Midlatitude Auroral Arcs of 6300 Å (O I) and the Concurrent Ionospheric Current System


  • M. Okuda,

  • T. Old,

  • J. S. Kim


A multiple midlatitude 6300-Å auroral arc occurred during the recovery phase of a geomagnetic storm on March 8/9, 1970. Variations of the arcs were characterized by a southward shift in position and by a diminution in intensity with time before midnight. During the recovery phase of the storm, well-defined magnetic baylike disturbances occurred. The vairations in both position and brightness of the concurrent arc were strongly correlated with changes in the H and D components of these geomagnetic field deviations. An equivalent current system is determined from these baylike disturbance fields observed at twenty-six magnetic observatories for periods when the correlation was strongest. The current system found is similar to that of the DP 1 field, with a superimposed DP 2 field. The changes in these fields that are associated with the bayklie disturbances are presented to account for the transient variations observed in the intensity and position of the midlatitude auroral arc.