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Several meters below the coastal ocean surface there are areas of high ecological activity that contain thin layers of concentrated motile phytoplankton. Gyrotactic trapping has been proposed as a potential mechanism for layer formation of…

Fluid Dynamics · Physics 2019-05-22 Smitha Maretvadakethope , Eric E. Keaveny , Yongyun Hwang

The convective stability associated with carbon sequestration is usually investigated by adopting an unsteady diffusive basic profile. The method of normal modes is not applicable due to the time dependence of the nonlinear base profile.…

Fluid Dynamics · Physics 2017-02-27 C. Taber Wanstall , Layachi Hadji

The fine-structure constant, $\alpha$, controls the strength of the electromagnetic interaction. There are extensions of the standard model in which $\alpha$ is dynamical on cosmological length and time-scales. The physics of the cosmic…

Cosmology and Nongalactic Astrophysics · Physics 2019-02-27 Tristan L. Smith , Daniel Grin , David Robinson , Davy Qi

This work aims at acquiring a more complete understanding of how lateral heterogeneities of the CMB heat flux affect the geodynamo while other relevant parameters are pushed towards realistic values. For this purpose, we ran geodynamo…

Earth and Planetary Astrophysics · Physics 2025-01-03 Thomas Frasson , Natanaël Schaeffer , Henri-Claude Nataf , Stéphane Labrosse

In 1D evolution models of gas giant planets, an outer convection zone advances into the interior as the surface cools, and multiple convective layers form beneath that convective front. To study layer formation below an outer convection…

Earth and Planetary Astrophysics · Physics 2023-11-08 J. R. Fuentes , A. Cumming , E. H. Anders

We model the deepest observable layers of dark sunspot umbral atmospheres in terms of an empirical model which equally describes observed near infrared continuum intensities and line profiles. We use the umbral continuum intensity at 1.67…

Solar and Stellar Astrophysics · Physics 2012-10-17 Goetz Stellmacher , Eberhard Wiehr

We investigate the convective stability of a thin, infinite fluid layer with a rectangular cross-section, subject to imposed heat fluxes at the top and bottom and fixed temperature along the vertical sides. The instability threshold depends…

Chemically peculiar Ap and Bp stars host strong large-scale magnetic fields in the range of $200$~G up to $30$~kG, which are often considered to be the origin of fossil magnetic fields. We assess the evolution of such fossil fields during…

Solar and Stellar Astrophysics · Physics 2023-06-30 Dominik R. G. Schleicher , Juan Pablo Hidalgo , Daniele Galli

A convection-driven MHD dynamo in a rotating spherical shell, with clearly defined structural elements in the flow and magnetic field, is simulated numerically. Such dynamos can be called deterministic, in contrast to those explicitly…

Astrophysics · Physics 2008-11-26 A. V. Getling , R. D. Simitev , F. H. Busse

There is strong observational evidence that the convective cores of intermediate-mass and massive main sequence stars are substantially larger than those predicted by standard stellar-evolution models. However, it is unclear what physical…

Solar and Stellar Astrophysics · Physics 2024-08-20 R. Andrassy , G. Leidi , J. Higl , P. V. F. Edelmann , F. R. N. Schneider , F. K. Roepke

In the present work the instability of a flat horizontal thin layer of a magnetic fluid (the depth of no more than 50 \mum) under the action of a uniform magnetic field is studied experimentally. It was revealed that the development of…

Fluid Dynamics · Physics 2017-04-28 Arthur Zakinyan , Levon Mkrtchyan , Yuri Dikansky

We present a new mechanism for generation of large-scale magnetic field by thermal convection which does not involve the alpha-effect. We consider weakly nonlinear perturbations of space-periodic steady convective magnetic dynamos in a…

Fluid Dynamics · Physics 2015-12-01 Roman Chertovskih , Vladislav Zheligovsky

As has been observed by Morse \cite{Mo}, any generic vector field $v$ on a compact smooth manifold $X$ with boundary gives rise to a stratification of the boundary $\d X$ by compact submanifolds $\{\d_j^\pm X(v)\}_{1 \leq j \leq \dim(X)}$,…

Geometric Topology · Mathematics 2014-06-27 Gabriel Katz

In this work we generalize the notion of convective inhibition to apply in cases where there is an infinite reservoir of condensible species (i.e., an ocean). We propose a new model for the internal structure and thermal evolution of…

Earth and Planetary Astrophysics · Physics 2022-09-07 Steve Markham , Dave Stevenson , Tristan Guillot

The convective envelopes of cool main-sequence stars harbour magnetic fields with a complex global and local structure. These fields affect the near-surface convection and the outer stellar atmospheres in many ways and are responsible for…

Solar and Stellar Astrophysics · Physics 2015-09-02 Benjamin Beeck , Manfred Schüssler , Robert H. Cameron , Ansgar Reiners

The stable atmospheric boundary layer (SABL) is broadly classified into two subtypes: the nocturnal SABL, driven primarily by surface cooling, and the long-lived SABL, in which ambient stratification coexists with surface cooling and…

Fluid Dynamics · Physics 2026-05-28 K. Chand , Cheng-Nian Xiao , Inanc Senocak

Magnetic activity is a ubiquitous feature of stars with convective outer layers, with implications from stellar evolution to planetary atmospheres. Investigating the mechanisms responsible for the observed stellar activity signals from days…

Solar and Stellar Astrophysics · Physics 2023-10-17 Emre Işık , Jennifer L. van Saders , Ansgar Reiners , Travis S. Metcalfe

The linear stability of a shear layer in a highly diffusive stably stratified atmosphere has been investigated. This study completes and extends previous works by Dudis (1974) and Jones (1977). We show that: (i) an asymptotic regime is…

Astrophysics · Physics 2007-05-23 F. Lignieres , F. Califano , A. Mangeney

Numerical MHD simulations play increasingly important role for understanding mechanisms of stellar magnetism. We present simulations of convection and dynamos in density-stratified rotating spherical fluid shells. We employ a new 3D…

Solar and Stellar Astrophysics · Physics 2015-09-03 Radostin D. Simitev , Alexander G. Kosovichev , Friedrich H. Busse

A persistent spatial organization of eddies is identified in the lowest portion of the stably-stratified planetary boundary layer. The analysis uses flow realizations from published large-eddy simulations (Sullivan et al., J Atmos Sci…

Fluid Dynamics · Physics 2023-09-01 Michael Heisel , Peter P Sullivan , Gabriel G Katul , Marcelo Chamecki