Abstract Habitability of super‐Earths likely requires self‐sustained magnetic fields to shield their atmospheres from stellar forcing. Extreme pressures and temperatures probably produce a long‐lived basal magma ocean (BMO), a potential source for these fields. To determine when the magnetic field is primarily powered by a BMO rather than a convective core, we examine the structural, thermal, buoyancy, and magnetic evolution of super‐Earths involving a coupled core, BMO, and mantle. We find that more massive planets host larger BMOs with prolonged, stronger silicate dynamos, that increasingly overlap with core dynamos, but produce stronger fields. In contrast, planets with larger cores have shorter‐lasting silicate dynamos, resulting in dominant core fields. Using a conservative electrical conductivity, we predict that silicate dynamos are likely sustained in super‐Earths, except in low‐mass planets with large cores. Strong silicate dynamos could facilitate the detection of magnetic fields on super‐Earths, constraining their internal structure and potential habitability.
Lherm et al. (Wed,) studied this question.