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- Title
An Eastward Current Encircling Mercury.
- Authors
Shi, Z.; Rong, Z. J.; Fatemi, S.; Slavin, J. A.; Klinger, L.; Dong, C.; Wang, L.; Zhong, J.; Raines, J. M.; Holmström, M.; Yuan, C. J.; Barabash, S.; Wei, Y.
- Abstract
Mercury has a terrestrial‐like magnetosphere which is usually taken as a scaled‐down‐version of Earth's magnetosphere with a similar current system. We examine Mercury's magnetospheric current system based on a survey of Mercury's magnetic field measured by the Mercury Surface, Space Environment, Geochemistry, and Ranging spacecraft as well as computer simulations. We show that there is no significant Earth‐like ring current flowing westward around Mercury, instead, we find, for the first time, an eastward current (EC) encircling the planet near the night‐side magnetic equator with an altitude of ∼500–1,000 km. The EC is closed with the dayside magnetopause current and could be driven by the gradient of plasma pressure as a diamagnetic current. Thus, Mercury's magnetosphere is not a scaled‐down Earth magnetosphere, but a unique natural space plasma laboratory. Our findings offer fresh insights to analyze data from the BepiColombo mission, which is expected to orbit Mercury in 2025. Plain Language Summary: Whether Mercury possesses an Earth‐like ring current has long been the focus of controversy in planetary science and space science. Here, based on the statistical analysis of the magnetic field measured by Mercury Surface, Space Environment, Geochemistry, and Ranging, we show that Mercury has no significant Earth‐like ring current which flows westward around the planet, but we discover for the first time that there is an eastward current encircling the planet near the night side. Our discovery is verified by computer simulations and shows well consistence with the observation signatures found in previous studies. Our discovery updates the knowledge of the current system of Mercury's magnetosphere and demonstrates that the Mercury's magnetosphere cannot be simply seen as a scaled‐down‐version of Earth's magnetosphere. Key Points: We discovered an eastward current (EC) encircling Mercury on the night side for the first timeThe EC can be well reproduced by hybrid simulations and well fits the signatures found in previous studiesThe EC could be a diamagnetic current driven by a plasma pressure peak, and becomes more significant when interplanetary magnetic field is northward
- Subjects
INTERPLANETARY magnetic fields; MERCURY; MERCURY (Planet); SPACE environment; SPACE sciences; PLANETARY science
- Publication
Geophysical Research Letters, 2022, Vol 49, Issue 10, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2022GL098415