Simulations of relativistic collisionless shocks: shock structure and particle acceleration

By A. Spitkovsky. 2005

170 citations recorded by the source corpus.

We discuss 3D simulations of relativistic collisionless shocks in electron-positron pair plasmas using the particle-in-cell (PIC) method. The shock structure is mainly controlled by the shock's magnetization (''sigma'' parameter). We demonstrate how the structure of the shock varies as a function of sigma for perpendicular shocks. At low magnetizations the shock is mediated mainly by the Weibel instability which generates transient magnetic fields that can exceed the initial field. At larger magnetizations the shock is dominated by magnetic reflections. We demonstrate where the transition occurs and argue that it is impossible to have very low magnetization collisionless shocks in nature (in more than one spatial dimension). We further discuss the acceleration properties of these shocks, and show that higher magnetization perpendicular shocks do not efficiently accelerate nonthermal particles in 3D. Among other astrophysical applications, this may pose a restriction on the structure and composition of gamma-ray bursts and pulsar wind outflows.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/94209af966734b8be1d2f962a6af39150e5d2f81

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In Astronomy and Astrophysics

1. L. Sironi
2. D. Giannios
3. M. Petropoulou
4. A. Spitkovsky
5. J. Arons
6. Bing Zhang
7. U. Keshet
8. M. Lemoine

In Nuclear and High Energy Physics

1. L. Sironi
2. M. Petropoulou
3. D. Giannios
4. A. Spitkovsky
5. J. Arons
6. U. Keshet
7. M. Lemoine
8. Bing Zhang

Citations in the corpus

• THE MAXIMUM ENERGY OF ACCELERATED PARTICLES IN RELATIVISTIC COLLISIONLESS SHOCKS (2013, methodology): “Unmagnetized Shocks As shown by Spitkovsky (2008b) and Sironi & Spitkovsky (2009b) in 2D and by Spitkovsky (2005) in 3D, unmagnetized shocks are mediated by the so-called Weibel instability (Weibel 1959; Medvedev & Loeb 1999; Gruzinov & Waxman 1999).4 The free energy for the instability comes from…”
• Gamma-Ray Bursts in the Swift Era (2007, background): “…and analytical studies have started to answer the fundamental questions about particle acceleration and magnetic field generation (e.g., Medvedev& Loeb 1999; Nishikawa et al. 2003, 2005; Liang & Nishimura 2004; Hededal & Nishikawa 2005; Spitkovsky 2005; Kato 2005; Milosavljevic & Nakar 2006a, b).”
• Plasmoids in relativistic reconnection, from birth to adulthood: first they grow, then they go (2016, methodology): “In order to reduce noise in the simulation, we filter the electric current deposited to the grid by the particles, effectively mimicking the role of a larger number of particles per cell (Spitkovsky 2005; Belyaev 2015).”
• PARTICLE ACCELERATION IN RELATIVISTIC MAGNETIZED COLLISIONLESS PAIR SHOCKS: DEPENDENCE OF SHOCK ACCELERATION ON MAGNETIC OBLIQUITY (2009, methodology): “PIC simulations of relativistic unmagnetized shocks have been presented by Spitkovsky (2005, 2008a), Chang et al. (2008) and Keshet et al. (2008); Spitkovsky (2008b) has shown that unmagnetized shocks naturally produce accelerated particles as part of the shock evolution.”
• RELATIVISTIC RECONNECTION: AN EFFICIENT SOURCE OF NON-THERMAL PARTICLES (2014, methodology): “We use the 3D electromagnetic PIC code TRISTANMP (Buneman 1993; Spitkovsky 2005) to study rela- ar X iv :1 40 1.”
• ACCELERATION OF PARTICLES AT THE TERMINATION SHOCK OF A RELATIVISTIC STRIPED WIND (2011, methodology): “Their counter-streaming with respect to the incoming flow can seed the filamentation (or Weibel) instability, as it happens for shocks propagating in unmagnetized plasmas (Spitkovsky 2005, 2008).”
• Relativistic Shocks: Particle Acceleration and Magnetization (2015, background): “This picture, first envisioned by Moiseev and Sagdeev (1963), has been recently demonstrated in ab initio PIC simulations (Spitkovsky 2005; Kato 2007; Spitkovsky 2008a).”
• NONLINEAR STUDY OF BELL'S COSMIC RAY CURRENT-DRIVEN INSTABILITY (2008, methodology): “We use the PIC code TRISTAN-MP (Buneman 1993; Spitkovsky 2005), which can run in one, two, and three dimensions.”
• PARTICLE ACCELERATION IN RELATIVISTIC MAGNETIZED COLLISIONLESS ELECTRON–ION SHOCKS (2010, methodology): “We use the 3D electromagnetic PIC code TRISTANMP (Spitkovsky 2005), which is a parallel version of the publicly available code TRISTAN (Buneman 1993) that was optimized for studying collisionless shocks.”