, (4)UCLA-IGPP, Los Angeles, CA, United States, (5)University of Colorado, Laboratory for Atmospheric and Space Physics, Boulder, United States, (6)NASA Goddard Space Flight Center, Greenbelt, United States, (7)NASA GSFC/UMBC, Greenbelt, United States, (8)Astronomical Institute, CAS, Ondrejov/Prague, Czech Republic, (9)Johns Hopkins Univ, Laurel, MD, United States, (10)JHU/APL, Laurel, MD, United States, (11)Academy of Athens, Space, Athens, Greece, (12)Johns Hopkins University Applied Physics Laboratory, Space Exploration Sector, Laurel, MD, United States, (13)University of Michigan, Ann Arbor, United States, (14)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (15)Catholic University of America, Washington, DC, United States, (16)Lamont-Doherty Earth Observatory, Palisades, NY, United States
Abstract:
Mercury has the distinction of having the smallest planetary magnetosphere in the solar system, in contrast to the mid-sized magnetosphere of Earth and the very large magnetospheres of the outer planets. Observations by the MESSENGER spacecraft in orbit around Mercury have established that Mercury’s magnetosphere has a global structure similar to those found in the other planetary magnetospheres, i.e., a foreshock, bow shock, magnetosheath, magnetopause, cusps, and magnetotail. There are also auroral signatures observed at Mercury associated with the precipitation of electrons; those signatures are not in the visible range, however, but rather appear as nightside X-ray fluorescence. Heavy ions (primarily Na+) from the planet surface mass load Mercury’s magnetosphere in a manner analogous to the internal sources of heavy ions in the other planetary magnetospheres, e.g., Earth’s ionosphere and moons of the outer planets. One feature not found at Mercury compared with the other planetary magnetospheres is the presence of a high-energy (> hundreds of keV) trapped radiation belt region. Although there are observations of high energy electron bursts within Mercury’s magnetosphere, these are not stably trapped and instead Mercury has a quasi-trapped population of ions and electrons with 1–10 keV bulk energies at about 1.5 RM (RM is Mercury’s radius = 2440 km) radial distance from the planet center. MESSENGER spacecraft observations and results from a global kinetic simulation model of the solar wind interaction with Mercury’s magnetosphere provide a basis for describing the transport, acceleration, and loss of plasma, those features and processes unique to Mercury, as well as those in common with other planetary magnetospheres in the solar system.
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