http://arxiv.org/abs/2009.11877
Particle energization in shear flows is invoked to explain non-thermal emission from the boundaries of relativistic astrophysical jets. Yet, the physics of particle injection, i.e., the mechanism that allows thermal particles to participate in shear-driven acceleration, remains unknown. With particle-in-cell simulations, we study the development of Kelvin-Helmholtz (KH) instabilities seeded by the velocity shear between a relativistic magnetically-dominated electron-positron jet and a weakly magnetized electron-ion ambient plasma. We show that, in their nonlinear stages, KH vortices generate kinetic-scale reconnection layers, which efficiently energize the jet particles, thus providing a first-principles mechanism for particle injection into shear-driven acceleration. Our work lends support to spine-sheath models of jet emission – with a fast core/spine surrounded by a slower sheath – and can explain the origin of radio-emitting electrons at the boundaries of relativistic jets.
L. Sironi, M. Rowan and R. Narayan
Mon, 28 Sep 20
2/52
Comments: 8 pages, 6 figures, 1 appendix
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