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arXiv 0908.0310astro-ph.SRastro-ph.CO
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在扇形日冕环中传播低频慢磁声波的Hinode/EIS观测

Hinode/EIS observations of propagating low-frequency slow magnetoacoustic waves in fan-like coronal loops

T. J. Wang, L. Ofman, J. M. Davila, J. T. Mariska

摘要:

我们报告的第一个观察到的多周期性传播的扰动沿扇形日冕结构同时检测到的强度和多普勒频移的Fe XII 195 A线与EUV成像光谱仪(EIS)机载日野。这一观测结果为冠状地震学的应用提供了新的思路。我们分析了EIS坐盯模式观测的振荡使用运行差异和小波技术。检测到两个周期为12和25分钟的谐波。我们测得多普勒频移幅度为1-2 km/s,相对强度幅度为3%-5%,视传播速度为100-120 km/s。强度和多普勒频移振荡之间的振幅关系提供了令人信服的证据,这些传播功能是慢磁声波的表现。25分钟波的检测长度(在该波长上波是可见的)约为70-90 μ m,比TRACE先前检测到的5分钟波的检测长度长得多。这种差异可以用阻尼长度对热传导波周期的依赖性来解释。基于线性波理论,我们推导出的磁场的视线约59 $\pm$ 8度,一个真正的传播速度为128 $\pm$ 25公里/秒和温度为0.7 $\pm$ 0.3 MK附近的环路的脚点从我们的测量的倾斜。

英文摘要:

We report the first observation of multiple-periodic propagating disturbances along a fan-like coronal structure simultaneously detected in both intensity and Doppler shift in the Fe XII 195 A line with the EUV Imaging Spectrometer (EIS) onboard Hinode. A new application of coronal seismology is provided based on this observation. We analyzed the EIS sit-and-stare mode observation of oscillations using the running difference and wavelet techniques. Two harmonics with periods of 12 and 25 min are detected. We measured the Doppler shift amplitude of 1-2 km/s, the relative intensity amplitude of 3%-5% and the apparent propagation speed of 100-120 km/s. The amplitude relationship between intensity and Doppler shift oscillations provides convincing evidence that these propagating features are a manifestation of slow magnetoacoustic waves. Detection lengths (over which the waves are visible) of the 25 min wave are about 70-90 Mm, much longer than those of the 5 min wave previously detected by TRACE. This difference may be explained by the dependence of damping length on the wave period for thermal conduction. Based on a linear wave theory, we derive an inclination of the magnetic field to the line-of-sight about 59$\pm$8 deg, a true propagation speed of 128$\pm$25 km/s and a temperature of 0.7$\pm$0.3 MK near the loop's footpoint from our measurements.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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