Behaviour of the quiet-day geomagnetic variation at Livingston Island and variability of the S_q focus position in the south American-Antarctic Peninsula region

Characteristics of the regular daily variation, including seasonal and solar cycle variabilites, at the relatively new geomagnetic observatory of Livingston Island (Antarctica) have been studied. Such studies of solar cycle variability were possible due to the current availability of more than 11 years of definitive data. The seasonal behaviour of the quiet-time daily field variations are in agreement with those of earlier studies for a mid-latitude observatory placed at the south of the southern hemisphere current focus. We also found a clear dependence of the S_q amplitude on solar activity, although the 5_q amplitude maximum occurs about 2 years later than the sunspot maximum. An analysis of contemporary data for solar cycle 23 was carried out for observatories located in the same longitudinal sector, with the aim of identifying the latitudinal displacements of the current focus that affect the observed 5_q variations. This was also determined for solar cycle 20 using data from a different set of observatories. The uncertainties associated with the method employed for determining the focus positions are due to the scarcity of observatory data in the South American-Antarctic Peninsula region, but based on our analysis, we can state with a certain reliability that focus latitudes are higher during the summer and at equinoxes than during the winter. However, it is difficult to establish a correlation between focus latitudes and solar sunspot numbers.