Understanding the day-to-day variability of the ionosphere and thermosphere requires unraveling the relative strengths of forcing mechanisms of the I-T system, including solar ultraviolet, extreme ultraviolet, and X-ray fluxes, magnetospheric processes resulting in geomagnetic activity and auroral effects, and propagation of dynamical variations driven by lower atmosphere weather and middle atmosphere tides. The National Center for Atmospheric Research (NCAR) Thermosphere - Ionosphere - Mesosphere - Electrodynamic - Global Circulation Model (TIME-GCM) is used to simulate this region depending on its forcing by the Sun. Recent work on improving the forcing of this model by including an improved description of the Extreme Ultra Violet (EUV) radiation has increased its ability to predict observed parameters such as satellite drag, but it does not capture all the observed hemispheric asymmetries. The implication is that forcing from the lower atmosphere, which is clearly asymmetric due to the location of continental masses, and is known to have very different dynamical features at solstices, is controlling the thermosphere. However, the TIME-GCM, with its 30-km lower boundary, does not contain these effects. The Community Atmosphere Model (CAM) simulates the variation in the atmosphere, and by coupling it to the TIME-GCM we plan to investigate how much of these asymmetries can be addressed by this forcing from below.

To implement the coupling between TIME-GCM and CAM this project will use the Earth System Modeling Framework (ESMF). This choice has several major benefits. Using the framework allows the project to leverage ESMF's existing infrastructure for doing the interpolation and transfer of data between the CAM and TIME-GCM models. It also allows the project to use ESMF's infrastructure for time management, control, and parallel distribution. On the ESMF side this project will be a demonstration of new ESMF functionality for coupling models running as separate executables. This new functionality is based on the InterComm library. InterComm is a runtime library and programming model for coupling separately executing parallel (and sequential programs), and is being used as the component coupling technology within the NSF Center for Integrated Space Weather Modeling. ESMF interfaces to InterComm functions have been contributed to the ESMF code repository, making it easy to use InterComm to transfer data into and out of ESMF components such as CAM. InterComm has also been used to directly couple earlier versions of the TIME-GCM to other space weather components.

This work will demonstrate new science and new functionality for implementing coupling to the community.