A New Model for Solar-Terrestrial Propagation of Solar Cosmic Rays

Abstract

A new solar-terrestrial propagation model is presented for solar cosmic rays, which includes a coronal distribution source of flare particles and the propagation equation for solar cosmic rays in interplanetary space. Based on observations of sunspot group characteristics of a solar cosmic ray flare, two-step coronal transport processes and transport equations are proposed for solar flare particles, which result from the annihilations of sunspots in a sunspot group with magnetic multi-polarities. A coronal distribution of flare particles is obtained, which is consistent with the observational properties relative to coronal transport. During the first step process, which is of about the same duration as the flare impulsive phase, the flaring region is filled nearly uniformly with accelerated particles, it leads to the formation of the fast propagation region (FPR). During the second step process, which follows the impulsive phase, accelerated particles gradully diffuse through ambient corona about the FPR, which are called the slower propagation process, and escape towards interplanetary space. The interplanetary propagation of solar cosmic rays is described by the equation for solar cosmic-ray propagation in an infinite, homogeneous and orthotropic medium. The intensity-time profiles given by numerical calculation of the proposed model are compared with the observations for the event on 24 September 1997 from SOHO. The predicted results give a good fit to the data.