Geomagnetic variations and ionospheric currents at southern high latitudes

Geomagnetic variations observed at three distances from the southern geomagnetic pole (at CGM latitudes -69.84°, -80.14° and -84.92) are studied and differentiated for season, geomagnetic activity and magnetic local time. Results show that the increase in variations during the local summer season is less significant than the increase in variations associated with higher geomagnetic activity (with Kp 3). Moreover, variations larger than (50) nT occur more frequently at latitude -80.14° CGM than at latitudes -69.84° or 84.92° CGM, have their components along the line between each station and the eccentric dip_pole (located at about geographic latitude 66° S and longitude 129° E) oriented in the sunward direction. This is in agreement with previous observations of sunward polar cup current, here this is a quite frequent feature (with occurrence above 90%) for that specific components, independent of season and geomagnetic activity. In particular the sense of these ionospheric-current components' directions are also independent of the interplanetary magnetic field, which is well known to affect the direction of the total polar cap current. The observations of the H variations at -69.84° CGM are in agreement with the expected auroral oval current pattern, indicating East-West components of ionospheric currents mostly in the westward direction near magnetic loval noon and in the eastward direction near magnetic local midnight sector. At latitudes -80.14° CGM, a reversal is observed for the East-West current components, in agreement with expected polar cap effects form the cusp and the auroral oval. A tendency for a second reversal for the East-West current components is seen at latitude -84.92° CGM, suggesting a rather structured, possible multi-cell, ionospheric current pattern in the southern polar cap.