Space Science Reviews

, Volume 42, Issue 3, pp 295–311

Field-aligned (Birkeland) currents

  • Thomas A. Potemra

DOI: 10.1007/BF00214990

Cite this article as:
Potemra, T.A. Space Sci Rev (1985) 42: 295. doi:10.1007/BF00214990


Following earlier suggestions of Edmond Halley and Anders Celsius for the “magnetic behavior” of auroral phenomena, Kristian Birkeland discovered in his polar expeditions of 1902–03 that large-scale electric currents were associated with the aurora. He was also the first to suggest that these currents originated far from earth and that they flowed into the upper polar atmosphere and out of it along magnetic field lines; the existence of such field-aligned currents was widely disputed until satellite and rocket-borne instruments confirmed their permanent existence. The importance of these “Birkeland currents” to the coupling between the magnetosphere and the polar ionosphere is emphasized by their intensity, which ranges between 106 and 107 amperes, and by the energy which they dissipate in the upper atmosphere, which can exceed by a considerable factor the energy dissipated there by auroral particles. The large- and small-scale average properties of field-aligned currents, determined from spacecraft observations, are reviewed here.

Copyright information

© D. Reidel Publishing Company 1985

Authors and Affiliations

  • Thomas A. Potemra
    • 1
  1. 1.The Johns Hopkins University Applied Physics LaboratoryLaurel