Effects of internal current-sheet structure on magnetic reconnection evolution

The effects of initial current-sheet structure on symmetric magnetic reconnection are investigated using 2.5D resistive two-fluid (electron–ion) simulations. With the background plasma parameters and the initial magnetic configuration held fixed, we systematically vary the plasma density and temperature within the initial current sheet to examine their impact on reconnection dynamics. High-density current sheets undergo prolonged thinning and energy accumulation followed by an abrupt transition to explosive reconnection with highly localized dissipation and enhanced peak reconnection rates. In contrast, low-density current sheets develop reconnection rapidly without pronounced compression, forming broad ion diffusion regions, strong macroscopic plasma outflows, and spatially distributed energy conversion. The results reveal that the internal current-sheet density acts as an effective organizing parameter that self-consistently affects the diffusion-region structure, plasma flow patterns, energy conversion pathways, and spatial distributions of temperature, electric fields, and density within the present model framework. By continuously varying the internal current-sheet density, the system exhibits a continuous transition between electron-dominated and ion-dominated evolution regimes. These results suggest a possible framework for interpreting the diversity of reconnection behaviors observed in space and laboratory plasmas.