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arXiv 0910.4059astro-ph.SR
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日珥中的大振幅振荡

Large Amplitude Oscillations in Prominences

D. Tripathi, H. Isobe, R. Jain

摘要:

自20世纪30年代首次报道日珥中的振荡以来,在理解这些振荡现象的性质方面取得了重大的理论和观测进展,从而导致了所谓的“日珥地震学”的全新领域。有两种类型的振荡现象观察到的双折射;“小振幅振荡”(~2-3 km s $^{-1}$),这是很常见的和“大振幅振荡”($>$ 20 km s $^{-1}$),其中的观测是稀缺的。在H $α$观测中发现了大振幅振荡,如“闪烁灯丝”,在H $α$、EUV、微波和He 10830观测中也发现了天面运动。历史上,人们认为,大振幅振荡的连续性是由扰动,如快模MHD波(莫顿波)产生的远程耀斑。此外,最近的观测表明,附近的耀斑或喷流也能在双折射中产生如此大的振幅振荡。在横向和纵向都可以观察到的大振幅振荡具有从几十分钟到几个小时不等的周期。利用观测到的振荡周期和简单的理论模型,获得的磁场在双折射已表现出相当好的协议与直接测量之一,因此,证明双折射地震学作为一个强大的诊断工具。在极少数情况下,当大振幅振荡已被观察到之前或期间的喷发,振荡可以被用来诊断的稳定性和喷发机制。本文综述了日珥地震学背景下大振幅振荡的观测特性及其触发机制和稳定性的最新进展和认识。

英文摘要:

Since the first reports of oscillations in prominences in 1930s there have been major theoretical and observational advances to understand the nature of these oscillatory phenomena leading to a whole new field of so called "prominence seismology". There are two types of oscillatory phenomena observed in prominences; "small amplitude oscillations" (~2-3 km s$^{-1}$) which are quite common and "large amplitude oscillations" ($>$20 km s$^{-1}$) for which observations are scarce. Large amplitude oscillations have been found as "winking filament" in H$α$ as well as motion in the sky plane in H$α$, EUV, micro-wave and He 10830 observations. Historically, it was suggested that the large amplitude oscillations in prominences were triggered by disturbances such as fast-mode MHD waves (Moreton wave) produced by remote flares. Recent observations show, in addition, that near-by flares or jets can also create such large amplitude oscillations in prominences. Large amplitude oscillations, which are observed both in transverse as well as longitudinal direction, have a range of periods varying from tens of minutes to a couple of hours. Using the observed period of oscillation and simple theoretical models, the obtained magnetic field in prominences has shown quite a good agreement with directly measured one and therefore, justifies prominences seismology as a powerful diagnostic tool. On rare occasions, when the large amplitude oscillations have been observed before or during the eruption, the oscillations may be applied to diagnose the stability and the eruption mechanism. Here we review the recent developments and understanding in the observational properties of large amplitude oscillations and their trigger mechanisms and stability in the context of prominence seismology.

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