Solar cycle evolution of high-speed solar wind streams

Large amplitude high-speed solar wind streams and streams with maximum speeds in excess of 700 km/sec are far more common in years of declining and minimum solar activity than near solar maximum. Further, the broadest solar wind streams observed directly with space probes during the years 1962-1974 occurred near solar minimum in 1974. Changes in the frequency and nature of solar wind stream structures at the orbit of earth appear to be directly related to the long-term evolution of regions of low density in the solar corona.