  Particle acceleration during magnetic reconnection is a long-standing topic
in space, solar and astrophysical plasmas. Recent 3D particle-in-cell
simulations of magnetic reconnection show that particles can leave flux ropes
due to 3D field-line chaos, allowing particles to access additional
acceleration sites, gain more 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 motions across field lines. Full 3D simulations, however,
are prohibitively expensive for most studies. Here, we attempt to reproduce 3D
results in 2D simulations by introducing ad hoc pitch-angle scattering to a
small fraction of the particles. 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 particle flux. We also study how
the scattering frequency influences the nonthermal particle spectra. This study
helps achieve a complete picture of particle acceleration in magnetic
reconnection.
