We propose a quantitative investigation of the ionospheric and thermospheric (IT) responses to acoustic and gravity waves (AWS and GWS or, here, agws when together in a spectrum) that combines data…

This is a grant for research awarded by the National Aeronautics and Space Administration (NASA) to Embry-Riddle Aeronautical University, Inc. The research focuses on quantifying the ionospheric and thermospheric responses to acoustic and gravity waves, using a combination of ground and space data along with advanced numerical modeling. The objectives are to investigate the natural atmospheric responses that shape the wave spectra, the signatures of these waves in ground-based total electron content (TEC) data, and the sensitivity of GNSS/GPS TEC measurements to the state of the ionosphere and thermosphere. This research builds a comprehensive understanding of how observable TEC responds to acoustic and gravity waves, which is relevant to NASA's upcoming ICON, GDC, and Dynamic Missions. The grant has a potential value of $483,322.92 and was awarded on June 7, 2018, with a completion date of November 21, 2022. There is no set-aside designation mentioned.

We propose a quantitative investigation of the ionospheric and thermospheric (IT) responses to acoustic and gravity waves (AWS and GWS or, here, agws when together in a spectrum) that combines data from ground and space with state-of-the-art numerical modeling. AWS are the first-arriving waves above meteorological sources and GWS, at small-scales (~10S-100S of KM) and short periods (~few to tens of minutes), provide a dominant mechanism for vertical coupling via their fluxes of momentum and energy from the lower atmosphere to the IT and mesosphere (ITM). GWS, in particular, strongly perturb species densities and are thus readily imaged in airglow and ionospheric total electron content (TEC) measured by dense networks of global navigation satellite system (gnss) receivers. Nevertheless, TEC data remain remarkably underutilized as a routine diagnostic of important IT coupling processes driven by AGW. IT is now necessary and timely to build a comprehensive, quantitative understanding of the observable TEC responses to agws. We will investigate, via theory, modeling, and data analysis, the spectrum of high phase velocity (>100 m/s) AWS and GWS that is strongly controlled by ITM temperatures, leading to "natural response" determined by reflection, ducting, and resonance combined with dissipation. These efforts form a key step towards separating and quantifying the agws that arise through primary or secondary forcing from below, and in establishing the utility of observed ITM wave spectra (which may be modal) in assessing AGW sources and effects. Equally, we seek to understand the physics of remotely-sensed TEC measurements that are strongly dependent on the state of the bottomside ionosphere and, further, that are spatially-integrated and thus inherently filtered. Thus, in support of the overarching science question: "what are the dominant, quantifiable, local-scale responses of the ionosphere and thermosphere to acoustic and gravity waves over short periods of time?", we pursue three objectives to investigate and quantify the: (1) natural (resonant, dominant) atmospheric responses that shape AGW spectra in the ITM; the (2) linear and nonlinear signatures of agws in ground-based TEC data; and the (3) sensitivity and dependence of gnss/GPS TEC observables on the state of the IT. To achieve closure, we will apply our new 3D high-resolution models to NASA mission and ground-based data to build a quantitative understanding of observable AGW signatures in TEC under realistic conditions via case studies. Analyses of ground-based gnss TEC will characterize ITM wave dynamics above broadband neutral forcing, such as due to severe weather. Analyses of timed's saber instrument data, together with climatologies and empirical models, will define the neutral ITM to investigate its role in controlling wave spectra. Further, this will provide realistic model environments for simulations of theoretical and observed AGW dynamics. Ionospheric maps of o/N2 ratio from timed's guvi, along with cosmic radio occultation measurements of electron density, JPL mapped TEC data products, and empirical models will provide insight, and will validate (and augment) our self-consistent ionospheric states to be used in modeling case studies. Together, our suite of models will investigate the compressible and nonlinear AGW dynamics that arise following broadband forcing, and the subsequent responses of a coupled and self-consistent dipole ionosphere and plasmasphere. To enable model-data comparisons, and to assess the 3D nature of wave fields, we will simulate TEC integrations along moving paths from satellites to receivers to leverage multiple lines-of-sight for assessments of agws via slant-TEC. Our unique modeling and analysis framework will address our science objectives and question, and will enable future applications to diverse problems in ITM AGW dynamics, with direct potential benefits for the pending icon and conceptualized GDC and dynamic missions.