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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 30, issue 4
Ann. Geophys., 30, 711–724, 2012
https://doi.org/10.5194/angeo-30-711-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 30, 711–724, 2012
https://doi.org/10.5194/angeo-30-711-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 19 Apr 2012

Regular paper | 19 Apr 2012

Magnetic field amplification in electron phase-space holes and related effects

R. A. Treumann1,2 and W. Baumjohann3 R. A. Treumann and W. Baumjohann
  • 1Department of Geophysics and Environmental Sciences, Munich University, Munich, Germany
  • 2Department of Physics and Astronomy, Dartmouth College, Hanover NH 03755, USA
  • 3Space Research Institute, Austrian Academy of Sciences, Graz, Austria

Abstract. Three-dimensional electron phase-space holes are shown to have positive charges on the plasma background, which produce a radial electric field and force the trapped electron component into an azimuthal drift. In this way electron holes generate magnetic fields in the hole. We solve the cylindrical hole model exactly for the hole charge, electric potential and magnetic field. In electron holes, the magnetic field is amplified on the flux tube of the hole; equivalently, in ion holes the field would be decreased. The flux tube adjacent to the electron hole is magnetically depleted by the external hole dipole field. This causes magnetic filamentation. It is also shown that holes are massive objects, each carrying a finite magnetic moment. Binary magnetic dipole interaction of these moments will cause alignment of the holes into chains along the magnetic field or, in the three-dimensional case, produce a magnetic fabric in the volume of hole formation. Since holes, in addition to being carriers of charges and magnetic moments, also have finite masses, they behave like quasi-particles, performing E × B, magnetic field, and diamagnetic drifts. In an inhomogeneous magnetic field, their magnetic moments experience torque, which causes nutation of the hole around the direction of the magnetic field, presumably giving rise to low frequency magnetic modulations like pulsations. A gas of many such holes may allow for a kinetic description, in which holes undergo binary dipole interactions. This resembles the polymeric behaviour. Both magnetic field generation and magnetic structure formation are of interest in auroral, solar coronal and shock physics, in particular in the problem of magnetic field filamentation in relativistic foreshocks and cosmic ray acceleration.

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