Elemental composition of the inner source pickup ions

Observations of the composition of inner source pickup ions in the solar wi nd, from the Solar Wind Ion Composition Spectrometer on Ulysses, are presen ted. The composition is similar to that of the solar wind and, in particula r, contains volatile elements such as neon. These observations suggest stro ngly, and perhaps conclusively, that inner source pickup ions result from s olar wind particles that are embedded in dust grains and then released. Our observations also suggest that inner source pickup ions may be an importan t source for particles accelerated at shocks surrounding corotating interac tion regions since the resulting composition will resemble that of the sola r wind, as is observed. Mechanisms are described whereby inner source picku p ions can be preferentially injected into die shock acceleration mechanism .