Summary: | This paper provides the first three-dimensional description of the ionospheric density structure of the Weddell Sea Anomaly (WSA). The WSA is characterized by a night-time ionospheric density greater than that in daytime in the Weddell Sea region during the southern hemisphere summer. It was first observed by ground-based ionosondes located in the Antarctica back in the 1950s. Recently, the WSA was further investigated by two-dimensional maps over the oceans using TEC measurements collected by the TOPEX/Poseidon. Although these TEC maps have provided two-dimensional views for tracking the time- evolution and spatial coverage of the WSA, the vertical distribution of this peculiar feature is still unavailable. With the vertical ionospheric density profiles observed by the FORMOSAT-3/COSMIC, three-dimensional density structure of the WSA is presented here for the first time. The altitudinal structure of the WSA suggests that the southward offset of the magnetic equator with respect to the geographic equator plays an important role for the formation of WSA.
|