Article
Astronomy & Astrophysics
D. G. Vlaykov, I Baraffe, T. Constantino, T. Goffrey, T. Guillet, A. Le Saux, A. Morison, J. Pratt
Summary: Stellar convection is a significant process responsible for heat and chemical species transport, enhanced by convective overshooting and excitation of internal gravity waves. The radial extent of global hydrodynamic simulations can affect convection dynamics, but the inner boundary has little impact while extending the outer boundary significantly increases velocity and temperature perturbations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Lucy O. McNeill, Bernhard Muller
Summary: The study reveals a quasi-stationary pattern of differential rotation in the convective oxygen shell of a rapidly rotating helium star, with a positive angular velocity gradient. The findings challenge current stellar evolution models and have implications for the formation of millisecond magnetars and neutron star birth spin periods. Future simulations will need to explore in more detail how buoyancy, inertial forces, and turbulent stresses shape differential rotation during late-stage convection in massive stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. Higl, E. Mueller, A. Weiss
Summary: The uncertainty of mixed regions around convective zones in stellar evolution is investigated through multi-dimensional hydrodynamic simulations to calibrate an overshooting parameter. Increasing the overshooting parameter beyond a certain value changes the mixing behavior completely, providing limits on the parameter. Diffusive mixing component due to internal gravity waves is identified, suggesting a need for a mass-dependent overshooting description in simulations of less massive stars.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
F. Rizzuti, R. Hirschi, C. Georgy, W. D. Arnett, C. Meakin, A. St J. Murphy
Summary: This study reveals major flaws in the convective boundary mixing in 1D stellar models, calling for significant revisions in how these models are implemented.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
N. Yokoi, Y. Masada, T. Takiwaki
Summary: This study investigates the mass, momentum, and heat transports in convective turbulence using the time-space double averaging procedure. By considering plumes as coherent fluctuations, a non-equilibrium model for convective turbulence is developed, which incorporates the change of turbulence characteristics along the mean stream into the expression of turbulent transport coefficients. The results demonstrate that incorporating plume motion into the turbulent transport model is an important extension of mean-field theory, and it successfully reproduces the enhanced and localized turbulent mass flux observed in surface cooling-driven convection.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
L. Horst, R. Hirschi, P. V. F. Edelmann, R. Andrassy, F. K. Roepke
Summary: The research on realistic parametrization of convection and convective boundary mixing in stellar evolution codes is ongoing. Multidimensional hydrodynamic simulations are used to study convection in stellar interiors and explore the benefits of using a low-Mach hydrodynamic flux solver. The study demonstrates the successful application of the AUSM(+)-up solver to a realistic astrophysical setup, showing promise for compressible simulations of convection in early phases at nominal stellar luminosity.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
R. Andrassy, J. Higl, H. Mao, M. Mocak, D. G. Vlaykov, W. D. Arnett, I Baraffe, S. W. Campbell, T. Constantino, P. V. F. Edelmann, T. Goffrey, T. Guillet, F. Herwig, R. Hirschi, L. Horst, G. Leidi, C. Meakin, J. Pratt, F. Rizzuti, F. K. Roepke, P. Woodward
Summary: Our ability to predict the structure and evolution of stars is limited by complex hydrodynamic processes. However, our simulations show that hydrodynamic simulations of flows in stellar interiors are reliable.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
J. R. Canivete Cuissa, R. Teyssier
Summary: This study conducted three-dimensional numerical simulations of magneto-hydrodynamics in stellar interiors and demonstrated the feasibility of the simulation method. The results showed an exponential growth of magnetic energy and a decrease in power of acoustic and internal gravity waves. The study highlights the importance of including magnetic fields in the study of pressure waves.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
F. Rizzuti, R. Hirschi, W. D. Arnett, C. Georgy, C. Meakin, A. StJ Murphy, T. Rauscher, V. Varma
Summary: In this study, 3D simulations of a convective neon-burning shell in a 20 M-circle dot star were performed, revealing the importance of convective zones in stellar structure and evolution. By revising the modeling of convective boundary mixing in 1D models, consistent results were obtained with multi-D simulations. This has significant implications for theoretical predictions related to stellar evolution, nucleosynthesis, supernova explosions, and compact remnants.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
