An ALMA Observation of Time Variations in Chromospheric Temperature of a Solar Plage Region
An ALMA Observation of Time Variations in Chromospheric Temperature of a Solar Plage Region
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DOI：
10.3389/fspas.2022.908249
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
M. Abe;T. Shimizu;M. Shimojo
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文献类型：
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作者：
M. Abe;T. Shimizu;M. Shimojo
太阳色球层中的纳米耀斑和磁流体动力波的激波形成被认为是色球层和日冕加热的关键物理机制。为了研究它们在毫米波长中的候选信号，使用阿塔卡马大型毫米和亚毫米阵列（ALMA）在3毫米处观察了位于太阳盘上的一个微小活动区域，并与轨道上的天文台（包括第4周期太阳活动（2017年3月19日）中的日出SOT分光偏振计）协调。 ALMA 的空间分辨率适中，远未达到最佳性能，但它提供了适合研究毫米波长时间变化的稳定条件。我们确定，在合成 ALMA 图像的 20 秒节奏时间序列中，1 小时内的噪声水平低于 20 K (σ)。在整个视场中观察到幅度高于噪声水平的时间变化，但超过 200 K 的变化（对应于色球层的能量输入约为 1020-22 erg）局限于两个位置。其中一个位置是极性反转线上，弱场中存在微小的集中磁斑，可能会出现微小的磁通量。另一个位置位于双极磁区的外缘，该区域正在发展中，连续出现一系列磁通量。这一观察结果表明，色球层中的纳耀斑级能量输入可能与新兴的通量活动相关。
Nanoflares and the shock formation of magnetohydrodynamic waves in the solar chromosphere have been considered as key physical mechanisms of the heating of the chromosphere and corona. To investigate candidates of their signature in the mm-wavelength, a tiny active region located on the solar disk was observed with the Atacama Large millimeter and sub-millimeter Array (ALMA) at 3 mm, coordinated with observatories on orbit including Hinode SOT spectro-polarimeter in the Cycle 4 solar campaign (19 March 2017). ALMA’s spatial resolution was moderate, far from the best performance, but it provided stable conditions that are suitable to investigate temporal variations in the mm-wavelength. We determined that the noise level is less than 20 K (σ) over 1 hour in the 20-s cadence time series of synthesized ALMA images. The time variations with amplitudes above the noise level were observed throughout the field of view, but variations exceeding 200 K, corresponding to energy input to the chromosphere on the order of 1020-22 erg, were localized in two locations. One location was on the polarity inversion line, where tiny concentrated magnetic patches exist in weak field and a tiny magnetic flux may be emergent. The other location was at the outer edge of a bipolar magnetic region, which was under development with a successive series of magnetic flux emergence. This observation suggests that nanoflare-class energy inputs in the chromosphere can occur associated with emerging flux activities.