Growth phase of magnetospheric substorms

The term 'magnetospheric substorm ' has According to Akaso[u 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; Akaso[u 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