ON THE OCCURRENCE RATE OF HIGH-SPEED SOLAR-WIND EVENTS

We have investigated the rate of occurrence of solar wind phenomena ob served between 1972-1984 using power-spectrum analysis. The data have been taken from the high-speed salar wind (HSSW) stream catalogue publ ished by Mavromichalaki, Vassilaki, and Marmatsouri (1988). The power- spectrum analysis of HSSW events indicates that HSSW stream events hav e a periodicity of 9 days. This periodicity of HSSW events is 1/3 of t he 27-day period of coronal holes, which are major sources of solar wi nd events. In our opinion, the 9-day period may be the energy build-up time for coronal hole regions to produce the HSSW stream events.