Electron fluxes at 1000 kilometers associated with the tail of the magnetosphere

Particle detectors on board the Alouette 1 satellite at an altitude of 1000 km occasionally detect electron fluxes at latitudes above the region where the boundary of the outer Van Allen radiation zone normally occurs. The latitude profiles of the electron fluxes are usually in the form of a fairly narrow spike, and some of the events have extremely high intensities; directional intensities of electrons above 40 kev approaching 109 cm−2 sec−1 ster−1 have been observed. The high latitude electron fluxes are found preferentially on the night side of the earth on lines of force which presumably connect to the ‘tail’ of the magnetosphere and at times when enhanced electron fluxes are observed in the outer radiation zone. It is suggested that electrons generated in the tail of the magnetosphere may form an important source of electrons for the outer radiation zone.