Evidence of Shock-driven Turbulence in the Solar Chromosphere
Evidence of Shock-driven Turbulence in the Solar Chromosphere
复制标题
太阳色球层中冲击驱动的湍流的证据
DOI：
10.1086/591790
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
A. Vecchio
中科院分区：
文献类型：
--
作者：
K. Reardon;F. Lepreti;V. Carbone;A. Vecchio
我们研究了太阳色球的声学特性在高频率制度使用的时间序列的速度测量色球Ca II 854.2 nm线采取的干涉二维光谱仪（IBIS）。我们专注于安静的太阳的行为，应用傅立叶分析，并表征观测的速度增量的概率密度函数（PDF）。我们确认存在显着的振荡波动功率以上的截止频率，并发现它服从幂律分布的频率高达我们的25兆赫奈奎斯特极限。色球PDF是非高斯和不对称的，并且它们在网络、原纤维和网络间区域之间不同。这表明色球层的高频功率并不是简单地从光球层向上传播的短周期波的结果，而是色球层内由截止频率附近的冲击振荡产生的湍流的特征。色球层中这种普遍存在的广泛运动可能对日冕环振荡的激发产生影响。
We study the acoustic properties of the solar chromosphere in the high-frequency regime using a time sequence of velocity measurements in the chromospheric Ca II 854.2 nm line taken with the Interferometric Bidimensional Spectrometer (IBIS). We concentrate on quiet-Sun behavior, apply Fourier analysis, and characterize the observations in terms of the probability density functions (PDFs) of velocity increments. We confirm the presence of significant oscillatory fluctuation power above the cutoff frequency and find that it obeys a power-law distribution with frequency up to our 25 mHz Nyquist limit. The chromospheric PDFs are non-Gaussian and asymmetric, and they differ among the network, fibril, and internetwork regions. This suggests that the chromospheric high-frequency power is not simply the result of short-period waves propagating upward from the photosphere but rather is the signature of turbulence generated within the chromosphere from shock oscillations near the cutoff frequency. The presence of this pervasive and broad spectrum of motions in the chromosphere is likely to have implications for the excitation of coronal loop oscillations.