Thermal instability and non-equilibrium in solar coronal loops: from coronal rain to long-period intensity pulsations
Thermal instability and non-equilibrium in solar coronal loops: from coronal rain to long-period intensity pulsations
复制标题
DOI：
10.1088/1361-6587/ab5406
复制
发表时间：
2019-11
影响因子：
2.2
通讯作者：
P. Antolin
中科院分区：
文献类型：
--
作者：
P. Antolin
磁场与物质的复杂相互作用是宇宙中多尺度观测到的一些最令人困惑的现象的关键，从实验室中的托卡马克等离子体约束实验到星际介质的结构。一个主要的天体物理学难题是日冕加热现象，太阳大气层的最外层，日冕，平均维持在数百万度的温度。然而，日冕也掩盖了一个冷却问题。事实上，最近的观测表明，更神秘的是，就像烤箱里的雪花一样，日冕拥有大量被称为日冕雨的冷物质，这些物质的温度和密度要低数百倍，它们构成了著名的日冕的种子。数值模拟表明，这种冷物质并不源于日冕加热机制的效率低下，而是由这些机制的特定时空特性造成的。因此，大部分日冕环（日冕的基本组成部分）被怀疑处于热非平衡状态（TNE），其特征是加热（蒸发）和冷却（冷凝）循环，其观测特征是热线中的长周期强度脉动和冷线中的热不稳定性驱动的日冕雨，现在都被普遍观察到。在本文中，我们回顾了TNE中观察到的热和冷物质的性质与不稳定性和潜在的日冕加热机制之间的密切联系。重点放在长期观察到的日冕雨上，与最近发现的长周期强度脉动相反，已经存在重要的研究。我们进一步确定了构成太阳物理学新的、快速发展的领域的悬而未决的问题。
The complex interaction of the magnetic field with matter is the key to some of the most puzzling observed phenomena at multiple scales across the Universe, from tokamak plasma confinement experiments in the laboratory to the filamentary structure of the interstellar medium. A major astrophysical puzzle is the phenomenon of coronal heating, upon which the most external layer of the solar atmosphere, the corona, is sustained at multi-million degree temperatures on average. However, the corona also conceals a cooling problem. Indeed, recent observations indicate that, even more mysteriously, like snowflakes in the oven, the corona hosts large amounts of cool material termed coronal rain, hundreds of times colder and denser, that constitute the seed of the famous prominences. Numerical simulations have shown that this cold material does not stem from the inefficiency of coronal heating mechanisms, but results from the specific spatio-temporal properties of these. As such, a large fraction of coronal loops, the basic constituents of the solar corona, are suspected to be in a state of thermal non-equilibrium (TNE), characterised by heating (evaporation) and cooling (condensation) cycles whose telltale observational signatures are long-period intensity pulsations in hot lines and thermal instability-driven coronal rain in cool lines, both now ubiquitously observed. In this paper, we review this yet largely unexplored strong connection between the observed properties of hot and cool material in TNE and instability and the underlying coronal heating mechanisms. Focus is set on the long-observed coronal rain, for which significant research already exists, contrary to the recently discovered long-period intensity pulsations. We further identify the outstanding open questions in what constitutes a new, rapidly growing field of solar physics.