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

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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.