Speaker
Description
The Earth’s hydrogen (H) corona has been observed from various platforms for over half a century and many of these measurements, particularly those made in recent times, leverage the observation of solar H-Lyman-α (121.6 nm) photons resonantly scattered by H. Interpreting these observations becomes increasingly complex in the optically thick region of the corona below 3 Earth-radii (RE) where the one-to-one correspondence between observed photons and scattering atoms breaks down due to multiple scattering effects. Solar occultation provides an alternative approach to observing the H corona in both the optically thin and thick regimes. In particular, solar occultation leverages absorption spectroscopy which is inherently less sensitive to multiple scattering effects allowing for direct observations of H density below 3 RE, albeit with its own set of complexities, assumptions and limitations.
In this study, we use new measurements of solar H-Lyman-α from the EUV and X-ray Irradiance Sensors (EXIS) aboard the Geostationary Operational Environmental Satellite (GOES) -R series satellites to measure H from 1.2 to 5 RE. The retrieval approach and its random uncertainty and systematic error in both the optically thin and optically thick regime are presented. Observations are compared with existing data and models.
