用太阳south pole附近的Hinode观测到的强度振荡：低频磁声波泄漏到日冕
Intensity oscillations observed with Hinode near the south pole of the Sun: leakage of low frequency magneto-acoustic waves into the solar corona
摘要：
目标。研究安静太阳磁网络上方太阳色球层/日冕的强度振荡。方法.本文分析了南极附近的太阳号上的极紫外成像光谱仪（EIS）观测到的He Ⅱ 256.32、Fe XI 188.23和Fe XII 195.12谱线的时间序列。然后，我们使用一个标准的小波工具，以产生功率谱的强度振荡以上的磁网络。结果在所有的谱线中得到~7 min的强度振荡，仅在He II中得到~13 min的强度振荡，概率为~96- 98%，这可能反映了磁声波在网络上方的传播过程。结论.我们认为，磁网络附近的双极磁冠下的无场空腔区域可以作为磁声波的谐振器。具有光球声速和颗粒尺度的空腔可以产生具有观测周期的波。波可以在过渡区/日冕中向上传播，并引起观察到的强度振荡。
英文摘要：
Aims. To study intensity oscillations in the solar chromosphere/corona above a quiet-Sun magnetic network. Methods. We analyse the time series of He II 256.32, Fe XI 188.23 and Fe XII 195.12 spectral lines observed by EUV Imaging Spectrometer (EIS) on board Hinode near the south pole. Then we use a standard wavelet tool to produce power spectra of intensity oscillations above the magnetic network. Results. We get ~7 min intensity oscillations in all spectral lines and ~13 min intensity oscillations only in He II with the probability of ~96-98 %, which probably reflects the process of magneto-acoustic wave propagation above the network. Conclusions. We suggest that field-free cavity areas under bipolar magnetic canopies in the vicinity of magnetic network may serve as resonators for the magneto-acoustic waves. The cavities with photospheric sound speed and granular dimensions may produce the waves with the observed periods. The waves may propagate upwards in the transition region/corona and cause observed intensity oscillations.
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