Haje Korth, The John Hopkins University
Title: "Structure and Dynamics of Mercury’s Magnetosphere Inferred from MESSENGER Observations"
Abstract: Since insertion of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft into orbit around Mercury on 18 March 2011, the probe’s plasma and magnetic field experiments have provided detailed insight into this planet’s unique magnetosphere. Because Mercury’s dynamo magnetic field is weak – the dipole moment is 190 nT RM3, where RM=2440 km is Mercury’s radius – the magnetopause stands, on average, only 1.45 RM off the subsolar surface. Consequently, Mercury’s magnetosphere is much smaller than that of the Earth, and evidence for rapid reconnection through frequent loading and unloading of the magnetic tail on ~2 min. time scales, commensurate with this magnetosphere’s Dungey cycle, is plentiful. Similar to the terrestrial magnetosphere, plasmas entering the nightside magnetosphere via reconnection and diffusion processes are transported toward the equatorial plane forming the plasma sheet and thence to the dayside by convection. However, owing to weak corotation and gradient-curvature drifts and highly variable convection electric fields and external magnetic fields, which exhibit magnitudes comparable to the dipole field even close to the planet, particle motion is much more chaotic and precipitation to the surface exhibits a strong north–south asymmetry resulting from the substantial, ~480 km, northward offset of the planetary field. This presentation will highlight observations of the structure and dynamics of Mercury’s magnetosphere inferred from observations by the MESSENGER Magnetometer and Fast Imaging Plasma Spectrometer. Then, using 10 months of orbital observations, the statistical spatial distribution of plasma within the magnetosphere is determined separately from data recorded by each instrument and the results are compared.
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