Large-scale traveling ionospheric disturbances observed by GPS receivers in Antarctica

Abstract

The paper examines the propagation direction and velocity of large-scale traveling ionospheric disturbances (LSTIDs) during extreme geomagnetic storms in the 23rd solar cycle (e.g., October 2003 and November 2003 storms) using GPS observations. In the analysis, the time delay between the vertical total electron content (VTEC) structures at Scott Base, McMurdo, Davis and Casey GPS stations and the distance between these stations were the main parameters in the determination of LSTIDs propagation speed and direction. The observations during October and November 2003 storms show obvious time delay between the total electron content (TEC) enhancement signatures at these stations. The time delay suggests a movement of the ionospheric disturbances from higher to lower latitudes during the October storm with a velocity of 800–1 200 m/s and poleward propagation of LSTIDs during the November storm with a velocity of 300–400 m/s. The equatorward or poleward expansion of LSTIDs during the October and November 2003 storms is probably caused by the disturbances of the neutral temperature occurring close to the dayside convection throat or by the neutral wind oscillation induced by atmospheric gravity waves (AGW) launched from the aurora region.