Magnetic Fields in Earth-like Exoplanets and Implications for Habitability around M-dwarfs

TL;DR

This study estimates magnetic moments of Earth-like exoplanets, revealing how rotation and other factors influence their magnetic fields, which are crucial for assessing habitability around M-dwarf stars.

Contribution

It introduces a method to estimate magnetic moments of terrestrial exoplanets considering their rotation, structure, and history, with implications for habitability assessments.

Findings

Fast rotators can have magnetic moments up to 80 times Earth's.

Slow rotators have magnetic moments up to 1.5 times Earth's.

Certain rocky exoplanets can sustain significant magnetic dynamos.

Abstract

We present estimations of dipolar magnetic moments for terrestrial exoplanets using the Olson & Christiansen (2006) scaling law and assuming their interior structure is similar to Earth. We find that the dipolar moment of fast rotating planets (where the Coriolis force dominates convection in the core), may amount up to ~80 times the magnetic moment of Earth, M_Earth, for at least part of the planets' lifetime. For very slow rotating planets (where the force of inertia dominates), the dipolar magnetic moment only reaches up to ~1.5 M_Earth. Applying our calculations to currently confirmed rocky exoplanets, we find that CoRoT-7b, Kepler-10b and 55 Cnc e can sustain dynamos up to ~ 18, 15 and 13 M_Earth, respectively. Our results also indicate that the magnetic moment of rocky exoplanets not only depends on their rotation rate, but also on their formation history, thermal state, age and composition, as well as the geometry of the field. These results apply to all rocky planets, but have important implications for the particular case of exoplanets in the Habitable Zone of M-dwarfs.