| Summary: | This paper investigates the night-time Weddell Sea Anomaly and TEC climatology during the 1996/97 southern summer. To ascertain the morphology of spatial TEC distribution in terms of hourly, geomagnetic, longitudinal and summer-winter variations, the TOPEX TEC, magnetic and published neutral wind velocity data are utilized. To understand the underlying physical processes, the TEC results are combined with inclination and declination data plus global magnetic field-line maps. To investigate spatial and temporal TEC variations, local times are computed. As results show, the night-time Weddell Sea Anomaly is a large (~1,600(o)2; ~22x106km2 estimated for a steady ionosphere) space weather feature. Extending between 200oE-300oE (geographic), it is an ionization enhancement peaking at 50oS-60oS/250oE-270oE and continuing beyond 66oS. It develops where the spacing between the magnetic field lines is wide/medium, easterly declination is large-medium (20o-50o), and inclination is optimum (~55oS). Its development and hourly variations are closely correlated with wind speed variations. There is a noticeable (~43%) area reduction during the 10 January storm. Southern TECs follow closely the variations of declination and field-line configuration, and therefore introduce a longitudinal division of four. Northern TECs are rather uniform longitudinally. Maps depict the expected strong asymmetry in TEC distribution about the magnetic dip equator.
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