Seminar: Flux Transfer Events in Mercury's Magnetosphere

Wednesday, March 03, 2021 - 3:00pm to 4:00pm

Speaker: Weijie Sun, Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor

Abstract: Mercury, the smallest and innermost planet in the Solar System, has a "miniature" magnetosphere under intense supersonic solar wind impact but without a significant neutral atmosphere. The magnetosphere can prevent most of the dayside surface from directly hitting of the streaming solar wind during most times. However, how the lowest solar wind Alfvénic Mach number (M_A = V_SW/V_A) among the planets in the Solar System influences the magnetosphere and exosphere dynamics of Mercury is still unknown. In this presentation, we show a comprehensive survey on the magnetic reconnection-generated flux transfer events (FTEs) on Mercury’s dayside magnetopause with the measurements from MESSENGER. FTEs are flux ropes that are generated by magnetic reconnection between the interplanetary magnetic field (IMF) and planetary magnetic field. They are widely observed in the Solar System, which contains helical magnetic field lines and strong magnetic field enhancements. FTEs emerge extremely frequently (~ 10 FTEs in one minute), termed the FTE “shower”, and are an important indicator of space weather at Mercury. FTE shower occurs under any magnetic shear angle between the two sides of the magnetopause, but is more frequent when the magnetic shear angle becomes larger. The magnetosheath plasma β (ratio between thermal pressure and magnetic pressure) also controls the occurrence of FTE showers, i.e., the lower the magnetosheath plasma β, the higher the occurrence of FTE showers. Further investigations have shown that the FTE shower plays a key role in driving Mercury's magnetospheric activities, and the multiple X-line reconnection, which forms the FTEs, are the primary reconnection form in Mercury's magnetosphere. The feature of FTEs in Mercury's magnetosphere are also compared with those in other planetary magnetospheres. In the last, we have investigated the injected particles associated with FTEs and their sputtering on the surface of planet’s cusp could influence the dynamics of Mercury’s exosphere.

This online seminar will take place on Zoom and will require a password to join. If you wish to watch the seminar and have not received a password via email, please contact Robbin McPherson at robbin.mcpherson@unh.edu.