发表机构
Institute for Advanced Studies in Basic Sciences (IASBS)（基础科学高等研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过MHD模拟揭示，大尺度极向盘磁场对稳定准直喷流的形成与维持至关重要，而恒星偶极磁场虽影响演化，但单独作用时喷流微弱不稳定。
AI 中文摘要
我们研究了在不同磁场构型穿透的磁扩散、亚开普勒吸积盘中喷流的形成。我们采用PLUTO代码，在球坐标下进行了二维、轴对称磁流体动力学模拟。结果表明，参考模拟（其中盘被初始的大尺度极向磁场穿透）达到了准稳态，并产生了良好准直的喷流。动能和磁力矩显著，并随时间平滑演化。吸积过程平稳建立，约26%的吸积物质被输送到外流中。相反，仅施加纯恒星偶极磁场会产生微弱且不稳定的外流，其特征是角动量输运效率低下，吸积受到强烈抑制。此外，在恒星偶极磁场与盘初始极向磁场同时存在的模拟中，盘磁场主要稳定系统，并促进盘中的角动量输运，维持显著的外流质量通量。进一步地，我们进行了额外模拟，明确包含了与盘截断区域相关的内间隙。这些模拟旨在检验最内盘区域处理的稳健性，并确认我们的主要结论对该间隙的存在不敏感。总体而言，我们的发现表明，尽管恒星偶极场的强度在吸积-喷流结构的演化中起着重要作用，但贯穿盘的大尺度极向磁场对于启动和维持稳定且良好准直的磁化喷流至关重要。
英文摘要
We study jet formation from a magnetically diffusive, sub-Keplerian accretion disk threaded by different magnetic field configurations. We present two dimensional, axisymmetric MHD simulations in spherical coordinates employing the PLUTO code. Our results show that the reference simulation, in which the disk is threaded by an initial large scale poloidal magnetic field, reaches a quasi steady state and produces a well collimated jet.Both kinetic and magnetic torques are significant and evolve smoothly over time. The accretion process is established smoothly, with about 26\% of the accreting material being delivered into the outflow. Alternatively, applying a purely stellar dipolar magnetic field produces weak and unstable outflows, characterized by inefficient angular momentum transport and strongly suppressed accretion. Additionally, in simulations where the stellar dipolar magnetic field is present alongside the disk's initial poloidal magnetic field, the disk magnetic field predominantly stabilizes the system. It also facilitates angular momentum transport from the disk and sustains a significant outflow mass flux. Furthermore, we performed additional simulations that explicitly include an inner gap associated with the disk truncation region. These simulations were designed as a robustness test of the treatment of the innermost disk region and confirm that our main conclusions are not sensitive to the presence of this gap. Overall, our findings demonstrate that although the magnitude of stellar dipole plays an important role in the evolution of the accretion-ejection structure, the large scale poloidal magnetic field threading the disk is essential for launching and sustaining a stable and well collimated magnetized jet.
Comments23 pages, 20 figures, Accepted for publication in Astrophysical Journal, comments are welcome
