Modelling solar irradiance variations: the influence of faculae and small-scale magnetic flux elements

模拟太阳辐照度变化：光斑和小尺度磁通量元素的影响

基本信息

批准号：
ST/I001972/1
负责人：
Yvonne Unruh
金额：
$ 37.28万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FI001972%2F1
关键词：
Modelling solar irradiance variations influence

项目摘要

The Sun is the main driver of the Earth's climate. The effect of its variability on the climate, however, remains poorly understood. This is due to a number of reasons, including the lack of a universally accepted mechanism for such an influence, the difficulties in attributing signals in the complex climate system unambiguously to the Sun as well as large uncertainties regarding the level of total and spectral solar variability over climate-relevant time scales. This proposal aims to provide state-of-the art solar irradiance reconstructions spanning all wavelengths from the UV to the IR. These will represent a major improvement compared to current reconstructions in two main respects: 1) We propose to combine non-LTE spectral synthesis calculations in parts of the UV spectrum with standard LTE calculations in the visible and IR. LTE calculations are sufficiently accurate over most of the visible and IR region and are computationally straightforward. We will complement these with non-LTE calculations where they are most needed, i.e., where our current LTE calculations are known to fail. The variability in the UV wavelength region is of particular interest as it currently the most promising mechanism to provide the Sun-climate coupling. 2) We will derive the intensities of the bright magnetic elements from magneto-convection simulations. This will allow us for the first time to obtain the spectral response for the small-scale magnetic elements that are thought to be the main cause for long-term irradiance variability. To our knowledge, this is currently the only way to estimate the long-term spectral variability. In addition, the magneto-convection simulations can be used to derive synthetic magnetograms that can then used to translate the observed magnetogram signals into intensities, thus dispensing with any free parameters in the irradiance reconstructions. As a by-product, we will test the simulations by deriving solar surface images that can be directly compared to observations, such as those taken by, e.g., Hinode or Sunrise.

太阳是地球气候的主要驱动力。然而，其变异性对气候的影响仍然很少了解。这是由于多种原因，包括缺乏这种影响的普遍接受的机制，在复杂的气候系统中不明式地归因于太阳的困难，以及有关与气候相关的时间尺度的总太阳可变性水平和光谱可变性水平的巨大不确定性。该提案旨在提供最先进的太阳辐照度重建，涵盖从紫外线到IR的所有波长。与在两个主要方面的当前重建相比，这些将代表重大改进：1）我们建议将紫外线光谱部分中的非LTE光谱合成计算与可见光和IR中的标准LTE计算相结合。在大多数可见区域和IR区域中，LTE计算足够准确，并且在计算上很简单。我们将使用最需要的非LTE计算来补充这些计算，即我们当前的LTE计算失败。紫外线波长区域的可变性特别令人感兴趣，因为它目前是提供太阳气候耦合的最有希望的机制。 2）我们将从磁传输模拟中得出明亮磁元素的强度。这将使我们首次获得小规模磁元素的光谱响应，这些磁性元素被认为是长期辐照度变化的主要原因。据我们所知，这是目前估计长期光谱变异性的唯一方法。此外，磁磁化模拟可用于得出合成磁图，然后可以将观察到的磁图信号转换为强度，从而将辐照度重建中的任何自由参数分配。作为副产品，我们将通过得出可以直接比较的太阳表面图像来测试模拟，例如，例如Hinode或Sunrise进行的观测值。