发表机构
SUPA School of Physics & Astronomy, University of Glasgow; Space Science Laboratory, University of California, Berkeley; University of Warwick; Rosseland Centre for Solar Physics, University of Oslo（格拉斯哥大学物理与天文学学院; 加州大学伯克利分校空间科学实验室; 华威大学; 奥斯陆大学罗瑟兰太阳物理中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用太阳动力学天文台EVE的观测，构建发射线质心波长的多普勒功率谱，研究太阳大气中对流驱动运动产生的变化，揭示谱特征，未发现柯尔莫哥洛夫湍流证据，检测到高于10mHz的EUV多普勒变化。
AI 中文摘要
太阳光球层中对流驱动的运动可在色球层、过渡区和日冕中产生宽带多普勒变化。本文利用太阳动力学天文台（SDO）上的极端紫外变率实验（EVE）的“恒星太阳”观测数据，通过对跨越35-104nm波长的发射线质心波长的3小时序列进行非相干求和，构建了高信噪比的多普勒功率谱。这些谱揭示了一个具有两个类似哈维分量的宽功率谱连续谱，其中一个分量延伸到50mHz的奈奎斯特频率，并具有陡峭的幂律尾部。与色球层/过渡区形成的谱线相比，日冕中形成的谱线在与米粒组织尺度对流相关的5mHz哈维分量中的多普勒幅度要小得多。基于观测到的连续谱，没有证据表明（在所研究的26条谱线中的任何一条）存在柯尔莫哥洛夫湍流，柯尔莫哥洛夫湍流预测了一个平坦的连续谱分量，其多普勒方差<v^2>~f^(-5/3)作为频率f的函数。推断出的总非热均方根速度（>0.1mHz）约为15km/s，与先前从非热线宽估计的日冕“微湍流”一致。这些观测首次清晰地检测到高于约10mHz的恒星太阳EUV多普勒变化，并证明了全圆盘EUV光谱学在探测整个太阳大气中湍流能量传输方面的潜力。
英文摘要
Convectively driven motions in the solar photosphere can generate broadband Doppler variability across the chromosphere, transition region and corona. Here we investigate this variability using "Sun-as-a-Star" observations from the Extreme Ultraviolet Variability Experiment (EVE) aboard the Solar Dynamics Observatory, constructing high signal-to-noise Doppler power spectra by incoherently averaging spectra from 3-hour sequences of the centroid wavelengths of emission lines that span wavelengths 35-104 nm. The spectra reveal a broad power-spectral continuum with two "Harvey" components, one of which extends to the Nyquist frequency at 50 mHz with a steep power-law tail. All emission lines have substantial power both above and below the nominal acoustic cutoff frequency at 5 mHz, but none of the power spectra show maxima corresponding to p-mode or chromospheric 3-minute oscillations. Lines formed in the corona, as compared with those of the chromosphere/transition region, have substantially less Doppler amplitude in the Harvey spectrum associated with granulation-scale convection. Based on the observed continuum, there is no evidence (in any of the 26 lines studied) for Kolmogorov turbulence, which predicts a flat continuum component with Doppler variance <v^2>~f^(-5/3) as a function of frequency f. The total inferred RMS velocities (>0.1 mHz) are roughly consistent with coronal microturbulence estimates from excess line widths. These observations provide the first clear detection of Sun-as-a-star EUV Doppler variability above ~10 mHz and demonstrate the potential of full-disk EUV spectroscopy to probe turbulent energy transport throughout a stellar atmosphere.
CommentsSubmitted to MNRAS
