Electron acceleration in interaction of magnetic islands in large temporal-spatial turbulent magnetic reconnection

A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at large temporal-spatial scale (LTSTMR), the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10¹⁰–10¹¹; the ratio of observed evolution time to electron gyroperiod is on the order of 10⁷–10⁹). The original combined acceleration model is known to be one of greatest importance in the interaction of magnetic islands; it assumes that the continuous kinetic-dynamic temporal-spatial scale evolution occurs as two separate independent processes. In this paper, we reconsider the combined acceleration mechanism by introducing a kinetic-dynamic-hydro full-coupled model instead of the original micro-kinetic or macro-dynamic model. We investigate different acceleration mechanisms in the vicinity of neutral points in magnetic islands evolution, from the stage of shrink and breakup into smaller islands (kinetic scale), to the stage of coalescence and growth into larger islands (dynamic scale), to the stages of constant and quasi-constant (contracting-expanding) islands (hydro scale). As a result, we give for the first time the acceleration efficiencies of different types of acceleration mechanisms in magnetic islands’ interactions in solar atmosphere LTSTMR activities (pico-, 10^–2–10⁵ m; nano-, 10⁵–10⁶ m; micro-, 10⁶–10⁷ m; macro-, 10⁷–10⁸ m; large-, 10⁸–10⁹ m).