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

Super-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...

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Bibliographic Details
Published in:Nature communications 2018-09, Vol.9 (1), p.3883-7, Article 3883
Main Authors: Soubiran, François, Militzer, Burkhard
Format: Article
Language:English
Subjects:
639/33/445/862
639/766/119/995
704/2151/214
704/445/862
Conductivity
Earth mantle
Electrical conductivity
Electrical resistivity
Extrasolar planets
GEOSCIENCES
Humanities and Social Sciences
Magma
Magnetic fields
Melting
multidisciplinary
Oceans
Optical properties
Rotating generators
Science
Science (multidisciplinary)
Sciences of the Universe
Silicates
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Summary:Super-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. With the discovery of large rocky exoplanets called Super-Earths, questions have arisen regarding the properties of their interiors and their ability to produce a magnetic field. Here, the authors show that under high pressure, molten silicates are semi-metallic and that magma oceans would host a dynamo process.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-018-06432-6