Variation of Sq focus latitudes in the Australian/Pacific region during a quiet sun year

Abstract

The latitudes of the north and south foci of the Sq current system are determined daily during the quiet sun year 1997 using stations in Australia and in China and neighbouring countries. The horizontal magnetic field variation Δ H is corrected for magnetic disturbance by subtracting the Dst index. We examine the day-to-day variations of the focus latitudes and also look for any relation to the strength of the electrojet as measured by Δ H at Baclieu in Vietnam. The day-to-day variability of the focus latitudes is greater in local winter than in local summer. We find the latitudes of the north and south foci are negatively correlated during December solstice months but have no significant correlation during the rest of the year. The seasonal variations of the average latitudes of the foci are determined, using magnetically quiet days, and these broadly agree with previous workers, showing a poleward shift of the northern focus in February and an equatorward shift of the southern focus in November.