Three-Dimensional Potential Structure Associated with Birkeland Currents

  1. Thomas A. Potemra
  1. Lars Block

Published Online: 21 MAR 2013

DOI: 10.1029/GM028p0315

Magnetospheric Currents

Magnetospheric Currents

How to Cite

Block, L. (1984) Three-Dimensional Potential Structure Associated with Birkeland Currents, in Magnetospheric Currents (ed T. A. Potemra), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM028p0315

Author Information

  1. Department of Plasma Physics, Royal Institute of Technology, S-100 44 Stockholm, Sweden

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1984

ISBN Information

Print ISBN: 9780875900551

Online ISBN: 9781118664131

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Keywords:

  • Magnetospheric currents—Congresses;
  • Plasma instabilities—Congresses

Summary

The U-shaped equipotential structures believed to exist above auroral arcs with upward Birkeland currents pose certain problems in terms of particle, momentum and current conservation. Supply of electrons must cover losses due to precipitation. The supply mechanism must be consistent with the observed energy gain and precipitation field-alignment.

Three-dimensional models of the potential structure which may account for the above requirements are discussed. Particles can be injected into the structure along equipotential surfaces, both from the ends of the Birkeland current sheet and sideways by means of an electric field component tangential to the sheet. The generator can inject particles sideways through equipotential surfaces against the electric field. These particles carry the perpendicular current, but they can only to a limited extent carry the Birkeland currents, which are mostly carried by ambient particles pushed away by the space charge generated parallel electric field. A consequence of this is that especially a thermo-electric generator replaces cold ambient electrons by hot gradient-drifting populations.

The nature of the parallel electric field is also discussed. The observed current sheet (or arc) thickness is inconsistent with a uniformly distributed parallel electric field. A field concentrated in a single strong double layer is inconsistent with the observed precipitation spectrum with substantial fluxes of electrons with energies below the total parallel potential drop. The multitude of weak double layers and solitons seen on the S3-3 satellite seems to agree with known facts.