It seems that the magnetic field source remains elusive. That natural nuclear reactor that was found in Gabon (it was extinct) is in the crust, so I wonder how much sense it really made for Herndon to extrapolate in the first place.
THe variability and reversals of the earth's magnetic field strongly suggest fluid currents that generate it by Maxwell's 4th equation, the +dE/dt term(occam's razor). Journey To The Core(to see if Herndon is right)is only a hollywood movie, nothing more. About the only way to "get there" is by micro-psi/remote viewing, any volunteers?