发表机构
Ludwig-Maximilians-Universität München; Excellence Cluster Origins; Max-Planck-Institut für Extraterrestrische Physik（慕尼黑大学; 起源卓越集群; 马克斯·普朗克地外物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究构建双相模型统一磁热风与光蒸发，揭示盘消散两种状态：高效磁通损失打开光蒸发间隙，磁通保持则推迟消散约2.7百万年，且两种状态均从内向外清除盘。
AI 中文摘要
原行星盘消散由两个通常分别建模的过程驱动：光蒸发和磁流体动力学（MHD）盘风。全球模拟表明，在内盘区域，这些并非不同的外流，而是单一的磁热风。我们构建了一个闭合形式的双相模型来尊重这一事实。一个单场线风，其基底由辐照温度和穿透柱密度决定，提供发射并驱动长期演化，光蒸发作为汇与之卷积。磁通闭合关系 $B_z\propto\Sigma^q$ 是自限制的：对于 $q\le1/2$，仅靠耗损无法使盘退磁，因此消散需要独立的磁通损失，由磁雷诺数 $\mathcal{R}_m$ 参数化。对耦合系统积分产生两种状态。高效磁通损失（$\mathcal{R}_m\lesssim1$）使磁化前沿后退超过一个数量级，并打开光蒸发间隙。磁通保持（$\mathcal{R}_m\gg1$）驱动前沿向外，维持吸积，并将消散推迟约2.7百万年。通过从恒星辐照推导基底而非预设，我们发现冷发射近似在盘演化的早期阶段有效：将基底锚定在等离子体均分（$\beta_{\rm base} \sim 1$）将辐照对磁力臂的影响限制在磁热环内，使峰值吸积率与入射通量解耦。两种状态均从内向外清除盘，要么通过光蒸发放大的腔壁，要么通过扩张的磁热前沿。
英文摘要
Protoplanetary disc dispersal is driven by two processes usually modelled separately: photoevaporative and magnetohydrodynamic (MHD) disc winds. Global simulations indicate that in the inner disc these are not distinct outflows but a single magnetothermal wind. We assemble a closed-form, two-phase model that respects it. A single-field-line wind, whose base is fixed by the irradiated temperature and penetration column, supplies the launch and feeds a secular evolution, with photoevaporation convolved on as a sink. The flux closure $B_z\proptoΣ^q$ is self-limiting: for $q\le1/2$ depletion alone cannot demagnetise the disc, so dispersal requires independent flux loss, parameterised by the magnetic Reynolds number $\mathcal{R}_m$. Integrating the coupled system yields two regimes. Efficient flux loss ($\mathcal{R}_m\lesssim1$) lets the magnetisation front recede by over an order of magnitude and opens a photoevaporative gap. Flux retention ($\mathcal{R}_m\gg1$) drives the front outward, sustains accretion, and defers dispersal by $\approx2.7$~Myr. Deriving the base from stellar irradiation instead of prescribing it, we find that the cold-launch approximation is valid during the early stages of disc evolution: anchoring the base at plasma equipartition ($β_{\rm base} \sim 1$) confines irradiation's influence on the magnetic lever arm to the magnetothermal annulus, decoupling the peak accretion rate from the incident flux. Both regimes clear the disc inside-out, through either a photoevaporatively amplified cavity wall or an expanding magnetothermal front.
Comments27 pages, 11 figures, submitted to MNRAS, comments are welcome
