A complete study of the precision of the concentric MacLaurin spheroid method to calculate Jupiter's gravitational moments

This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this recordA few years ago, Hubbard (2012, 2013) presented an elegant, non-perturbative method, called concentric MacLaurin spheroid (CMS), to calculate with very high accuracy the gravitational moments of a rotating fluid body following a barotropic pressure-density relationship. Having such an accurate method is of great importance for taking full advantage of the Juno mission, and its extremely precise determination of Jupiter gravitational moments, to better constrain the internal structure of the planet. Recently, several authors have applied this method to the Juno mission with 512 spheroids linearly spaced in altitude. We demonstrate in this paper that such calculations lead to errors larger than Juno's error bars, invalidating the aforederived Jupiter models at the level required by Juno's precision. We show that, in order to fulfill Juno's observational constraints, at least 1500 spheroids must be used with a cubic, square or exponential repartition, the most reliable solutions. When using a realistic equation of state instead of a polytrope, we highlight the necessity to properly describe the outermost layers to derive an accurate boundary condition, excluding in particular a zero pressure outer condition. Providing all these constraints are fulfilled, the CMS method can indeed be used to derive Jupiter models within Juno's present observational constraints. However, we show that the treatment of the outermost layers leads to irreducible errors in the calculation of the gravitational moments and thus on the inferred physical quantities for the planet. We have quantified these errors and evaluated the maximum precision that can be reached with the CMS method in the present and future exploitation of Juno's data

Impact of a new H/He equation of state on the evolution of massive brown dwarfs. New determination of the hydrogen burning limit

We have explored the impact of the latest equation of state (EOS) for dense hydrogen-helium mixtures (Chabrier \& Debras 2021), which takes into account the interactions between hydrogen and helium species, upon the evolution of very low mass stars and brown dwarfs (BD). These interactions modify the thermodynamic properties of the H/He mixture, notably the entropy, a quantity of prime importance for these fully convective bodies, but also the onset and the development of degeneracy throughout the body. This translates into a faster cooling rate, i.e. cooler isentropes for a given mass and age, and thus larger brown dwarf masses and smaller radii for given effective temperature and luminosity than the models based on previous EOSs. This means that objects of a given mass and age, in the range M\lesssim 0.1\,\msol, $\tau\gtrsim 10^8$ yr, will have cooler effective temperatures and fainter luminosities. Confronting these new models with several observationally determined BD dynamical masses, we show that this improves the agreement between evolutionary models and observations and resolves at least part of the observed discrepancies between the properties of dynamical mass determinations and evolutionary models. A noticeable consequence of this improvement of the dense H/He EOS is that it yields a larger H-burning minimum mass, now found to be 0.075\,\msol (78.5\,\mjup) with the ATMO atmosphere models for solar metallicity. These updated brown dwarf models are made publicly available.Comment: To appear in Astronomy & Astrophysic

Reliability of autonomic and vascular components of baroreflex sensitivity in adolescents.

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Improvements in the autonomic and vascular systems are implicated in cardiovascular disease risk reduction. Baroreflex sensitivity (BRS) is composed of vascular and autonomic components. This study aimed to investigate between- and within-day reliability of BRS and its autonomic and vascular determinants in adolescents. Thirteen male adolescents (14·1 ± 0·5 y) participated in this study. For between-day reliability, participants completed four experimental visits separated by a minimum of 48-h. For within-day reliability, participants repeated BRS assessments three times in the morning with one hour between the measures. BRS was evaluated using the cross-spectral gain (LFgain) between blood pressure and heart rate interval. BRS was further divided into: 1) vascular component using arterial compliance (AC); and 2) autonomic component measured as LFgain divided by AC (LFgain/AC). LFgain, AC and LFgain/AC presented between-day coefficient of variation (CV) of 20%, 17%, and 20%, respectively. Similarly, variables associated with blood pressure control, such as cardiac output, mean arterial pressure, heart rate and total peripheral resistance, presented CVs ranging from 6% to 15%. Within-day reliability was poorer compared to between-day for LFgain (25%), AC (25%), and LFgain/AC (31%), as well as all hemodynamic variables (CVs from 11% to 22%, except heart rate with presented CV of 6%). This study indicates suitable between- and within-reliability of BRS and its autonomic and vascular determinants, as well as hemodynamic variables associated with BRS, in adolescents.This research was partially funded by Science Without Borders, CAPES, Brazil, under the process number:10423‐13‐3

Eigenvectors, Circulation and Linear Instabilities for Planetary Science in 3 Dimensions (ECLIPS3D)

