High Energy Density Science Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street, New York, New York 10027, USA.
Phys Rev Lett. 2018 Dec 14;121(24):245101. doi: 10.1103/PhysRevLett.121.245101.
Relativistic magnetized jets from active galaxies are among the most powerful cosmic accelerators, but their particle acceleration mechanisms remain a mystery. We present a new acceleration mechanism associated with the development of the helical kink instability in relativistic jets, which leads to the efficient conversion of the jet's magnetic energy into nonthermal particles. Large-scale three-dimensional ab initio simulations reveal that the formation of highly tangled magnetic fields and a large-scale inductive electric field throughout the kink-unstable region promotes rapid energization of the particles. The energy distribution of the accelerated particles develops a well-defined power-law tail extending to the radiation-reaction limited energy in the case of leptons, and to the confinement energy of the jet in the case of ions. When applied to the conditions of well-studied bright knots in jets from active galaxies, this mechanism can account for the spectrum of synchrotron and inverse Compton radiating particles, and offers a viable means of accelerating ultrahigh-energy cosmic rays to 10^{20} eV.
活动星系的相对论磁化喷流是宇宙中最强大的加速器之一，但它们的粒子加速机制仍然是个谜。我们提出了一种与相对论喷流中螺旋扭结不稳定性发展相关的新加速机制，该机制导致喷流的磁场能量有效地转化为非热粒子。大规模的三维初始模拟表明，高度纠结磁场的形成和扭结不稳定性区域内的大尺度感应电场促进了粒子的快速激发。在相对论情况下，加速粒子的能量分布呈现出清晰的幂律尾巴，延伸到辐射反应限制的能量（对于轻子），以及喷流限制的能量（对于离子）。当应用于活动星系喷流中研究良好的亮结的条件时，这种机制可以解释同步辐射和逆康普顿辐射粒子的谱，并为加速超高能宇宙射线至 10^{20} eV 提供了一种可行的方法。
