Latitudinal reversal of polarization of the geomagnetic sudden commencement

Latitudinal variation of polarization of geomagnetic sudden commencements (sc) observed at geomagnetic latitude range 63°N–79°N is studied by the use of North American IMS magnetometer data from August 1978 to May 1979. Fourteen sc's out of 18 examined show clear polarization reversal between latitudes 64°N and 72°N. Among these, nine change their polarization direction from counterclockwise to clockwise with increasing latitude and the remaining 5 change it in the opposite sense. Clear local time dependence as shown statistically by Wilson and Sugiura (1961) could not be confirmed from this small data set. Their statistical results (Wilson and Sugiura, 1963), however, can be more reasonably interpreted by taking into account the existence of latitudinal polarization reversal described in this paper.