Induction Heating in Super-Earths: A Thermochemical Perspective

TL;DR

This work tackles how interior thermochemical properties control electromagnetic induction heating in super‑Earth mantles by building temperature‑ and composition‑dependent conductivity profiles and solving the planet‑scale induction problem. Using a refined electromagnetic framework and self‑consistent partial melting iterations, the authors show that higher mantle temperatures, iron contents, and melt fractions generally suppress induction heating due to enhanced conductivity and magnetic shielding, while in GJ 486b the heating can dominate over radiogenic and tidal sources, potentially driving persistent volcanism and early volatile loss. HD 3167b and GJ 357b experience negligible induction heating under plausible stellar fields, highlighting a strong dependence on stellar magnetic activity and orbital distance. The findings imply that induction heating is a key factor in the thermal and atmospheric evolution of close‑in super‑Earths around magnetically active stars, and motivate multi‑disciplinary studies linking interior dynamics to atmospheric outcomes. The study integrates interior modeling, experimental conductivity data, and electromagnetic calculations to quantify heating profiles across realistic thermochemical states, offering a framework for interpreting observations of exoplanet interiors and atmospheres.

Abstract

Electromagnetic induction heating has recently been proposed as an important internal heat source in the mantles of rocky exoplanets. However, its dependence on planetary interior properties remains poorly constrained. Here we construct electrical conductivity profiles for super-Earth mantles considering different temperatures and compositions, and evaluate induction heating in super-Earth mantles in both solid and partially molten states. We find that high mantle temperature, iron content, and melt fraction all suppress the overall induction heating efficiency due to increased mantle conductivity and magnetic shielding. In GJ 486b, induction heating likely exceeds both radiogenic heating and tidal heating, driving persistent surface volcanism and early volatile depletion, whereas HD 3167b and GJ 357b experience insignificant induction heating due to weak stellar magnetic fields. Our findings highlight induction heating as a critical factor in the thermal and atmospheric evolution of close-in super-Earths around magnetically active stars.

Figures (12)

• Figure 1: Mantle conductivity profiles for a 4 $M_\oplus$ super-Earth with an Earth-like core mass fraction (0.32). (a) Conductivity profiles with various potential temperatures. (b) Conductivity profiles with various Fe fractions ($X_\mathrm{Fe}$) in mantle silicates.
• Figure 2: Energy release per unit mass due to induction heating as a function of depth inside GJ 486b considering different potential temperatures (a) and Fe fraction ($X_\mathrm{Fe}$) in mantle silicates (b). The critical value of energy release that can keep the mantle rock molten ($10^{-11}$ W kg$^{-1}$) and its plausible range kislyakova_effective_2018guenther_searching_2020 are shown as dashed lines and shaded regions, respectively.
• Figure 3: Color maps and contour plots of three metrics of induction heating efficiency as a function of potential temperature and mantle Fe contents ($X_\mathrm{Fe}$) in GJ 486b (a--c), HD 3167b (d--f), and GJ 357b (g--i). (a, d, g) Total induction heating power inside the planet; (b, e, h) Maximum depth-dependent energy release per unit mass; (c, f, i) Depth of the partially molten mantle layer that has an energy release exceeding the critical value of $10^{-11}$ W kg$^{-1}$. The white dashed lines mark the equilibrium temperature of HD 3167b kislyakova_electromagnetic_2020.
• Figure 4: (a,b) Energy release due to induction heating as a function of depth in HD 3167b (a) and GJ 486b (b) with the presence of mantle partial melting with different potential temperatures. (c, d) The depth of the partial melt that can be sustained by induction heating in HD 3167b (c) and GJ 486b (d). (e, f) the surface heat flux produced by induction heating as a function of potential temperature in HD 3167b (e) and GJ 486b (f). The energy release due to tidal heating in Io lainey_strong_2009 is shown for comparison in (f). The gray curves labeled 1E-10 adopt a high critical threshold of $10^{-10}$ W kg$^{-1}$ for mantle partial melting. All other calculations use a threshold value of $10^{-11}$ W kg$^{-1}$. The pink and gray curves in panel f almost overlap. The mantle iron content is set to be an Earth-like value of 11 mol%.
• Figure A1: The electrical conductivity (a), the modulus of the time-varying magnetic field (b), and the energy release per unit mass due to induction heating (c) as a function of depth inside GJ 486b with or without post-perovskite (pPv) phase in the conductivity profile.