Abundance differences in solar wind double streams

Abstract

Eight examples of persistent double ion streams with simultaneously resolved protons and alpha particles have been found in the 1971 and 1972 data from the Los Alamos plasma analyzer on IMP 6. The proton streams are observed to have greater velocity separations than their alpha particle counterparts and the secondary stream is the higher velocity stream in each of these examples. Helium to hydrogen abundance ratios for the two streams observed simultaneously differ by up to a factor of ∼ 4; the average is 2.3. The secondary, higher velocity stream usually has the larger fraction of helium. Selection criteria may bias these results to some degree. Observations of double streams at 1 AU with large abundance differences in the separate streams provide evidence that their origin is in a corona with an inhomogeneous distribution of helium, although the evidence may not be considered conclusive at present. Several conceptual models are suggested for the formation of double streams which account for these abundance differences.