LSTID Behavior During Geomagnetic Storms Analyzed with SAMI3 seeded by GITM.

Large Scale Traveling Ionospheric Disturbance (LSTID) behavior is dependent on several factors including storm onset UT, storm amplitude, season, and IMF clock angle. We have analyzed these dependencies by modeling a simulated storm, adjusting the model inputs in a controlled way. LSTIDs are simulated with SAMI3 (SAMI3 is Also Model of the Ionosphere), which reads neutral atmosphere parameters from the Global Ionosphere Thermosphere Model (GITM). GITM on its own does not reliably model altitudes higher than ~600km and SAMI3 does not generate LSTIDs independently, hence the need for both models. For our simulated storms, we use varying IMF and Hemispheric Power inputs as both models depend on Weimer-2005 for high-latitude potential patterns and GITM’s precipitation and heating is dependent on HPI and IMF. We can thus adjust the strength, duration, and IMF clock-angle of the storm, as well as the date and time of the onset.

GITM is first run with the selected IMF and HPI inputs. The neutral density, winds, and temperature outputs from GITM are then used as inputs to SAMI3 to model the ionospheric response to the simulated geomagnetic storm data. The ionospheric parameters output by SAMI3 are used to show the speed and wavelength of LSTIDs, as well as the altitudinal and longitudinal behavior. A goal of this research is to understand the effect of the offset between the geographic and geomagnetic poles in addition to IMF parameters on the longitudinal distribution of LSTIDs. The simulations will aid in our understanding of measurements from actual storms, for example, how ionospheric density measurements in the topside ionosphere map to vertically integrated TEC from GNSS.