Movement of theSq foci in 1958

Summary Latitudinal locations of the foci of theSq ionospheric current systems are estimated for each month using geomagnetic data for five international quiet days of each month of the year 1958. It is found that: 1) The pattern of the monthly movement is different in the three sectors chosen for this investigation (North-South American Sector, European-African Sector and Asian-Australian Sector). 2) Regardless of the sector the foci generally seem to move together in the same direction like a rigid system; during the northern summer they shift towards a more northerly latitude than during the northern winter. 3) The positions of the foci differ considerably in adjacent months. 4) The largest movements of the foci are noted in the American sector where the magnetic dip equator is farthest south.Contribution from the Earth Physics Branch No. 453.