Evidence of Solar-Cycle Variations in the Solar Wind

Solar-wind observations are presented from 1965 July through 1971 June that show the first evidence for long-term variations in the solar wind associated with changes in the solar cycle. The observations indicate that the frequency of high-speed streams in the solar wind and their duration vary over the solar cycle. There are more days associated with high-speed streams during solar maximum than during solar minimum. The yearly average of the solar-wind speed varies over the solar cycle and is highest at solar maximum. These measurements also provide the first dfrect observational evidence for changes in the solar wind which can account for the solar-cycle modulation of the cosmic-ray intensity. Subject headings: cosmic rays solar activity - solar wind