Estimating the Earth's Dayside Exospheric Neutral Density Using XMM-Newton Soft X-ray Data

地球大气层的最外层是外逸层。这项研究使用来自天体物理卫星的x射线观测来探测外逸层，并了解它是如何受到太阳活动的影响的。这项工作与了解空间天气及其对卫星、高频通信、GPS和其他与商业利益和国家安全相关的技术系统的影响有关，这是《国家空间天气行动计划》中规定的国家优先事项。该项目将支持一名来自少数族裔服务机构中代表性不足群体的早期终身教职员工，以及一名研究生的博士论文工作。该项目由磁层物理项目和促进竞争研究的既定项目（EPSCoR）联合资助。该项目将通过将Connor &amp； Carter[2019]的方法应用于更大的XMM-Newton太阳风电荷交换（SWCX）数据集来研究太阳活动对日侧外逸层密度的影响。该项目将回答以下三个问题：1)在标称10 RE亚太阳位置的外逸层中性密度是什么？ 2)太阳极小期密度如何变化？ 3)太阳极大期密度如何变化？首先，将对XMM-Newton数据集进行分析，列出在相对恒定的太阳风条件下的强SWCX事件列表。为了避免磁鞘建模的复杂性，只考虑稳定的太阳风条件。然后，PI将选择至少10个强SWCX事件，其中5个为太阳极小期，5个为太阳极大期，并使用全球MHD模型模拟这些事件。他们将把模拟的磁鞘参数与当代日球层航天器任务（如Cluster、THEMIS和MMS）的现场观测结果进行比较。在验证测试之后，他们将计算MHD模型的磁鞘贡献，并从SWCX观测中减去它们的影响。最后，计算10 RE亚太阳位置的外逸层密度，研究太阳极小期和太阳极大期的密度变化。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 very outer edge of the Earth's atmosphere is the exosphere. This study uses X-ray observations from an astrophysics satellite to probe the exosphere and understand how it is impacted by solar activity. The work is relevant to understanding space weather and how it affects satellites, high frequency communications, GPS, and other technological systems relevant to commercial interests and national security - a national priority set out in the National Space Weather Action Plan. The project will support an early-career tenure-track faculty member from an underrepresented group at a minority-serving institution and a graduate student's Ph.D. thesis work. This project is jointly funded by the Magnetospheric Physics program and the Established Program to Stimulate Competitive Research (EPSCoR).This project will investigate solar activity impact on the dayside exospheric density by applying the methodology of Connor & Carter [2019] to the larger XMM-Newton solar wind charge exchange (SWCX) dataset. The project will answer the following three questions: 1) What is an exospheric neutral density at the nominal 10 RE subsolar location, 2) How does the density change during solar minimum, and 3) How does the density change during solar maximum? First, the XMM-Newton dataset will be analyzed to make a list of the strong SWCX events during relatively constant solar wind conditions. Only the stable solar wind conditions will be considered to avoid the complexity of magnetosheath modeling. Then, the PI will select at least 10 strong SWCX events, 5 for solar minimum and 5 for solar maximum, and simulate those events using a global MHD model. They will compare the modeled magnetosheath parameters with contemporary in-situ observations of the heliospheric spacecraft missions such as Cluster, THEMIS, and MMS. After the validation test, they will calculate the magnetosheath contributions from the MHD model and subtract their effect from the SWCX observations. Finally, the exospheric densities will be calculated at 10 RE subsolar location and investigate the density variation between solar minimum and solar maximum.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.