The Dynamic Hydrogen Exosphere of Earth: Simulating Space Weather Effects on Atmosphere Escape

Lara Waldrop, University of Illinois at Urbana-Champaign

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Hydrogen atoms are the primary constituent of the outermost layer of the terrestrial atmosphere, a region known as the exosphere. They are not only slowly evaporating into space, resulting in the permanent loss of our planet’s water reserves, but they also mediate the Earth’s transient response to impulsive space weather events through their energetic coupling with ambient ions. Recent studies of exospheric structure and dynamics have revealed the presence of a significant population of energetic H atoms along with large disturbances during solar storms. These discoveries have challenged classical theories and available numerical models, such that significant updates to both are urgently needed in order to advance understanding of the drivers of exosphere structure and kinetics. Here we propose to investigate the dynamics of ion-neutral coupling and atmospheric escape under different solar conditions by analyzing spacecraft observations of the exosphere using cutting-edge modeling techniques (SAMI2, 2-D radiative transfer model, and tomographic reconstruction). This project will also be used to conduct a concept study for a NASA Heliophysics Mission of Opportunity, which was recently selected for Phase A development.