A search for high-energy solar neutrons

Abstract

Two stacks of G-5 emulsions on a directional device were exposed to cosmic rays at a ceiling altitude of 114 000 ft on July 30, 1966, at Fort Churchill (geographic latitude 58.8 °N and longitude 94.1° W). An attempt to measure the flux of high-energy solar neutrons has been made by inspecting the difference in flux from the direction of the sun and from the symmetrical direction about the zenith. The flux of neutrons has been determined by making observations on the tracks of protons recoiling from elastic collisions of neutrons with hydrogen nuclei present in the emulsions. The preliminary result of the experiment has shown that in the energy region of 20–100 MeV an excess of 1.1 × 10−2neutrons cm−2 s−1from the direction of the sun was observed. On that day the sunspot number was 63, and no major solar flare was reported.