Inner source distributions: Theoretical interpretation, implications, and evidence for inner source protons

A new and important source of pickup ions has been recently observed for th e first time, the so-called inner source. We examine properties of inner so urce ions at high heliographic latitudes through analysis of data from the Solar Wind Ion Composition Spectrometer on the Ulysses satellite for a peri od extending through the year of 1994 while Ulysses achieved its southernmo st latitudes. As demonstrated by Gloeckler et al. [this issue], the relativ e abundances of inner source ions resemble those of the solar wind, which i mplies that the dominant production mechanism for the inner source ions inv olves the absorption and reemission of solar wind ions from interplanetary dust grains. A simple transport model is devised that compares favorably to observed distribution functions and provides an important consistency chec k for the previously mentioned production mechanism. The model comparison a lso allows for constraints to be placed on the total dust geometric cross s ection. The observed distribution function of protons reveals a significant contribution from the inner source, but the abundance of inner source prot ons relative to oxygen falls significantly below the universal abundance. W e postulate causes of this low relative abundance. We also find that inner source protons have a sizable pressure and may constitute an important ener getic population in the solar wind, particularly near the their source.