Adrian E. Fraser
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View article: Morphological Regimes of Rotating Moist Convection
Morphological Regimes of Rotating Moist Convection Open
Moist convection is a physical process in planetary atmospheres where the latent heat released by condensation acts as a buoyancy source that can enhance or even trigger an overturning convective instability. Since the saturation temperatu…
View article: Spontaneous generation of helical flows by salt fingers
Spontaneous generation of helical flows by salt fingers Open
We study the dynamics of salt fingers in the regime of slow salinity diffusion (small inverse Lewis number) and strong stratification (large density ratio), focusing on regimes relevant to Earth’s oceans. Using three-dimensional direct num…
View article: 3D Simulations Demonstrate Propagating Thermohaline Convection for Polluted White Dwarfs
3D Simulations Demonstrate Propagating Thermohaline Convection for Polluted White Dwarfs Open
Polluted white dwarfs (WDs) with small surface convection zones deposit significant concentrations of heavy elements to the underlying radiative interior, presumably driving thermohaline convection. Current models of polluted WDs frequentl…
View article: Morphological Regimes of Rotating Moist Convection
Morphological Regimes of Rotating Moist Convection Open
Moist convection is a physical process where the latent heat released by condensation acts as a buoyancy source that can enhance or even trigger an overturning convective instability. Since the saturation temperature often decreases with h…
View article: 3D Simulations Demonstrate Propagating Thermohaline Convection for Polluted White Dwarfs
3D Simulations Demonstrate Propagating Thermohaline Convection for Polluted White Dwarfs Open
Polluted white dwarfs (WDs) with small surface convection zones deposit significant concentrations of heavy elements to the underlying radiative interior, presumably driving thermohaline convection. Current models of polluted WDs frequentl…
View article: Evolution of Semiconvective Staircases in Rotating Flows: Consequences for Fuzzy Cores in Giant Planets
Evolution of Semiconvective Staircases in Rotating Flows: Consequences for Fuzzy Cores in Giant Planets Open
Recent observational constraints on the internal structure of Jupiter and Saturn suggest that these planets have “fuzzy” cores, i.e., gradients of the concentration of heavy elements that might span a large fraction of the planet’s radius.…
View article: An examination of nonlinear collisionless magnetic reconnection through eigenmode decomposition
An examination of nonlinear collisionless magnetic reconnection through eigenmode decomposition Open
This work investigates the nonlinear evolution of collisionless magnetic reconnection through a simple two-dimensional, two-fluid model that employs an eigenmode decomposition. The two-fluid model for collisionless reconnection is solved u…
View article: Predicting the Slowing of Stellar Differential Rotation by Instability-driven Turbulence
Predicting the Slowing of Stellar Differential Rotation by Instability-driven Turbulence Open
Differentially rotating stars and planets transport angular momentum (AM) internally due to turbulence at rates that have long been a challenge to predict reliably. We develop a self-consistent saturation theory, using a statistical closur…
View article: Magnetized Fingering Convection in Stars
Magnetized Fingering Convection in Stars Open
Fingering convection (also known as thermohaline convection) is a process that drives the vertical transport of chemical elements in regions of stellar radiative zones where the mean molecular weight increases with radius. Recently, Harrin…
View article: Predicting the Slowing of Stellar Differential Rotation by Instability-Driven Turbulence
Predicting the Slowing of Stellar Differential Rotation by Instability-Driven Turbulence Open
Differentially rotating stars and planets transport angular momentum internally due to turbulence at rates that have long been a challenge to predict reliably. We develop a self-consistent saturation theory, using a statistical closure app…
View article: Three-Dimensional Shear-Flow Instability Saturation via Stable Modes
Three-Dimensional Shear-Flow Instability Saturation via Stable Modes Open
Turbulence in three dimensions ($3$D) supports vortex stretching that has long been known to accomplish energy transfer to small scales. Moreover, net energy transfer from large-scale, forced, unstable flow-gradients to smaller scales is a…
View article: Three-dimensional shear-flow instability saturation via stable modes
Three-dimensional shear-flow instability saturation via stable modes Open
Turbulence in three dimensions (3D) supports vortex stretching that has long been known to accomplish energy transfer to small scales. Moreover, net energy transfer from large-scale, forced, unstable flow-gradients to smaller scales is ach…
View article: Nonlinear mode coupling and energetics of driven magnetized shear-flow turbulence
Nonlinear mode coupling and energetics of driven magnetized shear-flow turbulence Open
To comprehensively understand saturation of two-dimensional ($2$D) magnetized Kelvin-Helmholtz-instability-driven turbulence, energy transfer analysis is extended from the traditional interaction between scales to include eigenmode interac…
View article: Nonlinear mode coupling and energetics of driven magnetized shear-flow turbulence
Nonlinear mode coupling and energetics of driven magnetized shear-flow turbulence Open
To comprehensively understand the saturation of two-dimensional (2D) magnetized Kelvin–Helmholtz-instability-driven turbulence, energy transfer analysis is extended from the traditional interaction between scales to include eigenmode inter…
View article: Magnetized fingering convection in stars
Magnetized fingering convection in stars Open
Fingering convection (also known as thermohaline convection) is a process that drives the vertical transport of chemical elements in regions of stellar radiative zones where the mean molecular weight increases with radius. Recently, Harrin…
