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Title: On the electron dynamics during island coalescence in asymmetric magnetic reconnection

We present an analysis of the electron dynamics during rapid island merging in asymmetric magnetic reconnection. We consider a doubly periodic system with two asymmetric transitions. The upper layer is an asymmetric Harris sheet of finite width perturbed initially to promote a single reconnection site. The lower layer is a tangential discontinuity that promotes the formation of many X-points, separated by rapidly merging islands. Across both layers, the magnetic field and the density have a strong jump, but the pressure is held constant. Our analysis focuses on the consequences of electron energization during island coalescence. We focus first on the parallel and perpendicular components of the electron temperature to establish the presence of possible anisotropies and non-gyrotropies. Thanks to the direct comparison between the two different layers simulated, we can distinguish three main types of behavior characteristic of three different regions of interest. The first type represents the regions where traditional asymmetric reconnections take place without involving island merging. The second type of regions instead shows reconnection events between two merging islands. Finally, the third regions identify the regions between two diverging island and where typical signature of reconnection is not observed. Electrons in these latter regions additionally show amore » flat-top distribution resulting from the saturation of a two-stream instability generated by the two interacting electron beams from the two nearest reconnection points. Finally, the analysis of agyrotropy shows the presence of a distinct double structure laying all over the lower side facing the higher magnetic field region. This structure becomes quadrupolar in the proximity of the regions of the third type. The distinguishing features found for the three types of regions investigated provide clear indicators to the recently launched Magnetospheric Multiscale NASA mission for investigating magnetopause reconnection involving multiple islands.« less
Authors:
; ;  [1] ;  [2] ; ;  [3]
  1. Center for Mathematical Plasma Astrophysics, Department of Mathematics, K.U. Leuven (University of Leuven), Celestijnenlaan 200B, B-3001 Leuven (Belgium)
  2. PDC Center for High Performance Computing, KTH Royal Institute of Technology, Teknikringen 14, 10044 Stockholm (Sweden)
  3. Center for Integrated Plasma Studies, University of Colorado Boulder, Gamow Tower, Boulder, Colorado 80309-0390 (United States)
Publication Date:
OSTI Identifier:
22493749
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANISOTROPY; COALESCENCE; EARTH MAGNETOSPHERE; ELECTRON BEAMS; ELECTRON TEMPERATURE; ELECTRONS; LAYERS; MAGNETIC FIELDS; MAGNETIC ISLANDS; MAGNETIC RECONNECTION; MAGNETOPAUSE; PLASMA SIMULATION; TWO-STREAM INSTABILITY