LOw-frequency (1.7-6.7 mHz) geomagnetic-field fluctuations at high southern latitudes

The low-frequency (1.7-6.7 mHz) powers of the horizontal components H and D recorded at the Antarctic Italian geomagnetic observatory at Terra Nova Bay (geomagnetic coordinates 77.3S, 279.4E) during the austral summers 1987/1988 and 1989/1990 have been analysed. The activity level is higher during 1989/1990, corresponding to solar maximum, and the D power is always higher than the H one. The daily power distribution shows, for both components, a significative activity enhancement around the magnetic local noon, which more clearly emerges during quiet magnetospheric conditions. Good correlations have been obtained between the low-frequency power and the solar-wind velocity, the IMF standard deviation and the Kp index, suggesting that the low-frequency power is linked both to the K-H instability and to the penetration into the magnetosphere of inter-planetary turbulence local noon, when the power level is higher