Published December 24, 2023 | Version v1
Journal article Open

MMS Observations of Reconnection Separatrix Region in the Magnetotail at Different Distances From the Active Neutral X-Line

  • 1. St. Petersburg State University, Sanct-Petersburg, Russia
  • 2. Space Research Institute, Austrian Academy of Sciences, Graz, Austria
  • 3. Swedish Institute of Space Physics, Uppsala, Sweden
  • 4. Southwest Research Institute, San Antonio, TX, USA
  • 5. NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 6. IGPP/EPSS, University of California, Los Angeles, CA, USA
  • 7. Space Science Center, University of New Hampshire, Durham, NH, USA

Description

The region surrounding the reconnection separatrix consists of many particle and wave
transient features (electron, cold and hot ion beams, Hall E&B fields, kinetic Alfvén, LH, etc. waves)
whose pattern and parameters may vary depending on the distance from active neutral line. We study
nine quick MMS entries into the plasma sheet boundary layer (PSBL) from the tail lobe to address the
meso-scale pattern and other characteristics of phenomena for active separatrix crossings as deduced from
particle observations. The outermost thin layer (a fraction of ion inertial scale, di) of low-density plasma
consists of accelerated electron beams and lobe cold ions and displays density depletions (EBL region). It
is followed by hot proton beam (PBL region) in which the plasma density grows from lobe-like towards
plasma sheet-like values; the beam energy-dispersion is used to estimate the distance from the active
neutral line. Thin (usually ≤ di) region containing intense Hall-like Ez perturbations (HR) usually overlaps
with EBL and PBL regions. It often includes correlated B perturbations suggesting the Alfvén waverelated
transport from the reconnection source; the estimated Alfvénic ratio δE/(VA δB) varied between
0.3 and 1.3 in studied examples. The HR is associated with profound plasma property changes, including
the heating of cold ion beams in its innermost part, it hosts intense structured field-aligned currents
and intense E-field fluctuations. Surprisingly, most of abovementioned findings are valid for crossings
observed at large distances from the reconnection region (exceeding a few tens Re or >100 di) except for
longer time-scales and larger spatial scales of the pattern.

Files

sergeev_v_2021_jgr_126_e2020ja028694.pdf

Files (6.4 MB)

Name Size Download all
md5:a716a229e9d899cc10dd9f0d158f9a19
6.4 MB Preview Download