Collaborative Research: CEDAR--Thermospheric Effects on Polar Cap Ionospheric Structures

This project will examine ion-neutral coupling processes at high latitudes to understand how the thermospheric dynamics affect the electron density structures and associated ion outflow. The upper atmosphere above 100 km altitude consists of electrically neutral gases as well as electrically charged ions and free electrons. The neutral component is called the thermosphere, and the charged components are called the ionosphere. The ionosphere significantly alters the propagation of radio waves passing through it, including communication and navigation signals transmitted from satellites. Because of their impacts on radio propagation, understanding the processes creating structures in the ionosphere is a critical part of space weather research. This research will be conducted with numerical models of the coupled thermosphere and ionosphere as well as analysis of ionospheric data from radars and the global positioning system. The project will support a graduate student and the models will be open-source to the community. Results of the project will be used to create classroom examples of ionospheric phenomena for use in undergraduate and graduate classes at UCLA. The polar cap ionosphere contains a variety of mesoscale (100-1000 km) electron density structures, including polar cap patches and tongues of ionization. The electron density gradients associated with these structures can drive plasma instabilities and severely affect radio propagation at high latitudes. The polar cap ionosphere is also the source of significant ion outflow to the magnetosphere, and the polar wind reflects the structuring of the high-latitude ionosphere. Magnetospheric energy inputs drive significant variations in the high-latitude neutral thermosphere. This project will examine ion-neutral coupling processes at high latitudes to understand how the thermospheric dynamics affect the electron density structures and associated ion outflow. The specific science questions to be addressed are (1) How do thermospheric density and composition changes during geomagnetic storms affect the formation and evolution of high-latitude electron density structures? and (2) How do thermospheric variations modulate the supply of ion upflow and outflow? These questions will be addressed with controlled numerical experiments coupling the Thermosphere Ionosphere Electrodynamics General Circulation Model 3.0 (TIEGCM 3.0) model of the neutral thermosphere to the High-latitude Ionospheric Dynamics for Research Applications (HIDRA) model of the high-latitude ionosphere and polar wind. The team will contrast simulations using the coupled model to simulations using a static thermosphere to isolate ion neutral coupling effects. They will compare the simulation results to observations of high-latitude density structures from incoherent scatter radars (e.g. RISR) and GPS total electron content observations. 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.