Observation and model comparisons of the traveling atmospheric disturbances over the Western Pacific region during the 6-7 April 2000 magnetic storm

The ionospheric features of traveling atmospheric disturbances (TADs) over the Western Pacific region have been observed by the Wuhan, NCU-DPS, and Cebu ionosondes and the ROCSAT-1 satellite during the 6-7 April 2000 magnetic storm. The nighttime observations are further compared with the simulation results of the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). Both observation and model demonstrate that the TADs propagate equatorward with a phase speed of 610-650 m/s. The observations and corresponding TIEGCM simulations show a negative initial correlation between NmF₂ and HmF₂ caused by equatorward wind surges at various locations from midlatitudes to the equator. These qualitative agreements reveal that the TIEGCM is capable of simulating the TADs. The TIEGCM simulations of two locations located in the downwind hemisphere further show decreases in NmF₂ and HmF₂ mainly due to the enhanced transequatorial winds. After lowering the F₂ layer at the two locations, the HmF₂ is raised for several hours and shows slightly enhanced NmF₂ daytime values while the meridional wind is at background magnitude. We propose that this effect is caused by accumulation of plasma transported from northern latitudes. However, we also find that the NmF₂, HmF₂, and the lifetimes of HmF₂ uplift phase and equatorial vertical drift in the model results are quantitatively inconsistent with that in the observed data.