Paleomagnetic Evidence for Inverse Correspondence between the Relative Contribution of the Axial Dipole Field and CMB Heat Flux for the Past 270 Myr

We provide an evaluation of the paleolatitudinal dependence of the paleosecular variation throughout the Paleozoic-Mesozoic transition - linked to the high geomagnetic reversal frequency interval Illawarra Hyperzone of Mixed Polarity (IHMP; ~266.7-228.7 Myr). Our findings were compared with those for intervals of distinctive geomagnetic reversal frequencies within the Phanerozoic. Our results for the IHMP were conducted through estimates of angular dispersion (S_B) of virtual geomagnetic pole (VGP) data groups, taken from a high quality paleomagnetic database. Model G was fitted to these data, providing its shape parameters a and b (respectively related to the antisymmetric and symmetric harmonic terms for the time-average geomagnetic field). Results for the IHMP exhibited compatible patterns with two well-known intervals of higher reversal frequency - Jurassic and the last 5 Myr. A comparison of b/a ratio results - considered as an efficient indicator for the relative contribution of the axial dipole field - for the last 270 Myr, indicated an inverse correspondence with the relative core-mantle boundary (CMB) heat flux, according to recent discussions, clarifying the physical meaning of the Model G shape parameters a and b.

Simple mechanism for reversals of earth's magnetic field

We show that a model, recently used to describe all the dynamical regimes of the magnetic field generated by the dynamo effect in the von Kármán sodium experiment, also provides a simple explanation of the reversals of Earth's magnetic field, despite strong differences between both systems. The validity of the model relies on the smallness of the magnetic Prandtl number.