Observational Consequences of Shallow-water Magnetohydrodynamics on Hot Jupiters

Hindle, A. W.; Bushby, P. J.; Rogers, T. M.

doi:10.3847/2041-8213/ac0fec

Cited by 13 publications

(11 citation statements)

References 31 publications

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“…As a result of this assumption, we apply the drag only in the zonal (east-west) direction. This assumption remains reasonable when the magnetic Reynolds number is less than 1 (Menou 2012;Hindle et al 2021bHindle et al , 2021a. The magnetic Reynolds number can be approximated by et al 2021a), where U is the zonal wind speed, H is the pressure scale height, and η is the magnetic resistivity.…”

Section: Our Magnetic Drag Treatmentmentioning

confidence: 99%

“…The quintessential category of these planets is ultrahot Jupiters (UHJs), which orbit so close to their host star that their equilibrium temperatures exceed ∼2200 K. The extreme temperatures of these planets warrant a careful consideration of the relevant physical processes included in the models, as the increased irradiation results in different dominant mechanisms than those of their cooler cousins, "normal" hot Jupiters. While magnetic effects may begin to alter the circulation patterns of gas giant planets that reach temperatures ≈1500 K (Menou 2012;Rogers & Komacek 2014), it is not until planets reach an equilibrium temperature 2000 K that nonideal MHD effects are predicted to become very strong due to the coupling between the circulation and atmospheric magnetic field, potentially resulting in effects such as hot spot reversals (Hindle et al 2021a). Since no solar system analog exists for these planets, intricate multidimensional atmospheric modeling is critical for understanding and interpreting observations of their atmospheres.…”

Section: Introductionmentioning

confidence: 99%

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Exploring the Effects of Active Magnetic Drag in a General Circulation Model of the Ultrahot Jupiter WASP-76b

Beltz¹,

Rauscher²,

Roman³

et al. 2021

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Ultrahot Jupiters represent an exciting avenue for testing extreme physics and observing atmospheric circulation regimes not found in our solar system. Their high temperatures result in thermally ionized particles embedded in atmospheric winds interacting with the planet’s interior magnetic field by generating current and experiencing bulk Lorentz force drag. Previous treatments of magnetic drag in 3D general circulation models (GCMs) of ultrahot Jupiters have mostly been uniform drag timescales applied evenly throughout the planet, which neglects the strong spatial dependence of these magnetic effects. In this work, we apply our locally calculated active magnetic drag treatment in a GCM of the planet WASP-76b. We find the effects of this treatment to be most pronounced in the planet’s upper atmosphere, where strong differences between the day and night side circulation are present. These circulation effects alter the resulting phase curves by reducing the hot spot offset and increasing the day–night flux contrast. We compare our models to Spitzer phase curves, which imply a magnetic field of at least 3 G for the planet. We additionally contrast our results to uniform drag timescale models. This work highlights the need for more careful treatment of magnetic effects in atmospheric models of hot gas giants.

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Section: Our Magnetic Drag Treatmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exploring the Effects of Active Magnetic Drag in a General Circulation Model of the Ultrahot Jupiter WASP-76b

Beltz¹,

Rauscher²,

Roman³

et al. 2021

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“…from Parmentier et al (2021), suggesting even warmer daysides than expected from current theory. In our ∼1300 K sample, the hotter than expected dayside temperatures are further interesting due to their equilibrium temperature being below the threshold where MHD effects begin to affect the day-night heat transport (Menou 2012;Rogers & Komacek 2014;Hindle et al 2021aHindle et al , 2021b. As a result, unconsidered MHD effects cannot explain why Qatar-1b and WASP-52b have warmer than expected daysides compared to the Parmentier et al (2021) models.…”

Section: Population Trendsmentioning

confidence: 76%

A New Analysis of Eight Spitzer Phase Curves and Hot Jupiter Population Trends: Qatar-1b, Qatar-2b, WASP-52b, WASP-34b, and WASP-140b

