The Linkage between the Core Mass and the Magnetic Field of an Extrasolar Giant Planet from Future Radio Observations

Abstract

Close-in gas giants are expected to have a strong magnetic field of $\sim 10-100$G. Magnetic fields in extrasolar giant planets are detectable by future radio observations in $\gtrsim 10$MHz and the spectropolarimetry of atomic lines. In contrast, the elusive interiors of exoplanets remain largely unknown. Here we consider the possibility of inferring the existence of the innermost cores of extrasolar giant planets through the detection of planetary magnetic fields. We simulated the long-term thermal evolution of close-in giant planets with masses of $0.2-10M_{\mathrm{Jup}}$ to estimate their magnetic field strengths. A young, massive gas giant tends to have a strong magnetic field. The magnetic field strength of a hot Jupiter is insensitive to its core mass, whereas the core strongly affects the emergence of a planetary dynamo in a hot Saturn. No dynamo-driven magnetic field is generated in a hot Saturn with no core or a small one until $\sim 10-100$Myr if metallization of hydrogen occurs at $\gtrsim 1-1.5$Mbar. The magnetic field strength of an evolved gas giant after $\sim 100\mathrm{Myr}$ is almost independent of the stellar incident flux. Detecting the magnetic field of a young, hot Saturn as a good indicator of its core may be challenging because of the weakness of radio signals and the shielding effect of plasma in the Earth's ionosphere. Hot Jupiters with $\gtrsim 0.4M_{\mathrm{Jup}}$ can be promising candidates for future ground-based radio observations.

arXiv comment10 pages, 8 figures, accepted for publication in ApJ

References in corpus (34)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Low Temperature Opacities
• On the radiative equilibrium of irradiated planetary atmospheres
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• The Mass-Metallicity Relation for Giant Planets
• Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core
• Structure and evolution of super-Earth to super-Jupiter exoplanets: I. heavy element enrichment in the interior
• A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent stars
• Hot Jupiters and Hot Spots: The Short- and Long-term Chromospheric Activity on Stars with Giant Planets
• A new vision on giant planet interiors: the impact of double diffusive convection
• The Heavy Element Masses of Extrasolar Giant Planets, Revealed
• A New Window into Escaping Exoplanet Atmospheres: 10830 Å Line of Helium
• Nuclear Quantum Effects and Nonlocal Exchange-Correlation Functionals Applied to Liquid Hydrogen at High Pressure
• A magnetic field evolution scenario for brown dwarfs and giant planets
• Predicting low-frequency radio fluxes of known extrasolar planets
• Rocky core solubility in Jupiter and giant exoplanets
• Gas Giant Formation with Small Cores Triggered by Envelope Pollution by Icy Planetesimals
• Magnetic field strengths of hot Jupiters from signals of star-planet interactions
• Connecting Giant Planet Atmosphere and Interior Modeling: Constraints on Atmospheric Metal Enrichment
• Scaling Laws for Planetary Dynamos
• Helium Absorption at 1083 nm from Extended Exoplanet Atmospheres: Dependence on Stellar Radiation
• Structure and phase boundaries of compressed liquid hydrogen
• Critical core mass for enriched envelopes: the role of H2O condensation
• Star-planet magnetic interaction and evaporation of planetary atmospheres
• Estimating the magnetic field strength in hot Jupiters
• Interior Models of Saturn: Including the Uncertainties in Shape and Rotation
• Tidally-driven Roche-Lobe Overflow of Hot Jupiters with MESA
• Convection and Mixing in Giant Planet Evolution
• Scaling laws in spherical shell dynamos with free-slip boundaries
• Consistent scaling laws in anelastic spherical shell dynamos
• Surprisingly Weak Magnetism on Young Accreting Brown Dwarfs
• Detecting Magnetic Fields in Exoplanets with Spectropolarimetry of the Helium Line at 1083 nm
• Radio Emission from Red-Giant Hot Jupiters

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• Stellar spectral-type (mass) dependence of the dearth of close-in planets around fast-rotating stars. Architecture of Kepler confirmed single-exoplanet systems compared to star-planet evolution models
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