Triggering QED processes by reconnection in near critical magnetic fields

Magnetic reconnection in a relativistic pair plasma is investigated using both 2D and 3D particle-in-cell simulations, where the magnetic field approaches the critical (Schwinger) field, allowing for quantum electrodynamic (QED) radiation and pair-creation.  The simulations are performed with the QED module [1] of the OSIRIS framework that includes single photon emission by electrons and positrons (non-linear Compton scattering) and single photon decay into pairs (non-linear Breit-Wheeler).  We show that even when the magnetic fields initially do not exhibit QED effects, the reconnection leads to both energetic particles, and locally enhanced magnetic fields, such that radiative cooling and pair-production processes begin to play an important role.  We highlight that the radiation spectra that may be observable from such events differ strongly from the classical cases with much steeper spectra and the differences between 2D and 3D models.  This sets the stage for testing if magnetic reconnection may be a mechanism powering gamma-ray flares in magnetar magnetospheres. [1] T.  Grismayer et al., Physics of Plasmas 23, 056706 (2016)