Geomagnetic perturbations at low latitudes observed by Magsat

Geomagnetic perturbations (ΔH, ΔD, ΔZ, and ΔF) at low latitudes are studied by using Magsat data during the mission lifetime from November 1979 through May 1980, and the following characteristics are found: (1) ΔH generally shows negative values larger at dusk than at dawn, and it is in good correlation with the Dst index on both dawnside and duskside. The difference between dawnside and duskside shows good correlation with the AE index, (2) ΔD shows a distinct variation near the dip equator only on the duskside, with a small shift of the base line, (3) ΔZ shows a general tendency of being positive in the northern hemisphere and negative in the southern hemisphere, and (4) ΔF generally shows negative values larger at dusk than at dawn, and it changes sinusoidally with latitude. These characteristics are discussed in relation to ionospheric and magnetospheric currents.