木星系周星云中湍流黏度的上限
An Upper Limit on Turbulent Viscosity in the Circumjovian Nebula
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中文总结 AI 辅助
该研究通过分析木星系周盘的冰质固体漂移循环，结合Shakura-Sunyaev黏度参数，得出卫星形成区湍流黏度的上限，且该上限随冰质粒子碎裂阈值线性变化。
中文摘要 AI 辅助
行星周盘是开放的动力学系统，由子午环流维持，该环流沿近极向流线从母星云抽取气体和尘埃，最终通过黏性驱动的面内外流返回部分物质。在这类盘中，水冰线是固体质量的积累位点：向内漂移的冰质固体在冰线内侧升华，产生的蒸气被气体平流向外输送，在冰线外侧重新凝结使物质恢复至小斯托克斯数。这种漂移介导的循环的运行要求质量占主导的冰质聚集体的碎裂限制斯托克斯数超过固体径向漂移反转的平衡斯托克斯数。由于前者与Shakura-Sunyaev黏度参数α成反比，而后者与α成正比，这一要求对卫星形成区的湍流强度给出了紧凑的上限。采用被潮汐半径截断的主动加热稳态木星系周盘，对于冰质粒子碎裂阈值v_f≈1 m·s⁻¹（适用于黏附性质类似硅酸盐尘埃的冷冰），我们得到α≲10⁻³的边际界限；对于黏附性更强的暖冰（v_f≈5 m·s⁻¹），该界限线性缩放至α≲5×10⁻³。该界限无明确依赖于盘的质量通量，完全由木星系周星云的局地热状态、压力梯度和几何结构决定。
英文摘要
Circumplanetary disks are open, dynamic systems sustained by a meridional circulation that draws gas and dust from the parent nebula along nearly polar streamlines, and ultimately returns some of this material through a viscously driven, in-plane outflow. In such a disk, the water ice line acts as a site of solid-mass accumulation: inward-drifting icy solids sublimate interior to the ice line, the resulting vapor is advected outward by the gas, and recondensation beyond the ice line resets the material to a small Stokes number. The operation of this drift-mediated loop requires the fragmentation-limited Stokes number of the mass-dominant icy aggregates to exceed the equilibrium Stokes number at which the radial drift of solids reverses. Because the former scales inversely with the Shakura-Sunyaev viscosity parameter $α$ while the latter is directly proportional to it, this requirement yields a compact upper bound on the vigor of turbulence in the satellite-forming region. Adopting an actively heated, steady-state circumjovian disk truncated at the tidal radius, we find a marginal bound of $α\lesssim 10^{-3}$ for an icy-particle fragmentation threshold of $v_f\simeq1\,{\rm m\,s^{-1}}$ - appropriate for cold ice with sticking properties similar to silicate dust. This bound scales linearly with $v_f$, reaching $α\lesssim5\times10^{-3}$ for more adhesive, warm ice ($v_f\simeq5\,{\rm m\,s^{-1}}$). The bound carries no explicit dependence on the disk's mass flux, and is set entirely by the local thermal state, pressure gradient, and geometry of the circumjovian nebula.
发表机构
- California Institute of Technology（加州理工学院）
- University of Michigan（密歇根大学）
机构由 AI 辅助整理，请以论文原文为准。
