Imaging the Earth's magnetosphere response to solar wind variability

众所周知，软x射线是由地球外逸层中太阳风离子和中性离子之间的电荷交换过程在地球的磁鞘和尖端产生的。太阳风磁层电离层链路探测器（SMILE - https://mssl.ucl.ac.uk/SMILE/）是欧洲空间局和中国科学院的联合任务，将研究太阳风与地球磁层的相互作用。2024年底，该任务将携带四种仪器进入太空，其中两种是成像仪，软x射线成像仪（SXI）和紫外线成像仪（UVI）。SXI将拍摄昼侧磁层的x射线图像，目的是以一种全新的方式研究其对太阳风变化的响应。为了理解SMILE将返回的数据，我们正在模拟尖端和磁鞘发射的x射线以及SXI的输出。本博士项目的动机是研究日侧磁层顶的大规模磁重联和不同磁层模式之间的转换。日侧重联是由太阳风动压的增加和/或向南的行星际磁场（IMF）转向引起的。到目前为止，许多模拟和观测研究都致力于磁层对太阳风压力跳变（例如行星际冲击）和太阳风切向/旋转不连续的响应。这些现象是我们所说的“空间天气”的一部分，代表了太阳风变化对近地空间环境条件的影响，这可能对我们在空间和地面上的技术基础设施产生严重的破坏性后果。一个特别有趣的问题是磁层对IMF向南转向的反应。这在磁层物理学中是很重要的，因为与赤道平面正交的IMF分量被认为是太阳风-磁层相互作用最重要的驱动参数之一。这是一个应用SMILE成像进行研究的极具潜力的课题。该项目将试图寻找答案的问题包括：哪种类型的太阳风结构与向南的IMF转向有关？它们是导致地磁风暴和亚风暴的那种条件吗？此外，还有许多其他未解决的问题，该领域的博士项目可以解决。例如，我们知道磁层顶的形状和位置在向北和向南的IMF是不同的，但我们的经验模型和MHD模型并不能准确地描述它们。MHD模型的运行，结合宇宙飞船的观测，可以更好地约束磁层顶形状的数学形式。

It is known that soft X-rays are produced in the Earth's magnetosheath and cusps by the process of charge exchange between solar wind ions and neutrals in the Earth's exosphere. The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE - https://mssl.ucl.ac.uk/SMILE/) is a joint mission of the European Space Agency and the Chinese Academy of Sciences that will study the interaction of the solar wind with the Earth's magnetosphere. At the end of 2024 the mission will take into space four instruments, two of them being imagers, the Soft X-ray Imager (SXI) and the UV Imager (UVI). SXI will take X-ray images of the dayside magnetosphere with the purpose of studying its response to solar wind variations in a totally new way.In order to understand the data SMILE will return, we are simulating the X-rays emitted by the cusp and magnetosheath and the output of SXI.The motivation behind this PhD project is that of studying large-scale magnetic reconnection at the dayside magnetopause and transitions between different magnetospheric modes. Dayside reconnection is induced by an increase in the solar wind dynamic pressure and/or a southward interplanetary magnetic field (IMF) turning. So far, many modelling and observational studies have been devoted to the magnetospheric response to solar wind pressure jumps (e.g. interplanetary shocks) and to solar wind tangential/rotational discontinuities. These phenomena are part of what we call 'space weather', representing the impact of solar wind variability on environmental conditions in near Earth space, which can have severe disrupting consequences on our technological infrastructure, in space and on the ground. A particularly interesting issue is the magnetospheric response to southward IMF turnings. This is important in magnetospheric physics because the IMF component orthogonal to the equatorial plane is thought to be one of the most important driving parameters for the solar wind - magnetosphere interaction. And it is a topic that has great potential for investigations applying SMILE imaging.Questions that the project will try to find an answer to are like: Which types of solar wind structures are related to southward IMF turnings? Are they the sort of conditions that lead to geomagnetic storms and substorms? In addition, there are many other unresolved issues that a PhD project in this area can address. For example, we know that the magnetopause shape and position are different for northward and southward IMF but the empirical and MHD models we have do not describe them accurately. MHD model runs, combined with observations from spacecraft, could better constrain the mathematical form of the magnetopause shape.