Suprathermal O+ and H+ ion behavior during the March 22, 1979 (CDAW 6), substorms

We present measurements of energetic (approx.130 keV) O/sup +/ ions in the earth's magnetosphere during the two Coordinated Data Analysis Workshop 6 substorms on March 22, 1979. The behavior of thermal and suprathermal H/sup +/ (10--130 keV) and suprathermal He/sup + +/ (30--130 keV/e) ions is also discussed. The observations were made with the University of Maryland/Max-Planck-Institut ultralow energy charge analyzer (ULECA) sensor on ISEE 1 at geocentric distances approx.16 to 7 R/sub E/ in the earth's magnetotail. Approximately 15 min before the 1054 UT onset of the first substorm, energetic O/sup +/ ions are observed streaming tailward. H/sup +/ and He/sup + +/ ions at all energies were generally streaming tailward from approx.1059 to 1115 UT, consistent with the presence of a near-earth neutral line during this interval. From 1117 to 1124 UT the H/sup +/ and He/sup + +/ ions were observed flowing earthward, suggesting that at approx.1117 UT the neutral line retreated tailward. A brief interval in the southern tail lobe, from approx.1124 to 1126 UT, was highlighted by an intense O/sup +/ beam streaming tailward; the O/sup +//H/sup +/ ratio at 130 keV was 7 +- 2. This suggests that high energy O/sup +/ ions maymore » be accelerated directly out of the ionosphere. The recovery phase of the first substorm began a few minutes later and was characterized by large intensities of nearly isotropic suprathermal ions. The O/sup +//H/sup +/ differential intensity ratio at 130 keV was quite large (approx.1) during the recovery phase of both substorms.« less

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