Solar proton flux enhancements at auroral latitudes

Flux enhancements of solar protons at auroral latitudes have been studied for the April 1969 solar event. It is concluded that low-energy (∼1 MeV) proton intensities at these latitudes can exceed the intensity in interplanetary space. The position of the solar proton knee latitude as a function of local time and the observation that pitch angle distributions are isotropic above the knee latitude lead to the further conclusions that the proton enhancements occur on closed field lines and that the lifetime of the protons in this region is less than a few minutes.