May

Stevenson

Bean

et al. 2022

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With over 30 phase curves observed during the warm Spitzer mission, the complete data set provides a wealth of information relating to trends and three-dimensional properties of hot Jupiter atmospheres. In this work we present a comparative study of seven new Spitzer phase curves for four planets with equilibrium temperatures T eq ∼ 1300K: Qatar-2b, WASP-52b, WASP-34b, and WASP-140b, as well as a reanalysis of the 4.5 μm Qatar-1b phase curve due to the similar equilibrium temperature. In total, five 4.5 μm phase curves and three 3.6 μm phase curves are analyzed here with a uniform approach. Using these new results, in combination with literature values for the entire population of published Spitzer phase curves of hot Jupiters, we present evidence for a linear trend of increasing hotspot offset with increasing orbital period, as well as observational evidence for two classes of planets in apparent redistribution versus equilibrium temperature parameter space, and tentative evidence for a dependence of hotspot offset on planetary surface gravity in our ∼1300 K sample. We do not find trends in apparent heat redistribution with orbital period or gravity. Nonuniformity in literature Spitzer data analysis techniques precludes a definitive determination of the sources or lack of trends.

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“…This could drive the observed variability in wind dynamics in addition to the standard gyres, vortices, and other hydrodynamic instabilities predicted by hydrodynamic GCMs (Fromang et al 2016;Tan & Komacek 2019). MHD simulations also predict variability of winds, especially of zonal winds in the hottest HJs which can entirely reverse from eastward to westward (Rogers & Komacek 2014;Hindle et al 2021). Our measured scale of variability motivates further exploration of these models and their predictions for the day-to-nightside winds typically observed with high-resolution transmission spectroscopy in addition to the zonal winds commonly studied by theorists.…”

Section: Expectations From Gcmsmentioning

confidence: 91%

Variable and super-sonic winds in the atmosphere of an ultra-hot giant planet

Asnodkar,

Wang,

Eastman

et al. 2022

Preprint

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Hot Jupiters receive intense irradiation from their stellar hosts. The resulting extreme environments in their atmospheres allow us to study the conditions that drive planetary atmospheric dynamics, e.g., global-scale winds. General circulation models predict day-to-nightside winds and equatorial jets with speeds on the order of a few km s −1 . To test these models, we apply high-resolution transmission spectroscopy using the PEPSI spectrograph on the Large Binocular Telescope to study the atmosphere of KELT-9 b, an ultra-hot Jupiter and currently the hottest known planet. We measure ∼10 km s −1 day-to-nightside winds traced by Fe II features in the planet's atmosphere. This is at odds with previous literature (including data taken with PEPSI), which report no significant day-to-nightside winds on KELT-9 b. We identify the cause of this discrepancy as due to an inaccurate ephemeris for KELT-9 b in previous literature. We update the ephemeris, which shifts the mid-transit time by up to 10 minutes for previous datasets, resulting in consistent detections of blueshifts in all the datasets analyzed here. Furthermore, a comparison with archival HARPS-N datasets suggests temporal wind variability ∼5-8 km s −1 over timescales between weeks to years. Temporal variability of atmospheric dynamics on hot Jupiters is a phenomenon anticipated by certain general circulation models that has not been observed over these timescales until now. However, such large variability as we measure on KELT-9 b challenges general circulation models, which predict much lower amplitudes of wind variability over timescales between days to weeks.

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Observational Consequences of Shallow-water Magnetohydrodynamics on Hot Jupiters

Cited by 13 publications

References 31 publications

Exploring the Effects of Active Magnetic Drag in a General Circulation Model of the Ultrahot Jupiter WASP-76b

Exploring the Effects of Active Magnetic Drag in a General Circulation Model of the Ultrahot Jupiter WASP-76b

A New Analysis of Eight Spitzer Phase Curves and Hot Jupiter Population Trends: Qatar-1b, Qatar-2b, WASP-52b, WASP-34b, and WASP-140b

Variable and super-sonic winds in the atmosphere of an ultra-hot giant planet

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