Cosmic Rays and Magnetic Storms

Abstract

HOURLY records of the intensity of cosmic rays have been made during the past year. The apparatus used consisted of a battery of Geiger counters registering about 25,000 threefold coincidences each hour. The circuit used gave a negligibly small number of casual coincidences. No absorbing screens were used, but preliminary experiments with lead showed that the thickness of the counter walls was sufficient to cut out all radioactive rays and the very soft cosmic rays. To count such a rapid rate of coincidences without loss, a Wynn-Williams' scale-of-two counter¹was used. For this circuit the resolving time is so reduced that, at the counting rate of 400 per minute, the number of particles which is missed is not more than one per thousand. The number of pulses recorded by the telephone counter is photographed automatically every hour.