LOW-FREQUENCY (1.7-6.7MHZ) 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 Ter ra Nova Bay (geomagnetic coordinates 77.3 S, 279.4 E) during the austr al summers 1987/1988 and 1989/1990 have been analysed. The activity le vel is higher during 1989/1990, corresponding to solar maximum, and th e D power is always higher than the H one. The daily power distributio n shows, for both components, a significative activity enhancement aro und the magnetic local noon, which more clearly emerges during quiet m agnetospheric conditions. Good correlations have been obtained between the low-frequency power and the solar wind velocity, the IMF standard deviation and the K-p index, suggesting that the low-frequency power is linked both to the K-H instability and to the penetration into the magnetosphere of interplanetary turbulence. Correlation coefficients a ttain minimum values around the magnetic local noon, when the power le vel is higher.