Ionospheric Total Electron Content Derived from GNSS Signals by Double Thin-Shell Model near the Magnetic Equator and Implication in the Meridional Wind

A new technique was developed to estimate ionospheric total electron content (TEC) from GNSS satellite signals. The technique is based on the double thin-layer approximation of the ionosphere, i.e., the vertically distributed electron density is parameterized by two thin-shell layers. Total electron content (strictly speaking, partial electron content) associated with each shell is approximated by the functional fitting of spherical surface harmonics. The technique was applied to the dataset obtained by the meridional receiver network in the equatorial Southeast Asia. Characteristics of TEC distribution for the higher and lower layer exhibited different patterns. The north-south symmetry/asymmetry characteristics changed with the local time and layer. These features were ascribed to the thermospheric wind dynamics.