Using a Bistatic Fabry-Perot Interferometer System to Improve the Estimation of Thermospheric Winds

TitleUsing a Bistatic Fabry-Perot Interferometer System to Improve the Estimation of Thermospheric Winds
Publication TypeThesis
Year of Publication2010
AuthorsHedlund, PR
AdvisorMakela, JJ
Academic DepartmentDepartment of Electrical and Computer Engineering
Date Published05/2010
UniversityUniversity of Illinois at Urbana-Champaign

One significant cause of disruption in the propagation of low-power, trans- atmospheric radio waves is equatorial spread F (ESF). The Rayleigh-Taylor instability (RTI) causes the development of many types of ESF events. It has been theorized that thermospheric winds have a substantial effect on the growth rate of the RTI, but very little data has been gathered to verify or disprove this idea. This thesis proposes a method for synchronously using two ground-based Fabry-Perot interferometers (FPI) to estimate thermospheric winds. When a single FPI is used, assumptions must be made to obtain meaningful wind data, but there are inherent limitations to the usefulness of the data caused by the use of these assumptions. It must be assumed that either the vertical wind speed is zero or the vertical and horizontal winds are uniform for the entire observation area in order to obtain meaningful wind speed estimates. In addition, data from a single FPI cannot be used to identify complex struc- tures in the wind field. However, a bistatic FPI system (BFPIS) can be used to obtain full vector wind information in two or more locations. This observa- tion methodology also has potential for reducing the number of assumptions that must be made. For a BFPIS, it need only be assumed that the vertical wind is uniform for the observation area. We begin with a review of the physical principles and typical methods for using an FPI to estimate thermospheric winds and temperatures. We then propose a method for using a BFPIS to improve collected data, as compared to using a single FPI, and present simulations that validate this method.