P047-0001
MAVEN observations of variability in the twisted magnetotail configuration at Mars

Friday, 11 December 2020
Poster
Gina A DiBraccio1, Norberto Romanelli1, Jacob Gruesbeck1, Jasper S Halekas2, Suranga Ruhunusiri3, Jared R Espley1, Janet G Luhmann4, Shaosui Xu5, Charles Bowers6, Gangkai Poh1, John E P Connerney1, Yuki Harada7, Tristan David Weber8 and David Brain9, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)University of Iowa, Department of Physics and Astronomy, Iowa City, IA, United States, (3)Department of Physics and Astronomy, University of Iowa, Iowa City, IA, United States, (4)University of California Berkeley, Space Sciences Laboratory, Berkeley, CA, United States, (5)Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, United States, (6)University of Michigan Ann Arbor, Department of Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, (7)Kyoto University, Kyoto, Japan, (8)University of Colorado at Boulder, Boulder, CO, United States, (9)Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, United States
Abstract:
Recent investigations have demonstrated that the Martian magnetotail exhibits a highly twisted configuration, which has implications for atmospheric escape to space. Initial studies employing MAVEN magnetic field measurements, coupled with MHD simulations, described the twist to be ~45° away from the nominal interplanetary magnetic field (IMF) draping morphology, in either the clockwise or counterclockwise direction from the ecliptic plane. It has been suggested that this change in magnetotail configuration is likely a result of the sun-planetary interaction, including the interplay between the IMF and planetary crustal fields. As MAVEN continues to orbit and precess about Mars, several years of additional data are available to augment this initial work. Here, we analyze ~6000 orbits between November 2014 and November 2019 when MAVEN magnetic field observations were available in both the magnetotail and upstream solar wind. We utilize an IMF proxy to determine the upstream orientation for orbits when MAVEN did not cross the bow shock to directly measure the solar wind. With increased statistics, we are able to quantify the degree of tail twisting as a function of 1) strong crustal field location, 2) Mars season, and 3) downtail distance. The degree of tail twist is determined by first calculating the average magnetotail lobe locations, identified in the data as the regions of magnetic field behind the planet directed towards and away from Mars, for a given set of parameters. Then, the lobe centers are determined and compared to the theoretical lobe location, based on the assumption of nominal IMF draping. When assessing the degree of tail twist, events are separated by the upstream IMF dawn-dusk component. The results demonstrate that in all scenarios, the degree of tail twisting is larger when the IMF is oriented in the duskward direction, suggesting enhanced coupling between the IMF and planetary crustal fields for this orientation. Furthermore, we demonstrate that the tail twist exhibits different trends for crustal field orientations under dawnward versus duskward IMF. Seasonal variations indicate that tail twisting may change over the course of the Martian year, but additional data are needed during the northern fall and winter periods for confirmation. Finally, when assessing the tail twist with downtail distance we find that the degree of twisting increases with distance from the planet, similar to Earth. From these findings we confirm that the tail twist at Mars is likely influenced by the direct interaction between the IMF and the planetary crustal fields. This implies that magnetic reconnection on the dayside of Mars, between the IMF and crustal fields, may be favorable under specific IMF configurations.
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