太阳极区冕洞内小尺度结构的紫外光谱研究

SOHO/SUMER太阳紫外光谱仪的N Ⅳ谱线观测到太阳南极区冕洞内存在许多小尺度结构，其空间尺度约1～几角秒，寿命尺度约1～几min。小尺度结构沿狭缝方向呈条状，视向多普勒速度可至几十km·s-1。在有的南极区冕洞区域内，小尺度结构的视向多普勒速度呈红、蓝移准周期性交错分布，持续时间长达100 min。部分小尺度结构在同一观测窗口的高温Ne ⅤⅢ谱线还可清晰显现。有的小尺度结构在Ne ⅤⅢ速度演化图的时间和位置与N Ⅳ 谱线速度图基本一致，但它们在Ne ⅤⅢ速度演化图中更延展和弥散。N Ⅳ紫外光谱显示部分小尺度结构谱线呈现非高斯形状，谱线两翼速度可达150 km·s-1，与太阳过渡区爆发事件的光谱特征相似。太阳过渡区爆发事件常出现在宁静区，SOHO/SUMER太阳紫外光谱仪的N Ⅳ谱线显示在南极区冕洞也可产生爆发事件，且具有较强的动力学特征。

Ultraviolet Spectroscopic Study on the Fine Structures in the Solar Polar Hole

Fine structures in the south solar polar coronal hole were observed by N Ⅳ line of SOHO/SUMER spectrograph. The scales of the fine structures range spatially range from 1 arcsec to several arcsecs, temporally from 1 min to several minutes, and parts of them are in strip shape along the slit direction. The line-of-sight velocity of them is up to tens of km·s-1 with red and blue shift intercrossed occasionally, which appear periodically as long as 100 minutes in some regions. Part of the fine structures can be clearly observed at the Ne ⅤⅢ line with higher formation temperature in the same spectral window. The time and location of some fine structures with high velocity in the Ne ⅤⅢ spectrum are almost the same as that in N Ⅳ spectrum, but they are extended and diffused in the Ne ⅤⅢ spectrum. Some fine structures have non-Gaussian profiles with the line-of-sight Doppler velocities up to 150 km·s-1 in the N Ⅳ blue/red wings, which is similar with the explosive events in the transition region. In the past, explosive events are small-scale dynamic phenomena often observed in the quiet-sun (QS) region, while their properties in coronal holes (CHs) remain unclear. Here, we find the EE-like events with strong dynamics in the south solar polar coronal hole by N Ⅳ line of SOHO/SUMER spectrograph.