Journal
ASTROPHYSICAL JOURNAL
Volume 915, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/abfe5f
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Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC) [CITA 490888-16]
- Jeffrey L. Bishop Fellowship
- Government of Canada through the Department of Innovation, Science and Economic Development Canada
- Province of Ontario through the Ministry of Colleges and Universities
- NASA [NNX 17AK37G, 80NSSC20K1556]
- NSF [AST 2009453, PHY-1903412]
- Simons Foundation [446228]
- Humboldt Foundation
- Sloan Fellowship
- Cottrell Scholar Award
- DoE [DE-SC0021254]
- U.S. Department of Energy (DOE) [DE-SC0021254] Funding Source: U.S. Department of Energy (DOE)
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The dissipation mechanism involving the collision of two anti-aligned strong Alfven waves form a thin current sheet perpendicular to the background magnetic field, accelerating particles to high energies and dissipation a large fraction of wave energy. This fast dissipation process is activated when the amplitude ratio A > 1/2 and may occur in various objects with perturbed magnetic fields. The mechanism transitions to normal, slower magnetic reconnection at higher amplitude ratios A >> 1.
Magnetic energy around compact objects often dominates over plasma rest mass, and its dissipation can power the object's luminosity. We describe a dissipation mechanism that works faster than magnetic reconnection. The mechanism involves two strong Alfven waves with anti-aligned magnetic fields B (1) and B (2) that propagate in opposite directions along the background magnetic field B (0) and collide. The collision forms a thin current sheet perpendicular to B (0), which absorbs the incoming waves. The current sheet is sustained by an electric field E breaking the magnetohydrodynamic condition E < B and accelerating particles to high energies. We demonstrate this mechanism with kinetic plasma simulations using a simple setup of two symmetric plane waves with amplitude A = B (1)/B (0) = B (2)/B (0) propagating in a uniform B (0). The mechanism is activated when A > 1/2. It dissipates a large fraction of the wave energy, f = (2A - 1)/A (2), reaching 100% when A = 1. The plane geometry allows one to see the dissipation process in a one-dimensional simulation. We also perform two-dimensional simulations, enabling spontaneous breaking of the plane symmetry by the tearing instability of the current sheet. At moderate A of main interest, the tearing instability is suppressed. Dissipation transitions to normal, slower, magnetic reconnection at A >> 1. The fast dissipation described in this paper may occur in various objects with perturbed magnetic fields, including magnetars, jets from accreting black holes, and pulsar wind nebulae.
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