Poh_et_al-2018-Geophysical_Research_Letters.pdf (1.05 MB)
Transport of Mass and Energy in Mercury's Plasma Sheet
journal contributionposted on 2019-08-20, 09:13 authored by G Poh, JA Slavin, X Jia, WJ Sun, JM Raines, SM Imber, GA DiBraccio, DJ Gershman
We examined the transport of mass and energy in Mercury's plasma sheet (PS) using MESSENGER magnetic field and plasma measurements obtained during 759 PS crossings. Regression analysis of proton density and plasma pressure shows a strong linear relationship. We calculated the polytropic index γ for Mercury's PS to be ~0.687, indicating that the plasma in the tail PS behaves nonadiabatically as it is transported sunward. Using the average magnetic field intensity of Mercury's tail lobe as a proxy for magnetotail activity level, we demonstrated that γ is lower during active time periods. A minimum in γ was observed at R ~ 1.4 RM, which coincides with previously observed location of Mercury's substorm current wedge. We suggest that the nonadiabatic behavior of plasma as it is transported into Mercury's near-tail region is primarily driven by particle precipitation and particle scattering due to large loss cone and particle acceleration effect, respectively.
The authors acknowledged support provided by NASA Discovery Data Analysis Program (DDAP) grants NNX15K88G, NNX15AL01G, and NNX16AJ05G, Heliophysics Supporting Research (HSR) NNX15AJ68G, Living with a Star NNX16AJ67G, and Solar System Workings (SSW) Program grant NNX15AH28G to the University of Michigan.
CitationGeophysical Research Letters, 2018, 45 (22), pp. 12-170
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy
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