Investigation of Ionospheric Slab Thickness and Plasmaspheric TEC Using Satellite Measurements

摘要

The ionospheric slab thickness (τ) is a parameter which provides information about the nature of the distribution of ionization at a specific location and is defined as the ratio of the vertical Total Electron Content (vTEC) measured in TEC units (1 TECu = 10~(16) electrons m~(-2)) to the maximum ionospheric electron density in the F-region (NmF2). Slab thickness provides substantial information on the shape of the electron density profile as well as the neutral and ionospheric temperatures/gradients,composition and dynamics. On the other hand the electron content in the plasmasphere, termed plasmaspheric electron content (PEC) has received increasing interest in the last few years due to its significance in measuring and modeling the ionosphere to altitudes lower than GPS, in the context of transionospheric signal propagation.An investigation of the characteristics of these two parameters (r and PEC) is carried out based on 650 values of vTEC and NmF2 retrieved by a space-based technique (radio occul-tation measurements from the Constellation Observing System for Meteorology, Ionosphere, and Climate-FORMOSAT-3/COSMIC) and vTEC values based on a ground-based technique (IGS dual frequency GPS receivers facilitating monitoring of the ionosphere) taking advantage of the inherently excellent spatial coverage achieved by the satellite constellation and the relatively uniform distribution of GPS stations operating over European latitudes. To ensure that simultaneous measurements of GPS derived vTEC and COSMIC derived vTEC and NmF2 are used, the distance between the GPS stations and GPS occultation at the peak of the F layer is limited to 1° within a time interval of 5min. In addition only data during geomagnetically quiet conditions have been taken into account, as ionopsheric electron density irregularities give rise to erroneous determination of the peak density and height from GPS occultations due to significant fluctuations of the electron density profile.