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MESSENGER Observations of Disappearing Dayside Magnetosphere Events at Mercury

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journal contribution
posted on 2019-09-04, 11:08 authored by JA Slavin, HR Middleton, JM Raines, X Jia, J Zhong, WJ Sun, S Livi, SM Imber, GK Poh, M Akhavan-Tafti, JM Jasinski, GA DiBraccio, C Dong, RM Dewey, ML Mays
MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) measurements taken during passes over Mercury's dayside hemisphere indicate that on four occasions the spacecraft remained in the magnetosheath even though it reached altitudes below 300 km. During these disappearing dayside magnetosphere (DDM) events, the spacecraft did not encounter the magnetopause until it was at very high magnetic latitudes, ~66 to 80°. These DDM events stand out with respect to their extremely high solar wind dynamic pressures, Psw ~140 to 290 nPa, and intense southward magnetic fields, Bz ~ −100 to −400 nT, measured in the magnetosheath. In addition, the bow shock was observed very close to the surface during these events with a subsolar altitude of ~1,200 km. It is suggested that DDM events, which are closely associated with coronal mass ejections, are due to solar wind compression and/or reconnection-driven erosion of the dayside magnetosphere. The very low altitude of the bow shock during these events strongly suggests that the solar wind impacts much of Mercury's sunlit hemisphere during these events. More study of these disappearing dayside events is required, but it is likely that solar wind sputtering of neutrals from the surface into the exosphere maximizes during these intervals.

Funding

We are thankful to the MESSENGER Project and especially the FIPS and MAG instrument teams for providing the plasma and magnetic field data. The FIPS and MAG products used in this paper are available from the Planetary Data System (http://ppi.pds.nasa.gov/). This work was supported by NASA grants NNX16AJ67G, NNX15AL01G, NNX16AJ03G, and 80NSSC18K1137. The WSA‐ ENLIL + Cone simulation results were provided by the CCMC through their public Runs‐on‐Request system (http://ccmc.gsfc.nasa.gov; run number Ryan_Dewey_031417_SH_1). The WSA model was developed by N. Arge at NASA GSFC, and the ENLIL model was developed by D. Odstrcil at GMU.

History

Citation

Journal of Geophysical Research: Space Physics, 2019

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

  • VoR (Version of Record)

Published in

Journal of Geophysical Research: Space Physics

Publisher

American Geophysical Union (AGU), Wiley

issn

2169-9380

eissn

2169-9402

Acceptance date

2019-06-16

Copyright date

2019

Available date

2019-09-04

Publisher version

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JA026892

Notes

The FIPS and MAG products used in this paper are available from the Planetary Data System (http://ppi.pds.nasa.gov/). The WSA‐ ENLIL + Cone simulation results were provided by the CCMC through their public Runs‐on‐Request system (http://ccmc.gsfc.nasa.gov; run number Ryan_Dewey_031417_SH_1).

Language

en

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