Satellite studies of magnetospheric substorms on August 15, 1968: 5. Energetic electrons, spatial boundaries, and wave-particle interactions at Ogo 5

An examination of measurements of the flux of energetic electrons in the near magnetotail during two well-defined substorms on August 15, 1968, gives evidence that the boundary of the region in which energetic electrons are present moves inward during the growth phase and outward during the expansion phase of a substorm. An estimate of the velocity of inward motion yields ∼10 km sec−1. Pitch angle distributions are examined, and distributions peaked in a direction perpendicular to the magnetic field are shown in this event to be associated with ELF magnetic noise. During the expansion phase an interval of rapidly changing magnetic field is shown to be accompanied by betatron acceleration of electrons.