Benoit Cerutti, Gregory R. Werner, Dmitri A. Uzdensky, Mitchell C. Begelman
We report on the first study of angular distributions of energetic particles and radiation generated in relativistic collisionless electron-positron pair plasma reconnection, using two-dimensional particle-in-cell simulations. We discover a strong anisotropy of the particles accelerated by reconnection and the associated strong beaming of their radiation. The focusing of particles and radiation increases with their energy; in this sense, this "kinetic beaming" effect differs fundamentally from the relativistic Doppler beaming usually invoked in high-energy astrophysics, in which all photons are focused and boosted achromatically. We also present, for the first time, the modeling of the synchrotron emission as seen by an external observer during the reconnection process. The lightcurves exhibit super-fast time variability, comprising several bright symmetric bursts lasting about one tenth the light-crossing time of the system. The rapid variability in observed radiation is caused by the energetic beam of particles sweeping across the line of sight. This radiative signature can account for the brightness and variability of the gamma-ray flares in the Crab Nebula and in blazars.
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http://arxiv.org/abs/1205.3210
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