SM008-02
Observations of lower hybrid drift waves in a disturbed electron diffusion region in Earth’s magnetotail
Monday, 7 December 2020: 16:04
Virtual
Giulia Cozzani1, Mats Andre2, Yuri V Khotyaintsev3, Daniel Graham1, Alexandra Alexandrova4, Jan Egedal5, Andris Vaivads6, Per-Arne Lindqvist7, Olivier Le Contel8, Roy B Torbert9, Robert Ergun10, Barbara L Giles11, Thomas Earle Moore12, Christopher T Russell13, Rumi Nakamura14, Stephen A Fuselier15, Barry Mauk16 and James Burch15, (1)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (2)Swedish Inst Space Physics, Uppsala, Sweden, (3)Swedish Institute of Space Physics (IRF), Uppsala, Sweden, (4)Laboratoire de Physique des Plasmas, Ecole Polytechnique, Paris, France, (5)University of Wisconsin Madison, Madison, WI, United States, (6)School of Electrical Engineering and Computer Science, Royal Institute of Technology, Department of Space and Plasma Physics, Stockholm, Sweden, (7)KTH Royal Institute of Technology, Stockholm, Sweden, (8)Laboratoire de Physique des Plasmas (UMR7648), CNRS/Ecole Polytechnique/UPMC/Univ. Paris Sud/Obs. de Paris, Paris, France, (9)Univ New Hampshire, Durham, NH, United States, (10)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (11)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (12)NASA Goddard Space Flight Ctr, Greenbelt, MD, United States, (13)University of California, Los Angeles, CA, United States, (14)Space Research Institute, Graz, Austria, (15)Southwest Research Institute, San Antonio, TX, United States, (16)The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States
Abstract:
Magnetic reconnection is a fundamental energy conversion process in plasmas. The Electron Diffusion Region (EDR) is the key region in which both ions and electrons are demagnetized so that the topological rearrangement of field lines can take place, together with rapid heating and acceleration of plasma particles. A crucial question is whether the EDR has a laminar or turbulent structure. In particular, instabilities may be operating within the EDR and perturb its structure but observational evidences of these processes are still lacking.
We report MMS observations of an EDR encounter with weak guide field (13 % of the magnetic field in the inflow region in the lobes) in Earth's magnetotail when the inter-spacecraft separation was 20 km ∼ 1.5 de. We observe an extended region of clear electron demagnetisation and differences among the spacecraft indicating sharp gradients with characteristic scales comparable to the electron inertial length ( ∼ inter-spacecraft separation).
These signatures observed at the EDR and its proximity deviate from the standard laminar picture of the diffusion region.
A peculiar feature of this EDR encounter is the presence of electromagnetic fluctuations peaking in the center of the current sheet. The magnetic field fluctuations are significant since they reach 20 % of upstream magnetic field in the plasma sheet. The properties of these waves are consistent with lower hybrid drift waves (LHDW) that could be related to the non-linear phase of lower hybrid drift instability (LHDI) or the modified two stream instability (MTSI) operating in the center of the current sheet.
The presence of these fluctuations affects the structure of the EDR which becomes non-laminar and disturbed.
