Solar flare proton rigidity spectra deduced from cosmic ray neutron monitor observations

The solar flare proton rigidity spectra for several flares occurring between 1967 and 1972 have been deduced from the ground level cosmic ray neutron monitor observations. To obtain consistent agreement for all the ground level events (GLE's) analyzed, the specific yield functions of Lockwood and Webber (1967) must be reduced slightly below P=1.6 GV. The typical spectral indices of solar cosmic rays deduced for GLE's vary from 4 to 6 if the differential spectrum is represented by KP−γ. Only occasionally is the spectrum as steep as 8 or 9. The observed spectral index is independent of the magnitude of the integral solar proton flux above 1 GV.