The effect of convection and adiabatic deceleration on the time to maximum flux in energetic solar particle events

Using a Monte Carlo technique which traces the histories of particles released impulsively at the Sun, we solve the Fokker-Planck equation for the particle transport with an energy-dependent diffusion coefficient. Convection and adiabatic deceleration lead to considerable change in the time to maximum flux when compared with the pure diffusion solution. For a special case of the spectral exponent n of the interplanetary field power spectrum (n=3/2), adiabatic deceleration results in a time to maximum approximately proportional to the inverse of the velocity in a species splitting depending on the charge-to-mass ratio. The results are discussed in the context of recent measurements of heavy ions during a solar flare event