Electric Fields and Currents Observed by S3-2 in the Vicinity of Discrete ARCS

  1. Thomas A. Potemra
  1. William J. Burke

Published Online: 21 MAR 2013

DOI: 10.1029/GM028p0294

Magnetospheric Currents

Magnetospheric Currents

How to Cite

Burke, W. J. (1984) Electric Fields and Currents Observed by S3-2 in the Vicinity of Discrete ARCS, in Magnetospheric Currents (ed T. A. Potemra), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM028p0294

Author Information

  1. Usaf Geophysics Laboratory, Hanscom AFB, MA 01731

Publication History

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

ISBN Information

Print ISBN: 9780875900551

Online ISBN: 9781118664131



  • Magnetospheric currents—Congresses;
  • Plasma instabilities—Congresses


The high time resolution of the electric and magnetic field detectors on the polar orbiting satellite S3-2 made it possible to examine the details of auroral events down to discrete-arc scales. Depending on the instantaneous look direction of an electron detector, information about field-aligned accelerations above the satellite could also be obtained. Case studies of four arc events, three in the auroral oval and one in the polar cap, have been completed.

Field-aligned currents associated with arcs in the auroral oval appeared as matched pairs of oppositely directed current sheets. Magnetic deflections, almost exclusively in the east-west direction departed from and returned to baselines established by the large-scale Region 1/Region 2 currents. The upward currents had intensities of up to 145 μA/m2 and were carried by electrons that were accelerated through field aligned potential drops. The relationship between j and Φ is not inconsistent with predictions of a laminar flow model. The most intense return (downward) currents were in the 10 to 15 μA/m2 range. At satellite altitudes near 1000 km, these currents approximate the critical limit for current driven, ion cyclotron instabilities. The arc in the polar cap was sun-aligned and was found in a region of intense convective shear, with the electric field pointing toward the center of the arc. The field-aligned currents consisted of three sheets; two with currents flowing into and one out of the ionosphere. The upward current was carried by polar-rain electrons that had undergone a field-aligned acceleration of approximately 1 kV.