Kinetic Simulations of Relativistic Radiative Magnetic Reconnection

José Ortuño-Macı́as, Krzysztof Nalewajko

High energy astrophysical phenomena, such as blazars, gamma-ray bursts and pulsar wind nebulae, are associated with efficient particle acceleration sites because they show emission signatures of non-thermal particle distribution. Their common characteristic is strong magnetic field, which provides the condition for relativistic magnetic reconnection (RMR) to be the most efficient particle acceleration mechanism. By means of kinetic simulations it has been observed that during the reconnection process, highly energetic particles are enclosed within magnetic islands also termed as plasmoids. The properties of plasmoids have been studied through kinetic simulations with open boundaries where a steady-state RMR process was achieved. When the RMR outflows are unimpeded, a continuous chain of plasmoids is generated with stochastic plasmoid properties. A wide range of parameters has been used in order to model the emission properties of blazars, which are characterized by high variability and broad band spectrum. However, previous studies of plasmoid properties were based on simulations where emission effects have not been included. Recent work has shown that in the regime of high radiation efficiency the cooling affects the particle dynamics and thus it might also influence the generation of plasmoid chains. We performed 2D Particle-In-Cell (PIC) simulations of steady-state RMR with open boundaries with synchrotron radiation reaction and calculation of the resulting emission signatures from our computational domain. We find that the cores of the large-sized plasmoids are the main emission sites because of an increasing magnetic energy density and particle number density. The resulting synchrotron lightcurves reveal sharp flares originating from tail-on mergers between small/fast plasmoids and their large/slow targets.

Proceedings of the Polish Astronomical Society, vol. 10, 255-260 (2020)

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