2D Kinetic Simulations of Electron Acceleration during Magnetic Reconnection with ad-hoc Pitch Angle Scattering to Mimic 3D Effects*

Particle acceleration during magnetic reconnection is a long-standing topic in space physics and astrophysics. Recent 3D magnetic reconnection simulations show that particles can leave flux ropes due to 3D field-line chaos, allowing particles to access additional acceleration sites, gain energy through Fermi acceleration, and develop a power-law energy distribution. This 3D effect does not exist in traditional 2D simulations, where particles are artificially confined to magnetic islands due to their restricted motion across field lines. Full 3D simulations, however, are prohibitively expensive for most studies. Here, we attempt to reproduce and further extend 3D results in 2D simulations by introducing ad-hoc pitch-angle scattering to a small fraction of the electrons. We show that scattered particles are able to transport out of 2D islands and achieve more efficient Fermi acceleration, leading to a significant increase of energetic electron flux. We also study how the scattering frequency influences the nonthermal particle spectra.