Transport of Solar Flare Protons-Comparison of a New Analytic Model with Spacecraft Measurements

Abstract

An analytic solution has now been obtained to the complete Fokker-Planck equation including the effects of convection, interplanetary deceleration and acceleration, corotation, and anisotropic diffusion with κ∣∣ constant and with κ⊥∝r^2. With the boundary of the diffusing region at 2.3 AU, a solar wind velocity of 400 km sec^(-1), κ∣∣ ~7x10^(20) cm^2 sec^(-1), and impulsive injection on the line of force connecting to the earth, the solution yields a time to maximum for the particle flux of ~10 h and an exponential decay time of ~25 h. Several solar flare particle events have been observed with the Caltech Solar and Galactic Cosmic Ray Experiment on 0G0-6. Detailed comparisons of the calculated time dependence of the fluxes with these observations of 1-70 MeV protons show that the model adequately describes both the rise and decay times, indicating that κ∣∣ = constant is a better representation of conditions inside 1 AU than is κ∣∣ ∝r.