T. Constantino, I Baraffe, T. Goffrey, J. Pratt, T. Guillet, D. G. Vlaykov, L. Amard
Summary: Researchers utilized rotating 1D stellar evolution models to study the evolution of stars, incorporating modifications to the temperature gradient in convection zones and a criterion for convective instability inspired by rotating 3D hydrodynamical simulations. By suppressing convection and modifying the temperature gradient, they were able to simulate lithium depletion in rapidly rotating stars, matching observations of lithium spread in young open clusters.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
David Stephens, Falk Herwig, Paul Woodward, Pavel Denissenkov, Robert Andrassy, Huaqing Mao
Summary: This study presents two mixing models for convective-reactive i-process nucleosynthesis in rapidly accreting white dwarfs, including a 1D advective two-stream model with physically motivated mixing coefficients and a simpler approach using diffusion coefficients calculated from simulations. The results show that in this particular application, the diffusion method provides a globally similar abundance distribution as the advective two-stream mixing model.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
J. Ostrowski, A. S. Baran, S. Sanjayan, S. K. Sahoo
Summary: The results of evolutionary modelling of subdwarf B stars using new algorithms show that the convective pre-mixing scheme is the preferable one. Both methods are promising alternative methods of studying models of subdwarf B stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
F. Ahlborn, F. Kupka, A. Weiss, M. Flaskamp
Summary: This study proposes an improved model for calculating the dissipation rate of turbulent kinetic energy, which can be used in 1D stellar evolution calculations. By analyzing the contributions of different factors to the dissipation rate and suggesting a new method to account for some of these physical mechanisms, the authors show that the new model allows for a more complete description of convective overshooting and mixing in stars.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
F. Kupka, F. Ahlborn, A. Weiss
Summary: In this study, an improved model for computing the dissipation rate of turbulent kinetic energy in non-local models of stellar convection is proposed. The new model allows for a more accurate description of convective overshooting and mixing in stars.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
I Baraffe, J. Clarke, A. Morison, D. G. Vlaykov, T. Constantino, T. Goffrey, T. Guillet, A. Le Saux, J. Pratt
Summary: In this study, two-dimensional numerical simulations were performed to investigate core convection in zero-age main-sequence stars with masses ranging from 3 to 20 solar masses. The study found that the overshooting distance scales with stellar luminosity and convective core radius. This scaling provides important insights for predicting the overshooting distance in one-dimensional stellar evolution models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Geochemistry & Geophysics
Thomas Gastine, Julien Aubert, Alexandre Fournier
GEOPHYSICAL JOURNAL INTERNATIONAL
(2020)
Article
Multidisciplinary Sciences
Raphael Raynaud, Jerome Guilet, Hans-Thomas Janka, Thomas Gastine
Editorial Material
Multidisciplinary Sciences
Johannes Wicht, Thomas Gastine
NATURE COMMUNICATIONS
(2020)
Article
Geochemistry & Geophysics
T. Schwaiger, T. Gastine, J. Aubert
Summary: This passage discusses the importance of measuring length scales with both energetic and dynamic relevance in fluid dynamics. It analyzes two length scales in magnetic and non-magnetic models that achieve this dual relevance, revealing different interpretations and misrepresentations of force balance. By focusing on these scales, the study uncovers insights into the underlying mechanisms of dynamo systems and their dominant length scales.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Theo Tassin, Thomas Gastine, Alexandre Fournier
Summary: This study examines the impact of double-diffusive convection on magnetic field generation in the liquid outer core of the Earth through 3-D global geodynamo models. The findings suggest that the addition of a second buoyancy source facilitates the onset of convection and the transition between dipole-dominated and multipolar dynamos depends on the nature of the buoyancy forcing. Classical parameters expected to govern this transition fail to capture the dipole breakdown, and instead, a scale-dependent analysis of force balance is necessary to understand the dynamics.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Astronomy & Astrophysics
T. Gastine, J. Wicht
Summary: The ongoing NASA's Juno mission has placed new constraints on the internal dynamics of Jupiter, revealing a complex internal structure with a dipole-dominated surface magnetic field and a stratification of metallic and molecular hydrogen. The simulations show that in Jupiter's metallic core, magnetic energy is nearly an order of magnitude larger than kinetic energy, while kinetic energy is mainly pumped into zonal flows in the molecular envelope.
