Electrical conductivity and magnetic dynamos in magma oceans of Super-Earths

• DOI: 10.1038/s41467-018-06432-6
• Publication Date: 2018-09-18T13:47:20Z
• Authors: François Soubiran; Burkhard Militzer
• Keywords: [SDU] Sciences of the Universe [physics]; 0301 basic medicine; 03 medical and health sciences; 550; [SDU]Sciences of the Universe [physics]; 13. Climate action; Science; Q; 500; Article

AbstractSuper-Earths are extremely common among the numerous exoplanets that have been discovered. The high pressures and temperatures in their interiors are likely to lead to long-lived magma oceans. If their electrical conductivity is sufficiently high, the mantles of Super-Earth would generate their own magnetic fields. With ab initio simulations, we show that upon melting, the behavior of typical mantle silicates changes from semi-conducting to semi-metallic. The electrical conductivity increases and the optical properties are substantially modified. Melting could thus be detected with high-precision reflectivity measurements during the short time scales of shock experiments. We estimate the electrical conductivity of mantle silicates to be of the order of 100 Ω−1 cm−1, which implies that a magnetic dynamo process would develop in the magma oceans of Super-Earths if their convective velocities have typical values of 1 mm/s or higher. We predict exoplanets with rotation periods longer than 2 days to have multipolar magnetic fields.