Abstract
For a period of 4 yr near the maximum of solar cycle 21 iron and helium fluxes were measured in the solar wind. The ratio of the summed fluxes from 45,000 spectra is 400 (+50 percent, -30 percent) which is approximately 5 times lower than estimates of the solar surface value. This difference is attributed to the difference of first ionization potentials between the two elements, which leads to a preferential feeding of iron (with a lower ionization potential) into the coronal plasma, whereas helium has a tendency to remain below as a neutral species. A marked increase of the He/Fe ratio is observed in the driver gas following interplanetary shocks. Marginal depletions of helium relative to iron are found at the sector boundaries of the interplanetary magnetic field. 41 references.
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