Direct Observation of Expanding Flux Transfer Events Embedded in the Earth’s Magnetopause

Zhao, Cong

Direct Observation of Expanding Flux Transfer Events Embedded in the Earth’s Magnetopause

Tuesday, 11 July 2017

Furong Room (Cynn Hotel)

Cong Zhao¹, Christopher T Russell², Robert J Strangeway², Petrinec M Steven³, William R Paterson⁴, Meng Zhou⁵, Brian J Anderson⁶, Wolfgang Baumjohann⁷, Kenneth R Bromund⁴, Mark Chutter⁸, Barbara L Giles⁴, David Fischer⁹, Guan Le⁴, Rumi Nakamura¹⁰, Ferdinand Plaschke¹¹, Roy B Torbert¹² and Hanying Wei¹³, (1)University of California Los Angeles, IGPP/EPSS, Los Angeles, CA, United States, (2)University of California Los Angeles, Earth, Planetary, and Space Sciences, Los Angeles, CA, United States, (3)Lockheed Martin Space Systems, Cupertino, CA, United States, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)Nanchang University, Nanchang, China, (6)Johns Hopkins University, Baltimore, MD, United States, (7)Space Research Institute (IWF)/Austrian Academy of Sciences, Graz, Austria, (8)University of New Hampshire, Durham, NH, United States, (9)Space Research Institute, Graz-St Peter, Austria, (10)Austrian Academy of Sciences, Vienna, Austria, (11)IWF Institute for Space Research, Graz, Austria, (12)University of New Hampshire Main Campus, Durham, NH, United States, (13)University of California Los Angeles, Los Angeles, CA, United States

Abstract:

During science phase 1 of Magnetospheric Multiscale Mission (MMS), the four identical spacecraft formed a nearly regular tetrahedron with a separation varies from 160km to 7km. Since the separation is much smaller than the scale size of the ion-scale flux transfer events (FTE) (~1000km), the multi-spacecraft timing method can be utilized to calculate the velocity along the normal direction. We applied this timing method at different locations within the flux transfer events, and obtained the velocity as a function of time. We find that mean FTE velocity is along the magnetopause. As the spacecraft moves through the FTE, the FTE velocity appears to vary. In the frame of the motion of the FTE, the velocity is positive on the inbound side and becomes negative on the outbound. This suggests that the FTE is actually expanding. Based on the measured expansion rate and FTE dimension in the cross-sectional plane, the FTE is estimated to be formed several seconds before the observation. The force analysis is consistent with the expansion hypothesis.