A multispacecraft study of the injection and transport of solar energetic particles

Abstract

The November 22, 1977 and December 27, 1977 solar energetic particle (SEP) events observed simultaneously by the Helios and the Voyager space probes and the ISEE 1 satellite are described. The spacecraft instruments indicated flux increases for H, He, and (for November 22) for O and Fe, with the energy range of 0.5-20 MeV per nucleon. It was found that the data can be well fitted by a model based on the spherically symmetric Fokker-Planck equation including convection, diffusion, and adiabatic deceleration, assuming that the radial interplanetary diffusion coefficient increases in proportion to the heliocentric radius to the power of 0.6 and that there is an extended particle injection at the sun. This extended injection is of crucial importance for the event of November 22, where the injection functions are strongly dependent on times associated with a soft energy spectrum.