Magnetic Storm-Related Energetic Electrons Penetrating into the Magnetosphere, Deduced from Ground-Based Measurements of Resonant Waves.

Abstract

Energetic electrons observed by the NOAA-6 satellite are compared with the LF whistlermode signals from a Decca navigation station (Biei, L = 1.54, fc = 85.725 kHz), measured in the magnetic conjugate area of the transmitter around Birdsville, Australia. These electron data are also compared with VLF/ELF emissions observed at Moshiri (L = 1.57) and Kagoshima (1.2). The VLF/ELF emissions occurred almost simultaneously with enhanced amoral electrojet (AE) activities. The intensity increase of the LF signals were the largest on one day after the maximum depression phase of Dst, and the intensity peaks appeared with time delays behind enhanced AE activities. These indicate that energetic electrons associated with enhanced AE activities, rapidly penetrate into the plasmapause latitude, where they genarate VLF/ELF emissions by cyclotron resonance interactions. Futhermore, energetic electrons of 50-100 keV invade with time delays deep into the low-L shell region below -2, where the wave growth of the LF signals may be caused by additional injection of these electrons, superimposed on energetic electrons more than 30 keV penetrating at the maximum D,t phase. So, the penetration of energetic electrons deep into the magnetosphere may be deduced from ground-based measurements of resonant waves at low latitudes.