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arXiv 0912.0345astro-ph.SR
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太阳宁静区和活动区的过渡区

Solar transition region in the quiet Sun and active regions

H. Tian, W. Curdt, J. -S. He

摘要:

太阳过渡区(TR)是光球层上温度迅速升高、密度急剧下降的区域,它在日冕加热和太阳风加速中起着重要作用。长期持续的上升流存在于TR上部,并被解释为宁静太阳中大日冕环的质量供应的特征。日冕亮点是一种局部加热现象,我们在其中一个亮点中发现了不同的多普勒频移模式,这可能与扭曲环系统有关。在较低TR中的主要能量损失是Ly-alpha发射。已经发现,大多数Ly-alpha辐射分布在蓝色峰中更强,这是与高阶莱曼线相反的不对称性。当TR中部的下行流较强时,这种不对称性较强,表明TR流在谱线形成过程中起着重要作用。发现Ly-alpha的峰值分离在冕洞中比在安静的太阳中大,反映了两个区域之间不同的磁结构和辐射场。莱曼线轮廓在太阳黑子羽流区和本影区不发生反转,而在周围谱斑区有明显的反转。在TR温度下,太阳黑子羽流和本影的密度是比谱斑低10倍,这表明在TR温度下发射的太阳黑子等离子体更高,并且可能比谱斑区域更高。

英文摘要:

The solar transition region (TR), in which above the photosphere the tempera- ture increases rapidly and the density drops dramatically, is believed to play an important role in coronal heating and solar wind acceleration. Long-lasting up-flows are present in the upper TR and interpreted as signatures of mass supply to large coronal loops in the quiet Sun. Coronal bright points (BPs) are local heating phenomena and we found a different Doppler-shift pattern at TR and coronal temperatures in one BP, which might be related to the twisted loop system. The dominant energy loss in the lower TR is the Ly-alpha emission. It has been found that most Ly-alpha radiance profiles are stronger in the blue peak, an asymmetry opposite to higher order Lyman lines. This asymmetry is stronger when the downflow in the middle TR is stronger, indicating that the TR flows play an important role in the line formation process. The peak separation of Ly-alpha is found to be larger in coronal holes than in the quiet Sun, reflecting the different magnetic structures and radiation fields between the two regions. The Lyman line profiles are found to be not reversed in sunspot plume and umbra regions, while they are obviously reversed in the surrounding plage region. At TR temperatures, the densities of the sunspot plume and umbra are a factor of 10 lower than of the plage, indicating that the sunspot plasma emitting at TR temperatures is higher and possibly more extended above sunspots than above the plage region.

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