Waves and Flows: Linking the Solar Photosphere to the Corona

太阳是人类最重要的天体之一，太阳活动造成“空间天气”，对地球环境产生深远影响。我们可以通过地球上迷人的景象，如北极光，直接看到太阳强大辐射的影响。然而，正是太阳温度结构的矛盾性首先吸引了我的注意力。困扰物理学家的最大科学问题之一是太阳的外层大气比其表面热得多。常识使我们相信，当我们远离太阳6000 K的表面温度时，当地的温度会下降。然而，日冕，一个离地表几千公里的大气层，辐射出超过一百万度的温度。50多年来，对加热过程的理解一直处于观测和理论研究的前沿，产生了一种流行的理论，称为波加热。这种机制表明，在太阳表面附近通过等离子体的持续搅动产生的波向上传播，最终耗散其能量并加热太阳的外层大气。一个很好的类比是想象海浪在撞击海岸线之前穿越海洋，最终在这个过程中释放出巨大的能量。然而，太阳大气层在本质上是高度磁性的。磁场强度通常超过0.3特斯拉（类似于医院中的现代开放式MRI扫描仪的强度），导致波模式变得高度修改，并产生磁流体动力学（MHD）现象。我的愿望是帮助提高我们对太阳大气层中工作的物理过程的理解，太阳大气层对地球上的生命具有如此重要的影响。了解太阳磁场效应的一个自然结果将是预测太阳活动的能力，这将最终使我们能够保护自己免受空间天气的猛烈爆发。为了实现这一关键议程，我们需要观察和模拟太阳大气层内在尺度上发生的过程。英国最近受益于一种新的高分辨率太阳仪器，包括太阳大气快速振荡（ROSA），太阳动力学天文台（SDO），日出和IRIS设施，这将首次允许以前所未有的详细程度研究与磁能释放相关的基本过程。作为STFC研究员，我将使用现代地面和空间望远镜，其中包含各种各样的高分辨率成像和光谱仪器。我的研究的观测部分将集中在个别MHD波的区别，允许关键特征进行评估。这些包括振荡模式（纵向、横向等），速度、等离子体密度和温度，它们可以结合起来提供详细的能量估计。能量耗散的速率将与日冕的加热要求进行比较，并明确确定波在太阳日冕加热中的确切作用。从高分辨率观测中推导出的基本参数将被纳入先进的计算机模拟。拥有200多个CPU的大型计算机集群将用于研究波对磁场的3D影响，这些磁场干扰了整个太阳大气层。将在模拟的太阳结构中研究与波有关的特征，采用正向建模技术，以便与将要进行的物理观测进行直接比较，最终得出更加精确的太阳大气加热模型。随着过去几年太阳物理学领域的快速发展，最终解决大气加热悖论的能力现在已经成为现实。

The Sun is one of the most important objects for humankind, with solar activity driving "space weather" and having a profound effect on the Earth's environment. We can directly see the effects of the Sun's powerful radiation through fascinating sights on Earth, such as the aurora borealis. However, it was the paradoxical nature of our Sun's temperature structure that first captivated my attention. One of the greatest scientific problems plaguing physicists is the fact that the outer atmosphere of our Sun is much hotter than its surface. Common sense leads us to believe that the local temperature will decrease as we move away from the Sun's 6000 K surface temperature. However, the corona, an atmospheric layer a few thousand km above the surface, radiates with a temperature exceeding one million degrees. Efforts to understand the heating processes responsible have remained at the forefront of observational and theoretical research for over 50 years, producing a popular class of theory known as wave heating. This mechanism suggests that waves, generated near the solar surface through the continual churning of plasma, propagate upwards, ultimately dissipating their energy and heating the Sun's outer atmosphere. A good analogy is to envisage ocean waves that travel vast distances across the sea before crashing on to shorelines, ultimately releasing immense quantities of energy in the process. However, the solar atmosphere is highly magnetic in nature. Magnetic field strengths often exceed 0.3 Tesla (similar in strength to modern open MRI scanners found in hospitals), resulting in wave modes becoming highly modified, and producing magneto-hydrodynamic (MHD) phenomena.It is my desire to help improve our understanding of the physical processes at work within the Sun's atmosphere, an object that is so influential to life on Earth. A natural consequence of understanding the effects of solar magnetism will be the ability to predict solar activity, something that will ultimately allow us to protect ourselves from fierce outbursts of space weather. To pursue this crucial agenda, we need to observe and model the processes occurring in the Sun's atmosphere on their intrinsic scales. The UK has recently benefitted from a new breed of high-resolution solar instrumentation, including the Rapid Oscillations in the Solar Atmosphere (ROSA), Solar Dynamics Observatory (SDO), Hinode, and IRIS facilities, which will allow for the first time fundamental processes associated with the release of magnetic energy to be studied at an unprecedented level of detail. As an STFC Fellow, I will use modern ground- and space-based telescopes containing a wide assortment of high-resolution imaging and spectroscopic instrumentation. The observational component of my research will focus on the distinction of individual MHD waves, allowing key characteristics to be evaluated. These include the modes of oscillation (longitudinal, transverse, etc.), velocities, plasma densities, and temperatures, which can be combined to provide detailed energy estimates. The rate at which energy is dissipated will be compared to the heating requirements of the corona, with the exact role waves play in the heating of the Sun's corona unequivocally determined. Fundamental parameters deduced from high-resolution observations will be incorporated into advanced computer simulations. Large computer clusters, with 200+ CPUs, will be used to examine the 3D effects of waves on magnetic fields which intertwine the entire solar atmosphere. Characteristics associated with the waves will be studied in simulated solar structures, with forward modelling techniques implemented to allow direct comparisons with the physical observations to be undertaken, culminating in much refined heating models of the solar atmosphere. With the rapid advancements made in the field of solar physics over the last number of years, the ability to finally resolve the atmospheric heating paradox is now a reality.