arXiv 2303.030462023-03astro-ph.SRphysics.space-ph

太阳活动与辐照度的长期变化

Long-term changes in solar activity and irradiance

Theodosios Chatzistergos, Natalie A. Krivova, Kok Leng Yeo

备注：: 17 pages, 8 figures, accepted for publication in JASTP

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AI总结：

本文综述了太阳活动与辐照度长期变化的研究，指出长期趋势存在不确定性，并强调利用三维磁流体动力学模拟和历史Ca II K观测改进辐照度重建的潜力。

摘要：

太阳是地球的主要能量来源，理解其变异性对气候研究具有直接意义。自1978年以来，存在总太阳辐照度的测量数据，但相对于与气候相关的时间尺度，这一时段过于短暂。这些测量来自多种不同仪器，需要进行交叉校准，而这一过程并非易事，因此已构建了多个合成记录。所有这些记录均表明自1996年以来存在轻微下降趋势。大多数合成记录还显示出在整个观测期间存在微弱下降，这一现象在太阳表面磁场的观测中同样可见，并进一步得到Ca II K数据的支持。然而，仍存在一些不一致之处，总体而言，长期趋势的幅度乃至其存在与否仍不确定。目前已开发了多种模型，用于理解卫星观测期间的辐照度变异性，并将太阳辐照度记录回溯至更早时期。这些模型在方法上各不相同，但均需以太阳磁活动代理指标作为输入。最广泛使用的代理指标分别是太阳黑子记录（用于百年尺度）和宇宙成因同位素数据（用于千年尺度）。然而，这些均未能对导致太阳增亮的谱斑和网络结构的长期演化提供足够良好且独立的描述。这导致了太阳辐照度长期变化幅度存在不确定性。在此，我们回顾了近期在改善太阳周期以上时间尺度辐照度重建方面的工作，以及减少现有长期变异性幅度不确定性的努力。特别地，我们强调了将太阳大气三维磁流体动力学模拟作为更具物理基础的辐照度模型输入，以及利用可追溯至1892年的历史全日面Ca II K观测（其编码了直接的谱斑信息）的潜力。

英文摘要：

The Sun is the main energy source to Earth, and understanding its variability is of direct relevance to climate studies. Measurements of total solar irradiance exist since 1978, but this is too short compared to climate-relevant time scales. Coming from a number of different instruments, these measurements require a cross-calibration, which is not straightforward, and thus several composite records have been created. All of them suggest a marginally decreasing trend since 1996. Most composites also feature a weak decrease over the entire period of observations, which is also seen in observations of the solar surface magnetic field and is further supported by Ca II K data. Some inconsistencies, however, remain and overall the magnitude and even the presence of the long-term trend remain uncertain. Different models have been developed, which are used to understand the irradiance variability over the satellite period and to extend the records of solar irradiance back in time. Differing in their methodologies, all models require proxies of solar magnetic activity as input. The most widely used proxies are sunspot records and cosmogenic isotope data on centennial and millennial time scale, respectively. None of this, however, offers a sufficiently good, independent description of the long-term evolution of faculae and network responsible for solar brightening. This leads to uncertainty in the amplitude of the long-term changes in solar irradiance. Here we review recent efforts to improve irradiance reconstructions on time scales longer than the solar cycle and to reduce the existing uncertainty in the magnitude of the long-term variability. In particular, we highlight the potential of using 3D magnetohydrodynamical simulations of the solar atmosphere as input to more physical irradiance models and of historical full-disc Ca II K observations encrypting direct facular information back to 1892.

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