Quantifying the uncertainty associated with solar energetic particle transport models

Using magnetically well-connected solar energetic particle (SEP) observations, we derive the electron and proton parallel mean-free-paths (MFPs) by comparing in-situ observations to one-dimensional simulation results. These inferred MFPs are compared to theoretical estimates which have been constrained by solar wind turbulence observations. We show that these derived and theoretical values are mostly consistent for both protons and electrons, but do show significant inter-event variations which can be explained by changing solar wind turbulence conditions. To illustrate the influence of these changing scattering conditions on particle transport, we simulate SEP time profiles for magnetically connected and unconnected observers for different transport and/or acceleration parameters. We show that this can explain the observer inter-event variations observed for SEP events. Additionally, we show that such an ensemble modeling approach can be used to quantify the uncertainty in the underlying model assumptions and can, in principle, be used in physics-based SEP predictive models to produce SEP predictions that include an uncertainty band.