Signatures of Alfvén waves in the polar coronal holes as seen by EIS/Hinode
Signatures of Alfvén waves in the polar coronal holes as seen by EIS/Hinode
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DOI：
10.1051/0004-6361/200912242
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发表时间：
2009-06
影响因子：
6.5
通讯作者：
D. Banerjee;D. Pérez-Suárez;J. G. Doyle
中科院分区：
文献类型：
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作者：
D. Banerjee;D. Pérez-Suárez;J. G. Doyle
上下文我们诊断的性质的羽流和羽流间区域在极地冕洞和波的作用，在太阳风的加速。目标。我们试图检测阿尔芬波是否存在于极冕洞通过EUV线宽的变化。方法.使用光谱观测在极冕洞区域与EIS光谱仪日出，我们研究的线宽和电子密度的变化作为高度的函数。我们使用Fe XII 186.88 A和195.119 A以及Fe XIII 203.82 A和202.04 A的密度敏感线对。结果在极区，谱线宽度资料表明，非热视线速度从临边10 "处的2 6 km s-1增加到临边15 0“处的4 2km s-1（约11万km）。在相同的距离上，电子密度从3.3 × 109 cm-3下降到1.9 × 108 cm-3。这些结果意味着，非热速度是成反比的平方根的电子密度，在很好的协议与无阻尼径向传播的线性阿尔芬波的预测。我们的数据提供了极冕洞区域阿尔芬波的特征，这对太阳风的加速可能很重要。© 2009 ESO。
Context. We diagnose the properties of the plume and interplume regions in a polar coronal hole and the role of waves in the acceleration of the solar wind. Aims. We attempt to detect whether Alfven waves are present in the polar coronal holes through variations in EUV line widths. Methods. Using spectral observations performed over a polar coronal hole region with the EIS spectrometer on Hinode, we study the variation in the line width and electron density as a function of height. We use the density sensitive line pairs of Fe XII 186.88 A and 195.119 A and Fe XIII 203.82 A and 202.04 A. Results. For the polar region, the line width data show that the nonthermal line-of-sight velocity increases from 26 km s -1 at 10′′ above the limb to 42 km s -1 some 150′′ (i.e. ∼110 000 km) above the limb. The electron density shows a decrease from 3.3 × 10 9 cm -3 to 1.9 × 10 8 cm -3 over the same distance.Conclusions. These results imply that the nonthermal velocity is inversely proportional to the quadratic root of the electron density, in excellent agreement with what is predicted for undamped radially propagating linear Alfven waves. Our data provide signatures of Alfven waves in the polar coronal hole regions, which could be important for the acceleration of the solar wind. © 2009 ESO.