Annual Variation of the Geomagnetic Field in Polar Regions (b. Electric Fields and Current System) (Proceedings of the First Symposium on Coordinated Observations of the Ionosphere and the Magnetosphere in the Polar Regions (Part I))

Abstract

The annual variations of the geomagnetic field H and Z are studied by means of the data from worldwide stations during 1957-1964. The amplitudes and phases of the annual variations change smoothly with geomagnetic latitudes, except for the data within the auroral zones. The amplitudes of the annual variations of H and Z in the polar regions show a clear dependence on the solar cycle. The solar-cycle modulation of the amplitudes is in approximate proportion to the geomagnetic activity rather than to the sunspot number. The modulation of H is different from that of Z in some years. The amplitudes of the annual variations of H and Z in polar regions depend clearly on the north-south component of interplanetary magnetic field, B_z. When B_z is southward the amplitudes are larger in comparison with the cases of northward B_z. The B_z -dependence of the annual variation amplitudes is greater for H than for Z