Joint two-dimensional observations of ground magnetic and ionospheric electric fields associated with auroral currents. 5. Current system associated with eastward drifting omega bands

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D. Andre
W. Baumjohann


Magnetograms from the Scandinavian Magnetometer Array (SMA) and ionospheric electric field measurements from the Scandinavian Twin Auroral Radar Experiment (STARE) have been evaluated during the passage of several omega bands (or eastward travelling surges) over Northern Scandinavia around 0400 MLT on 16 February 1977. The eastward motion of the omega bands was a pure E × B drift and was associated with Ps6 disturbances of the east-west component particularly of magnetic and electric fields. The two-dimensional distributions of electric and magnetic disturbance fields strongly support the hypothesis of a three-dimensional current system which is embedded in a rather homogeneous westward Hall current and where north-south aligned localized regions of field-aligned currents, flowing upward close to the omega band's wave-crest and downward east and west of it, are travelling eastward with the omega band. These field-aligned currents are associated with eastward and westward electric field disturbances and southward and northward Hall currents between them. It remains unclear whether these Hall currents close within the ionosphere, i.e. forming counterclockwise and clockwise ellipsoidal Hall current vortices, or if they diverge from the ionosphere as field-aligned currents at the southern and northern boundary of the region that is disturbed by the omega band.

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Andre, D., and W. Baumjohann. 1981. “Joint Two-Dimensional Observations of Ground Magnetic and Ionospheric Electric Fields Associated With Auroral Currents. 5. Current System Associated With Eastward Drifting Omega Bands”. Journal of Geophysics 50 (1), 194-201.
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