Characterized by cyclic axisymmetric perturbations to both the magnetic and fluid parameters, magnetohydrodynamic fast sausage modes (FSMs) have proven useful for solar coronal seismology given their strong dispersion. This review starts by summarizing the dispersive properties of the FSMs in the canonical configuration where the equilibrium quantities are transversely structured in a step fashion. With this preparation we then review the recent theoretical studies on coronal FSMs, showing that the canonical dispersion features have been better understood physically, and further exploited seismologically. In addition, we show that departures from the canonical equilibrium configuration have led to qualitatively different dispersion features, thereby substantially broadening the range of observations that FSMs can be invoked to account for. We also summarize the advances in forward modeling studies, emphasizing the intricacies in interpreting observed oscillatory signals in terms of FSMs. All these advances notwithstanding, we offer a list of aspects that remain to be better addressed, with the physical connection of coronal FSMs to the quasi-periodic pulsations in solar flares particularly noteworthy.

中文翻译：

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日冕中的磁流体动力快速香肠波

磁流体动力学快速香肠模式 (FSM) 的特点是对磁参数和流体参数都有循环轴对称扰动，因为它们具有很强的色散性，因此已被证明可用于太阳日冕地震学。本综述首先总结了规范配置中 FSM 的色散特性，其中平衡量以阶梯方式横向构造。通过这种准备，我们然后回顾了最近关于日冕 FSM 的理论研究，表明规范色散特征在物理上得到了更好的理解，并在地震学上得到了进一步的利用。此外，我们表明偏离规范平衡配置导致了质量上不同的色散特征，从而大大拓宽了 FSM 可以用来解释的观察范围。我们还总结了前向建模研究的进展，强调了根据 FSM 解释观察到的振荡信号的复杂性。尽管取得了所有这些进展，我们还是提供了一系列有待更好解决的方面，其中日冕 FSM 与太阳耀斑中准周期性脉动的物理联系特别值得注意。