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Thermal Processes Governing Hot-Jupiter Radii

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 Added by David Spiegel
 Publication date 2013
  fields Physics
and research's language is English




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There have been many proposed explanations for the larger-than-expected radii of some transiting hot Jupiters, including either stellar or orbital energy deposition deep in the atmosphere or deep in the interior. In this paper, we explore the important influences on hot-Jupiter radius evolution of (i) additional heat sources in the high atmosphere, the deep atmosphere, and deep in the convective interior; (ii) consistent cooling of the deep interior through the planetary dayside, nightside, and poles; (iii) the degree of heat redistribution to the nightside; and (iv) the presence of an upper atmosphere absorber inferred to produce anomalously hot upper atmospheres and

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109 - Kristen Menou 2019
Global Circulation Models (GCMs) of atmospheric flows are now routinely used to interpret observational data on Hot Jupiters. Localized equatorial $beta$-plane simulations by Fromang et al. (2016) have revealed that a barotropic (horizontal shear) instability of the equatorial jet appears at horizontal resolutions beyond those typically achieved in global models; this instability could limit wind speeds and lead to increased atmospheric variability. To address this possibility, we adapt the computationally efficient, pseudo-spectral PlaSim GCM, originally designed for Earth studies, to model Hot Jupiter atmospheric flows and validate it on the Heng et al. (2011) reference benchmark. We then present high resolution global models of HD209458b, with horizontal resolutions of T85 (128x256) and T127 (192x384). The barotropic instability phenomenology found in $beta$-plane simulations is not reproduced in these global models, despite comparably high resolutions. Nevertheless, high resolution models do exhibit additional flow variability on long timescales (of order 100 planet days or more), which is absent from the lower resolution models. It manifests as a breakdown of north-south symmetry of the equatorial wind. From post-processing the atmospheric flows at various resolutions (assuming a cloud-free situation), we show that the stronger flow variability achieved at high resolution does not translate into noticeably stronger dayside infrared flux variability. More generally, our results suggest that high horizontal resolutions are not required to capture the key features of hot Jupiter atmospheric flows.
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