The sources of large-scale heliospheric disturbances

Observations on a grid of 900 radio sources were used to map and to track large-scale structures in the solar wind at distances of 0.6-1.5 AU from the Sun. Most of the disturbances were shells of enhanced density followed by high-speed streams lasting for several days, although more stable corotating interaction regions were also observed. Ninety-six disturbances were mapped during Aug. 1978-Sept. 1979, and those of the erupting stream-type were usually accompanied by shocks and geomagnetic activity if they encountered the Earth. Back-projection to the Sun indicated sources that were always associated with coronal holes. Possible associations with solar flares and disappearing filaments occurred, but on many occasions, no flare or filament activity was evident anywhere on the disk within a suitable time interval. It is concluded that erupting streams are transients generated by coronal hole activity. Evidence is presented which suggests that coronal mass ejections of the curved-front variety may be identified with these erupting streams.