The goal of this project is to obtain empirical estimates of night-time atomic hydrogen (H) density and vertical flux as a function of altitude from the lower thermosphere into the exosphere based on a coupled analysis of measured H airglow intensity and a sophisticated forward model of radiative transport for spectral line profile analysis. Knowledge of these parameters is important for understanding the chemical and dynamical coupling between atmospheric regions. This effort will utilize existing measurements of multi-line H emission at unprecedented precision, acquired from a suite of mature, ground-based, spectroscopic instruments, as well as new data from a novel spectroscopic instrument, which will be tested and deployed as part of this project. Additional goals of this work are to characterize the dependence of the H distribution on geomagnetic and solar variability and to search for signatures of dynamical populations of exospheric H atoms. H density profiles are useful for improving empirical atmospheric models and aiding data interpretation and analysis from other observational research techniques, such as neutral atom imaging.
