Low altitude observations of the energetic electrons in the outer radiation belt during isolated substorms

The low energy (1–20 keV) detector registering particles onboard the polar-orbiting low altitude (~ 850 km) DMSP-F2 and -F3 satellites also records high energy electrons penetrating the detector walls. Thus we can study the dynamics of this electron population at L = 3.5, during isolated periods of magnetospheric substorms identified by the indices of auroral electrojet (AE), geomagnetic (K_p) and ring current (D_st). Temporal changes in the electron flux during the substorms are observed to be an additional contribution riding over the top of the pre-storm (or geomagnetically quiet-time) electron population ; the duration of the interval of intensity variation is observed to be about the same as that of the enhancement of the AE index. This indicates the temporal response of the outer radiation belt to the substorm activity, since the observation was made in the “horns” of the outer radiation belt. The observed enhanced radiation at low altitude may associate with the instantaneous increase and/or dumping of the outer radiation belt energetic electrons during each isolated substorm activity.