Magnetic field-aligned plasma currents in gravitational fields

Abstract

Abstract. Analytical models are presented for currents along vertical magnetic field lines due to slow bulk electron motion in plasmas subject to a gravitational force. It is demonstrated that a general feature of this problem is a singularity in the plasma pressure force that develops at some finite altitude when a plasma that is initially in static equilibrium is set into slow motion. Classical fluid models thus do not allow general steady-state solutions for field-aligned currents. General solutions have to be non-stationary, varying on time scales of many periods of a plasma equivalent to the BruntVäisälä frequency. Except for very special choices of parameters, a steady-state solution exists only in an average sense. The conditions at large altitudes turn out to be extremely sensitive to even small changes in parameters at low altitudes. Low frequency fluctuations detected at large altitudes in the polar regions need not be caused by local low frequency instabilities, but merely reflect small fluctuations in conditions at low altitudes.

Spectral properties of electrostatic drift wave turbulence in the laboratory and the ionosphere

“…While rocket data give a reasonably coherent picture of the observed spectral indices, satellite data need further scrutiny. It has recently been suggested (Garcia and Péc-seli, 2013;Garcia et al, 2015) that the ionospheric plasma at high altitudes can be very sensitive to even small lowaltitude plasma variations when a slow bulk electron flow causes field-aligned currents. Spectra observed at high polar altitudes can thus be influenced by distant low-altitude perturbations.…”

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