The data for all 32 ground-level cosmic-ray events (GLEs) observed from 1942 through 1978 are reviewed, and injection onset times for the 2 GeV protons, 1 MeV electrons, and 100 keV electrons are inferred. Contrary to previous investigations, no compelling evidence is found for a systematic delay in GLE onset times. The most likely time of GeV proton injection onset in these large flares appears to be near the maximum of the first significant microwave peak. GLEs with long delays to onset tend to be small in size. In addition, the data indicate a systematic phase relationship among the injection onsets of the three particle species considered, with the low-energy electron onset times preceding those of the relativistic protons by not more than 5 min, and the relativistic electrons following the GeV protons by not less than 5 min. This phase relationship holds even when the inferred injection times of all three species follow the flare flash phase by more than 20 min. To account for these observations, a picture is suggested in which the earliest observed particles are injected when an outward moving acceleration region at a shock front intersects the open field lines connecting to earth.
No takes yet. Share an insight, caveat, or question.
Cliver et al. (1982) studied this question.