Coronal propagation of low-energy solar protons

The onset times at 1 AU of solar protons produced by discrete flare events are investigated as a function of solar flare longitude and particle energy for protons of energy 0.6–25 Mev. The results are interpreted in terms of particle transport in the solar corona; a coronal diffusion coefficient κc ≈ 3 × 1018 cm²/sec at an altitude of ∼5Rs above the photosphere would explain the observations quite well. This value of κc is consistent with the coronal diffusion coefficient determined by Fisk and Schatten (1972) from considerations of the azimuthal spread of solar particles during the decay phase of several solar particle events.