A statistical analysis of low-frequency magnetic pulsations at cusp and cap latitudes in Antarctica

We report a statistical analysis of low-frequency magnetic variations (magnetic
pulsations, 0.8–7 mHz) at South Pole (74 S corrected geomagnetic latitude) and Terra
Nova Bay (80 S) during 1996. The results show that at South Pole (at cusp latitudes) the
pulsation power exhibits two maxima during the day, one in the local premidnight and the
other in the morning. The first maximum disappears when the analysis is restricted to
northward interplanetary magnetic field conditions (Bz > 1 nT), suggesting that it might be
associated to substorm phenomena. During closed magnetospheric conditions, when the
cusp is expected to be located poleward with respect to the station, the spectral and
polarization characteristics of pulsations between 1 and 3 mHz suggest that resonant
oscillations of the outermost closed field lines commonly occur at South Pole in the local
morning. At Terra Nova Bay, in the polar cap, the pulsation power is much lower and its
diurnal variation is characterized by a single maximum, which occurs around local noon,
when the station approaches the cusp. The corresponding polarization pattern indicates
that Terra Nova Bay is always located poleward with respect to resonant field lines.