Observations of intense trapped electron fluxes at synchronous altitudes

The concept of flux limiting in the outer radiation belt proposed by Kennel and Petschek (1966) has been tested in a dynamic situation by using data acquired with instruments aboard the SCATHA satellite. A case-by-case analysis of 12 events for evidence of flux limiting under various magnetospheric conditions is made. The reuslts indicate qualitative agreement with the flux limiting theory for all the events studied. Even the quiescent events and hard-spectrum events are consistent with flux limiting. The limiting flux level at any instant appears to depend strongly on the recent history of the trapped electrons and plasma in the outer magnetosphere.