R. A. Treumann, W. Baumjohann
Three-dimensional electron phase space holes are shown to be 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 ExB, 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 is 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.
View original:
http://arxiv.org/abs/1202.5428
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