Propagation of Energetic Solar Particles.

Data are compiled for 52 polar cap absorption (PCA) events and 14 events in which solar particles of relativistic energies were detected at ground level (GLE). In particular, evidence is sought that these particles are guided along magnetic lines of force joining the earth and the sun, curved because of solar rotation. In this case, one expects particles to reach the earth more frequently and more promptly from flares located in the sun's western hemisphere. For ground-level events, a strong western excess is found, with arrival of particles at the earth delayed by a shorter time after western flares. Particles of lower energy, associated with PCA, fail to show this effect. PCA events without GLE occur most frequently with central flares, without significant western excess. Delay times are shorter for central flares than for western flares, with no significant east-west difference. Thus, PCA data are inconsistent with guidance in an extensive curved solar field. Particles in both energy ranges show considerable increase in delay time with approach toward maximum of the solar activity cycle, but only GLE decrease in frequency of occurrence, relative to other forms of solar activity, near maximum.