Towards a 3D dynamo model of the PMS star BP Tau

Bessolaz, Nicolas; Brun, A. S.

doi:10.1002/asna.201111612

Cited by 7 publications

(7 citation statements)

References 18 publications

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“…Note that a central source of energy assumed in our model is more consistent with a low-mass fully convective star than a fully convective pre-mainsequence T Tauri star where the gravitational contraction provides an energy source distributed throughout the convection zone (e.g. see Bessolaz & Brun 2011).…”

Section: Simulationmentioning

confidence: 72%

Explaining the Coexistence of Large-Scale and Small-Scale Magnetic Fields in Fully Convective Stars

Yadav

Christensen

Morin

et al. 2015

ApJ

127

139

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Despite the lack of a shear-rich tachocline region low-mass fully convective stars are capable of generating strong magnetic fields, indicating that a dynamo mechanism fundamentally different from the solar dynamo is at work in these objects. We present a self-consistent three dimensional model of magnetic field generation in low-mass fully convective stars. The model utilizes the anelastic magnetohydrodynamic equations to simulate compressible convection in a rotating sphere. A distributed dynamo working in the model spontaneously produces a dipole-dominated surface magnetic field of the observed strength. The interaction of this field with the turbulent convection in outer layers shreds it, producing small-scale fields that carry most of the magnetic flux. The Zeeman-Doppler-Imaging technique applied to synthetic spectropolarimetric data based on our model recovers most of the large-scale field. Our model simultaneously reproduces the morphology and magnitude of the large-scale field as well as the magnitude of the small-scale field observed on low-mass fully convective stars.

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Section: Simulationmentioning

confidence: 72%

Explaining the Coexistence of Large-Scale and Small-Scale Magnetic Fields in Fully Convective Stars

Yadav

Christensen

Morin

et al. 2015

ApJ

127

139

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“…Yet these issues must be explored if the behavior of stellar rotation is to be understood. Rapid advances in supercomputing have enabled global-scale three-dimensional (3D) simulations of convection coupled with rotation that are shedding light on the dynamics of the flow achieved within stars (Bessolaz & Brun 2011;Brown et al 2008;Miesch et al 2008). In a similar spirit, we are reporting on the dynamics of turbulent global-scale convection in a realistically stratified computational domain in two main-sequence F-type stars that are each studied over a range of rotation rates.…”

Section: Global Models Of F-type Star Convectionmentioning

confidence: 98%

Convection and Differential Rotation in F-Type Stars

Augustson

Brown

Brun

et al. 2012

ApJ

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Differential rotation is a common feature of main-sequence spectral F-type stars. In seeking to make contact with observations and to provide a self-consistent picture of how differential rotation is achieved in the interiors of these stars, we use the three-dimensional anelastic spherical harmonic (ASH) code to simulate global-scale turbulent flows in 1.2 and 1.3 M F-type stars at varying rotation rates. The simulations are carried out in spherical shells that encompass most of the convection zone and a portion of the stably stratified radiative zone below it, allowing us to explore the effects of overshooting convection. We examine the scaling of the mean flows and thermal state with rotation rate and mass and link these scalings to fundamental parameters of the simulations. Indeed, we find that the differential rotation becomes much stronger with more rapid rotation and larger mass, scaling as ΔΩ ∝ M 3.9 Ω 0.6 0 . Accompanying the growing differential rotation is a significant latitudinal temperature contrast, with amplitudes of 1000 K or higher in the most rapidly rotating cases. This contrast in turn scales with mass and rotation rate as ΔT ∝ M 6.4 Ω 1.6 0 . On the other hand, the meridional circulations become much weaker with more rapid rotation and with higher mass, with their kinetic energy decreasing as KE MC ∝ M −1.2 Ω −0.8 0 . Additionally, three of our simulations exhibit a global-scale shear instability within their stable regions that persists for the duration of the simulations. The flow structures associated with the instabilities have a direct coupling to and impact on the flows within the convection zone.

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“…34 left Fig. 34 Left surface radial convective velocity for a young, rapidly rotating star, red tones correspond to upflows, from Bessolaz and Brun (2011a); right 3-D dynamo simulations of a young solar like-star (BPtau) and comparison with observed field (Bessolaz and Brun 2011b) panel. They show that larger aspect ratio yield more solar-like differential rotation (e.g., prograde equator/slow poles), such that earlier in the PMS phase the star is most certainly prograde but that state could change as the surface convective envelope shrinks for more massive F-stars as they arrive on the ZAMS.…”

Section: Young Starsmentioning

confidence: 99%

“…They show that larger aspect ratio yield more solar-like differential rotation (e.g., prograde equator/slow poles), such that earlier in the PMS phase the star is most certainly prograde but that state could change as the surface convective envelope shrinks for more massive F-stars as they arrive on the ZAMS. - Bessolaz and Brun (2011b) further simulated the young star BPtau, a 0.7 M star rotating about 4 times the solar rate see Fig. 34 right panel.…”

Section: Young Starsmentioning

confidence: 99%

Magnetism, dynamo action and the solar-stellar connection

Brun

Browning

2017

Living Rev Sol Phys

252

182

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The Sun and other stars are magnetic: magnetism pervades their interiors and affects their evolution in a variety of ways. In the Sun, both the fields themselves and their influence on other phenomena can be uncovered in exquisite detail, but these observations sample only a moment in a single star's life. By turning to observations of other stars, and to theory and simulation, we may infer other aspects of the magnetism-e.g., its dependence on stellar age, mass, or rotation rate-that would be invisible from close study of the Sun alone. Here, we review observations and theory of magnetism in the Sun and other stars, with a partial focus on the "Solar-stellar connection": i.e., ways in which studies of other stars have influenced our understanding of the Sun and vice versa. We briefly review techniques by which magnetic fields can be measured (or their presence otherwise inferred) in stars, and then highlight some key observational findings uncovered by such measurements, focusing (in many cases) on those that offer particularly direct constraints on theories of how the fields are built and maintained. We turn then to a discussion of how the fields arise in different objects: first, we summarize some essential elements of convection and dynamo theory, including a very brief discussion of mean-field theory and related concepts. Next we turn to simulations of convection and magnetism in stellar interiors, highlighting both some peculiarities of field generation in different types of stars and some unifying physical processes that likely influence dynamo action in general. We conclude with a brief

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Towards a 3D dynamo model of the PMS star BP Tau

Abstract: International audienc

Cited by 7 publications

References 18 publications

Explaining the Coexistence of Large-Scale and Small-Scale Magnetic Fields in Fully Convective Stars

Explaining the Coexistence of Large-Scale and Small-Scale Magnetic Fields in Fully Convective Stars

Convection and Differential Rotation in F-Type Stars

Magnetism, dynamo action and the solar-stellar connection

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