We study geomagnetic field variations from 1 min data at three Antarctic sites (Mario Zucchelli Station, Scott Base, Talos Dome) along the 80° S geomagnetic parallel. The daily variation depends on local time, due to the polar extension of midlatitude ionospheric currents. The ~1–7 mHz power maximizes around 12 MLT, close to the cusp, and the coherence does so between stations around 24 MLT. The wave propagation is consistent with a daytime solar wind source and with nighttime substorm processes.