Advanced models of the solar transition region and corona

当前和即将到来的太阳任务正在提供丰富的上层色球层、过渡区和日冕的新观测。它们将是我们解决各种科学问题的关键，例如：能量是如何在色球层和日冕之间传递的？能量是如何在日冕中释放的，它与太阳风有什么联系？观测可以提供关键的等离子体参数，如密度、温度、化学丰度和日冕磁场。测量过渡区和日冕的化学丰度是很重要的，因为它们的变化可能与日冕中发生的（尚未知的）等离子体加热过程有关，并作用于色球层。此外，它们还可以作为太阳风的示踪剂。日冕磁场主导着日冕的能量学，但直到最近，它的测量一直难以捉摸。然而，要充分科学地利用这些观测结果，需要在理论和建模方面进行长期的努力。本项目通过构建和向社区提供先进的模型（包括额外的物理模型）做出了重大贡献。这些模型还将用于改进上述关键等离子体参数的测量。主要设施，与STFC强有力的支持，是太阳轨道器和DKIST。太阳轨道器的主要科学目标之一，现在已经进入了它的科学阶段，是了解太阳风是如何和在哪里被释放和加速的，通过比较现场与遥感观测等离子体参数，在近距离接触（0.3 AU以内）与太阳。SPICE是一台在英国建造的紫外光谱仪，主要提供色球层和过渡区的观测。先进的模型将改进SPICE对温度和化学丰度的测量。它们还将为研究尚不清楚的色球层和日冕之间的联系提供基础，这种联系很难建模，因为它需要复杂的非局部输运、时间依赖效应和非lte原子物理。开展氦、氧离子形成机理的研究。DKIST是第一个大型太阳望远镜，将对色球（盘上）和日冕进行前所未有的常规光谱偏振观测，主要是在近红外（NIR）波段。我们将用先进的原子模型预测氦日冕辐射，建立其形成机制，并从DKIST观测中获得氦日冕丰度和磁场。我们还将通过即将到来的AIR-Spec和CORSAIR任务来提高我们对NIR的了解。最后，我们计划利用现有的Hinode EIS观测数据，通过考虑仪器校准的改进和以前未考虑的各种物理效应（例如不透明度和非热电子），来修正最近对活动区域日冕磁场的测量。

Current and upcoming solar missions are providing a wealth of novel observations of the upper chromosphere, transition region, and corona. They will be key in our efforts to address various science questions such as: how is energy transferred between the chromosphere and the corona? How is energy released in the corona and what is the connection with the solar wind?The observations can provide key plasma parameters such as densities, temperatures, chemical abundances and coronal magnetic fields. Measuring chemical abundances in the transition region and corona is important as their variations are likely related to the (yet unknown) plasma heating processes occurring in the corona and acting in the chromosphere. Also, as they can be used as a tracer for the solar wind. The coronal magnetic field dominates the energetics in the solar corona, yet its measurements have been elusive until recently. However, the full scientific exploitation of these observations requires a long-term effort on the theory and modelling side. The present project provides a significant contribution by building and providing to the community advanced models, with additional physics included. These models will also be used to improve measurements of the above key plasma parameters.Major facilities, with strong STFC support, are Solar Orbiter and DKIST. One of the main science goals of Solar Orbiter, which has now entered its science phase, is to understand how and where the solar wind is released and accelerated, by comparing in-situ with remote-sensing observations of the plasma parameters, during close encounters (to within 0.3 AU) with the Sun. SPICE, a UV spectrometer built in the UK, is mainly providing observations of the chromosphere and transition region.The advanced models will improve the SPICE measurements of temperatures and chemical abundances. They will also provide a building block for studies of the poorly understood connection between the chromosphere and the corona, which is very difficult to model as it requires complex non-local transport, time-dependent effects and non-LTE atomic physics. Studies on the formation mechanisms of helium and oxygen ions will be carried out. DKIST is the first large-scale solar telescope that will be performing unprecedented routine spectro-polarimetric observations of the chromosphere (on-disk) and the corona, mostly in the near-infrared (NIR). We will predict with the advanced atomic models the helium coronal emission, needed to establish its formation mechanism and to obtain the He coronal abundance and the magnetic field from DKIST observations. We will also improve our knowledge of the NIR with upcoming AIR-Spec and CORSAIR missions. Finally, we plan to revise recent measurements of active region coronal magnetic fields using existing Hinode EIS observations, by taking into account improvements in the instrument calibration and various physical effects (e.g. opacity and non-thermal electrons) not previously considered.