One of the most significant gaps in our knowledge of the space environment surrounding Earth concerns its exosphere, or geocorona. As the outermost layer of the atmosphere, it plays a critical role in mediating Earth’s response to solar forcing and in permanent atmospheric evolution through the gravitational escape of its constituent hydrogen atoms. Reliable characterization of its spatial structure and temporal variability is notoriously difficult, owing mainly to the challenges of global and routine sensing over its vast extent, which ranges from ~500 kilometers above Earth’s surface to more than 150,000 km, about halfway to lunar orbit.
In this talk, I will summarize the historical approaches to exospheric sensing and introduce an upcoming NASA mission known as the Global Lyman-alpha Imager of the Dynamic Exosphere (GLIDE). Following its launch in 2025, the GLIDE mission will acquire wide-field, high-resolution, and high-cadence images of exospheric emission in the far ultraviolet from its distant vantage in halo orbit around the Earth-Sun L1 Lagrange point, ~1.5 million km from Earth. Using state-of-the-art data analysis techniques, including radiative transfer model inversion and optical tomography, GLIDE will reveal the nature and physical drivers of global exospheric structure and energetics and thereby advance understanding of the climatology and secular evolution of Earth’s atmosphere. Meanwhile, GLIDE’s measurements of transient exospheric variability during geomagnetic storms will provide unprecedented constraints on space weather models of the boundary region that separates our neutral atmosphere from the space plasma which surrounds it
Topic: Astronomy Colloquium SP22
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