Physics
Scientific paper
May 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agusmsm51a..12b&link_type=abstract
American Geophysical Union, Spring Meeting 2002, abstract #SM51A-12
Physics
2700 Magnetospheric Physics, 2722 Forecasting, 2776 Polar Cap Phenomena, 2409 Current Systems (2708)
Scientific paper
Geomagnetic variations observed at three distances from the southern geomagnetic pole (at CGM latitudes 69.84° S, 80.14° S and 84.92° S) are studied and differentiated for season, geomagnetic activity and magnetic local time. Results show that the geomagnetic activity effect is much more significant than the seasonal effect in enhancing the observed variations. Moreover, variations larger than |50| nT occur more frequently at latitude 80.14° S CGM than at latitudes 69.84° S or 84.92° S CGM, specially during the local summer. The observations of the H variations at 69.84° S CGM are in agreement with the expected auroral oval current pattern, indicating ionospheric currents mostly westward in the near noon and eastward in the near midnight sectors. In contrast, at 80.14° S CGM latitudes, these currents tend to have east-west directions opposite to those at 69.84° S CGM location, in agreement with the expectations related to the presence of a polar cap return current from the cusp and the auroral oval. A second east-west reversal is shown at latitudes 84.92° S CGM with respect to 80.14° S CGM observations, suggesting a rather structured, possible multi-cell, ionospheric current pattern in the southern polar cap. The observations of the D geomagnetic variations indicate that the ionospheric currents, both at 80.14° S and 84.92° S CGM, have their component along the line between each station and the eccentric dip_pole (located at about geographic latitude 66° S and longitude 129° E) directed in the sense away from the Sun. The significant recurrence (during different seasons, geomagnetic activity and magnetic local time) of this feature and its independence of the interplanetary magnetic field orientation suggest the possibility of obtaining a good prediction of at least one component of the southern polar cap ionospheric currents.
Ballatore Paola
Lanzerotti Louis J.
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