Magnetic field line random walk and solar energetic particle path lengths

Context. In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/IS?IS instrument suite at ?0.35 AU from Sun. From standard velocity-dispersion analysis, apparent path length is ?0.625 onset of each event. Aims. We develop a formalism for estimating random-walking magnetic field lines to explain why an event greatly exceeds radial distance Sun these events. Methods. developed analytical estimates average increase in lines, relative unperturbed mean field. Monte Carlo simulations line and particle trajectories model wind turbulence used validate study lengths guiding-center full-orbital trajectories. The was implemented global model, results are compared with inferred IS?IS observations. Results. Both simple estimate rigorous theoretical formulation obtained field-lines’ as function along large-scale simulated trajectories, we find that guiding centers can have somewhat shorter than length, while orbits substantially longer due their gyromotion nonzero effective pitch angle. Conclusions. long during be explained (1) random walk (2) transport about center angle scattering. Our computing accounting turbulent fluctuations, may useful application general.