Ionospheric TEC Estimations with the Signals of Various Geostationary Navigational Satellites

Abstract:

The development of GNSS and SBAS systems provides the possibility to retrieve ionospheric TEC from the dual frequency observations from a number of geostationary satellites using the same approach as for dual frequency GPS/GLONASS observations. In this connection, the quality of geostationary data, first of all the level of noise in TEC estimations is of great interest and importance. In this work we present the results of the comparison of the noise patterns in TEC estimations using signals of geostationary satellites of augumentation systems – indian GAGAN, european EGNOS and american WAAS, as well as the signals of chinees COMPASS/Beidou navigational system. We show that among above mentioned systems geostationary COMPASS/Beidou satellites provide best noise level in TEC estimations (RMS~0.1TECU), which corresponds to those of GPS/GLONASS, while GAGAN and WAAS TEC RMS could reach up to 1.5 TECU with typical values of 0.25-0.5 TECU which is up to one order greater than for common GPS/GLONASS observations. EGNOS TEC estimations being even more noisy (TEC RMS up to 10TECU) than WAAS and GAGAN ones at present time are not suitable for ionospheric studies.

We also present geostationary TEC response to increasing solar X-Ray and EUV ionizing radiation during several recent X-class flares. Good correlation was found between TEC and EUV flux for the stations at the sunlit hemisphere. We also present geostationary TEC response to geomagnetic field variations during strong and moderate geomagnetic storms (including G4 St. Patricks Day Storm of 2015) showing examples of both positive and negative TEC anomalies of order of tens of TECU during main storm phase.

Our results show the capability of geostationary GNSS and SBAS observations for continuous monitoring of ionospheric TEC. Intensively growing networks of dedicated receivers (for example MGEX network) and increasing number of dual-frequency geostationary satellites in SBAS and GNSS constellations potentially make it a powerful instrument for TEC climatology.