Pi2 pulsations and the substorm current wedge - ground observations

Results obtained by relating Pi2 polarization characteristics to the current wedge location using data from the AFGL Magnetometer Network (54 N corrected geomagnetic latitude) are reviewed. Inside and outside the wedge the horizontal polarization ellipse azimuth exhibits a longitudinal pattern explained by a three-dimensional current system and pointing towards its center. For secondary pulsations in a Pi2 series, the azimuth pattern is displaced relative to the wedge center, suggesting that pre-existing currents affected the determination of the current wedge. The sense of polarization is generally anticlockwise, but there are more examples of clockwise polarization outside the current wedge. Phase differences between stations show westward (eastward) phase propagation dominating west of and inside (east of) the current wedge.