New Solution of Diffusion-Advection Equation for Cosmic-Ray Transport   Using Ultradistributions
  In this paper we exactly solve the diffusion-advection equation for cosmic-ray transport. With this purpose we use the Theory of Ultradistributions of J. Sebastiao e Silva, to give a general solution for this equation. From this solution, we obtain several approximations as limiting cases of various situations of physical and astrophysical interest. One of them involves Solar cosmic-rays' diffusion. 
M. C. Rocca, A. Plastino, A. R. Plastino, A. L. De Paoli
math-ph astro-ph.HE cond-mat.stat-mech math.MP