LAUSR

Convection of the liquid iron (Fe) outer core and electrical properties of Fe are responsible for the geodynamo that generates the geomagnetic field. Recent results showed the thermal conductivity of the core and related conductive heat flux may be much larger than previously accepted, suggesting that thermal convection would not be an energy source to power the geodynamo. Here we report experimental measurements of the electrical resistivity of solid and liquid Fe which show invariant values along the melting boundary at pressures up to 24 GPa. The observed resistivity invariance was extrapolated to Earth's predominantly Fe solid inner core and liquid outer core conditions and, using the Wiedemann‐Franz law, the thermal conductivity was calculated. We calculate a conductive core heat flow of 8–9 TW at the core‐mantle boundary. These results provide strong support for thermal convection as a geodynamo energy source.