Calibrating MMS Electron Drift Instrument (EDI) Ambient Electron Flux Measurements and Characterizing 3D Electric Field Signatures of Magnetic Reconnection

Friday, 18 December 2015
Poster Hall (Moscone South)
Jason R Shuster1, Roy B Torbert1, Hans Vaith1, Matthew R Argall1, Guanlai Li1, Li-Jen Chen2, Robert E Ergun3, Per-Arne Lindqvist4, Goran Tage Marklund5, Yuri V Khotyaintsev6, Christopher T Russell7, Werner Magnes8, Olivier Le Contel9, Craig J Pollock10 and Barbara L Giles2, (1)University of New Hampshire Main Campus, Durham, NH, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)University of Colorado, Laboratory for Atmospheric and Space Research, Boulder, CO, United States, (4)KTH Royal Institute of Technology, Stockholm, Sweden, (5)Royal Inst Technology, KTH/EES, Stockholm, Sweden, (6)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (7)University of California Los Angeles, IGPP/EPSS, Los Angeles, CA, United States, (8)Space Research Institute, Austrian Academy of Sciences, Graz, Austria, (9)Laboratoire de Physique des Plasmas (UMR7648), CNRS/Ecole Polytechnique/UPMC/Univ. Paris Sud/Obs. de Paris, Paris, France, (10)NASA Goddard Space Flight Center, Heliophysics Sci. Div., Greenbelt, MD, United States
The electron drift instruments (EDIs) onboard each MMS spacecraft are designed with large geometric factors (~0.01cm2 str) to facilitate detection of weak (~100 nA) electron beams fired and received by the two gun-detector units (GDUs) when EDI is in its "electric field mode" to determine the local electric and magnetic fields. A consequence of the large geometric factor is that “ambient mode” electron flux measurements (500 eV electrons having 0°, 90°, or 180° pitch angle) can vary depending on the orientation of the EDI instrument with respect to the magnetic field, a nonphysical effect that requires a correction. Here, we present determinations of the θ- and ø-dependent correction factors for the eight EDI GDUs, where θ (ø) is the polar (azimuthal) angle between the GDU symmetry axis and the local magnetic field direction, and compare the corrected fluxes with those measured by the fast plasma instrument (FPI). Using these corrected, high time resolution (~1,000 samples per second) ambient electron fluxes, combined with the unprecedentedly high resolution 3D electric field measurements taken by the spin-plane and axial double probes (SDP and ADP), we are equipped to accurately detect electron-scale current layers and electric field waves associated with the non-Maxwellian (anisotropic and agyrotropic) particle distribution functions predicted to exist in the reconnection diffusion region. We compare initial observations of the diffusion region with distributions and wave analysis from PIC simulations of asymmetric reconnection applicable for modeling reconnection at the Earth’s magnetopause, where MMS will begin Science Phase 1 as of September 1, 2015.