Wave structures in the electron density profile in the ionospheric D- and E-layers observed by radio holography analysis of the GPS/MET radio occultation data

Vertical distribution of the electron density in the upper atmosphere can be studied using high-precision global positioning system (GPS). In this paper, we show that the radio holography method allows one to determine the vertical profile of the electron density and monitoring wave structures in the upper atmosphere. As an example of this approach, results of analysis of data corresponding to four GPS/Meteorology (GPS/MET) radio occultation events are presented. The radio holograms of the D-layer of the ionosphere reconstructed from radio occultation data revealed wave structures with vertical scales of about 1-8 km and variations in the vertical gradient of the electron density from τ5 x 10³ to τ⁸ × 10³ electrons/(cm³ km) at altitudes of 72-95 km. These structures may be caused by wind shear and atmospheric internal waves with vertical scales ranging from a few hundred meters to several kilometers, which produce vertical convergence of the plasma velocity and plasma advection. Theoretical consideration shows a possibility of qualitative determination of the vertical gradient of the horizontal wind velocity in the E-layer and estimation of the temperature variations in the neutral gas in the D-layer region from observed profiles of the electron density. Variations in the electron density are connected with the temperature changes. The connection coefficient depends on the vertical velocity of the neutral gas motion in the mesosphere. Maximums of the temperature deviation correspond to those in the electron density profile. The results indicate a possibility to estimate the form of the small-scale temperature vertical perturbations in the mesosphere using the radio occultation data.