This is the final version. Available on open access from EDP Sciences via the DOI in this recordContext. The study of linear waves and instabilities is necessary to understand the physical evolution of an atmosphere, and can provide physical interpretation of the complex flows found in simulations performed using Global Circulation Models (GCM). In particular, the acceleration of superrotating flow at the equator of hot Jupiters has mostly been studied under several simplifying assumptions, the relaxing of which may impact final results. Aims. We develop and benchmark a publicly available algorithm to identify the eigenmodes of an atmosphere around any initial steady state. We also solve for linear steady states. Methods. We linearise the hydrodynamical equations of a planetary atmosphere in a steady state with arbitrary velocities and thermal profile. We then discretise the linearised equations on an appropriate staggered grid, and solve for eigenvectors and linear steady solutions with the use of a parallel library for linear algebra: ScaLAPACK. We also implement a posteriori calculation of an energy equation in order to obtain more information on the underlying physics of the mode. Results. Our code is benchmarked against classical wave and instability test cases in multiple geometries. The steady linear circulation calculations also reproduce expected results for the atmosphere of hot Jupiters. We finally show the robustness of our energy equation, and its power to obtain physical insight into the modes. Conclusions. We have developed and benchmarked a code for the study of linear processes in planetary atmospheres, with an arbitrary steady state. The calculation of an a posteriori energy equation provides both increased robustness and physical meaning to the obtained eigenmodes. This code can be applied to various problems, and notably to further study the initial spin up of superrotation of GCM simulations of hot Jupiter.European Union Horizon 2020Leverhulme TrustScience and Technology Facilities Council (STFC

Effects of exercise intensity on vascular and autonomic components of the baroreflex following glucose ingestion in adolescents.

This is the final version. Available from the publisher via the DOI in this record.PURPOSE: To investigate the effects of an oral glucose tolerance test (OGTT) on baroreflex sensitivity (BRS) in a sample of healthy adolescents, and how acute exercise bouts of different intensities alter the effects of the OGTT on BRS. METHODS: Thirteen male adolescents (14.0 ± 0.5 years) completed three conditions on separate days in a counterbalanced order: (1) high-intensity interval exercise (HIIE); (2) moderate-intensity interval exercise (MIIE); and (3) resting control (CON). At ~ 90 min following the conditions, participants performed an OGTT. Supine heart rate and blood pressure were monitored continuously at baseline, 60 min following the conditions, and 60 min following the OGTT. A cross-spectral method (LFgain) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain divided by AC (LFgain/AC) was used as the autonomic component. RESULTS: Although non-significant, LFgain moderately decreased post-OGTT when no exercise was performed (pre-OGTT = 24.4 ± 8.2 ms mmHg- 1; post-OGTT = 19.9 ± 5.6 ms mmHg- 1; ES = 0.64, P > 0.05). This was attributed to the decrease in LFgain/AC (pre-OGTT = 1.19 ± 0.5 ms µm- 1; post-OGTT = 0.92 ± 0.24 ms µm- 1; ES = 0.69, P > 0.05). Compared to CON (Δ = - 4.4 ± 8.7 ms mmHg- 1), there were no differences for the pre-post-OGTT delta changes in LF/gain for HIIE (Δ = - 3.5 ± 8.2 ms mmHg- 1) and MIIE (Δ = 1.3 ± 9.9 ms mmHg- 1) had no effects on BRS following the OGTT (all ES < 0.5). Similarly, compared to CON (Δ = - 0.23 ± 0.40 ms µm- 1) there were no differences for the pre-post-OGTT delta changes in LF/gain for HIIE (Δ = - 0.22 ± 0.49 ms µm- 1) and MIIE (Δ = 0.13 ± 0.36 ms µm- 1). CONCLUSION: A moderate non-significant decrease in BRS was observed in adolescents following a glucose challenge with no apparent effects of exercise.Science Without Border

Results from a set of three-dimensional numerical experiments of a hot Jupiter atmosphere

We present highlights from a large set of simulations of a hot Jupiter atmosphere, nominally based on HD 209458b, aimed at exploring both the evolution of the deep atmosphere, and the acceleration of the zonal flow or jet. We find the occurrence of a super-rotating equatorial jet is robust to changes in various parameters, and over long timescales, even in the absence of strong inner or bottom boundary drag. This jet is diminished in one simulation only, where we strongly force the deep atmosphere equator-to-pole temperature gradient over long timescales. Finally, although the eddy momentum fluxes in our atmosphere show similarities with the proposed mechanism for accelerating jets on tidally-locked planets, the picture appears more complex. We present tentative evidence for a jet driven by a combination of eddy momentum transport and mean flow.Comment: 26 pages, 22 Figures. Accepted for publication in Astronomy and Astrophysic

The Limits of the Primitive Equations of Dynamics for Warm, Slowly Rotating Small Neptunes and Super Earths (article)

