Alternative parameterisations of the external magnetic field and its induced counterpart for 2001 and 2002 using Orsted, champ and observatory data

A better parameterisation of the field generated by the large-scale magnetospheric current systems is required to avoid the need for further Filtering of the data when modelling the crustal magnetic field. Using Orsted and observatory data for year 2001, we investigate new parameterisations where internal and external degree one Gauss coefficients are computed daily. These models are compared with models where the external field is parameterised with a linear dependence on the Dst index. For both types of model the overall fits to the data are similar but the rapid variations in the magnetospheric currents and their induced counterparts are better captured using the new parameterisations.