Statistical study of solar protons, alpha particles, and Z ≥ 3 nuclei in 1967-1968

Comprehensive measurements of protons, α particles, and Z>3 nuclei of E≳0.5 Mev/nucleon obtained with the lunar-orbiting Explorer 35 spacecraft for the period July 20, 1967, to May 14, 1968, are reported. The major results of this study are the following, (a)Protons of E≥0.5 Mev are present (exceeding 1.3 (cm2 sec ster)−1) in the interplanetary medium at least 63% of the time. (b)Protons, α particles and Z≥3 (medium) nuclei always appear together although in variable mixtures. (c)Events with harder proton spectrums have smaller p/α ratios. (d)The α/M nuclei ratio of 20±10 characterizes most events. (e)The event-integrated p/α ratio varies from 10 to 150. (f)There exists a directional anisotropy in the p/α ratio, believed to be observed for the first time. (g)By combining spectroscopic data of Lambert (1967) with the observed α/M ratio, a value of ∼50 for the p/α ratio at the sun is obtained. The data are discussed in the context of particle propagation and properties of the solar source region.