Rocket observations of stimulated electron acceleration associated with the Trigger Experiment

Abstract

Evidence for a strong enhancement of the electron flux associated with a cesium cloud release from the ‘Trigger’ rocket payload, launched from Esrange on February 11, 1977, will be presented. The up to three orders of magnitude enhancement of the electron flux first appeared some ˜150 ms after the cesium injection and prevailed for about 1 s. A remarkable feature of this enhancement is that it was not only field aligned (at 2 keV) in the downward direction, but also in the center of this electron ‘burst’, field‐aligned in the upward direction. A possible interpretation for the quasi periodic modulation of the 2 keV electron flux in the center part of the ‘burst’, may be that a ‘bunch’ of electrons was locally trapped between two potential barriers. From the bouncing period, the velocity of the 2 keV electrons, and the time dispersion versus pitch angle, the altitude as well as the relative thickness of these potential barriers could be estimated. The altitude and the average parallel electric field strength of the upper (accelerating) potential drop was estimated to be around 500 km and ∼60 mV/m, respectively. The strong field alignment of the upward directed electrons suggests that a reflecting potential barrier was located below the rocket altitude (∼162 km). Although the most evident consequence of the cesium release from particle point of view was the very intense and short‐lived burst of accelerating electrons, there were also indications of a more prolonged effect on the high energy particle population (>40 keV).