Equivalent current systems for the annual and semiannual <i>S</i>_<i>q</i> variations observed along the 210°MM CPMN stations

Abstract

We analyzed ground magnetometer data for the 10 International Quiet Days during 1996–2007. The data were obtained from 19 stations along 210°magnetic meridian (MM) of the Circum‐pan Pacific Magnetometer Network (CPMN) covering both the Northern Hemisphere and Southern Hemisphere. From the daily variations of the geomagnetic field, we deduced the latitude‐local time (LAT‐LT) diagram of the equivalent S q current system, which can be regarded as the superposition of the following three current systems: Sq 0 , Sq 1 , and Sq 2 . The Sq 0 , Sq 1 , and Sq 2 current systems are equivalent current systems for the yearly average, annual variation, and semiannual variation of the S q field, respectively. We have examined temporal and spatial features of these current systems. The principal features are as follows: (1) The total current intensities of the Sq 1 and Sq 2 current systems are about 35% and 15% of that of the Sq 0 current system, respectively. (2) The Sq 0 and Sq 2 current systems have a dayside vortex in each hemisphere, while the Sq 1 current system has a single vortex centered at the equatorial region in the morning sector (∼1000 LT).