Growth phase of magnetospheric substorms

The term magnetospheric substorm has According to Akasou et al. [1966a, the sub-been used recently to describe the collection of storm has two characteristic phases, an expan-phenomena that occur throughout the magneto- sion phase and a recovery phase. For magnetic sphere at times of auroral and magnetic sub- observatories near midnight a northward expan-storm activity e.g., Brice, 1967; McPherron sion of auroral and magnetic disturbance et al., 1967; Coroniti et al., 1968. This concept causes an obvious change in sign of the vertical is an extension of the ideas of Akasofu and component as the disturbance passes overhead co-workers, who through extensive surface Akaso[u et al., 1966b. Similarly, a station observations of auroral and magnetic distur- several hours before midnight experiences a bances developed models of the auroral sub- very sudden decrease in the horizontal corn-storm Akasof•, 1964 and the polar magnetic ponent as the westward surge passes overhead substorm Akaso[u et al., 1965; Akaso•u et al., [Akaso•u et al., 1966a. Stations still earlier, 1966a; Akasou and Meng, 1969. In these near dusk in a region normally dominated by phenomenological models the authors were able positive disturbances in the horizontal compo-to show that various features of the aurora nent, experience a negative indentation [Meng