Relativistic Reconnection with Inverse Compton Radiaction*

Relativistic reconnection converts magnetic energy to particle energy, giving rise to heating and nonthermal particle acceleration (NTPA). The resulting highly relativistic particles can subsequently convert their energy to synchrotron and inverse Compton radiation; thus reconnection-driven NTPA may ignite spectacular high-energy flares in exotic astrophysical environments. However, radiation reaction forces (`radiaction' for short) may impede NTPA. With particle-in-cell simulation, we investigate relativistic reconnection in collisionless electron-positron plasmas with self-consistent inverse Compton radiaction. Unsurprisingly, weak radiaction scarcely alters NTPA, yielding a now-familiar power-law particle spectrum that radiates long after reconnection. With strong radiaction, however, a broken power-law spectrum forms as dissipated magnetic energy is rapidly converted from particle to photon energy, giving off a luminosity proportional to the reconnection rate. The particle spectrum has an unaltered power law at lower energies, and, above the break, a steeper power law that fluctuates in time due to the stochastic influence of plasmoids. The time-integrated photon spectrum roughly reflects the time-averaged luminosity-weighted particle spectrum.