Seasonal and Interhemispheric Comparisons of Model-Generated Intensities of Upper Atmospheric Balmer-𝛼 Using WACCM-X and Lyao_rt

Dual etalon Fabry-Perot Interferometers (FPIs) have been surveying the sky in the northern hemisphere since the late 1970s. The Wisconsin H-Alpha Mapper (WHAM) is a dual etalon FPI that operated at Kitt Peak National Observatory (KPNO), Arizona, from 1996-2008 where it obtained northern hemispheric observations of geocoronal and Galactic hydrogen Balmer-𝛼 (H𝛼) emission. WHAM is currently located at the Cerro-Tololo Inter-American Observatory (CTIO), Chile, where it conducts southern hemispheric observations of H𝛼 emission. Geocoronal H𝛼 emission data have also been obtained from a similar instrument. Currently, the Investigating Near Space Interaction Regions (INSpIRe) FPI is located at the Pine Bluff Observatory, Wisconsin. In this study, seasonal and interhemispheric variabilities of upper thermospheric hydrogen are analyzed using the Whole Atmosphere Community Climate Model-eXtended (WACCM-X) with a focus on summer and winter for all three observatories, as previous ground-based observations have shown a seasonal dependence, particularly at low shadow altitudes [Gallant et al., 2019]. Additionally, a solar cycle comparison of the modeled H𝛼 emission intensities is presented and analyzed. The WACCM-X outputs are characterized for the years 1972-1976 and 2001-2005, and various observing conditions specific to that of KPNO, CTIO, and PBO. These modeled outputs are used as inputs to the lyao_rt forward model of Bishop [1999] to obtain Balmer-𝛼 emission intensities and are compared to ground-based observations from WHAM and INSpIRe. Overall, comparisons between ground-based observations and model outputs will guide future observations and support model validation of WACCM-X over these time and spatial scales. This work is partially supported by NSF award 2050077 and is a collaborative effort between ERAU, UW-Madison, & NSF NCAR.