Composition of Anomalous Cosmic Rays and Other Ions from Voyager Observations

Abstract

We present energy spectra of e leven cosmic ray elements with energies from ~5 to ~500 MeV/nuc using da1<1 obtained from the Voyager spacecraft in the outer heliosphere from early 1993 to the end of 1998. The lowe ncrgy intensity increases observed in all these spectra arc consistent with the shapes expected 10 be exhibited by primarily singly-<:harged anomalous cosmic rays (ACRs). One o f these elements is Na, which is being repo11ed a~ a member of the ACR component for the first time. We find that the tensity increa5e below ~ 10 MeV/nuc in the Si spectrum in the outer heliosphere is not dominated by re-accelerated solar wind. There is also evidence for a non-ACR component in the energy spectra of Mg. Si. and S observed at I AU by the Wind spacecraft below ~5 MeV/nuc. We see evidence in the energy spectm of Ar in both the inner and outer heliosphere for multiply-charged ACRs above ~360 MeV. Using a fi t to the ACR intensities with a full-drift, two-dimensional numerical model o f the acceleration and propagation of singly-charged ACRs. we present a table of the relative abu ndances of the seed particles of eleven elements m the solar wind 1em1ination shock.

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