Solar energetic particle event onsets at different heliolongitudes: The effect of turbulence in Parker spiral geometry

Solar energetic particles (SEPs), accelerated during solar eruptions, are observed to rapidly reach a wide heliolongitudinal range in the interplanetary space. To access these locations, SEPs must have either been at particle source, or propagated across mean Parker spiral magnetic field. We study propagation of new model heliospheric turbulence which takes geometry average field into account, evaluate how this improved description affects SEP path lengths and overall evolution intensities 1~au. use full-orbit test simulations 100-MeV protons dominated by modes that transverse 2D with respect spiral. find spread along meandering lines arrive 60$^\circ$ 1~au within an hour their injection Sun, consistent extent lines. The onset times asymmetric location connected source spiral, westward locations seeing earlier arrival higher peak intensity. inferred length first-arriving is 1.5-1.7~au, 30-50\% longer than 20\% Subsequently, distribution broadens, diffusive spreading Our results indicate can propagate Spiral longitudes, even without source. modelled times, intensity subsequent replicate several event features. Further studies be required investigate relative importance transport size different environments.