Electron vortex magnetic holes: a nonlinear coherent plasma structure

Abstract

We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional PIC 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 short scale lengths in other astrophysical plasmas.

Accepted by Physics of Plasmas

References in corpus (3)

• The dissipation of solar wind turbulent fluctuations at electron scales
• Reconnection and electron temperature anisotropy in sub-proton scale plasma turbulence
• Magnetic field amplification in electron phase-space holes and related effects

Cited by in corpus (10)

• Evidence for Electron Landau Damping in Space Plasma Turbulence
• Magnetospheric Multiscale Observations of Electron Vortex Magnetic Hole in the Magnetosheath Turbulent Plasma
• Observations of kinetic-size magnetic holes in the magnetosheath
• Compressive Coherent Structures at Ion Scales in the Slow Solar Wind
• Kinetic Turbulence in Astrophysical Plasmas: Waves and/or Structures?
• Whistler Waves As a Signature of Converging Magnetic Holes in Space Plasmas
• Large Scale Linear Magnetic Holes with Magnetic Mirror Properties in Hybrid Simulations of Solar Wind Turbulence
• Comparison of linear modes in kinetic plasma models
• Kinetic turbulence in space plasmas observed in the near-Earth and near-Sun solar wind
• In Situ Detection of Kinetic-Size Magnetic Holes in the Martian Magnetosheath