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Title: Electron vortex magnetic holes: A nonlinear coherent plasma structure

We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at shortmore » scale lengths in other astrophysical plasmas.« less
Authors:
; ;  [1] ;  [2]
  1. School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)
  2. Multiscale Dynamics, Centrum Wiskunde and Informatica (CWI), Amsterdam (Netherlands)
Publication Date:
OSTI Identifier:
22407995
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 1; 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; ANGULAR VELOCITY; ANISOTROPY; DISTURBANCES; INCLINATION; IONS; MAGNETIC FIELDS; NONLINEAR PROBLEMS; ORBITS; PLASMA; PLASMA SHEET; PLASMA SIMULATION; TEST PARTICLES; TRAPPED ELECTRONS; TURBULENCE; TWO-DIMENSIONAL CALCULATIONS; VORTICES