Elemental Composition of the Very Local Interstellar Medium as Deduced from Observations of Anomalous Cosmic Rays

We present a new determination of the relative abundances of the interstellar neutral atoms CI, NI, 0 I, and Ar I. These abundances are derived from Voyager observations of the energy spectra of the anomalous cosmic ray- (ACR) component (He, C, N, 0, Ne, and Ar), using a new analysis technique. We find that the abundances of NI, 0 I, and Ar I are in good agreement with solar system abundances, while the abundance of CI is ~1/100 of the solar system value, consistent with the expectation that C is mostly ionized in the local interstellar medium. As we have reported earlier, we find no evidence for charge-changing interactions associated with the heliopause region