[en] The scanning beam riometer at Syowa station, Antarctica (66.1deg inv. lat.), detects north-south (N-S) and east-west (E-W) movement of auroral absorptions with a time resolution of 10 sec and spatial resolution of 10 km at the ionospheric height. It is shown that auroral absorptions drift eastward in the post-midnight to pre-noon sectors, and drift westward in the noon to pre-midnight sectors, with speeds ranging from 60 to 700 m/s. The E-W drift direction is reversed around the 10 MLT sector where the drift direction is poleward. The E-W drift direction is also reversed in the pre-midnight sector where the drift is equatorward. This local time dependence of the absorption drift coincides with the ionospheric projection of the magnetospheric convection deduced from IS radar and balloon observations. The fact that the eastward (westward) drift corresponds to the negative (positive) geomagnetic H deflection with respect to the quiettime level strongly suggests that the magnetospheric source region for the energetic electron precipitation drifts due to the E x B drift. It is inferred that the auroral absorption is spatially elongated in the form of a belt. The width of a typical absorption belt ranges from 30 to 60 km. The observed belt-shaped auroral absorption suggests an existence of a sheet-like structure of magnetospheric plasma, where the pitch angle diffusion causes the precipitation of energetic electrons responsible for the auroral absorption. (author)