Storm time changes of geomagnetic field at Magsat altitudes (325–550 km) and their comparison with changes at ground locations

The values of H, X, Y, and Z at MAGSAT altitudes were first expressed as residuals ΔH, ΔX, ΔY, and ΔZ after subtracting model values HMD, XMD, YMD, and ZMD. The storm time variations of ΔH showed that ΔH (dusk) was larger (negative) than ΔH (dawn) and occurred earlier, indicating a sort of hysteresis effect. Effects at MAGSAT altitudes were roughly the same (10% accuracy) as at ground, indicating that these effects were mostly of magnetospheric origin. The ΔY component also showed large storm time changes. The latitudinal distribution of storm time ΔH showed north‐south asymmetries varying in nature as the storm progressed. It seems that the central plane of the storm time magnetospheric ring current undergoes latitudinal meanderings during the course of the storm.