PARTICLE ACCELERATION AND PLASMA DYNAMICS DURING MAGNETIC RECONNECTION IN THE MAGNETICALLY DOMINATED REGIME

By Fan Guo, Yi‐Hsin Liu, William S. Daughton, Hui Li. 2015

213 citations recorded by the source corpus.

Magnetic reconnection is thought to be the driver for many explosive phenomena in the universe. The energy release and particle acceleration during reconnection have been proposed as a mechanism for producing high-energy emissions and cosmic rays. We carry out two- and three-dimensional (3D) kinetic simulations to investigate relativistic magnetic reconnection and the associated particle acceleration. The simulations focus on electron–positron plasmas starting with a magnetically dominated, force-free current sheet ( &sgr; ≡ B 2 / ( 4 &pgr; n e m e c 2 ) ≫ 1 ?> ). For this limit, we demonstrate that relativistic reconnection is highly efficient at accelerating particles through a first-order Fermi process accomplished by the curvature drift of particles along the electric field induced by the relativistic flows. This mechanism gives rise to the formation of hard power-law spectra f ∝ ( γ − 1 ) − p ?> and approaches p = 1 for sufficiently large σ and system size. Eventually most of the available magnetic free energy is converted into nonthermal particle kinetic energy. An analytic model is presented to explain the key results and predict a general condition for the formation of power-law distributions. The development of reconnection in these regimes leads to relativistic inflow and outflow speeds and enhanced reconnection rates relative to nonrelativistic regimes. In the 3D simulation, the interplay between secondary kink and tearing instabilities leads to strong magnetic turbulence, but does not significantly change the energy conversion, reconnection rate, or particle acceleration. This study suggests that relativistic reconnection sites are strong sources of nonthermal particles, which may have important implications for a variety of high-energy astrophysical problems.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/90f6e2a81ee6f62f6794672ff502fcc764611292

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Citations in the corpus

Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection (2016, methodology): “…particle energy distributions f(ε) ∼ ε−p have power-law indices p < 2 (as in ultrarelativistic electron-positron reconnection: Sironi & Spitkovsky 2014; Guo et al. 2015; Werner et al. 2016), indicating that most of the particle kinetic energy resides in particles with energies much higher than…”
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.”