Thermo-Resistive Instability of Hot Planetary Atmospheres

Abstract

The atmospheres of hot Jupiters and other strongly-forced exoplanets are susceptible to a thermal instability in the presence of ohmic dissipation, weak magnetic drag and strong winds. The instability occurs in radiatively-dominated atmospheric regions when the ohmic dissipation rate increases with temperature faster than the radiative (cooling) rate. The instability domain covers a specific range of atmospheric pressures and temperatures, typically P ~ 3-300 mbar and T ~ 1500-2500K for hot Jupiters, which makes it a candidate mechanism to explain the dayside thermal "inversions" inferred for a number of such exoplanets. The instability is suppressed by high levels of non-thermal photoionization, in possible agreement with a recently established observational trend. We highlight several shortcomings of the instability treatment presented here. Understanding the emergence and outcome of the instability, which should result in locally hotter atmospheres with stronger levels of drag, will require global non-linear atmospheric models with adequate MHD prescriptions.

13 pages, 3 figures, accepted for publication in ApJL

References in corpus (5)

• On the radiative equilibrium of irradiated planetary atmospheres
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• Inflating Hot Jupiters With Ohmic Dissipation
• Atmospheric Circulation of Hot Jupiters: Three-dimensional circulation models of HD 209458b and HD 189733b with Simplified Forcing
• Constraints on Deep-seated Zonal Winds Inside Jupiter and Saturn

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• Evidence for a Dayside Thermal Inversion and High Metallicity for the Hot Jupiter WASP-18b
• New Avenues for Thermal Inversions in hot Jupiters
• Magnetically Controlled Circulation on Hot Extrasolar Planets
• Thermal Processes Governing Hot-Jupiter Radii
• Structure and Evolution of Internally Heated Hot Jupiters
• Short Circuits in Thermally Ionized Plasmas: A Mechanism for Intermittent Heating of Protoplanetary Disks
• The hottest hot Jupiters may host Atmospheric Dynamos
• Assessing Spectra and Thermal Inversions due to TiO in Hot Jupiter Atmospheres
• Stellar Magnetic Fields as a Heating Source for Extrasolar Giant Planets
• Variability from thermo-resistive instability in the atmospheres of hot jupiters
• Unveiling the atmospheres of giant exoplanets with an EChO-class mission
• Inflated hot Jupiters: Inferring average atmospheric velocity via Ohmic models coupled with internal dynamo evolution
• Spitzer phase curve observations and circulation models of the inflated ultra-hot Jupiter WASP-76b
• Stellar Wind -- Magnetosphere Interactions in Hot Jupiters