Interplanetary magnetic field polarity and low-latitude geomagnetic field

Abstract

The relationship between the low latitude magnetic field and the polarity of the interplanetary magnetic field, inferred by Svalgaard for a period of about 4 solar cycles, is derived and discussed for low and high solar activity conditions. The field reacts differently during the passage of A (away) and C (toward) sectors and, during the passage of sector boundary, the response is substantially different depending upon the nature of the change, i.e.A to C or C to A; a change of sector from A to C is found to be associated with a large depression in the field. It is also observed that the night-time field in low latitudes is best correlated with the AC index and that the correlation, observed throughout the period of 1929-1957, breaks down after 1962. The results computed from Alibag observations are confirmed by an examination of the data from Hermanus and San Juan.