Reconnection-driven Particle Acceleration in Relativistic Shear Flows

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