Contribution of nonionospheric currents to the quiet daily magnetic variations at the Earth's surface

The quiet day variations in the earth's surface magnetic field caused by the magnetopause, neutral sheet, and ring currents have been calculated. All three model current systems produce variations similar to the ‘average Sq pattern’ but smaller in magnitude. However, the systems combine to produce a 10−γ daily range during magnetically quiet periods. Because of the large observed fluctuations in solar wind parameters (which determine the strengths of these currents), it is suggested that magnetospheric currents may make a significant contribution to the day-to-day variability in Sq.