AI 中文总结
本研究通过三维GRMHD模拟探究多磁环黑洞吸积流的喷流形成条件，推导合成发射特征，结果与Sgr A*宁静态观测约束相符，揭示了喷流变异性的磁学机制。
AI 中文摘要
相对论性喷流是黑洞吸积的常见产物，但其存在与变异性强烈依赖于吸积流的磁学与动力学状态。部分系统如 blazar 与类星体会产生强大的持续喷流，而包括银心黑洞 Sgr A* 在内的其他系统仅表现出微弱或瞬态外流，导致喷流活动启动或抑制的物理条件仍未被充分理解。本研究旨在探究能产生瞬态喷流或抑制喷流形成的吸积流条件，以深化对无强稳定外流的吸积黑洞的认识，并预测总发射与偏振发射中的观测特征，用于与近期 Sgr A* 从射电到γ射线宁静态的观测结果对比。我们对被极性交替的极向多环磁场缠绕的 torus 环绕的吸积黑洞开展三维 GRMHD 模拟，追踪吸积率、磁通量与喷流功率的演化，并分析角动量传输；此外，采用包含康普顿散射的辐射传输计算推导合成总发射与偏振发射。模拟显示，初始极性磁环吸积阶段喷流功率呈现强变异性，后续系统趋近半-MAD（磁化吸积盘）态时活动减弱；吸积盘发射相对稳定、偏振度低，与 Sgr A* 宁静态的观测值相符；最终喷流发射被强烈抑制，因周围冷等离子体中的法拉第旋转与转换而退偏振；逆康普顿计算得到的近红外（NIR）高能光变曲线符合 Sgr A* 宁静态 NIR 与 X 射线流量的观测约束。
英文摘要
Relativistic jets are a common outcome of accretion onto black holes, yet their presence and variability depend strongly on the magnetic and dynamical state of the accretion flow. While some systems, such as Blazars and Quasars, launch powerful persistent jets, others, including the Galactic Centre black hole Sgr~A$^\star$, show only weak or transient outflows. The physical conditions leading to the onset or suppression of jet activity remain poorly understood. We investigate the accretion flow conditions that produce transient jets or inhibit jet formation, aiming to improve our understanding of black holes that accrete without strong, steady outflows. We further predict observational signatures in total and polarized emission for comparison with recent observations of Sgr~A$^\star$ in the quiescent state from the radio to the $γ$-ray regime. We perform three-dimensional GRMHD simulations of an accreting black hole surrounded by a torus threaded by a poloidal multi-loop magnetic field of alternating polarities. We follow the evolution of the accretion rate, magnetic flux, and jet power, and analyze angular momentum transport. In addition, radiative transfer calculations including Compton scattering are used to derive synthetic total and polarized emission. The simulations show strong variability in jet power while the initial magnetic polarity loops accrete, followed by weaker activity at later times as the system approaches a semi-MAD state. The emission from the disk is relatively stable, weakly polarized and consistent with the quiet state values reported for SgrA$^\star$. The resulting jet emission is strongly suppressed, depolarized by Faraday rotation and conversion in the surrounding cold plasma. Upscattering calculations yield near-infrared (NIR) high energy light curves that respect observational constraints of the quiescent NIR and X-ray fluxes in SgrA$^\star$
Comments15 pages, 14 figures, submitted to A&A
