Ice Giant Atmospheric Science

Dahl, Emma; Brueshaber, Shawn; Cosentino, R.; Palotai, Csaba; Rowe-Gurney, Naomi; Sankar, Ramanakumar; Sayanagi, Kunio M.; Aslam, Shahid; Baines, K. H.; Barth, Erika L.; Chanover, N. J.; Fletcher, Leigh; Guerlet, Sandrine; Hammel, Heidi B.; Hofstadter, Mark; Hyder, Ali; Leonard, Erin; Livengood, T. A.; Momary, T. W.; Orton, Glenn S.; Pater, Imke de; Retherford, K. D.; Sinclair, J. B.; Soderlund, K. M.; Spilker, L. J.; Sromovsky, L. A.; Wong, Michael H.

doi:10.48550/arxiv.2010.08617

Cited by 4 publications

(4 citation statements)

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“…Uranus and Neptune are still underexplored compared to the gas giants, and the scientific yield of prospective in-situ missions to these planets are being rigorously examined by the planetary science community (see e.g., Hofstadter et al 2019;Beddingfield et al 2020;Dahl et al 2020;Fletcher et al 2020aFletcher et al , 2020bHelled & Fortney 2020b;Moore et al 2020;Zwick et al 2022). Furthermore, various mission concepts have already been suggested (e.g., Cartwright et al 2020;Cohen et al 2020;Jarmak et al 2020;Simon et al 2020;Rymer et al 2021).…”

Section: Discussionmentioning

confidence: 99%

Zonal Winds of Uranus and Neptune: Gravitational Harmonics, Dynamic Self-gravity, Shape, and Rotation

Soyuer

Neuenschwander

Helled

2022

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Uranus and Neptune exhibit fast surface zonal winds that can reach up to a few hundred meters per second. Previous studies on zonal gravitational harmonics and ohmic dissipation constraints suggest that the wind speeds diminish rapidly in relatively shallow depths within the planets. Through a case-by-case comparison between the missing dynamical gravitational harmonic J 4 ′ from structure models, and with that expected from fluid perturbations, we put constraints on zonal wind decay in Uranus and Neptune. To this end, we generate polytropic empirical structure models of Uranus and Neptune using fourth-order theory of figures that leave hydrostatic J 4 as an open parameter. Allotting the missing dynamical contribution to density perturbations caused by zonal winds (and their dynamic self-gravity), we find that the maximum scale height of zonal winds are ∼2%–3% of the planetary radii for both planets. Allowing the models to have J 2 solutions in the ±5 × 10−6 range around the observed value has similar implications. The effect of self-gravity on J 4 ′ is roughly a factor of ten lower than that of zonal winds, as expected. The decay scale heights are virtually insensitive to the proposed modifications to the bulk rotation periods of Uranus and Neptune in the literature. Additionally, we find that the dynamical density perturbations due to zonal winds have a measurable impact on the shape of the planet, and could potentially be used to infer wind decay and bulk rotation period via future observations.

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Section: Discussionmentioning

confidence: 99%

Zonal Winds of Uranus and Neptune: Gravitational Harmonics, Dynamic Self-gravity, Shape, and Rotation

Soyuer

Neuenschwander

Helled

2022

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show abstract

“…Uranus and Neptune are still under-explored compared to the gas giants, and the scientific yield of prospective in-situ missions to these planets are being rigorously examined by the planetary science community (see e.g. Hofstadter et al 2019;Helled & Fortney 2020b;Dahl et al 2020;Fletcher et al 2020a,b;Beddingfield et al 2020;Moore et al 2020;Zwick et al 2022). Furthermore, various mission concepts have already been suggested (e.g.…”

Section: Discussionmentioning

confidence: 99%

Zonal winds of Uranus and Neptune: Gravitational harmonics, dynamic self-gravity, shape, and rotation

