Authors: RD Strauss (CSR)

Various processes contribute to the longitudinal spread of solar energetic particles, including broad accelerators and transport effects. The relative importance of the different processes, however, differ from event to event and, for a typical event, several of these processes most likely contribute to the observed (generally large) longitudinal spread of solar energetic particles (SEPs). In this presentation we discuss several observations, supported by numerical modelling, that underscores the importance of perpendicular diffusion to the longitudinal spread of these particles. We argue that, for a complete picture of SEP acceleration and propagation, this process must be taken into account. By also investigating the natural variability in the perpendicular diffusion coefficient, we illustrate that this variable process can also contribute to the observed variability of SEP events and manifests itself more prominently in certain events.