MEASUREMENTS OF OUTFLOW VELOCITIES IN ON-DISK PLUMES FROM EIS/HINODE OBSERVATIONS
MEASUREMENTS OF OUTFLOW VELOCITIES IN ON-DISK PLUMES FROM EIS/HINODE OBSERVATIONS
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DOI：
10.1088/0004-637x/794/2/109
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发表时间：
2014-08
期刊：
影响因子：
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通讯作者：
H. Fu;L. Xia;Bo Li;Zhenghua Huang;Fangran Jiao;Chaozhou Mou
中科院分区：
文献类型：
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作者：
H. Fu;L. Xia;Bo Li;Zhenghua Huang;Fangran Jiao;Chaozhou Mou
在过去的几十年里，羽流对太阳风的贡献一直是热门话题。Hinode上的极紫外成像光谱仪提供了一种独特的手段，通过对日冕发射线的直接多普勒频移测量来推断日冕高度的外流速度。这样的直接多普勒频移测量是不可能与以前的光谱仪。我们测量的外流速度在日冕高度在几个磁盘上的长时间的羽流，这是位于冕洞（CH），并在整个观测期间显示出显着的蓝移。在一种情况下，一个羽状物是相隔四个小时测量的。推导出的出流速度是一致的，表明流动是准定常的。此外，我们还提供了沿着羽流的外流速度剖面，发现在1.02 R时修正视线效应后的速度可达10 km s−1，在1.03 R时可达15 km s−1，在1.05 R时可达25 km s−1。这种稳定加速的明显特征，再加上羽流底部没有明显的蓝移，为羽流模型提供了一个重要的限制。在1.03 R的高度，EIS还推导出密度为1.3 × 108 cm−3，导致质子通量约为4.2 × 109 cm−2 s−1，换算为1 Au，这比假设径向膨胀的典型太阳风的质子输入高出一个数量级。这表明CH羽流可能是太阳风的一个重要来源。
The contribution of plumes to the solar wind has been subject to hot debate in the past decades. The EUV Imaging Spectrometer (EIS) on board Hinode provides a unique means to deduce outflow velocities at coronal heights via direct Doppler shift measurements of coronal emission lines. Such direct Doppler shift measurements were not possible with previous spectrometers. We measure the outflow velocity at coronal heights in several on-disk long-duration plumes, which are located in coronal holes (CHs) and show significant blueshifts throughout the entire observational period. In one case, a plume is measured four hours apart. The deduced outflow velocities are consistent, suggesting that the flows are quasi-steady. Furthermore, we provide an outflow velocity profile along the plumes, finding that the velocity corrected for the line-of-sight effect can reach 10 km s−1 at 1.02 R☉, 15 km s−1 at 1.03 R☉, and 25 km s−1 at 1.05 R☉. This clear signature of steady acceleration, combined with the fact that there is no significant blueshift at the base of plumes, provides an important constraint on plume models. At the height of 1.03 R☉, EIS also deduced a density of 1.3 × 108 cm−3, resulting in a proton flux of about 4.2 × 109 cm−2 s−1 scaled to 1 AU, which is an order of magnitude higher than the proton input to a typical solar wind if a radial expansion is assumed. This suggests that CH plumes may be an important source of the solar wind.