均匀重力下的扭曲日冕环
Twisted coronal loops in uniform gravity
摘要：
日冕环发射剖面通常沿其整个长度具有非常恒定的宽度，这与基于模型日冕磁场强度随高度降低的预期相矛盾。与此同时，保罗·贝兰（Paul Bellan）提出了一个理论模型，在这个模型中，一个最初空的、扭曲的、无力的环，在没有显著的引力效应的情况下，通过每个脚点的上升流被等离子体填充，形成一个狭窄的、恒定横截面的环形。在本文中，我们专注于平衡态，包括分层的均匀重力，同时保留磁场扭曲的影响。比较这些与相关的无力平衡，它被发现，低$β$等离子体在日冕条件下的注射是不太可能改变的形状的一个循环显着。这些线性平衡仅适用于环路的内部和边界，外部影响由边界总压力模拟。总压与周围环境的平衡和重力分层的影响是抑制环箍缩到恒定的横截面。只有当等离子体$β$足够高以使等离子体重新配置外场，并且流体静力学标度高度远大于环的尺寸时，最终状态才可能具有几乎恒定的截面。我们不希望这种情况发生在日冕中。
英文摘要：
Coronal loop emission profiles are often of remarkably constant width along their entire lengths, contradicting expectations based on model coronal magnetic field strengths decreasing with height. Meanwhile Paul Bellan has produced a theoretical model in which an initially empty, twisted force-free loop, on being filled with plasma via upflow at each foot point, in the absence of significant gravitational effects, forms a narrow, filamentary loop of constant cross-section. In this paper, we focus on equilibrium states that include stratification by uniform gravity while retaining the effects of magnetic field twist. Comparing these with related force-free equilibria, it is found that injection of low-$β$ plasma under coronal conditions is not likely to change the shape of a loop significantly. These linear equilibria apply to the interiors and boundaries of loops only, with external influences modeled by boundary total pressures. The effects of total pressure balance with surroundings and of gravitational stratification are to inhibit the pinching of a loop to a constant cross-section. Only if the plasma $β$ were high enough for the plasma to reconfigure the external field and the hydrostatic scale height much greater than the loop size could the final state have nearly constant cross section. We do not expect this to occur in the corona.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
