SM053-0008
Estimation of the moving direction of the Martian magnetotail flux ropes: MAVEN observations

Wednesday, 16 December 2020
Poster
Takuya Hara1, Yuki Harada2, Zesen Huang3, David L Mitchell1, Gina A DiBraccio4 and David Brain5, (1)Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, United States, (2)Kyoto University, Kyoto, Japan, (3)Department of Earth, Planetary and Space Sciences, University of California Los Angels, Los Angels, CA, United States, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, United States
Abstract:
Mars does not possess a global intrinsic magnetic field; however, it has a strong regional crustal magnetic field primarily distributed in the southern hemisphere. As the upper atmosphere of Mars can be energized via its direct interaction with the solar wind, a large amount of the upper atmosphere is accelerated, resulting in the atmospheric escape into space.

Flux ropes are characteristic twisted helical magnetic field structures, widely considered to form as consequences of magnetic reconnection and/or plasma instabilities. Indeed, these helical flux rope structures are common among the unmagnetized planets like Mars and Venus. In particular, detached flux ropes filled with a large amount of ionospheric plasmas can potentially provide a significant contribution to the ion escape from the unmagnetized planets. If the Martian flux ropes are formed by magnetotail reconnection, they should move either tailward or sunward. The direction of motion of the magnetotail flux ropes can potentially provide us with a clue of the typical location of magnetic reconnection in the Martian magnetotail; however, it is far from understood yet.

Here we investigated the moving direction of the flux ropes especially observed within near-Mars magnetotail current sheets based on MAVEN observations. The direction of motion of the Martian magnetotail flux ropes was estimated the sense of relative change of the bipolar signatures viewed from the minimum variance analysis (MVA) coordinates. We found that the flux ropes moving tailward tend to be observed relatively closed to the planet rather than those moving sunward. Moreover, those moving tailward tend to be more frequently observed in the southern hemisphere than in the northern hemisphere. This result indicates that the Martian crustal magnetic field might play an important role on creating the flux ropes moving tailward in near-Mars magnetotail.

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