Nonlinear Effects in Three-minute Oscillations of the Solar Chromosphere. II. Measurement of Nonlinearity Parameters at Different Atmospheric Levels
Nonlinear Effects in Three-minute Oscillations of the Solar Chromosphere. II. Measurement of Nonlinearity Parameters at Different Atmospheric Levels
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太阳色球层三分钟振荡的非线性效应。
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Y. Litvinenko
中科院分区：
文献类型：
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作者：
J. Chae;Kyuhyoun Cho;D. Song;Y. Litvinenko
最近的理论研究表明，在每个大气层的三分钟速度振荡的非线性可以量化的两个独立的参数-陡峭化参数和速度振幅参数。我们第一次测量了这两个参数在不同的大气水平，通过分析一组光谱线形成的太阳黑子的不同高度范围内的温度最低的过渡区。光谱数据由古德太阳望远镜的快速成像太阳光谱仪和界面区域成像光谱仪拍摄。其结果是，从小波功率谱的速度振荡在不同的高度，我们清楚地确定了增长的二次谐波振荡与陡峭的速度振荡，表明周期为1.2至1.5分钟的高频振荡起源于非线性的三分钟振荡在上色球层。我们还发现，测量的非线性参数的变化是一致的理论预期，即三分钟振荡的非线性随高度的增加，激波形成在上层色球。然而，理论和观测之间也存在差异，这表明需要改进理论和测量技术。
Recent theoretical studies suggest that the nonlinearity of three-minute velocity oscillations at each atmospheric level can be quantified by the two independent parameters—the steepening parameter and the velocity amplitude parameter. For the first time, we measured these two parameters at different atmospheric levels by analyzing a set of spectral lines formed at different heights of sunspots ranging from the temperature minimum to the transition region. The spectral data were taken by the Fast Imaging Solar Spectrograph of the Goode Solar Telescope, and by the Interface Region Imaging Spectrograph. As a result, from the wavelet power spectra of the velocity oscillations at different heights, we clearly identified the growth of the second harmonic oscillations associated with the steepening of the velocity oscillation, indicating that higher-frequency oscillations of periods of 1.2 to 1.5 minutes originate from the nonlinearity of the three-minute oscillations in the upper chromosphere. We also found that the variation of the measured nonlinearity parameters is consistent with the theoretical expectation that the nonlinearity of the three-minute oscillations increases with height, and shock waves form in the upper chromosphere. There are, however, discrepancies as well between theory and observations, suggesting the need to improve both theory and the measurement technique.