William Béthune
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View article: Multiscale turbulence synthesis: Validation in 2D hydrodynamics
Multiscale turbulence synthesis: Validation in 2D hydrodynamics Open
Context . Numerical simulations can follow the evolution of fluid motions through the intricacies of developed turbulence. However, they are rather costly to run, especially in 3D. In the past two decades, generative models have emerged th…
View article: Exploring the formation of multiple dust-trapping rings in the inner Solar System
Exploring the formation of multiple dust-trapping rings in the inner Solar System Open
Context . Isotopic properties of meteorites provide evidence that multiple dust trap or pressure bumps had to form and persist in the inner Solar System on a timescale of millions of years. The formation of a pressure bump at the outer edg…
View article: On inertial forces (indirect terms) in problems with a central body
On inertial forces (indirect terms) in problems with a central body Open
Gravitational systems in astrophysics often comprise a body – the primary – that far outweights the others, and which is taken as the centre of the reference frame. A fictitious acceleration, also known as the indirect term, must therefore…
View article: Multiscale Turbulence Synthesis: Validation in 2D Hydrodynamics
Multiscale Turbulence Synthesis: Validation in 2D Hydrodynamics Open
Numerical simulations can follow the evolution of fluid motions through the intricacies of developed turbulence. However, they are rather costly to run, especially in 3D. In the past two decades, generative models have emerged which produc…
View article: exoALMA. XVI. Predicting Signatures of Large-scale Turbulence in Protoplanetary Disks
exoALMA. XVI. Predicting Signatures of Large-scale Turbulence in Protoplanetary Disks Open
Turbulent gas motions drive planet formation and protoplanetary disk evolution. However, empirical constraints on turbulence are scarce, halting our understanding of its nature. Resolving signatures of the large-scale perturbations driven …
View article: Normal mode analysis of fluid discontinuities: Numerical method and application to magnetohydrodynamics
Normal mode analysis of fluid discontinuities: Numerical method and application to magnetohydrodynamics Open
Fluid discontinuities, such as shock fronts and vortex sheets, can reflect waves and become unstable to corrugation. Analytical calculations of these phenomena are tractable in the simplest cases only, while their numerical simulations are…
View article: Normal mode analysis of fluid discontinuities: numerical method and application to magnetohydrodynamics
Normal mode analysis of fluid discontinuities: numerical method and application to magnetohydrodynamics Open
Fluid discontinuities, such as shock fronts and vortex sheets, can reflect waves and become unstable to corrugation. Analytical calculations of these phenomena are tractable in the simplest cases only, while their numerical simulations are…
View article: The Planetary Accretion Shock. III. Smoothing-free 2.5D Simulations and Calculation of H<i>α</i> Emission
The Planetary Accretion Shock. III. Smoothing-free 2.5D Simulations and Calculation of H<i>α</i> Emission Open
Surveys have looked for H α emission from accreting gas giants but found very few objects. Analyses of the detections and nondetections have assumed that the entire gas flow feeding the planet is in radial freefall. However, hydrodynamical…
View article: The Planetary Accretion Shock. III. Smoothing-free 2.5D simulations and calculation of H alpha emission
The Planetary Accretion Shock. III. Smoothing-free 2.5D simulations and calculation of H alpha emission Open
Surveys have looked for H alpha emission from accreting gas giants but found very few objects. Analyses of the detections and non-detections have assumed that the entire gas flow feeding the planet is in radial free-fall. However, hydrodyn…
View article: Gravitoturbulent dynamo in global simulations of gaseous disks
Gravitoturbulent dynamo in global simulations of gaseous disks Open
Context. The turbulence driven by gravitational instabilities (GIs) can amplify magnetic fields in massive gaseous disks. This GI dynamo may appear in young circumstellar disks, whose weak ionization challenges other amplification routes, …
View article: Gravitoturbulent dynamo in global simulations of gaseous disks
Gravitoturbulent dynamo in global simulations of gaseous disks Open
The turbulence driven by gravitational instabilities (GIs) can amplify magnetic fields in massive gaseous disks. This GI dynamo may appear in young circumstellar disks, whose weak ionization challenges other amplification routes, as well a…
View article: Migration of Jupiter mass planets in discs with laminar accretion flows
