<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Zhang, Hao</style></author><author><style face="normal" font="default" size="100%">Sironi, Lorenzo</style></author><author><style face="normal" font="default" size="100%">Giannios, Dimitrios</style></author><author><style face="normal" font="default" size="100%">Petropoulou, Maria</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The Origin of Power-law Spectra in Relativistic Magnetic Reconnection</style></title><short-title><style face="normal" font="default" size="100%">The Astrophysical Journal</style></short-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">739</style></keyword><keyword><style  face="normal" font="default" size="100%">Astrophysics - High Energy Astrophysical Phenomena</style></keyword><keyword><style  face="normal" font="default" size="100%">High energy astrophysics</style></keyword><keyword><style  face="normal" font="default" size="100%">Physics - Plasma Physics</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2023</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2023/10/1</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://ui.adsabs.harvard.edu/abs/2023ApJ...956L..36Z</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">IOP</style></publisher><volume><style face="normal" font="default" size="100%">956</style></volume><pages><style face="normal" font="default" size="100%">L36</style></pages><isbn><style face="normal" font="default" size="100%">0004-637X</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Magnetic reconnection is often invoked as a source of high-energy particles, and in relativistic astrophysical systems it is regarded as a prime candidate for powering fast and bright flares. We present a novel analytical model-supported and benchmarked with large-scale three-dimensional kinetic particle-in-cell simulations in electron-positron plasmas-that elucidates the physics governing the generation of power-law energy spectra in relativistic reconnection. Particles with Lorentz factor γ ≳ 3σ (here, σ is the magnetization) gain most of their energy in the inflow region, while meandering between the two sides of the reconnection layer. Their acceleration time is ${t}_{\mathrm{acc}}\sim \gamma \,{\eta }_{\mathrm{rec}}^{-1}{\omega }_{{\rm{c}}}^{-1}\simeq 20\,\gamma \,{\omega }_{{\rm{c}}}^{-1}$ , where η &lt;SUB&gt;rec&lt;/SUB&gt; ≃ 0.06 is the inflow speed in units of the speed of light and ω &lt;SUB&gt;c&lt;/SUB&gt; = eB &lt;SUB&gt;0&lt;/SUB&gt;/mc is the gyrofrequency in the upstream magnetic field. They leave the region of active energization after t &lt;SUB&gt;esc&lt;/SUB&gt;, when they get captured by one of the outflowing flux ropes of reconnected plasma. We directly measure t &lt;SUB&gt;esc&lt;/SUB&gt; in our simulations and find that t &lt;SUB&gt;esc&lt;/SUB&gt; ~ t &lt;SUB&gt;acc&lt;/SUB&gt; for σ ≳ few. This leads to a universal (i.e., σ-independent) power-law spectrum ${{dN}}_{\mathrm{free}}/d\gamma \propto {\gamma }^{-1}$ for the particles undergoing active acceleration, and ${dN}/d\gamma \propto {\gamma }^{-2}$ for the overall particle population. Our results help to shed light on the ubiquitous presence of power-law particle and photon spectra in astrophysical nonthermal sources.</style></abstract></record></records></xml>