The time variations of solar cosmic rays during July 1959 at Minneapolis

Abstract

Abstract : The cosmic ray particles followed directly the appearance of three large solar flares occurring on July 10 at 0210 UT, on July 14 at 0325 UT, and on July 16 at 2114 UT. At Minneapolis the cosmic ray events were well separated. Each flare was followed, in from one to two days, by a strong geomagnetic disturbance during which the main intensity of the cosmic rays appeared. The solar cosmic ray intensity at Minneapolis dropped to zero at the termination of each period of geomagnetic activity, and cosmic ray levels remained at the galactic background until the next event began. However, precursor effects and many other fluctuations were observed during the storms. The time variations observed at Minneapolis are not characteristic of the polar cap time variations. In the polar regions prompt effects were noticed at the time of the flares and also continuous large intensities which decayed slowly for many days and were unrelated to geomagnetic activity. (Author)