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A flare plasma cloud model is proposed which has a characteristic magnetic field asymmetry that develops as a natural consequence of the interaction between the expanding solar plasma region and the spiral magnetic field set up by the solar wind. It is a basic characteristic that leads to an understanding of various solar-terrestrial relationships, such as observed asymmetries in polar cap absorptions and Forbush decreases. These events show pronounced differences, depending on whether the associated flares are east or west. Both a large increase in absorption at the time of storm sudden commencement and a large Forbush decrease are caused almost exclusively by eastern and central flares but not by western flares. The 'east-wesff differences require an asymmetrical trapping of solar proto.n• and an asymmetrieM field configuration relative to the sun-earth line.

Systematic examination of all unusual solar radio and optical emission before the onset of 43 polar‐cap absorption events shows which type of solar activity most frequently precedes PCA. This provides an objective basis for assignment of the solar event most probably associated with each of the individual PCA events. Relations among various characteristics of solar and PCA events are examined. These data present little evidence for association of PCA with solar flares that occur on the far side of the sun, nor do they indicate any significant dependence of occurrence or of delay time of PCA on position of the associated flare. Delay from flare to absorption varies from values of several minutes, appropriate to the energy of the solar particles, up to several hours. A definite relation is found between delay time and phase of the solar cycle, with long delay times near the time of maximum solar activity.

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