Statistical roles of storms and substorms in changing the entire outer zone relativistic electron population

Since storms/substorms can lead to flux enhancements of relativistic electrons (E > 500 keV) in one region of the outer zone (L ∼ 2–7) and simultaneously to flux decreases in another region, the final effects of storms/substorms on changing the entire outer zone relativistic electron population are indicated by the total flux variation of the entire outer zone relativistic electrons. The total flux of the relativistic electrons is the summation of their omnidirectional integral fluxes over the entire outer zone. By analyzing the total flux variations of relativistic electrons in the entire outer zone during about 18 storms from August 1990 to March 1991, this paper investigates the statistical relationships between the total flux variations of the entire outer zone relativistic electrons and the intensities of storms/substorms. The statistical results indicate that the primary impact of a storm development is the net loss of relativistic electrons from the entire outer zone via the main phase losses of relativistic electrons, whereas the continuous intense substorm activity (average AE > 200 nT) can lead to the net increases of the relativistic electrons in the entire outer zone. Furthermore, the more intense the substorm activity, the larger the increases of the relativistic electrons, indicating that the continuous intense substorm activity can effectively supply relativistic electrons for the entire outer zone. Since the net increases of the relativistic electrons usually occur during the continuous intense substorm activity, the effective acceleration of the relativistic electron is correlated with the continuous intense substorm activity, e.g., the stochastic acceleration of electron by whistler mode chorus waves.