Field-Aligned Plasma Transport Induced by Alfven Wave as a Mechanism of TEC Modulation by Pc5 Pulsations

Abstract:

Monitoring of the ionospheric total electron content (TEC) variations by global satellite navigation system GPS has turned out to be a sensitive method to study the propagation of transient disturbances in the ionosphere, induced by internal gravity waves and magnetohydrodynamic (MHD) waves. However, the effect of TEC modulation by MHD waves is not well examined and a responsible mechanism has not been firmly identified. During periods with intense global Pc5 waves during the recovery phase of strong magnetic storms distinct pulsations with the same periodicity were found in the TEC data from high-latitude GPS receivers. We analyze jointly signatures of Pc5 pulsations in the TEC/GPS, ionospheric radar (EISCAT), and ground magnetometer data. Comparison of periodic fluctuations of the electron density at different altitudes from EISCAT shows that main contribution into TEC pulsations is provided by the lower ionosphere, namely the E- and lower F-layers. This observational fact favors the TEC modulation mechanism by field-aligned plasma transport induced by Alfven wave. Numerical modeling supports the conjecture that TEC modulation is caused by periodic pumping/depleting the ionospheric plasma density by the field-aligned current between the magnetosphere and ionosphere transported by Alfven wave.