Equivalent current systems for the annual and semiannual Sq 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 Sq current system, which can be regarded as the superposition of the following three current systems: Sq0, Sq1, and Sq2. The Sq0, Sq1, and Sq2 current systems are equivalent current systems for the yearly average, annual variation, and semiannual variation of the Sq 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 Sq1 and Sq2 current systems are about 35% and 15% of that of the Sq0 current system, respectively. (2) The Sq0 and Sq2 current systems have a dayside vortex in each hemisphere, while the Sq1 current system has a single vortex centered at the equatorial region in the morning sector (∼1000 LT).