Earth and Planetary Science
EPS Atmosphere, Oceans, and Climate

How Super-Earths Generate Their Magnetic Fields

Monday, September 24, 2018
Solid silicates (blue line) are semi-conductors that have excitation gap (green region). Liquid silicates (red line) have no gap and are thus semi-metals. They conduct electricity reasonably well.

How Super-Earths Generate Their Magnetic Fields

With the Kepler satellite, thousands of new exoplanets were discovered. Many of them are Super-Earths because they are larger than Earth and have a rocky composition. Their interiors are not much hotter than Earth's and part of their mantles are liquid. In our recent article, we showed that the electronical conductvity of liquid mantles are sufficiently high so that Super-Earth can generate a magnetic fields with their mantles. This is a new regime for the generation of planetary magnetic fields. On Earth, the field is generated in the liquid outer iron core. On Jupiter, it arises from the convection of liquid metallic hydrogen. On Uranus and Neptune, it is assumed to be generated in their ice layers. Now we have added molten rocks to this diverse list of field generating materials. This also implies that the magma ocean that existed on the early Earth generated a magnetic field.