Non-thermal particle acceleration in rotating jets

The mechanisms by which relativistic magnetized jets from AGN produce non-thermal particles and radiation remain a long-standing puzzle. Recent large-scale particle-in-cell (PIC) simulations have shown that the onset of hydromagnetic instabilities in jets can lead to efficient non-thermal particle acceleration. These studies examined columns of non-rotating magnetized pair plasma, with toroidal magnetic field tension balanced by a combination of axial magnetic fields and thermal pressure gradients. Importantly, these studies highlighted the sensitivity of non-thermal particle acceleration to the details of the plasma and magnetic field conditions in the jet.

Here we examine the role of rotational velocity of the jet on the development of hydromagnetic instabilities and associated on non-thermal particle acceleration. We conduct systematic comparisons with non-rotating jet equilibria, examining non-thermal particle acceleration, field fluctuations, and rate of energy dissipation. With a cold rotating jet, (compared to a relativistically hot, non-rotating jet), the development of the non-linear kink is greatly delayed. Once the jet reaches the non-linear stage, it's field structure is significantly modified due to the presence of shearing layers, and additional unstable modes (with higher azimuthal mode numbers) have developed in the process. While the jet still accelerates particles to non-thermal energies, these modifications result in a steeper slope of the non-thermal spectra, and therefore less efficient particle acceleration. By exploring these field structure changes, we can connect the effect of rotational flow velocity on the development of non-thermal spectra. These simulations probe new, relevant configurations for jets that result in non-thermal particle acceleration applicable to relativistic, magnetized, astrophysical jets.