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arXiv 1006.0140astro-ph.SR
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日冕中的大尺度亮锋--“EIT波”述评

Large-scale Bright Fronts in the Solar Corona: A Review of "EIT waves"

Peter T. Gallagher, David M. Long

摘要:

"EIT波”是大规模的日冕亮锋(CBF),首次在使用\emph{Solar and Heliospheric Observatory (SOHO)}上的极紫外成像望远镜(EIT)获得的195幅日冕图像中观察到。CBF通常被称为"EIT波”,它通常表现为以100- 700 km/s $^{-1}$的速度伪径向传播穿过太阳盘的扩散波前,波前宽度为50-100 μ m。($c_s\leq$ 200 km s $^{-1}$)和当地阿尔文速度($v_A\leq$ 1000 km s $^{-1}$),它们最初被解释为快模磁声波($v_{f}=(c_s^2 + v_A^2)^{1/2}$)。现在已知它们的传播会被磁声波速度变化的区域所改变,例如活动区域和冕洞,但也有证据表明冕洞边界处存在静止的CBF。后者导致了这样的建议,它们可能是焦耳加热或磁重联等过程的表现,而不是与波有关的现象。虽然CBF的一般形态学和运动学特性及其与日冕物质抛射的关系现在已经得到了很好的描述,但关于它们的激发和传播还有许多问题。特别是,这些神秘的事件作为磁流体动力学波或由于磁拓扑结构的变化的理论解释仍然是很多争论的话题。

英文摘要:

``EIT waves" are large-scale coronal bright fronts (CBFs) that were first observed in 195 Å images obtained using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the \emph{Solar and Heliospheric Observatory (SOHO)}. Commonly called ``EIT waves", CBFs typically appear as diffuse fronts that propagate pseudo-radially across the solar disk at velocities of 100--700 km s$^{-1}$ with front widths of 50-100 Mm. As their speed is greater than the quiet coronal sound speed ($c_s\leq$200 km s$^{-1}$) and comparable to the local Alfvén speed ($v_A\leq$1000 km s$^{-1}$), they were initially interpreted as fast-mode magnetoacoustic waves ($v_{f}=(c_s^2 + v_A^2)^{1/2}$). Their propagation is now known to be modified by regions where the magnetosonic sound speed varies, such as active regions and coronal holes, but there is also evidence for stationary CBFs at coronal hole boundaries. The latter has led to the suggestion that they may be a manifestation of a processes such as Joule heating or magnetic reconnection, rather than a wave-related phenomena. While the general morphological and kinematic properties of CBFs and their association with coronal mass ejections have now been well described, there are many questions regarding their excitation and propagation. In particular, the theoretical interpretation of these enigmatic events as magnetohydrodynamic waves or due to changes in magnetic topology remains the topic of much debate.

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。

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