E-region electron density profile estimation from radio occultation measurements K. Agrawal. E. Howell, G.S.Bust, R.Fevig, D.Olsen

The Earth's geomagnetic field is generated by a core dynamo process. Geomagnetic fields are altered by solar wind and the solar magnetic field. This dynamic geomagnetic field, along with solar outbursts, causes changes in ionospheric current flows. The ionosphere is divided into three layers: D-region, E-region and F-region. This research focuses on the E-region electron density profile because it affects ionospheric conductance directly. In other words, the electrical conductance of this region defines the ionosphere's overall electric-circuit properties. So, the E-region electron density profile estimation yields fundamental information about ionospheric conductivity, which in turn informs other areas of research. E-region electron density profile can also be used for the analysis of the equatorial electrojet near the Earth's magnetic equator, to estimate severe ionospheric changes during auroral activity and for space weather forecasting which is important for high frequency communication in polar regions. The primary purpose of this research is to estimate and analyze the space-time variability of the E-region electron density profiles in the auroral regions after eliminating F-region contributions using radio occultation measurements coupled with other appropriate models. In this approach, F-region contributions in the estimated radio occultation total electron content (ROTEC) are obtained from the Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm. To get the E-region ROTEC, the F-region's contribution will be subtracted. Then, the E-region electron density profile will be calculated using an inverse Abel transform of ROTEC. The IDA4D algorithm takes into account the horizontal gradients in the F-regions and therefore produces more accurate E-region densities than a standard Abel inversion. E-region profiles obtained from this approach during the auroral activity will compare with the E-region profiles obtained when there is no auroral activity.