Soyuer¹,

Neuenschwander²,

Helled³

2022

Preprint

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Uranus and Neptune exhibit fast surface zonal winds that can reach up to few hundred meters per second. Previous studies on zonal gravitational harmonics and Ohmic dissipation constraints suggest that the wind speeds diminish rapidly in relatively shallow depths within the planets. Through a caseby-case comparison between the missing dynamical gravitational harmonic J 4 from structure models, and with that expected from fluid perturbations, we put constraints on zonal wind decay in Uranus and Neptune. To this end, we generate polytropic empirical structure models of Uranus and Neptune using 4 th -order Theory of Figures (ToF) that leave hydrostatic J 4 as an open parameter. Allotting the missing dynamical contribution to density perturbations caused by zonal winds (and their dynamic self-gravity), we find that the maximum scale height of zonal winds are ∼ 2 − 3% of the planetary radii for both planets. Allowing the models to have J 2 solutions in the ±5 × 10 −6 range around the observed value has similar implications. The effect of self-gravity on J 4 is roughly a factor of ten lower than that of zonal winds, as expected. The decay scale heights are virtually insensitive to the proposed modifications to the bulk rotation periods of Uranus and Neptune in the literature. Additionally, we find that the dynamical density perturbations due to zonal winds have a measurable impact on the shape of the planet, and could potentially be used to infer wind decay and bulk rotation period via future observations.

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“…The scientific potential of space missions to Uranus and Neptune is currently being thoroughly assessed by the planetary science community (see e.g. Hofstadter et al 2019;Helled & Fortney 2020;Dahl et al 2020;Fletcher et al 2020a,b;Beddingfield et al 2020;Moore et al 2020;Soyuer et al 2021), and various mission concepts have already being discussed (e.g. Jarmak et al 2020;Cohen et al 2020;Cartwright et al 2020;Simon et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Linking Uranus' temperature profile to wind-induced magnetic fields

Soyuer,

Helled

2021

Preprint

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The low luminosity of Uranus is still a puzzling phenomenon and has key implications for the thermal and compositional gradients within the planet. Recent studies have shown that planetary volatiles become ionically conducting under conditions that are present in the ice giants. Rapidly growing electrical conductivity with increasing depth would couple zonal flows to the background magnetic field in the planets, inducing poloidal and toroidal field perturbations 𝑩 𝜔 = 𝑩 𝜔 𝑃 + 𝑩 𝜔 𝑇 via the 𝜔-effect. Toroidal perturbations 𝑩 𝜔 𝑇 are expected to diffuse downwards and produce poloidal fields 𝑩 𝛼 𝑃 through turbulent convection via the 𝛼-effect, comparable in strength to those of the 𝜔-effect; 𝑩 𝜔 𝑃 . To estimate the strength of poloidal field perturbations for various Uranus models in the literature, we generate wind decay profiles based on Ohmic dissipation constraints assuming an ionically conducting H 2 -He-H 2 O interior. Due to the higher metallicities in outer regions of hot Uranus models, zonal winds need to decay to ∼0.1% of their surface values in the outer 1% of Uranus to admit decay solutions in the Ohmic framework. Our estimates suggest that colder Uranus models could potentially have poloidal field perturbations that reach up to O (0.1) of the background magnetic field in the most extreme case. The possible existence of poloidal field perturbations spatially correlated with Uranus' zonal flows could be used to constrain Uranus' interior structure, and presents a further case for the in situ exploration of Uranus.

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Ice Giant Atmospheric Science

Cited by 4 publications

References 0 publications

Zonal Winds of Uranus and Neptune: Gravitational Harmonics, Dynamic Self-gravity, Shape, and Rotation

Zonal Winds of Uranus and Neptune: Gravitational Harmonics, Dynamic Self-gravity, Shape, and Rotation

Zonal winds of Uranus and Neptune: Gravitational harmonics, dynamic self-gravity, shape, and rotation

Linking Uranus' temperature profile to wind-induced magnetic fields

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