THE MEAN IONIC CHARGE-STATE OF SOLAR ENERGETIC FE IONS ABOVE 200 MEV PER NUCLEON

We have analyzed the geomagnetic transmission of solar energetic Fe io ns at similar to 200-600 MeV per nucleon during the great solar energe tic particle (SEP) events of 1989 September-October. By comparing flue nces from the Chicago charged-particle telescope on IMP-8 in interplan etary space and from NRL's Heavy Ions in Space (HIIS) experiment aboar d the Long Duration Exposure Facility (LDEF) in low-Earth orbit, we ob tain a mean ionic charge [Q] = 14.2 +/- 1.4. This result is significan tly lower than [Q] observed at similar to 1 MeV per nucleon in impulsi ve, He-3-rich SEP events, indicating that neither acceleration at the flare site nor flare-heated plasma significantly contributes to the hi gh-energy Fe ions we observe. But it agrees well with the (Q) observed in gradual SEP events at similar to 1 MeV per nucleon, in which ions are accelerated by shocks driven by fast coronal mass ejections, and h ence shows that particles are accelerated to very high energies in thi s way. We also note apparent differences between solar wind and SEP ch arge state distributions, which may favor a coronal (rather than solar wind) seed population or may suggest additional ionization in the amb ient shock-region plasma.