Collaborative Research: CEDAR--Upper Atmospheric Hydrogen Variability on Timescales from Dusk-Dawn to Multidecadal

This award will use results obtained from the combination of hydrogen interferometric nightglow observations and general circulation modeling to study the variability in upper atmospheric hydrogen density over various time scales ranging from night-to-night to multi-decades. Observing the morphology and climatology of atomic hydrogen density, a key constituent in the thermosphere and exosphere composition, will achieve an improved understanding of space-weather processes, neutral atmosphere plasmasphere coupling processes, and non-Maxwellian physics present in the upper thermosphere and exosphere regions.

Hydrogen is also a by-product of molecular reactions taking place at lower altitudes involving species such as water vapor and methane, two of the greenhouse gases most important for the energy balance of the Earth’s atmosphere. Thus, tracking the H density over several decades will provide insight into any significant climate change taking place within the mesosphere region.

These results will improve the understanding of the mechanisms driving the observed hydrogen variability and will determine the response of exospheric hydrogen density to increases in greenhouse gases over the time span of observations. Broader impacts of this award will include involvement of one graduate student as well as several undergraduate students, participation by a faculty member from a two-year Wisconsin campus, as well as education and outreach in climate science and aeronomy.

Students will have the opportunity to take and analyze new observations with these two remote observatories. The students will also learn the use of the WACCM-X model to achieve the simulations necessary for these comparisons.

Application of forward modeling methodology will compare existing and new high signal-to-noise Fabry-Perot observations of geocoronal hydrogen emissions with model simulations extracted from the outputs of the National Center for Atmospheric Research Whole Atmosphere Community Climate Model eXtended (WACCM-X). These data sets would be combined with the model results to study the variability in existing Southern Hemisphere (SH) hydrogen emission observations by comparing its variations to that observed for the Northern Hemisphere (NH) Fabry-Perot Balmer-alpha observations once the SH and NH data for the first coincident Balmer-alpha observations using the INSpIRe and WHAM Fabry-Perot interferometer instruments have been collected.

The new observations from Wisconsin and Chile will provide near-simultaneous, carefully-calibrated measurements of hydrogen nightglow emissions from NH and SH mid-latitudes. The award will also use for this study the observations drawn from existing NH and SH upper atmospheric hydrogen Balmer alpha emission data sets. Comparing these results will detect any hemispheric asymmetries in hydrogen variability.

WACCM-X simulations will provide for the investigation of mechanisms contributing to Balmer alpha variability through diagnostic analysis. Finally, WACCM-X climate simulations will be analyzed to study the expected response of hydrogen-containing constituents to increases in greenhouse gases.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.