The Evolution of Arguments Regarding the Existence of Field-Aligned Currents
- Thomas A. Potemra
Published Online: 21 MAR 2013
Copyright 1984 by the American Geophysical Union.
How to Cite
Dessler, A. J. (1984) The Evolution of Arguments Regarding the Existence of Field-Aligned Currents, in Magnetospheric Currents (ed T. A. Potemra), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM028p0022
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1984
Print ISBN: 9780875900551
Online ISBN: 9781118664131
- Magnetospheric currents—Congresses.;
- Plasma instabilities—Congresses
We did not arrive at our present understanding of Birkeland (magnetically-field-aligned) currents by a direct, logical course. The story is rather more complex. Starting at the end of the 19th century, the Norwegian scientist Kristian Birkeland laid out a compelling case, supported by both theory and experiment, for the existence of field-aligned currents that cause both the aurora and polar geomagnetic disturbances. Sydney Chapman, the British geophysicist, became the acknowledged leader and opinion maker in the field in the decades following Birkeland's death. Chapman proposed, in contradistinction to Birkeland's ideas, equivalent currents that were restricted to flow in the ionosphere with no vertical or field-aligned components. Birkeland's ideas may have faded completely if it had not been for Hannes Alfvén, who became involved well after Chapman's ideas gained predominance. Alfvén kept insisting that Birkeland's current system made more sense because field-aligned currents were required to drive most of the ionospheric currents. I became personally involved when Zmuda et al.  submitted to the Journal of Geophysical Research a paper reporting satellite data showing magnetic disturbances above the ionosphere that were consistent with field-aligned Birkeland currents, but which they did not interpret as being due to such currents.