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

地球大气层的最外边缘就是地外圈。这项研究使用一颗天体物理学卫星的X射线观测来探测外星层，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如何影响卫星、高频通信、全球定位系统和其他与商业利益和国家安全相关的技术系统有关--这是国家空间天气行动计划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不足的群体的早期职业生涯终身制教师，以及一名研究生的博士论文工作。该项目由磁层物理计划和已建立的刺激竞争研究计划(EPSCoR)共同资助。该项目将通过将Connor&amp；Carter[2019]的方法应用于更大的XMM-牛顿太阳风电荷交换(SWCX)数据集来调查太阳活动对日侧外层密度的影响。该项目将回答以下三个问题：1)在标称的10 RE次太阳位置的外圈中性密度是什么，2)在太阳活动最小期间密度是如何变化的，以及3)在太阳活动高峰期间密度是如何变化的？首先，将分析XMM-牛顿数据集，以列出在相对恒定的太阳风条件下发生的强SWCX事件。只考虑稳定的太阳风条件，避免了磁鞘建模的复杂性。然后，PI将选择至少10个强SWCX事件，其中5个为太阳最小事件，5个为太阳最大事件，并使用全球MHD模式模拟这些事件。他们将把模拟的磁鞘参数与对星团、THEMIS和MMS等日球层航天器任务的当代现场观测进行比较。验证测试后，他们将从MHD模型计算磁鞘贡献，并从SWCX观测中减去它们的影响。最后，将在10RE次太阳位置计算外层密度，并调查太阳最小值和太阳最大值之间的密度变化。这一裁决反映了NSF的法定任务，并通过使用基金会的智力优势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.