A comparative analysis study of two GNSS-based Ionospheric imaging models applied to South Africa and South America

B. OPPERMAN; GENDE M.; AZPILICUETA F.; P. CILLIERS; MCKINNEL L.A

Durban, South Africa.

Congreso; 54th Annual Conference of the South African Institute of Physics; 2009

South African Institute of Physics

The electrified space plasma in Earth?s ionosphere is a dispersive medium which modulates radio signals transmitted from Global Navigation Satellite System (GNSS) signals orbiting Earth at 20 200 km. Up to twelve ionospheric slant Total Electron Content (TEC) measurements per second, per receiver may be quantified from the ionospheric group delay experienced on the GNSS L1 and L2 carrier waves. Combined slant TEC measurements from a regional GNSS receiver network supply a dense spatial observation set suitable for imaging the regional TEC distribution. Various imaging techniques exist which employ various slant to vertical mapping functions, co-ordinate systems and techniques for estimating of and correction for GNSS satellite and ground receiver Differential Clock Biases (DCBs). Two independently-developed models were used in a comparative study in imaging the ionosphere over South Africa and South America. The Hermanus ionosphere model (Hermion) and the Argentinean La Plata Ionosphere Model (LPIM) both employ spherical harmonic analyses adapted to their respective regions? unique geomagnetic characteristics. The comparative study was conducted in two phases. In the first phase the correct implementation of estimated DCBs were verified by comparing the DCB-corrected slant TEC values from two co-located GNSS receivers using both models. The second phase involved the ionospheric imaging over both regions using both models with various mapping functions and co-ordinate systems. Special focus was placed on the models? ability to resolve the very intricate ionospheric equatorial anomaly over South America, the so called ?fountain effect? North and South of the geomagnetic equator.