FF-model

The FF-model is a geomagnetic field model for epoch 2005.4 that has been built from one year of CHAMP and observatory data. In this model, the flow at the top of the liquid outer core is co-estimated together with the field model using the radial diffusion-less induction equation. The constraints are applied exclusively on the flow model. This approach leads to a magnetic field model that is compatible in time with the frozen-flux approximation. In particular, the field model acceleration at spherical harmonic degrees higher than 5 correspond to the acceleration that would be obtained for a static flow. This component of the acceleration is much weaker than the contribution due to the time variation of the flow (see Figure 1). It can be downward continued to the CMB (Figure 2).


Figure 1: Power spectra of the FF_model calculated for year 2005.4 at 6371.2 km. Is also presented the power spectrum of the acceleration corresponding to a static flow.


Figure 2: Vertical down component at the CMB for year 2005.4 of the FF_model acceleration part that corresponds to a static flow.