Particle acceleration in an MHD-scale system of multiple current sheets

Abstract

We investigate particle acceleration in an MHD-scale system of multiple current sheets by performing 2D and 3D MHD simulations combined with a test particle simulation. The system is unstable for the tearing-mode instability, and magnetic islands are produced by magnetic reconnection. Due to the interaction of magnetic islands, the system turns into a turbulent state. The 2D (3D) case yields both $-5/3$ ($-11/3$ and $-7/3$) power-law spacetra for magnetic and velocity fluctuations. Particles are efficiently energized by the generated turbulence, and it forms a power-law tail with an index of $-2.2$ and $-4.2$ in the energy distribution function for the 2D and 3D case, respectively. We find more energetic particles outside magnetic islands rather than inside. We observe super-diffusion in the 2D ($\sim t^{2.27}$) and 3D ($\sim t^{1.2}$) case in the energy space of energetic particles.