Intensity variations of the equivalent Sq current system along the 210° magnetic meridian

Abstract

The total current intensity (Jtotal) of the equivalent S q current system along the 210° magnetic meridian shows the following variations: (1) solar activity variations, (2) seasonal variations, and (3) day-to-day variations. These variations arise from different physical mechanisms. The main objective of the present paper is to determine the relative amount contributed by each variation to the Jtotal. First, the empirical Sq field model by Yamazaki et al. (2011) is analyzed to examine the impact of solar activity and seasonal variations. The results show that Jtotal changes by ±33% with the change of solar radiation activity in one solar cycle and by ±17% with the change of season. Next, observation data are analyzed to examine day-to-day variations. The daily values of Jtotal from 2000 to 2002 are derived after removal of the solar activity and seasonal contributions. The results show that J total changes by ±14% from day to day. Therefore, we conclude that variations in Jtotal are mainly controlled by solar radiation activity, while the impact of seasonal effects is about half of the solar activity contribution and the impact of day-to-day effects is also about half of the solar activity contribution. Copyright 2011 by the American Geophysical Union.