Seasonal and Interhemispheric Comparisons of Geocoronal Hα Observations and WACCM-X and NRLMSISE-00 Forward Modeled Simulations

Ground-based geocoronal hydrogen Balmer-α (Hα) observations were obtained from Pine Bluff Observatory (PBO; 43.08ºN, 270.33ºE) in Wisconsin from 2000-2001 using a high spectral resolution Fabry-Perot annular summing spectrometer (Mierkiewicz et al., 2012). Gallant et al. (2019) compared these observations to NRLMSISE-00 forward modeled intensities and found that the PBO Fabry-Perot Hα emission intensities are higher than the NRLMSISE-00 modeled intensities by 1.5-2.5 Rayleighs depending on time of night and season. Here, we focus on the analysis of seasonal variations of upper thermospheric hydrogen in the Whole Atmosphere Community Climate Model-eXtended (WACCM-X) for the PBO and Cerro Tololo, Chile geographic locations using the lyao_rt radiative transport forward modeling code (Bishop, 1999) to calculate Hα column emission intensities. This work builds off the study by Gallant et al., 2019 where both WACCM-X and NRLMSISE-00 forward modeled results are compared to the 2000-2001 PBO Fabry-Perot observations. Preliminary results indicate that WACCM-X offers better agreement with the observations than NRLMSISE-00. Furthermore, the Wisconsin H-Alpha Mapper (WHAM) is a dual etalon Fabry-Perot that operated at Kitt Peak National Observatory (KPNO; 31.98ºN, 111.60ºW) in Arizona from 1996-2008 where northern hemispheric observations of geocoronal and Galactic Hα emission were obtained. WHAM is now located in Chile at the Cerro Tololo Inter-American Observatory (CTIO; 30.17ºS, 70.80ºW) conducting southern hemispheric observations of Hα emission during this current solar maximum period and through the decline in solar activity. There is also the Investigating Near Space Interaction Regions (INSpIRe) Fabry-Perot now located at PBO taking observations for this current solar cycle. In the future, we plan to compare observations from both WHAM and INSpIRe to one another as well as to WACCM-X and NRLMSISE-00 forward modeled results for KPNO, CTIO, and PBO. This work is supported by NSF CEDAR 2050077 (a collaborative effort between ERAU, UW-Madison, and NCAR), NSF Astronomy 2009276, and NASA HTMS 80NSSC20K1278.