Composition of the September 2, 1966 solar particle event

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Abstract
Three Nike-Apache sounding rockets were launched from Fort Churchill, Manitoba, Canada to study the composition and the characteristics of the September 2, 1966 solar flare event. These launches occurred approximately 9, 16, and 36 hours following the event. Nuclear emulsions were used to study all the components, namely, the singly, doubly, and multiply charged nuclei emitted in the solar event and propagated within the solar system. The helium nuclei were separated from protons by using grain density and range measurements and from multiply charged nuclei by δ-ray density and range measurements. The multiply charged nuclei were identified as to charge from δ-ray density and range measurements. The energies of these nuclei were determined mainly from their residual range in the emulsion. The energy spectra measured in the event are much steeper than those reported for events in which the composition studies were made previously. The measured ratio of helium to medium (C, N, O, F) nuclei for energies above 12.7 MeV/nucleon in the first flight is 54 ± 8 to 1. This value is in agreement with the previous measurements, which strongly supports the ideas held that the acceleration mechanism does not appreciably alter the spectroscopically observed abundance of the solar photosphere.