Accuracy of magnetic-field scaling for K2-18b

Determine how accurately the Sano (1993) magnetic-field scaling law and the assumed interior structure, core radius, core density, and tidal-locking rotation state estimate the intrinsic magnetic field strength of K2-18b.

Background

The paper has no direct measurement of K2-18b’s magnetic field and relies on the scaling law of Sano (1993) to estimate an intrinsic surface field strength of 1.7 μT. This estimate depends on poorly constrained properties of the planet’s interior and rotation, including an assumed Earth-like core density, a core radius of 1 Earth radius, and tidal locking to the host star.

Because the estimated magnetic field strongly affects the modeled shielding of galactic cosmic rays and stellar energetic particles, establishing the accuracy of the scaling law and its underlying assumptions is necessary for reliable predictions of the particle environment and atmospheric energy deposition of K2-18b.