标题： 盘磁层中的部分场开放与电流片形成 显示英文标题

标题： Partial Field Opening and Current Sheet Formation in the Disk Magnetosphere

摘要： 在本文中，我分析了导电吸积盘磁层中薄电流结构形成的過程，这是由于盘相对于中心恒星的旋转引起的场线扭转所引起的。 我考虑了一个轴对称的无力磁连恒星-盘配置，并研究了极向场线的扩展以及由于恒星和非均匀旋转盘之间的差分旋转引起的部分场线开放。 我提出一个简单的解析模型，描述了在强扩展极限下场的渐近行为。 我证明存在一个有限（约一弧度）的临界扭转角，超过该角度后，极向场开始迅速膨胀。 如果相对恒星-盘扭转在盘的某些有限区域增强（这可能发生在开普勒盘延伸到比共转半径更靠近中心恒星的情况下），那么，当扭转增加一定量时，场会接近部分开放的配置，一些场线会延伸到无限远。 与此同时，一个非常薄且径向扩展的电流层形成，从而为盘磁层中的重联提供了一条途径。 重联反过来导致了一个有趣的准周期行为场景，即磁连恒星-盘系统经历场膨胀、开放和重联的连续循环。 显示英文摘要

摘要： In this paper I analyze the process of formation of thin current structures in the magnetosphere of a conducting accretion disk in response to the field-line twisting brought about by the rotation of the disk relative to the central star. I consider an axisymmetric force-free magnetically-linked star--disk configuration and investigate the expansion of the poloidal field lines and partial field-line opening caused by the differential rotation between the star and a nonuniformly-rotating disk. I present a simple analytical model that describes the asymptotic behavior of the field in the strong-expansion limit. I demonstrate the existence of a finite (of order one radian) critical twist angle, beyond which the poloidal field starts inflating very rapidly. If the relative star--disk twist is enhanced locally, in some finite part of the disk (which may be the case for a Keplerian disk that extends inward significantly closer to the central star than the corotation radius), then, as the twist is increased by a finite amount, the field approaches a partially-open configuration, with some field lines going out to infinity. Simultaneous with this partial field opening, a very thin, radially extended current layer forms, thus laying out a way towards reconnection in the disk magnetosphere. Reconnection, in turn, leads to a very interesting scenario for a quasi-periodic behavior of magnetically-linked star--disk systems with successive cycles of field inflation, opening, and reconnection.