Recently, Walker et al. (1979) have shown by suitability of the Scandinavian twin auroral radar experiment facility for Pc 5 pulsation studies. They consider that in the ionosphere the hydromagnetic wave causing the geomagnetic pulsation produces a periodic electric field superimposed on the ambient background field. In this paper STARE measurements of ionospheric electric fields are used to obtain Pc 5 polarization maps covering all the STARE field of view. These fields are deduced from electron Hall drift velocites measured with high spatial (20¿20 km2) and temporal (29 s or 60 s) resolution over a large area (160,000 km2). The fast Fourier transform algorithm is applied to time series of both the north-south and east-west electric field components for each of the ~400 geographic points within the STARE field of view. By retaining both the amplitudes of and relative phase between the north-south and east-west Fourier transformed components, the complete polarization state of the Pc 5 electric field can be determined at each geographic point and for each of the discrete frequencies obtained from the fast Fourier transform algorithm. The analysis of a number of selected events that support the hydromagnetic field line resonance theory of micropulsations is presented.