Relativistic electrons in the Earth’s magnetospheric tail during solar activity minima

Particle fluxes in the Earth’s magnetosphere at great distances from the Earth (20 Re and more) are measured very rarely, though their behaviour is important for understanding the mechanisms of solar particle penetration into magnetosphere. The orbit and equipment of the IMP-8 Earth satellite help to overcome this deficiency to some extent. An analysis of electron fluxes with MeV energies in different parts of the IMP-8’s orbit is performed, both inside and outside the magnetosphere, and upon entering and leaving it. Bursts of electron fluxes are observed in the magnetotail during quiet periods of solar activity. These bursts could be caused by acceleration in the magnetosphere, the penetration of solar and Galactic particles, or electrons from the Jovian magnetosphere.