Recordings of solar protons during October 26-29, 1968

The composite events causing increased influx of solar particles during October 26-29, 1968 are studied using data from the polar orbiting ESRO IA satellite. Details on protons of 0.1-10 MeV are presented, and their interplanetary propagation characteristics discussed. Diffusion model fit to the prompt event commencing October 26, suggests an interplanetary diffusion coefficient for 200-350 keV protons of (2.8π+0.7).1020cm2s-1. The most likely parent flare for this event is the 1N flare of 0119 UT October 26, occuring in McMath plage region 9740 at 32 deg E solar longitude. The slow decay of the event is then accounted for by co-rotation effects. The flares occurring in the same solar region on October 27 and leading to the delayed events of October 29, did not result in prompt events seen near the Earth, showing the great variability in energetic particle propagation conditions of interplanetary space. (auth)