SIMULATIONS OF PARTICLE ACCELERATION BEYOND THE CLASSICAL SYNCHROTRON BURNOFF LIMIT IN MAGNETIC RECONNECTION: AN EXPLANATION OF THE CRAB FLARES

By B. Cerutti, Gregory R. Werner, Dmitri A. Uzdensky, M. Begelman. 2013

166 citations recorded by the source corpus.

It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of two-dimensional particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/f0e4a5d7dff94e2afb4e92ff1dcce83c8e4eba73

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In Astronomy and Astrophysics

1. L. Sironi
2. A. Spitkovsky
3. D. Giannios
4. A. Philippov
5. M. Petropoulou
6. B. Cerutti
7. M. Begelman
8. Dmitri A. Uzdensky

In Nuclear and High Energy Physics

1. L. Sironi
2. D. Giannios
3. A. Spitkovsky
4. M. Petropoulou
5. A. Philippov
6. B. Cerutti
7. Hui Li
8. Fan Guo

Citations in the corpus

• Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection (2016, background): “…Jaroschek et al. 2004; Lyubarsky & Liverts 2008; Jaroschek & Hoshino 2009; Liu et al. 2011; Bessho & Bhattacharjee 2012; Kagan et al. 2013; Cerutti et al. 2012b, 2013, 2014a,b; Sironi & Spitkovsky 2011, 2014; Guo et al. 2014, 2015; Liu et al. 2015; Nalewajko et al. 2015; Sironi et al.…”
• RELATIVISTIC RECONNECTION: AN EFFICIENT SOURCE OF NON-THERMAL PARTICLES (2014, background): “2a, we find that the early phases are governed by the DK mode, in agreement with previous studies (Zenitani & Hoshino 2008; Cerutti et al. 2013b).”
• Modelling high-energy pulsar light curves from first principles (2015, methodology): “In ZELTRON, each macro-particle radiates a single “macro-photon” (or simply “photon” in the following) in the simulation frame.”
• Particle acceleration in axisymmetric pulsar current sheets (2014, methodology): “2.1 The Zeltron code in spherical coordinates In this study, we use the explicit, massively parallel, electromagnetic PIC code Zeltron, initially developed for relativistic reconnection studies (Cerutti et al. 2013, 2014).”
• PARTICLE ACCELERATION AND PLASMA DYNAMICS DURING MAGNETIC RECONNECTION IN THE MAGNETICALLY DOMINATED REGIME (2015, background): “The results show that magnetic reconnection may be the site of extreme particle acceleration required to explain high energy emissions from the Crab flares (see also Cerutti et al. 2013).”
• Plasmoids in relativistic reconnection, from birth to adulthood: first they grow, then they go (2016, background): “This might explain why earlier works (Cerutti et al. 2013a; Guo et al. 2015; Kagan et al. 2016) claimed that the outflow speed from relativistic reconnection seems systematically lower than Lyubarsky(2005)’s prediction.”