Magnetic Field Evolution of Hot Exoplanets

Abstract

Numerical simulations have shown that the strength of planetary magnetic fields depends on the convective energy flux emerging from planetary interiors. Here we model the interior structure of gas giant planets using \texttt{MESA}, to determine the convective energy flux that can drive the generation of magnetic field. This flux is then incorporated in the Christensen et al. dynamo formalism to estimate the maximum dipolar magnetic field $B_{\mathrm{dip}}^{(\max )}$ of our simulated planets. First, we explore how the surface field of intensely irradiated hot Jupiters ($\sim 300M_{\oplus }$) and hot Neptunes ($\sim 20M_{\oplus }$) evolve as they age. Assuming an orbital separation of 0.1 au, for the hot Jupiters, we find that $B_{\mathrm{dip}}^{(\max )}$ evolves from 240 G at 500 Myr to 120 G at 5~Gyr. For hot Neptunes, the magnetic field evolves from 11 G at young ages and dies out at $\gtrsim$ 2 Gyr. Furthermore, we also investigate the effects of atmospheric mass fraction, atmospheric evaporation, orbital separations $\alpha$ and additional planetary masses on the derived $B_{\mathrm{dip}}^{(\max )}$. We found that $B_{\mathrm{dip}}^{(\max )}$ increases with $\alpha$ for very close-in planets and plateaus out after that. Higher atmospheric mass fractions lead in general to stronger surface fields, because they allow for more extensive dynamo regions and stronger convection.

10 pages, 8 figures, MNRAS in press

References in corpus (13)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Roche lobe effects on the atmospheric loss of "Hot Jupiters"
• Estimating the magnetic field strength in hot Jupiters
• Magnetospheric Emissions from the Planet Orbiting tau Boo: A Multi-Epoch Search
• How Expanded Ionospheres of Hot Jupiters Can Prevent Escape of Radio Emission Generated by the Cyclotron Maser Instability
• How does the mass and activity history of the host star affect the population of low-mass planets?
• Can we detect aurora in exoplanets orbiting M dwarfs?
• Planetary Magnetism as a Parameter in Exoplanet Habitability
• Thermal Evolution and magnetic history of rocky planets
• The Linkage between the Core Mass and the Magnetic Field of an Extrasolar Giant Planet from Future Radio Observations
• The key impact of the host star's rotational history on the evolution of TOI-849b
• Effects of Planetesimal Accretion on the Thermal and Structural Evolution of Sub-Neptunes

Cited by in corpus (3)

• Star-Planet Interactions: A Computational View
• Helium escape signatures are generally strongest during younger ages but this age dependence is lost in the diversity of observed exoplanets
• Inflated hot Jupiters: Inferring average atmospheric velocity via Ohmic models coupled with internal dynamo evolution