CEDAR: Resolving Thermosphere Response Times to Auroral and Solar Energy Inputs and Improving Neutral Density Predictions

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

This project is to refine and enhance a new computer model that provides temperatures in the thermosphere (the atmosphere region from about 80 to 600 km above sea level). The temperature in the thermosphere varies in response to solar energy input and auroral events at high latitudes and is also closely related to the atmospheric density. This improved model will help better predict the atmospheric temperature and density in the thermosphere. Since the density is the key parameter that determines satellite drag, this improvement will help better predict satellite drag and space weather in response to changes in solar radiation and associated disturbances in Earth’s electromagnetic field. The new model is referred to with the acronym EXTEMPLAR, for EXospheric TEMperatures on a PoLyhedrAl gRid. The method relies on converting satellite density measurements into exospheric temperatures and sorting these values into bins based on their location on a geodesic grid. By fitting the data in each bin to the environmental conditions at the time, maps of the exospheric temperature can be obtained from the regression coefficients. These temperatures can be used to obtain neutral densities at any location and altitude, by substituting for the values in the empirical model of the thermosphere by the Naval Research Laboratory. Project activities include: (1) Measuring the time delays between auroral energy inputs and exospheric temperature response, and how these delays vary around the globe. (2) Investigating the occurrence of regions having decreasing density during major heating events. (3) Improving the modeling of the thermosphere's response to variable solar radiation. (4) Construction of an improved neutral density prediction model. (5) Validate the neutral density predictions with comparisons to measurements. The project has the potential to advance the knowledge and understanding of how the thermosphere responds on regional and global scales to energy that is transferred from both solar radiation and auroral electrodynamic heating. The timings between the energy input and the thermosphere's response will be established as a function of global coordinates. The development of methods using triangulated geodesic grids has the potential to transform modeling and analysis techniques within the space science community. The successful conclusion to this project will result in an empirical model that will be useful to other research in the scientific community, particularly those related to the objectives of the NSF CEDAR program, including simulations of the coupled, ionosphere/thermosphere system. The research has potential benefits to society at large, such as through better predictions of the variations in neutral mass density that can change the orbits of satellites. This capability is important to national security, the success of commercial space enterprises, as well as the safety of human spaceflight. 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.