In TGD Universe BE having nominal value .5 Gauss has two parts: monopole flux tube part and non-monopole part analogous to Maxwellian magnetic field. Monopole part is perhaps identifiable as the endogenous magnetic field Bend = 2BE/5=.2 Gauss explaining Blackman's findings about quantal effects of ELF em fields on vertebrate brain in terms of the identification of dark matter as phases of the ordinary matter with effective Planck constant heff=n×h0. No currents are needed to maintain the monopole part whereas the non-monopole requires current maintaining it. Bend corresponds to a flux tube radius of about L(169) then the minimal radius for flux tube would be about L(163) ≈ 640 nm.
Non-monopole part of BE would be naturally parallel to the rotation axis of Earth since it is generated by the rotation of the outer core. Monopole part could correspond to the magnetic axis. The change of the direction of BE would be induced by the change of the direction of the monopole part and induce currents changing the non-monopole part. Monopole part together with this refreshing mechanism would explain the maintenance of BE (see this). The magnetic North pole is recently moving rather rapidly towards Siberia and the strength of BE has been decreasing suggesting that the refreshing operation has been activated. This mechanism would force transfer of energy needed to refresh the current maintaining the non-monopole part.
See the article TGD inspired model for magneto-reception and circadian rhythm.
For a summary of earlier postings see Latest progress in TGD.