Space weather effects on transionospheric radio wave propagation on 6 April 2000

Abstract

The ionosphere region plays an active role in the complex space weather relationships. So a permanent monitoring of the ionospheric state on global scale is required. The world-wide use of Global Navigation Satellite Systems (GNSS) such as GPS and GLONASS offer the unique chance for a permanent monitoring of the total ionization (Total Electron Content -- TEC) of the global ionosphere/plasmasphere up to about 20000 km height. In this paper we focus on space weather phenomena on 6--7 April 2000 in the ionosphere based on GPS, GLONASS and ionosonde measurements over Europe and over the northern polar cap. Depending on the density of the actual ground station distribution the horizontal resolution of the derived TEC maps is in the order of 500--1000 km. While discussing the special space weather event on 6--7 April 2000 it will be shown that TEC is very sensitive to perturbation induced dynamic forces such as particle precipitation, electric fields and meridional thermospheric winds. We suppose that the strong impact on the magnetosphere/ionosphere systems is due to the southward direction of the interplanetary magnetic field in the evening hours of 6 April. The ionosphere impact on navigation signals is demonstrated by analyzing 1Hz sampled data of GPS and GLONASS satellites. The derived signal phase irregularities due to ionospheric irregularities that degrade navigation and positioning applications indicate highly variable horizontal structures.