The Effects of Interplanetary and CME Properties on Solar Energetic Particle Fluences

Among the variable properties that have been identified as influencing the peak intensities and fluences of Solar Energetic Particle (SEP) events are CME properties, solar wind conditions [magnetic field strength (B), turbulence level (dB/B), and solar wind density (np)], and the density of suprathermal seed particles (nST). Motivated by the significant decline in SEP ion fluences in solar cycle 24 compared to those in cycles 22 and 23, we have used the improved Particle Acceleration and Transport in the Heliosphere (iPATH) model to investigate the relative roles of four of these parameters (Vcme, B, (dB2)/B2 and nST) in determining SEP peak intensities, spectral breaks, and event-integrated fluences. We report on the relative importance of these parameters and their possible roles in accounting for solar-cycle variations in SEP properties.