The SQP magnetic variation, equivalent current, and field‐aligned current distribution obtained from the IMS Alaska Meridian Chain of magnetometers

Abstract

The solar quiet day daily variation (Sqp) in the polar region is studied by using magnetic records on March 12, 1978 (ΣKp = 6−), and on March 25, 1978 (ΣKp = 6−), from the International Magnetospheric Study Alaska meridian chain. The results are somewhat different from those obtained by earlier studies which dealt with an exceptionally quiet day (ΣKp = ∼1+). The results are discussed in terms of the ionospheric current distribution and field‐aligned current distribution, computed on the basis of the Sqp magnetic field vector distribution. On a quiet day the type I and type II field‐aligned currents and the connected ionospheric currents are mostly confined in the dayside half of the polar region. Comparing these current distributions with those on a moderately disturbed day, one can see that both current systems extend along the auroral oval to the nightside half of the polar cap on a disturbed day. It is also shown that it is not justifiable to infer the convection pattern by using the distribution of magnetic vectors (thus by assuming that Sqp variations are caused mainly by the Hall current).