论文标题
相对论喷气机中的扭结磁重新连接：X射线极光线的后果
Kink-driven magnetic reconnection in relativistic jets: consequences for X-ray polarimetry of BL Lacs
论文作者
论文摘要
我们通过研究BL LAC射流的耗散物理学来研究，通过研究磁性主导的等离子体柱中的扭结不稳定性加速的颗粒的同步加速器极化特征。扭结不稳定性的非线性阶段会产生电流板，可以通过磁重新连接有效地加速粒子。我们将电流板识别为S = J D/B高于某些预定义阈值的区域（其中B是磁场强度，J电流密度和电网尺度），并假设颗粒注入效率尺度与电流正方形成正比。 X射线发射颗粒的冷却时间很短，因此它们仅探测其注入位点的场几何形状。相比之下，光条中发出的颗粒在冷却时散发出远离注入位点时会遵循它们的粒子，因此可以预期它们会产生不同的极性特征。我们发现X射线和光条之间的极化程度大致相同，因为由于缺乏足够的扭结生成的湍流，即使是光学发射颗粒也不会远离注入当前纸的远处。由于X射线和光学发射颗粒探测的不同区域，极化角显示了两个频段之间的时间演变不同。鉴于即将到来的IXPE卫星，我们的结果可以帮助限制扭结引起的重新连接（而不是冲击）是否可以成为BL LAC的多波长发射的来源。
We investigate with relativistic MHD simulations the dissipation physics of BL Lac jets, by studying the synchrotron polarization signatures of particles accelerated by the kink instability in a magnetically-dominated plasma column. The nonlinear stage of the kink instability generates current sheets, where particles can be efficiently accelerated via magnetic reconnection. We identify current sheets as regions where s = J d/B is above some predefined threshold (where B is the field strength, J the current density and d the grid scale), and assume that the particle injection efficiency scales as proportional to the square of the current. X-ray emitting particles have short cooling times, so they only probe the field geometry of their injection sites. In contrast, particles emitting in the optical band, which we follow self-consistently as they propagate away from their injection sites while cooling, sample a larger volume, and so they may be expected to produce different polarimetric signatures. We find that the degree of polarization is roughly the same between X-ray and optical bands, because even the optical-emitting particles do not travel far from the current sheet where they were injected, due to lack of sufficient kink-generated turbulence. The polarization angle shows a different temporal evolution between the two bands, due to the different regions probed by X-ray and optical emitting particles. In view of the upcoming IXPE satellite, our results can help constrain whether kink-induced reconnection (as opposed to shocks) can be the source of multi-wavelength emission from BL Lacs.
