Evidence for Parametric Decay Instability in the Lower Solar Atmosphere
Evidence for Parametric Decay Instability in the Lower Solar Atmosphere
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DOI：
10.3847/1538-4357/ac7147
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Michael Hahn;Xiangrong Fu;D. Savin
中科院分区：
文献类型：
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作者：
Michael Hahn;Xiangrong Fu;D. Savin
我们发现的参数衰减不稳定性（PDI）在太阳低层大气中的第一次观察的证据。特别是，我们发现，太阳过渡区附近的密度波动的功率谱类似的速度波动的功率谱，但与频率轴放大约2倍。这些结果来自于对界面区成像光谱仪在极冕洞过渡区观测到的Si iv线的分析。我们还发现，密度涨落的径向速度约为75 km s−1，而速度涨落要快得多，估计速度为250 km s−1，正如在过渡区分别对声波和阿尔文波的预期。理论计算表明，这种频率关系是一致的预期从PDI的等离子体条件的观察区域。这些测量表明，在过渡区声波和阿尔芬波之间的相互作用，这是参数衰减不稳定性的证据。
We find evidence for the first observation of the parametric decay instability (PDI) in the lower solar atmosphere. In particular, we find that the power spectrum of density fluctuations near the solar transition region resembles the power spectrum of the velocity fluctuations but with the frequency axis scaled up by about a factor of 2. These results are from an analysis of the Si iv lines observed by the Interface Region Imaging Spectrometer in the transition region of a polar coronal hole. We also find that the density fluctuations have radial velocity of about 75 km s−1 and that the velocity fluctuations are much faster with an estimated speed of 250 km s−1, as is expected for sound waves and Alfvén waves, respectively, in the transition region. Theoretical calculations show that this frequency relationship is consistent with those expected from PDI for the plasma conditions of the observed region. These measurements suggest an interaction between sound waves and Alfvén waves in the transition region, which is evidence for the parametric decay instability.