Rapid Particle Acceleration due to Recollimation Shocks and Turbulent Magnetic Fields in Injected Jets with Helical Magnetic Fields

One of the key open questions in the study of relativistic jets is how magnetic reconnection occurs and whether it can effectively accelerate the jet's electrons. We investigate the evolution of an electron-proton relativistic jet containing helical magnetic fields, focusing on the interaction with the ambient plasma. We have performed 3D particle-in-cell (PIC) simulations of a jet containing a relatively large radius with embedded helical magnetic fields, in order to examine how the helical magnetic field excites kinetic instabilities such as the Weibel instability (WI), the kinetic Kelvin-Helmholtz instability (kKHI) and the mushroom instability (MI). In our simulations these kinetic instabilities are indeed excited and particles are accelerated. We observe recollimation shocks near the center of the jet at the linear stage. As the electron-proton jet evolves, the helical magnetic field becomes untangled due to a reconnection-like phenomena at the end of the nonlinear stage, and electrons are further accelerated by multiple magnetic reconnection events/sites within the turbulent magnetic field.