HELIORADIUS DEPENDENCE OF INTERPLANETARY CARBON AND OXYGEN ABUNDANCESDURING 1991 SOLAR-ACTIVITY

A comparison of the heliocentric dependence of the relative abundance of low energy (similar to 1 MeV nucleon(-1)) carbon and oxygen on the Ulysses (similar to 3-4 AU) and Voyager 1 and 2 (similar to 35 and sim ilar to 47 AU) spacecraft shows that the C/O abundance ratio is signif icantly smaller at the larger radial distances. This finding is attrib uted to a more abundant seed population for anomalous cosmic-ray oxyge n than for carbon in the outer solar system, where the seed population can be accelerated by shocks in global merged interaction regions. Th e energy spectra of carbon and oxygen at the different locations are a pproximately the same.