The contribution of geomagnetic observatories and magnetic models to the study of secular variation and jerks in Antarctica

Some of the most interesting features of the geomagnetic field and its time variations are displayed in polar
areas. Observatory monthly means usually provide an excellent opportunity to study the temporal changes of the
magnetic field at a given location. Unfortunately, on the Antarctic continent the distribution of the permanent ground-
based observatories does not permit a uniform coverage of the examined area. Furthermore, the magnetic records are
characterized by intense external disturbances and noise that make the analysis of the magnetic field difficult. To improve our knowledge of the secular variation and detect the presence of secular variation impulses (geomagnetic
jerks) in Antarctica, we use both observatory data and the CM4 quiet time magnetic field model. In particular CM4
improves our knowledge of geomagnetic jerks over Antarctica through the study of the sign changes of the secular
acceleration maps.