SM019-0019
MMS Survey of Dissipating Earthward Propagating Flux Rope Through Re-reconnection with Geomagnetic Field

Thursday, 10 December 2020
Poster
Gangkai Poh1, Wei-Jie Sun2, Dogacan Su Ozturk3, Yuxi Chen4, James A Slavin5, Guan Le1 and Xianzhe Jia4, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)University of Michigan Ann Arbor, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, (3)University of Michigan Ann Arbor, AOSS, Ann Arbor, MI, United States, (4)University of Michigan, Ann Arbor, MI, United States, (5)University of Michigan Ann Arbor, Department of Climate and Space Sciences and Engineering, Ann Arbor, MI, United States
Abstract:
The formation of flux ropes (FRs) is an integral part of the magnetotail dynamics that have important consequences for the onset and subsequent evolution of reconnection in the tail. Global hybrid simulations and in-situ observations have shown that earthward-moving flux ropes can undergo “re-reconnection” with the near-Earth dipole field in the region earthward of the Near Earth Neutral Line to create DFs-like signatures. Recently, Poh et al., [2019] analyzed MMS observation of fields and plasma signatures associated with the encounter of an ion diffusion region ahead of an earthward-moving FR. The signatures of this re-reconnection event were: (i) +/- BZ reversal, (ii) -/+ bipolar-type BY variations as part of the quadrupolar Hall magnetic fields, (iii) northward Alfvénic electron outflow jet, (iv) presence of Hall electric field and intense currents, and (v) positive J·E’. Their analysis suggests that the MMS spacecraft encountered the ion diffusion region but misses the electron diffusion region and estimated that the FR would have fully dissipated by XGSM ~ -15 RE. In this study, we conducted a statistical survey of signatures associated with the encounter of “re-reconnection” X-line events preceding observations of earthward-moving flux ropes using five years of MMS magnetic field and plasma measurements. We also compared our observations of re-reconnection signatures and analysis results with simulation results from the BATS-R-US MHD with Embedded PIC (MHD-EPIC) numerical model to understand the flux rope dissipation process and the kinetic physics of re-reconnection from a realistic global perspective. Through correlation analysis, we further demonstrated that there is clear relationship between the dissipation of earthward-moving FRs, global ionospheric current systems and substorm activity in the auroral zone, consistent with earlier observations.
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