Suppressed reflection of electric fields induced in a stressed X-point collapse

Magnetic reconnection is a basic physical process in which the magnetic field energy is converted into plasma heating and plasma kinetic energy through non-thermal particle acceleration. To investigate collisionless magnetic reconnection, particle-in-cell (PIC) simulations of a stressed (magnetic) X-point collapse have been performed, and the simulation results are highly similar to those obtained for the well-known Harris-type current sheet model. However, through careful study, we found that the stressed X-point configuration initially induces electric fields, which propagate outward, are reflected from the simulation boundaries, and then influence the reconnection physics. In this study, we performed precise PIC simulations of a stressed X-point collapse by introducing an absorption region. The results show that the electric fields propagating outward are damped in the absorption region and their reflection from the boundaries is largely suppressed. The influence of the reflected electric fields on the X-point is therefore removed from the system. Hence, the introduction of an absorption region is highly effective for investigating the physics of a stressed X-point collapse. (author)