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，只有一个细小的外星层，它的磁层面临着比地球更强的星际磁场(IMF)和更低的阿尔夫尼克马赫数，因为它离太阳很近。这些因素影响太阳风和磁层之间的耦合，以及在低海拔关闭场向电流。然而，很少有研究探索水星耦合的性质。这项提议将对水星和地球的太阳风-磁层耦合进行全面的比较。这些结果将产生很大的影响，有助于我们更广泛地了解太阳风-磁层耦合过程，特别是IMF和场向电流闭合在这两个地面型磁层的磁层动力学和空间天气中的作用。该项目将支持一名博士生、一名早期职业科学家、一名女性科学家，以及美国和英国之间的国际合作。拟议的项目旨在全面研究水星磁层的磁层模式，并将它们与在地球磁层中观察到的模式进行比较。磁通量环流的磁层响应模式，包括孤立的亚暴、稳定的磁层对流和锯齿振荡，是太阳风-磁层耦合过程中的基本耦合模式和重要的空间天气现象。然而，缺乏对水星磁层中磁层模式的性质和驱动条件的全面研究，也缺乏对地球磁层和水星磁层之间类似过程的性质和驱动因素的全面比较。我们将分析信使号的测量结果，并将它们与地球磁层中类似过程的当前知识和模式进行比较。需要解决的具体科学问题包括：i)调查水星磁层对向南的行星际磁场(IMF)和行星际日冕物质抛射(ICME)的响应；ii)将类似的过程与地球磁层中的过程进行比较；以及iii)确定从地球和水银之间的相似过程的比较中可以学到什么。这一奖项反映了美国国家科学基金会的法定任务，并通过使用基金会的智力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.