Solar cosmic rays of July 13, 1961

We present the results of a detailed phenomenological study of the characteristics of the conspicuous increase in the flux of the low-energy protons, observed aboard the State University of Iowa (SUI) satellite Injun 1 after the sudden commencement magnetic storm of July 13, 1961. We have re-examined distinguishing features of this increase in reference to the associated solar, interplanetary, and geophysical phenomena. This study leads us to believe that the observed post-sc increase in the flux of low-energy protons was either the manifestation of a ‘quasi-trapped’ component of solar cosmic rays temporarily confined within the ‘microstructures’ in a blast wave or else these protons were part of the energetic particles being generated on the sun for several tens of hours after the visible traces of the optical solar flare had vanished. It is concluded that the evidence presently available indicates that the latter possibility is perhaps more generally favored by nature. Arguments are presented against the hypothesis that the protons participating in the post-sc increase of July 13 might have been of interplanetary origin.