Ionospheric Variations Associated, with Geomagnetic Disturbances

Abstract

Variations in the densities and heights of the ionospheric Es and F2 regions during magnetic storms are studied. At the moderate latitudes in summer solstice and at the equatorial zone, the disturbance variation of the Es in both local time (SD) and storm time (Dst) is obtained by statistical examination, although the individual values of the Es data may not always be accurate.The amplitude of the SD variation of the Es at the moderate latitudes is about 0.5Mc/s in frequency (15% for mean ionized density), and the phase of the variation seems to be opposite to that of the F2.At the equatorial zone, the SD variations of the Es and the F2 regions and the Dst variation for f0F2 are rather peculiar for the phase, compared with those at the moderate latitudes. The geomagnetic SD variation at this zone is also a little different from that in the moderate latitudes.On the other hand, the current system for the SD field is calculated by the dynamo theory, taking into consideration the anisotropic electrical-conductivity. A production mechanism of the Es is supposed, and the possibility that the ionospheric SD variations are due to the effect of a drift by the earth's magnetic field and the electric field of the SD current is discussed.