Direct observations of dumping of electrons at 1000‐kilometer altitude and high latitudes

Quiescent dumping of electrons with energy above 40 kev in intensities of the order of 104 particles (cm2 sec ster)−1 was detected by the Injun I satellite at altitudes about 1000 km and high latitudes around July 1, 1961. In 16 passes between longitudes of 230°E and 340°E, the angular distribution of electrons about the magnetic vector B showed there was dumping in every one of 8 passes between 1200 and 1500 local time, and in only one of 8 passes between 1900 and 2300. When there was no dumping, the directional intensity of electrons at ∼20° from the normal to B was less than 1 per cent of that normal to B. When there was dumping, the corresponding value was of the order of 100 per cent, and the intensity at about 50° from the normal to B was of the order of 10 per cent of that normal to B. Appreciable intensities of electrons were backscattered. Dumping was seen over very wide ranges of latitude between L∼2 and L∼10 and was uncorrelated with Kp. It is pointed out that the dumped electrons may be either new, freshly injected or accelerated particles, or they may be old, formerly trapped particles, which were perturbed in their orbits. The obervations are further evidence that acceleration mechanisms must occur frequently at altitudes above 1000 km.