Composition Of The Inner Source Measured With The Solar Wind Ion Composition Spectrometer On Ulysses

Abstract

To explain the unexpected discovery of C⁺, the existence of an inner source of pickup ions close to the Sun was proposed. We report on detailed analyses of the composition and the radial and latitudinal variations of inner source pickup ions measured with the Solar Wind Ion Composition Spectrometer on Ulysses from 1991 to 1998, approaching and during solar minimum. We find that the C⁺ intensity drops off with radial distance R as R^-1.53, peaks at mid latitudes and drops to its lowest value in the ecliptic. In addition to C⁺, N⁺, O⁺, Ne⁺, Na⁺, Mg⁺, Ar⁺, S⁺, K⁺, CH⁺, NH⁺, OH⁺, H₂O⁺, H₃O⁺, MgH⁺, HCN⁺, C₂H₄⁺, SO⁺ and many other heavy ions and molecular ions are observed. Possible causes for the unexpected latitudinal variations and the neutral source(s) producing the inner source pickup ions are discussed.