Migration of Jupiter mass planets in discs with laminar accretion flows Open
Context. Migration of giant planets in discs with low viscosity has been studied recently. Results have shown that the proportionality between migration speed and the disc’s viscosity is broken by the presence of vortices that appear at th…
View article: Survival of planet-induced vortices in 2D disks
Survival of planet-induced vortices in 2D disks Open
Context. Several observations of protoplanetary disks reveal non-axisymmetric features, which are often interpreted as vortices. Numerical modeling has repeatedly shown that gap-opening planets are capable of producing large and long-lasti…
View article: Spiral structures in gravito-turbulent gaseous disks
Spiral structures in gravito-turbulent gaseous disks Open
Context. Gravitational instabilities can drive small-scale turbulence and large-scale spiral arms in massive gaseous disks under conditions of slow radiative cooling. These motions affect the observed disk morphology, its mass accretion ra…
View article: Migration of Jupiter-mass planets in low-viscosity discs
Migration of Jupiter-mass planets in low-viscosity discs Open
Context. Type-II migration of giant planets has a speed proportional to the disc’s viscosity for values of the α viscosity parameter larger than 10−4. Previous studies based on two-dimensional simulations, have shown that, at even lower vi…
View article: Electric heating and angular momentum transport in laminar models of protoplanetary discs
Electric heating and angular momentum transport in laminar models of protoplanetary discs Open
The vertical temperature structure of a protoplanetary disc bears on several processes relevant to planet formation, such as gas and dust grain chemistry, ice lines, and convection. The temperature profile is controlled by irradiation from…
View article: Self-gravitating planetary envelopes and the core-nucleated instability
Self-gravitating planetary envelopes and the core-nucleated instability Open
Planet formation scenarios can be constrained by the ratio of the gaseous envelope mass relative to the solid core mass in the observed exoplanet populations. One-dimensional calculations find a critical (maximal) core mass for quasi-stati…
View article: Envelopes of embedded super-Earths – II. Three-dimensional isothermal simulations
Envelopes of embedded super-Earths – II. Three-dimensional isothermal simulations Open
Massive planetary cores embedded in protoplanetary discs are believed to accrete extended atmospheres, providing a pathway to forming gas giants and gas-rich super-Earths. The properties of these atmospheres strongly depend on the nature o…
View article: Envelopes of embedded super-Earths – I. Two-dimensional simulations
Envelopes of embedded super-Earths – I. Two-dimensional simulations Open
Measurements of exoplanetary masses and radii have revealed a population of massive super-Earths – planets sufficiently large that, according to one-dimensional models, they should have turned into gas giants. To better understand the orig…
View article: Order out of Randomness: Self-Organization Processes in Astrophysics
Order out of Randomness: Self-Organization Processes in Astrophysics Open
Self-organization is a property of dissipative nonlinear processes that are governed by a global driving force and a local positive feedback mechanism, which creates regular geometric and/or temporal patterns, and decreases the entropy loc…
View article: Global simulations of protoplanetary disks with net magnetic flux
Global simulations of protoplanetary disks with net magnetic flux Open
The planet-forming region of protoplanetary disks is cold, dense, and\ntherefore weakly ionized. For this reason, magnetohydrodynamic (MHD) turbulence\nis thought to be mostly absent, and another mechanism has to be found to\nexplain gas a…
View article: Self-organisation in protoplanetary discs
Self-organisation in protoplanetary discs Open
Context. Recent observations have revealed organised structures in protoplanetary discs, such as axisymmetric rings or horseshoe concentrations, evocative of large-scale vortices. These structures are often interpreted as the result of pla…
View article: Self-organisation in protoplanetary disks: global, non-stratified Hall-MHD simulations
Self-organisation in protoplanetary disks: global, non-stratified Hall-MHD simulations Open
Recent observations revealed organised structures in protoplanetary disks, such as axisymmetric rings or horseshoe concen- trations evocative of large-scale vortices. These structures are often interpreted as the result of planet-disc inte…
View article: Self-organisation in protoplanetary discs. Global, non-stratified Hall-MHD simulations
Self-organisation in protoplanetary discs. Global, non-stratified Hall-MHD simulations Open
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