An overall view of temperature oscillations in the solar chromosphere with ALMA
An overall view of temperature oscillations in the solar chromosphere with ALMA
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DOI：
10.1098/rsta.2020.0174
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发表时间：
2020-10
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通讯作者：
S. Jafarzadeh;S. Wedemeyer;B. Fleck;M. Stangalini;D. Jess;R. Morton;M. Szydlarski;V. Henriques;X. Zhu;T. Wiegelmann;J. C. Guevara Gómez;S. Grant;B. Chen;K. Reardon;S. White
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作者：
S. Jafarzadeh;S. Wedemeyer;B. Fleck;M. Stangalini;D. Jess;R. Morton;M. Szydlarski;V. Henriques;X. Zhu;T. Wiegelmann;J. C. Guevara Gómez;S. Grant;B. Chen;K. Reardon;S. White
通过直接测量气体温度，阿塔卡马大毫米/亚毫米阵列(ALMA)为研究太阳色球提供了一种新的诊断工具。在这里，我们概述了几个高质量和高时间分辨率(即1和2 S韵律)时间序列的太阳观测期间获得的亮度-温度起伏分别集中在3毫米(100 GHz)和1.25毫米(239 GHz)中心的波段3和波段6。不同的数据集代表了具有不同磁通量水平的太阳区。我们执行快速傅立叶变换和Lomb-Scarger变换来测量主要频率的空间结构和振荡的平均全局频率分布(即，在整个视场上平均)。我们发现，观测到的频率从一个数据集到另一个数据集有很大的不同，这是根据观测捕获的太阳区域来讨论的(即与其潜在的磁拓扑联系在一起)。虽然对于最静止的磁数据集，在3-5 MHz的频率范围内存在增强的功率，但当受到强烈的底层磁场集中的显著影响时(存在于观察视场的内部和/或附近)，较低的频率占主导地位。我们在这里讨论了在ALMA观测中可能对5.5 MHz左右的功率抑制做出贡献的一些原因。然而，目前尚不清楚其他色球诊断数据(Hα线芯强度除外)如何不受类似效应的影响，即它们显示出非常明显的3分钟振荡，主导着色球的动力学，而在这里分析的10个ALMA数据集中，只有很小一部分像素显示峰值功率接近5.5兆赫兹。本文是西奥·墨菲会议特刊《低太阳大气中的高分辨率波动动力学》的一部分。
By direct measurements of the gas temperature, the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here, we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e. 1 and 2 s cadence) time series of images obtained during the first 2 years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perform fast Fourier and Lomb–Scargle transforms to measure both the spatial structuring of dominant frequencies and the average global frequency distributions of the oscillations (i.e. averaged over the entire field of view). We find that the observed frequencies significantly vary from one dataset to another, which is discussed in terms of the solar regions captured by the observations (i.e. linked to their underlying magnetic topology). While the presence of enhanced power within the frequency range 3–5 mHz is found for the most magnetically quiescent datasets, lower frequencies dominate when there is significant influence from strong underlying magnetic field concentrations (present inside and/or in the immediate vicinity of the observed field of view). We discuss here a number of reasons which could possibly contribute to the power suppression at around 5.5 mHz in the ALMA observations. However, it remains unclear how other chromospheric diagnostics (with an exception of Hα line-core intensity) are unaffected by similar effects, i.e. they show very pronounced 3-min oscillations dominating the dynamics of the chromosphere, whereas only a very small fraction of all the pixels in the 10 ALMA datasets analysed here show peak power near 5.5 mHz. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.