KINK AND SAUSAGE MODES IN NONUNIFORM MAGNETIC SLABS WITH CONTINUOUS TRANSVERSE DENSITY DISTRIBUTIONS
KINK AND SAUSAGE MODES IN NONUNIFORM MAGNETIC SLABS WITH CONTINUOUS TRANSVERSE DENSITY DISTRIBUTIONS
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DOI：
10.1088/0004-637x/814/1/60
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
Hui Yu;Bo Li;Shao-Xia Chen;M. Guo
中科院分区：
文献类型：
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作者：
Hui Yu;Bo Li;Shao-Xia Chen;M. Guo
我们研究了横向于日冕板的连续密度结构对其所支持的基本站立扭结和香肠模式的色散特性的影响。我们推导了无压直板中具有一般横向密度分布的线性快波的一般频散关系(DRS)，并重点讨论了密度不均匀发生在任意宽度和任意形式的层中的情况。通过相应的依赖于时间的计算，证明了解与DRS的物理相关性。对于所考察的所有剖面，无论纵向波数k如何，最低阶扭结模都被俘获。当k是相对于密度剖面呈阶跃函数形式的情况的观测范围时，连续密度分布导致它们的周期相差≲为13%。香肠模式和其他扭结模式的分支在小k处是泄漏的，它们的周期和衰减时间受横向密度分布的规定，特别是长度尺度的影响很大。这些模式具有足够高的质量，只有代表耀斑循环的物理参数才能观察到。我们的结论是，虽然与阶跃函数分布相关的较简单的DR可以用于低阶扭结模，但关于横向密度结构的详细信息需要被纳入到香肠模和高阶扭结模的研究中。
We examine the influence of a continuous density structuring transverse to coronal slabs on the dispersive properties of fundamental standing kink and sausage modes supported therein. We derive generic dispersion relations (DRs) governing linear fast waves in pressureless straight slabs with general transverse density distributions, and focus on cases where the density inhomogeneity takes place in a layer of arbitrary width and in arbitrary form. The physical relevance of the solutions to the DRs is demonstrated by the corresponding time-dependent computations. For all profiles examined, the lowest order kink modes are trapped regardless of longitudinal wavenumber k. A continuous density distribution introduces a difference to their periods of ≲13% when k is the observed range relative to the case where the density profile takes a step function form. Sausage modes and other branches of kink modes are leaky at small k, and their periods and damping times are heavily influenced by how the transverse density profile is prescribed, in particular the length scale. These modes have sufficiently high quality to be observable only for physical parameters representative of flare loops. We conclude that while the simpler DR pertinent to a step function profile can be used for the lowest order kink modes, the detailed information on the transverse density structuring needs to be incorporated into studies of sausage modes and higher order kink modes.