This flow chart shows the different computation steps and the data flow, which is needed to determine the electromagnetic core-mantle coupling torques. In the upper left corner is shown the radial component of the geomagnetic field at the Earth's. Using the NHDC we can compute the poloidal geomagnetic field at the CMB, based on the geomagnetic field at the surface and a radially dependent conductivity stratification. As an example the radial component is shown (like in Figure 2. By the inversion of the frozen-flux equations and under the assumption tangential geostrophy it is possible to determine the fluid flow velocity beneath the CMB which is provided by I. Wardinski (see also Figure 3). This calculations are based on the poloidal geomagnetic field at the CMB. The induction equation for the toroidal geomagnetic field at the CMB can be solved, using the poloidal geomagnetic field and the fluid flow velocity at the CMB. The example shows the phi-component of the toroidal geomagnetic field at the CMB, as in Figure 7. Based on poloidal and toroidal geomagnetic field components at the CMB we can compute the electromagnetic coupling torques LP and LT.
