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Equatorially-confined warm trapped ions at 3-5 RE M. Yamauchi Where? ~4 RE, confined near the equator (Cluster perigee) Species? H+ and He+ of 20 eV ~ keV (CIS energy range) Energy? Pancake-like trapped ions (cf. Olsen et al., 1987) In this work: First time to examine features for > 50 eV New results: ring-like Ion distribution + temporal change Van-Allen radiation belt Cluster satellites Contamination Contamination from radiation belt MeV particles is always a problem at perigee (equator) for Cluster. The contamination is near 90° pitch angle at perigee. But we can yet identify.... AE=small AE=quiet Equatorial trapped 100 eV H+ divide by sectors 1 SC motion 2 4 5 8 7 spin axis equator H+ & He+ signatures Only in the direction Confined near equator Ring distribution or Heated distribution? equator Flattened gyrotropic distribution. difficult to check “ring vs hot” dist fn ~ exp[-(v-u0)2/T] dv3 ~ E1/2 exp[-(√E-√E0)2/T] dE flux ~ E exp[-(√E-√E0)2/T] dE energy flux (JE) ~ E2 exp[-(√E-√E0)2/T] dE check SC-1 HIA covers low energy 1.00E+11 1.00E+10 1.00E+09 1.00E+08 1.00E+07 1.00E+06 1.00E+05 1.0 para(H 1278) perp(He 45) 10.0 100.0 perp(H 45) para(ion 1278) 1000.0 para(He 1278) perp(ion 45) difficult due to contamination statistics (only 2001-2002) The observation probability ~ 35-45% (more in noon/dusk than night-dawn) statistics (continued) He+ energy : Selected all “intense” H+ signature (> 3·106 keV cm-2s-1str-1keV-1) in traversals when He+ channel is not severely contaminated. Total 29 traversals. * He+ energy >> H+ energy : 10 events * He+ energy ~ H+ energy : 6 (H+ contamination?) * Without He+ signature : 13 events Energy ratio between He+ and H+ varies (new!) Dominated by H+ with variable content of He+ (mostly < 5%) multi-spacecraft equator Energy-time dispersion (new!) Appearing in 40 min (new!) equator equator The energy time dispersion indicates a drift from a remote source (magnetic drift = energy dependent). The difference in the drift speed between 150 eV ions and 30 eV ions ~0.04 MLT/h at 4 RE. At 17 MLT, drift takes about 3 min (time lag in the dispersion in SC-3) to travel 0.04 MLT. Drift time is expected to be 1 hour. Agrees with the sudden appearance in 40 min. statistics (continued) Energy-time dispersion: out of the same 29 events, 5 events is with clear dispersion (not often) Summary (1) Non-thermal ring distribution rather than pancake distribution. (2) Energy ratio of the ring between He+ and H+ = 1~10. (3) Some events show energy-time dispersion, indicating the drift. (4) The time scale of the development ~ 1 h. (5) Pitch angle ~ 90° for also > 30 eV. (6) Observation probability at 4~4.5 RE is ~ 40-45% in noon and dusk sectors and about 20-25% in the night-to-dawn sector. (7) Dominated by tens eV H+ with variable content of He+. The He+/H+ ratio is much less than 5% for the majority of the cases. (8) Co-located with wave-defined equator Future work composition & wave (1) He+ is sometimes seen, but normally less that 5% of H+ (2) (n+(1/2))fce wave is accompanied