Developing a new model for gradual SEP events: Peak intensities and fluences within 1.6 AU

In order to correctly asses the particle radiation environment that missions like Solar Orbiter or Solar Probe Plus may encounter it is necessary to model the contribution of interplanetary collisionless shocks to particle intensities and fluences of SEP events. Within the Solar Energetic Particle Environment Modeling (SEPEM) Project we developed a method to couple a statistical model of SEP events at 1 AU with the outputs of a physics-based model for the description of gradual SEP events from 0.2 AU to 1.6 AU in the ecliptic plane. This latter model combines 2D MHD simulations of propagation of shocks (from 4 solar radii up to 1.6 AU) with a particle transport model to obtain the intensity-time profiles of 5-200 MeV protons, as seen by different observers. We consider an armada of 98 spacecraft located at 14 longitudes (from W85 to E65 at 1 AU) and at seven radial distances. The observers placed out of 1 AU are sitting along the same interplanetary magnetic field lines passing through the 1 AU-observers. We calibrate the resulting profiles with 1 AU data and we estimate the event fluences and the upstream time-intensity profiles at the other radial distances. We apply this method to a few SEP events and derive the radial variations of the peak intensity and fluence. We discuss the results and propose a way to extend the statistical model to other radial distances.