Auroral X-rays, electron bombardment and trapped radiation

Recent measurements of the characteristics of energetic particles incident on the top of the atmosphere, presumably precipitated from the earth's trapped radiation, are discussed. The incident flux varies widely, from 10⁸ to 10¹⁰ particles/cm² sec for electrons. Other characteristics of the flux also vary from event to event, independently of the flux and of each other. During the most intense events, which are the ones which correspond to aurorae, the lifetime of an electron in the trapping region is only a few seconds. Clearly, violent processes go on during such events, so violent as to destroy the effectiveness of the trap. Several mechanisms, including one presented in an appendix to the paper, are examined and it is concluded that no one process accounts for all observations.