Abstract
The evolution of the ring current for the September 4-7, 1984 storm is studied with data from the Medium Energy Particle Analyzer (MEPA) on the AMPTE/CCE spacecraft. From an examination of particle pressures and current densities, it is found that the leading and trailing edges of particle injections are associated with depressions and enhancements of westward current densities, respectively. The separation of the locations for the maximum particle presure and for the most intense westward ring current density can be several earth radii apart. Based on the ion composition measurements which cover the bulk of the ring current population, the contribution of the 0+ ions to the westward ring current density is estimated to be no more than ~25% for this magnetic storm.
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