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’.

中文翻译：

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使用 ALMA 全面了解太阳色球层的温度振荡


通过直接测量气体温度，阿塔卡马大型毫米/亚毫米阵列（ALMA）提供了一种研究太阳色球层的新诊断工具。在这里，我们概述了在 ALMA 太阳观测的前 2 年中获得的几个高质量和高时间分辨率（即 1 秒和 2 秒节奏）时间序列图像的亮度-温度波动，波段 3频段 6 的中心分别为 3 毫米 (100 GHz) 和 1.25 毫米 (239 GHz)。各种数据集代表具有不同磁通量水平的太阳区域。我们执行快速傅里叶和 Lomb-Scargle 变换来测量主频率的空间结构和振荡的平均全局频率分布（即整个视场的平均值）。我们发现，一个数据集与另一个数据集之间观测到的频率存在显着差异，这是根据观测捕获的太阳区域（即与其底层磁拓扑相关联）进行讨论的。虽然对于大多数静态磁数据集而言，在 3–5 mHz 频率范围内存在增强功率，但当强底层磁场集中（存在于观测到的内部和/或紧邻的区域）产生显着影响时，较低的频率占主导地位。视野）。我们在此讨论了可能导致 ALMA 观测中 5.5 mHz 左右功率抑制的多种原因。然而，目前尚不清楚其他色球诊断（Hα线核强度除外）如何不受类似效应的影响，即 它们显示出非常明显的 3 分钟振荡主导色球的动态，而此处分析的 10 个 ALMA 数据集中的所有像素中只有很小一部分显示出接近 5.5 mHz 的峰值功率。本文是 Theo Murphy 会议问题“太阳低层大气中的高分辨率波动力学”的一部分。