An Increase of the Primary Cosmic-Ray Intensity Following a Solar Flare

An increase of 15.4±{}4.3 percent has been detected in the intensity of cosmic rays at altitudes between 95,000 and 100,000 feet, occurring approximately 19 hours after the commencement of the outstanding solar flare of May 10, 1949. The observations were conducted with a quadruple-coincidence counter train inclined at a zenith angle of 60^∘{}, and containing an interposed absorber of 1 cm of Pb. Complications introduced by atmospheric absorption, possible directional asymmetry, and multiplicative effects preclude a precise evaluation of the increase in terms of absolute primary particle intensity. The effect of the particles emitted by the sun during the chromospheric eruption does not manifest itself at altitudes below approximately 55,000 feet.