The Role of Magnetic Reconnection-Associated Processes in Local Particle Acceleration in the Solar Wind

Recent studies of unusual or atypical energetic particle flux events (AEPEs) observed at 1 AU show that there is one more mechanism apart from diffusive shock acceleration (DSA) that can energize particles locally in the solar wind. The mechanism proposed by Zank et al. (2014) suggests the occurrence of numerous small-scale magnetic islands (SMIs) either contacting or merging and experiencing multiple magnetic reconnection in the super-Alfvénic solar wind flow. As a result, charged particles are accelerated stochastically by the anti-reconnection electric field in the latter case. In the former case, a first/second order Fermi mechanism is involved due to compression-induced changes of the shape of SMIs and their developing dynamics. Observations show that the both processes often co-exist in the solar wind. The occurrence of SMIs depends on the presence of strong current sheets like the heliospheric current sheet (HCS), and related AEPEs are found to occur within magnetic cavities formed by stream-stream, stream-HCS or HCS-shock interactions and filled with SMIs. In previous works, case studies were supported by the comparative analysis of observations with theoretical predictions. Meantime, the analysis was qualitative. Here we present quantitative theoretical predictions of AEPEs based on several events, including a detailed analysis of the corresponding observations. The study is aimed at illustrating the necessity of taking into account local processes of particle acceleration in the solar wind.