Shear Particle Acceleration in Astrophysical Jets

宇宙中的带电粒子在哪里以及如何加速到它们的极端能量？也许最有希望的地点之一包括活动星系核(AGN)中平行的相对论外流或喷流。人们越来越认识到，这些喷流可能表现出显著的速度剪切，这在最近引发了各种研究，探讨其对非热粒子加速和排放的影响。快速剪切流原则上可以通过几种方式促进高能粒子的加速。在这个项目中，我们将通过数值、解析和唯象方法来解决和解决活动星系核喷流中费米型剪切粒子加速的关键问题。我们特别针对(A)剪切圆柱形喷流的相对论粒子输运方程的数值解，这将能够评估当前使用的简化加速模型的充分性，(B)通过蒙特卡罗模拟以及对各向异性散射的扩展，对剪切粒子加速的基本概念进行数值验证，以及(C)根据详细的源模型，对其产生超高能宇宙线的潜力和最近在大型活动星系核喷流中检测到的TeV排放的来源进行现象学评估。我们希望这些结果将决定性地推进我们对宇宙粒子加速的概念理解，并允许对其现象学含义做出合格的判断。因此，这些结果可望成为进一步研究的中心参考。

Where and how are the charged particles seen in the Universe accelerated to their extreme energies? Perhaps one of the most promising sites includes the collimated, relativistic outflows or jets in Active Galactic Nuclei (AGN). The growing realisation that these jets are likely to exhibit significant velocity shearing has in recent times triggered a variety of studies exploring its consequences for non-thermal particle acceleration and emission. Fast shear flows can in principle facilitate energetic particle acceleration by several means. One key possibility includes a stochastic Fermi-type process, in which particle energisation occurs as a result of elastically scattering off differentially moving magnetic inhomogeneities embedded in a shearing background flow.In this project we will address and resolve key issues of Fermi-type shear particle acceleration in the jets of AGN by means of numerical, analytical and phenomenological methods.We specifically aim at (a) a numerical solution of the relativistic particle transport equation for sheared, cylindrical jets, that will enable assessing the adequacy of simplified acceleration models currently used, (b) a numerical verification of the fundamental concept of shear particle acceleration by means of Monte Carlo simulations along with extensions towards anisotropic scattering, and (c) a phenomenological assessment of its potential for ultra-high-energy cosmic-ray production and the origin of the recently detected TeV emission in large-scale AGN jets based on detailed source modelling. We expect these results to decisively advance our conceptual understanding of cosmic particle acceleration and to allow a qualified judgement of its phenomenological implications. As such the results are expected to become the central reference for further studies.