View article: Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models
Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models Open
Observations show an almost ubiquitous presence of extra mixing in low-mass upper giant branch stars. The most commonly invoked explanation for this is thermohaline mixing. One-dimensional stellar evolution models include various prescript…
View article: MESA histories for "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models"
MESA histories for "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models" Open
This repository provides MESA history files for each of the stellar models in the publication "Characterizing Observed Extra Mixing Trends in Red Giants using theReduced Density Ratio from Thermohaline Models". Runs are organized into tarb…
View article: MESA histories for "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models"
MESA histories for "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models" Open
This repository provides MESA history files for each of the stellar models in the publication "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models". The MESA version used was s…
View article: MESA histories for "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models"
MESA histories for "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models" Open
This repository provides MESA history files for each of the stellar models in the publication "Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models". The MESA version used was s…
View article: Near-cancellation of up- and down-gradient momentum transport in forced magnetized shear-flow turbulence
Near-cancellation of up- and down-gradient momentum transport in forced magnetized shear-flow turbulence Open
Visco-resistive magnetohydrodynamic turbulence, driven by a two-dimensional unstable shear layer that is maintained by an imposed body force, is examined by decomposing it into dissipationless linear eigenmodes of the initial profiles. The…
View article: Mechanism for sequestering magnetic energy at large scales in shear-flow turbulence
Mechanism for sequestering magnetic energy at large scales in shear-flow turbulence Open
Straining of magnetic fields by large-scale shear flow, which is generally assumed to lead to intensification and generation of small scales, is reexamined in light of the persistent observation of large-scale magnetic fields in astrophysi…
View article: Resistive instabilities in sinusoidal shear flows with a streamwise magnetic field
Resistive instabilities in sinusoidal shear flows with a streamwise magnetic field Open
We investigate the linear stability of a sinusoidal shear flow with an initially uniform streamwise magnetic field in the framework of incompressible magnetohydrodynamics (MHD) with finite resistivity and viscosity. This flow is known to b…
View article: Schwarzschild and Ledoux are equivalent on evolutionary timescales
Schwarzschild and Ledoux are equivalent on evolutionary timescales Open
Stellar evolution models calculate convective boundaries using either the Schwarzschild or Ledoux criterion, but confusion remains regarding which criterion to use. Here we present a 3D hydrodynamical simulation of a convection zone and ad…
View article: Schwarzschild and Ledoux are Equivalent on Evolutionary Timescales
Schwarzschild and Ledoux are Equivalent on Evolutionary Timescales Open
Stellar evolution models calculate convective boundaries using either the Schwarzschild or Ledoux criterion, but confusion remains regarding which criterion to use. Here we present a 3D hydrodynamical simulation of a convection zone and ad…
View article: Supplemental Materials for "Schwarzschild and Ledoux are equivalent on evolutionary timescales"
Supplemental Materials for "Schwarzschild and Ledoux are equivalent on evolutionary timescales" Open
This Zenodo repository contains a .tar file which contains datasets which can be used along with the code in the associated Github repository (https://github.com/evanhanders/schwarzschild_or_ledoux, an copy of which is also included here a…
View article: Supplemental Materials for "Schwarzschild and Ledoux are equivalent on evolutionary timescales"
Supplemental Materials for "Schwarzschild and Ledoux are equivalent on evolutionary timescales" Open
This Zenodo repository contains a .tar file which contains datasets which can be used along with the code in the associated Github repository (https://github.com/evanhanders/schwarzschild_or_ledoux, an copy of which is also included here a…
View article: Supplemental Materials for "Schwarzschild and Ledoux are equivalent on evolutionary timescales"
Supplemental Materials for "Schwarzschild and Ledoux are equivalent on evolutionary timescales" Open
This Zenodo repository contains a .tar file which contains datasets which can be used along with the code in the associated Github repository (https://github.com/evanhanders/schwarzschild_or_ledoux, an copy of which is also included here a…
View article: Role of stable modes in driven shear-flow turbulence
Role of stable modes in driven shear-flow turbulence Open
A linearly unstable, sinusoidal $E \times B$ shear flow is examined in the gyrokinetic framework in both the linear and nonlinear regimes. In the linear regime, it is shown that the eigenmode spectrum is nearly identical to hydrodynamic sh…
View article: Coupling of damped and growing modes in unstable shear flow
Coupling of damped and growing modes in unstable shear flow Open
Analysis of the saturation of the Kelvin-Helmholtz instability is undertaken to determine the extent to which the conjugate linearly stable mode plays a role. For a piecewise-continuous mean flow profile with constant shear in a fixed laye…
View article: Momentum Transport and Stable Modes in Kelvin-Helmholtz Turbulence
Momentum Transport and Stable Modes in Kelvin-Helmholtz Turbulence Open
The Kelvin-Helmholtz (KH) instability, which arises in astrophysical and fusion systems where turbulent momentum transport is important, has an unstable and a stable mode at the same scales. We show that in KH turbulence, as in other types…