This is the author accepted manuscript. The final version is available from American Astronomical Society / IOP Publishing via the DOI in this record.The dataset associated with this article is located in ORE at: https://doi.org/10.24378/exe.1023We present significant differences in the simulated atmospheric flow for warm, tidally-locked small Neptunes and super Earths (based on a nominal GJ 1214b) when solving the simplified, and commonly used, primitive dynamical equations or the full Navier-Stokes equations. The dominant prograde, superrotating zonal jet is markedly different between the simulations which are performed using practically identical numerical setups, within the same model. The differences arise due to the breakdown of the so-called `shallow-fluid' and traditional approximations, which worsens when rotation rates are slowed, and day{night temperature contrasts are increased. The changes in the zonal advection between simulations solving the full and simplified equations, give rise to significant differences in the atmospheric redistribution of heat, altering the position of the hottest part of the atmosphere and temperature contrast between the day and night sides. The implications for the atmospheric chemistry and, therefore, observations need to be studied with a model including a more detailed treatment of the radiative transfer and chemistry. Small Neptunes and super Earths are extremely abundant and important, potentially bridging the structural properties (mass, radius, composition) of terrestrial and gas giant planets. Our results indicate care is required when interpreting the output of models solving the primitive equations of motion for such planets.Leverhulme TrustScience and Technology Facilities CouncilEuropean Research Counci

The acceleration of superrotation in simulated hot Jupiter atmospheres

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordContext. Atmospheric superrotating flows at the equator are a nearly ubiquitous result when conducting simulations of hot Jupiters. One theory explaining how this zonally-coherent flow reaches equilibrium has already been developed in the literature. This understanding, however, relies on the existence of either an initial superrotating flow or a sheared flow, coupled with a slow evolution that permits a linear steady state to be reached. Aims. A consistent physical understanding of superrotation is needed for arbitrary drag and radiative timescales, along with the relevance of taking linear steady states into account, needs to be assessed. Methods. We obtained an analytical expression for the structure, frequency, and decay rate of propagating waves in hot Jupiter atmospheres around a state at rest in the 2D shallow-water β–plane limit. We solved this expression numerically and confirmed the robustness of our results with a 3D linear wave algorithm. We then compared it with 3D simulations of hot Jupiter atmospheres and studied the nonlinear momentum fluxes. Results. We show that under strong day-night heating, the dynamics do not transit through a linear steady state when starting from an initial atmosphere in solid body rotation. We further demonstrate that non–linear effects favor the initial spin-up of superrotation and that acceleration due to the vertical component of the eddy–momentum flux is critical to the initial development of superrotation . Conclusions. We describe the initial phases of the acceleration of superrotation, including the consideration of differing radiative and drag timescales, and we conclude that eddy-momentum-driven superrotating equatorial jets are robust, physical phenomena in simulations of hot Jupiter atmospheres.Leverhulme TrustScience and Technology Facilities Counci

Results from a set of three-dimensional numerical experiments of a hot Jupiter atmosphere.

ArticleThis is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.We present highlights from a large set of simulations of a hot Jupiter atmosphere, nominally based on HD 209458b, aimed at exploring both the evolution of the deep atmosphere, and the acceleration of the zonal flow or jet. We find the occurrence of a super-rotating equatorial jet is robust to changes in various parameters, and over long timescales, even in the absence of strong inner or bottom boundary drag. This jet is diminished in one simulation only, where we strongly force the deep atmosphere equator–to–pole temperature gradient over long timescales. Finally, although the eddy momentum fluxes in our atmosphere show similarities with the proposed mechanism for accelerating jets on tidally-locked planets, the picture appears more complex. We present tentative evidence for a jet driven by a combination of eddy momentum transport and mean flow

Effects of high-intensity interval training on the vascular and autonomic components of the baroreflex at rest in adolescents

This is the author accepted manuscript. The final version is available from Human Kinetics via the DOI in this recordPurpose: In a sample of healthy adolescents, we aimed to investigate the effects of high intensity interval exercise (HIIE) training and detraining on baroreflex sensitivity (BRS) and its vascular and autonomic components at rest Methods: Nineteen volunteers were randomly allocated to: 1) four weeks HIIE training performed three times per week; or 2) a control (CON) condition with no intervention for the same duration as HIIE training. PRE, POST and following two weeks of detraining (DET) resting supine heart rate and blood pressure were measured and a cross-spectral method (LFgain) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain divided by AC (LFgain/AC) was used as the autonomic determinant of BRS. Results: HIIE training was completed with 100% compliance. HIIE did not change resting LFgain (P=0.66; effect size (ES)=0.21), AC (P=0.44; ES=0.36) or LFgain/AC (P=0.68; ES=0.19) compared to CON. Conclusion: Four weeks of HIIE training does not change BRS and its autonomic and vascular determinant in a sample of healthy adolescents at rest