Increase of Horizontal Force caused before Commencement of Geomagnetic Storm
Yanagihara, K.
Abstract
Dst of gradually commenced storm is studied using Sugiura's equatorial Dst during 1961−63. When the time of sharp decrease in horizontal force is taken as a reference point of storm time instead of the beginning vaguely determined, Dst of gradually commenced storm is clear. A gradual increase of horizontal force is found for one day or more before the reference point which is clearly the starting time of main phase. Many examples of SC-storm show also the same gradual increase before ssc. The gradual increase in the initial period may be a substantial character of storm phenomena, except severe isolated storms, without regard to occurrence of ssc.
