Thermospheric Wind Effects on the Evolution of Dayside Ionospheric Total Electron Content (TEC)

Abstract:

The ionospheric electron density is a highly varying quantity and significantly affects the propagation of radio signals that pass through or are reflected by the ionosphere. During moments of enhanced geomagnetic activity, in particular geomagnetic storms, Ionospheric total electron content (TEC) anomalies can form that have very severe spatial and temporal gradients. Occasionally, these anomalies can be large enough to reduce the accuracy of positioning and timing service from GPS causing serious problems for planes and other systems. This research targets on a particular TEC structure, named TEC plumes, a region of high TEC extending from the mid-latitudes to the higher latitudes and polar areas in the north hemisphere. It has been found recently that the growth and decay of the plumes can be affected by the interplanetary conditions through convection as well as the thermospheric winds. In particular, this research focuses on thermospheric wind effects on plume evolution in terms of longitudinal and hemispheric asymmetries. We use the International Geomagnetic Reference Field (IGRF) model to specify the geomagnetic field lines as well as idealized thermospheric wind pattern to identify the wind effects at different longitudes. We found that the thermospheric wind would be most effective in changing TEC at two longitudinal sectors in the Northern Hemisphere, i.e. near Alaska and East Europe, and one longitudinal sector in the Southern Hemisphere, i.e. near Antarctic Peninsula. We also compare the results to TEC data through event and statistical analysis and to ionosphere-thermosphere simulation results. Preliminary results show that the TEC value dips are coincident with these longitudinal sectors.