GEOMAGNETIC POLAR CAP INDEX (from SGD Explanation of Data Reports)

Geomagnetic Polar Cap (PC) Index -- PC is an index for magnetic activity in the (P)olar (C)ap. It is based on data from a single nearpole station, and aimed to monitor the polar cap magnetic activity generated by such solar wind parameters as the southward component of the interplanetary magnetic field (IMF), the azimuthal component of the IMF (By), and the solar wind velocity v. The station Thule, located in the village Qaanaaq in Greenland at 86.5 geomagnetic invariant latitude, fulfills the requirement of being close to the magnetic pole in the northern hemisphere. The station Vostok at 83.3 does the same in the southern hemisphere. The PC index is derived independently for these two stations.

The PC-index is based on an idea by Troshichev et al. (1979) and developed in papers by Troshichev and Andrezen (1985), Vennerstrom and Friis-Christensen (1989), Troshichev et al. (1988), Vennerstrom (1991), and Vennerstrom et al. (1991). Earlier data for 1975-1982 appear in Troshichev et al. (1991). The data from 1975 to 1993 are published in Report UAG-103. Monthly plots from Thule appear regularly in SGD since October 1993.