Authors: Rubaiya Khondoker Shikha (Dept. of Space Science, UAH), Jakobus A. le Roux (Dept. of Space Science, UAH, CSPAR)

The acceleration and transport of solar energetic particles (SEPs) are known to be significantly influenced by quasi-perpendicular shocks; however, the mechanisms that underlie these phenomena frequently differ from classical diffusive models. In this study, we investigated SEP acceleration and transport at a quasi-perpendicular shock at 1 AU detected with the ACE spacecraft on August 26, 1998 (Prete et al. 2021), using a recently developed theory for tempered superdiffusive shock acceleration at a perpendicular shock (le Roux & Shikha, 2025). The theory elucidates the transition from superdiffusive to normal diffusive energetic particle transport in the shock vicinity of the shock. By fitting analytical solutions of this model to SEP flux data across several energy channels upstream and downstream of the shock, we identified clear signatures of superdiffusive SEP behavior. The degree of superdiffusion increased with SEP energy, and surprisingly, was more prominent in the downstream region. To investigate the origin of this behavior, we examined the statistical characteristics of coincident magnetic field turbulence. We observed enhanced kurtosis (heavy-tailed distributions) indicating intermittent, non-Gaussian turbulence on both sides of the shock, but found the kurtosis to be higher downstream compared to upstream.  The intensified intermittency and non-Gaussian features of the downstream turbulence appear to be responsible for the enhanced degree of superdiffusive transport downstream of the shock. We also identified regions both upstream and downstream of the shock where SEP transport appears to transition from superdiffusive to normal diffusive behavior. In summary, the results provide a convincing case for superdiffusive SEP transport and acceleration occurring at a quasi-perpendicular shock, while suggesting the presence of tempering effects and a potential link between the degree of superdiffusion and the level of intermittency in the coinciding magnetic turbulence.