Mercury's Nightside Magnetosphere Response to Southward IMF and ICMEs: MESSENGER Investigation and Comparisons With Earth’s Magnetosphere

太阳风和磁层之间的耦合导致了强烈而独特的磁层和地磁活动，即地球上的空间天气。水星的磁层在结构上与地球相似，但在几个重要方面有所不同。水星没有电离层，只有一个脆弱的外逸层，由于它靠近太阳，它的磁层面临着比地球更强的行星际磁场（IMF）和更低的阿尔夫萨奇马赫数。这些因素影响了太阳风和磁层之间的耦合以及低空场向流的闭合。然而，很少有研究探索水星上耦合的本质。该提案将对水星和地球上的太阳风-磁层耦合进行全面比较。这些结果将对我们理解太阳风-磁层耦合过程，特别是IMF和场向电流闭合在这两个陆相磁层的磁层动力学和空间天气中的作用具有重要影响和广泛贡献。该项目将支持一名博士生、一名早期科学家、一名女科学家以及美英之间的国际合作。该项目旨在全面研究水星磁层的磁层模式，并将其与地球磁层观测到的磁层模式进行比较。孤立亚暴、稳定磁层对流和锯齿振荡是太阳风-磁层耦合的基本耦合模式和重要的空间天气现象。然而，对水星磁层模式的性质和驱动条件的全面研究，以及对地球和水星磁层之间类似过程的性质和驱动因素的全面比较，都是缺乏的。我们将分析信使号的测量结果，并将其与地球磁层中类似过程的现有知识和模式进行比较。要解决的具体科学问题包括：1)研究水星磁层对向南行星际磁场（IMF）和行星际日冕物质抛射（ICMEs）的响应；ii)将类似的过程与地球磁层的过程进行比较；（三）确定可以从地球和水星之间类似过程的比较中学到什么。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The coupling between the solar wind and magnetosphere causes strong and distinct magnetospheric and geomagnetic activities, known as space weather on Earth. Mercury’s magnetosphere is structurally similar to Earth’s but differs in several important ways. Mercury does not have an ionosphere, but only a tenuous exosphere, and its magnetosphere faces stronger interplanetary magnetic fields (IMF) and lower Alfvénic Mach numbers than Earth due to its proximity to the Sun. These factors affect the coupling between the solar wind and the magnetosphere and the closure of field-aligned currents at low altitudes. However, few studies have explored the nature of the coupling at Mercury. This proposal will conduct a comprehensive comparison of the solar wind-magnetosphere coupling at Mercury and Earth. The results will be highly impactful and contribute broadly to our understanding of solar wind-magnetosphere coupling processes, especially the roles of the IMF and field-aligned current closure in magnetospheric dynamics and space weather at these two terrestrial-style magnetospheres. This project will support a Ph.D. student, an early career scientist, a female scientist, and international collaborations between the US and UK.The proposed project aims to comprehensively investigate the magnetospheric modes of Mercury’s magnetosphere and compare them with those observed in Earth’s magnetosphere. Magnetospheric response modes of flux circulations, including isolated substorms, steady magnetospheric convection, and sawtooth oscillations, are fundamental coupling modes and important space weather phenomena during solar wind-magnetosphere coupling. However, comprehensive investigations into the properties and driver conditions of magnetospheric modes in Mercury’s magnetosphere are lacking, as are comprehensive comparisons of the properties and drivers of similar processes between the magnetospheres of Earth and Mercury. We will analyze measurements from MESSENGER and compare them with the current knowledge and modes of similar processes in Earth’s magnetosphere. The specific science questions to be addressed include: i) investigating the response of Mercury’s magnetosphere to the southward interplanetary magnetic field (IMF) and interplanetary coronal mass ejections (ICMEs); ii) comparing similar processes to those in Earth’s magnetosphere; and iii) determining what can be learned from the comparison of similar processes between Earth and Mercury.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.