RELATIVISTIC RECONNECTION: AN EFFICIENT SOURCE OF NON-THERMAL PARTICLES

Journal Article · Sat Mar 01 00:00:00 EST 2014 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/783/1/L21· OSTI ID:22363950

Sironi, Lorenzo ^[1]; Spitkovsky, Anatoly ^[2]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States)

In magnetized astrophysical outflows, the dissipation of field energy into particle energy via magnetic reconnection is often invoked to explain the observed non-thermal signatures. By means of two- and three-dimensional particle-in-cell simulations, we investigate anti-parallel reconnection in magnetically dominated electron-positron plasmas. Our simulations extend to unprecedentedly long temporal and spatial scales, so we can capture the asymptotic state of the system beyond the initial transients, and without any artificial limitation by the boundary conditions. At late times, the reconnection layer is organized into a chain of large magnetic islands connected by thin X-lines. The plasmoid instability further fragments each X-line into a series of smaller islands, separated by X-points. At the X-points, the particles become unmagnetized and they get accelerated along the reconnection electric field. We provide definitive evidence that the late-time particle spectrum integrated over the whole reconnection region is a power law whose slope is harder than –2 for magnetizations σ ≳ 10. Efficient particle acceleration to non-thermal energies is a generic by-product of the long-term evolution of relativistic reconnection in both two and three dimensions. In three dimensions, the drift-kink mode corrugates the reconnection layer at early times, but the long-term evolution is controlled by the plasmoid instability which facilitates efficient particle acceleration, analogous to the two-dimensional physics. Our findings have important implications for the generation of hard photon spectra in pulsar winds and relativistic astrophysical jets.

• OSTI ID: 22363950
• Journal Information: Astrophysical Journal Letters, Vol. 783, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
ASTROPHYSICS
ASYMPTOTIC SOLUTIONS
BOUNDARY CONDITIONS
COSMIC GAMMA BURSTS
ELECTRIC FIELDS
ELECTRONS
GALAXIES
LAYERS
MAGNETIC ISLANDS
MAGNETIC RECONNECTION
MAGNETIZATION
PHOTONS
POSITRONS
PULSARS
RELATIVISTIC RANGE
THREE-DIMENSIONAL CALCULATIONS
TWO-DIMENSIONAL CALCULATIONS