Neutron monitor and Pioneer 6 and 7 studies of the January 28, 1967 solar flare event

Abstract

A discussion of the January 28, 1967 solar flare event is presented. High energy data from several neutron monitor stations are supplemented by low energy data from the interplanetary space probes Pioneers 6 and 7. A study of the data obtained from these three observation stations widely separated in solar azimuth has shown (1) the most probable location for the responsible flare was ≈ 60° beyond the western solar limb, (2) other than the large emitted particle flux, the phenomena associated with the January 28 activity are not atypical of other solar flare effects, (3) both the ≳ 0.5 GeV and ≳ 7.5 MeV fluxes observed at the earth were isotropic, indicative of particle diffusion across the interplanetary magnetic field lines, (4) the spectral exponent of the differential rigidity spectrum at high energies was - 4.8 ± 0.2, and (5) there was an indication of low energy solar injection prior to the high energy event of January 28. A technique is also described for obtaining the differential rigidity spectral index for an isotropic flux as a function of the relative enhancements of any pair of neutron monitors sufficiently separated in latitude.