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arXiv 2507.08093astro-ph.SR
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利用uGMRT对太阳射电噪暴小尺度空间结构的观测与建模

Observation and Modeling of Small Spatial Structures of Solar Radio Noise Storms using the uGMRT

Surajit Mondal, Peijin Zhang, Devojyoti Kansabanik, Divya Oberoi, Gillian Pearce

备注：
Accepted for publication in Solar Physics
发表信息：
Solar Physics (2025) 300:109
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AI总结：

本文首次利用uGMRT在250–500 MHz频段观测到太阳射电噪暴中稳定持续15–30分钟的极小尺度结构，并通过比较III型射电暴和建模分析，提出局部等离子体环境可显著降低理论预测的最小可观测源尺寸。

摘要：

太阳噪暴是米波和十米波段最常观测到的太阳射电源之一。这些射电源通常与活动区相关，并被认为由等离子体辐射机制驱动。由于等离子体辐射主要在本地等离子体频率的基频和谐频处发射，因此它会显著受到日冕密度不均匀性的影响。由于密度不均匀性引起的折射所导致的多路径传播，射电源可能会发生显著的散射展宽。过去的观测和理论估计表明，日冕中存在某种最小可观测源尺寸。然而，这一极限的具体细节取决于所采用的建模方法和所选择的日冕湍流模型的具体情况。因此，将最小可观测源尺寸推向更小的值有助于约束所观测射电源的等离子体环境。在这项工作中，我们首次利用升级后的巨米波射电望远镜（uGMRT）在250--500 MHz频段的数据，确定了噪暴中多个极小尺度结构的实例。我们还发现这些结构在15--30分钟的时间尺度上保持稳定。通过比较过去对III型射电暴和噪暴的观测，我们假设在噪暴中探测到这些小尺寸射电源的主要原因在于噪暴的局部环境。我们还构建了一个说明性模型，并提出了一些条件，在这些条件下，理论模型所预测的最小可观测源尺寸可以显著降低。

英文摘要：

One of the most commonly observed solar radio sources in the metric and decametric wavelengths is the solar noise storm. These are generally associated with active regions and are believed to be powered by the plasma emission mechanism. Since plasma emission emits primarily at the fundamental and harmonic of the local plasma frequency, it is significantly affected by density inhomogeneities in the solar corona. The source can become significantly scatter-broadened due to the multi-path propagation caused by refraction from the density inhomogeneities. Past observational and theoretical estimates suggest some minimum observable source size in the solar corona. The details of this limit, however, depends on the modeling approach and details of the coronal turbulence model chosen. Hence pushing the minimum observable source size to smaller values can help constrain the plasma environment of the observed sources. In this work, we for the first time, use data from the upgraded Giant Metrewave Radio Telescope in the 250--500 MHz band, to determine multiple instances of very small-scale structures in the noise storms. We also find that these structures are stable over timescales of 15--30 minutes. By comparing the past observations of Type III radio bursts and noise storms, we hypothesize that the primary reason behind the detection of these small sources in noise storm is due to the local environment of the noise storm. We also build an illustrative model and propose some conditions under which the minimum observable source size predicted by theoretical models, can be lowered significantly.

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