Our results suggest that sea–land interface affects the polarization parameters at coastal stations. We proposed a method for directly estimating, in the frequency domain, the normal field variations at coastal stations, by inverting the linear relationship between horizontal field measurements at coastal and reference stations. Our techniques could also be used to detect possible anomalous effects due to sporadic changes in ground conductivity.

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.