Article
Computer Science, Interdisciplinary Applications
Venkatesh Gopinath, Alexandre Fournier, Thomas Gastine
Summary: This article analyzes the behavior of time integrators applied to the semi discrete problem resulting from the spectral discretization of Boussinesq thermal convection equations. Different schemes of various orders are assessed for laminar and turbulent regimes, and it is found that some high-order IMEX-RK methods exhibit occasional order reduction. Comparing with the reference integrator CNAB2, six schemes consistently outperform CNAB2 in terms of accuracy and performance. In the most turbulent setup, 13 IMEX-RK integrators outperform CNAB2 in terms of both accuracy and efficiency.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Astronomy & Astrophysics
Raphael Raynaud, Pablo Cerda-Duran, Jerome Guilet
Summary: Gravitational waves provide a unique window to constrain dynamics in proto-neutron stars during core collapse supernovae. Convection and magnetic fields play important roles in neutron star formation, with magnetic fields slightly affecting gravitational wave amplitude in slow rotation regimes and dramatically changing it in fast rotation scenarios. The observed excess of low-frequency gravitational waves at the transition to a strong field dynamo could be used to determine dynamo efficiency in proto-neutron stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Geochemistry & Geophysics
O. Barrois, T. Gastine, C. C. Finlay
Summary: This study investigates rapidly rotating convection in a thick spherical shell geometry relevant to planetary cores. The results are compared between quasi-geostrophic (QG), 3-D, and hybrid QG-3D models. The study finds that the 3-D model and QG model show similar results under strong driving, while the hybrid model and 3-D model are closer under weak driving. This research provides insights into convection patterns in planetary cores and the importance of different modeling approaches.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Astronomy & Astrophysics
P. Barrere, J. Guilet, A. Reboul-Salze, R. Raynaud, H-T Janka
Summary: Magnetars are young neutron stars with incredibly strong magnetic fields. This study proposes a new scenario for magnetar formation involving slowly rotating progenitors and the spin-up of a proto-neutron star by supernova fallback. The findings suggest that magnetars can be formed from slow-rotating progenitors for accreted masses compatible with recent supernova simulations.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
B. Zaire, L. Jouve, T. Gastine, J-F Donati, J. Morin, N. Landin, C. P. Folsom
Summary: This paper investigates the diversity of surface magnetic field configurations of cool stars using numerical simulations. The results show that dipolar solutions can exist in strongly stratified simulations, contrary to previous beliefs. The simulations resemble the outlier stars observed at Rossby numbers larger than 0.1, suggesting that the relative importance of inertial and Lorentz forces controls the dipolar to multipolar transition. Additionally, the ratio of kinetic to magnetic energies can also capture the transition in field morphology.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jerome Guilet, Alexis Reboul-Salze, Raphael Raynaud, Matteo Bugli, Basile Gallet
Summary: Using zero-net flux shearing box simulations, we investigated the MRI-driven dynamo at high Pm values. The results show that the stress and turbulent energy are proportional to Pm until a certain threshold, beyond which they remain stable.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Mechanics
Thomas Gastine, Jonathan M. Aurnou
Summary: Convection dynamics in polar regions differ from those in lower latitudes. In spherical shell simulations, polar convection is triggered when the buoyancy forcing exceeds the critical equatorial forcing by a factor of 20. The heat transfer in polar regions increases much faster than in equatorial regions with increasing Rayleigh number. At high Rayleigh numbers, the heat fluxes in polar and equatorial regions become comparable.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Geosciences, Multidisciplinary
Rafael Lago, Thomas Gastine, Tilman Dannert, Markus Rampp, Johannes Wicht
Summary: The article discusses two parallelization schemes for the MagIC code, an open-source, high-performance pseudo-spectral code for solving magnetohydrodynamics equations. The first scheme uses MPI and OpenMP, while the second scheme involves a new two-dimensional MPI decomposition implementation. The authors also highlight algorithmic optimizations and data distribution layouts, indicating that the two-dimensional distribution configuration may be more efficient than the one-dimensional distribution.
GEOSCIENTIFIC MODEL DEVELOPMENT
(2021)