The Association of Bursts and Penetrating Showers

Local cosmic-ray bursts and penetrating showers have been studied together using an arrangement of ionization chambers and shielded counters. The experiment investigated (1) the occurrence of penetrating showers associated with large bursts, and (2) the occurrence of bursts associated with large penetrating showers. Evidence is presented to show that the bursts are mainly locally generated large electronic cascades. Nearly 60 percent of bursts larger than 25 Bev (about 250 electrons) contained observed penetrating component. The transition effect of penetrating and nonpenetrating bursts was in qualitative agreement with a nuclear cascade process. Bursts of a few hundred electrons contained on the average about 1 percent of penetrating particles. Essentially no penetrating showers of multiplicity over 14 were unaccompanied by fairly large electronic cascades. The consistent association of cascade bursts with penetrating showers and vice versa is in qualitative agreement with present neutral meson concepts. The main experimental work was done at Echo Lake, Colorado (elev. 3260 m).