High-Resolution Calculations of the Solar Global Convection With the Reduced Speed of Sound Technique. I. The Structure of the Convection and the Magnetic Field Without the Rotation

Hotta, Hideyuki; Rempel, Matthias; Yokoyama, T.

doi:10.1088/0004-637x/786/1/24

Cited by 70 publications

(72 citation statements)

References 42 publications

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“…Overall, among the multi-dimensional hydrodynamical simulations, density fluctuations up to ∼ 10% could be introduced around the edges of the convective zone of oxygen burning shell in ∼ 20 M stars (Bazán & Arnett 1998;Meakin & Arnett 2006, 2007a and in the envelope of a 5 M of red giant (Viallet et al 2013). For lower mass stars, high resolution 3D global hydrodynamical simulations of the solar convection (Hotta et al 2014(Hotta et al , 2015 and He shell flash in a post-AGB star (Herwig et al 2014) have been performed but the amplitudes of the density fluctuations introduced seem to be small. Smith & Arnett (2014) discussed the discordance between the predictions from stellar evolution models and the last stages of massive stars, some of which (progenitors of Type IIn supernovae) exhibit eruptive mass ejection a decade before the core-collapse.…”

Section: Issues In Stellar Evolution Models and Impacts Of Possible Lmentioning

confidence: 99%

Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-star and Binary Merger Progenitor Models for SN 1987A

Ono

Nagataki

Ferrand

et al. 2020

ApJ

104

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We perform three-dimensional hydrodynamic simulations of aspherical core-collapse supernovae focusing on the matter mixing in SN 1987A. The impacts of four progenitor (pre-supernova) models and parameterized aspherical explosions are investigated. The four pre-supernova models include a blue supergiant (BSG) model based on a slow merger scenario developed recently for the progenitor of SN 1987A (Urushibata et al. 2018. The others are a BSG model based on a single star evolution and two red supergiant (RSG) models. Among the investigated explosion (simulation) models, a model with the binary merger progenitor model and with an asymmetric bipolar-like explosion, which invokes a jetlike explosion, best reproduces constraints on the mass of high velocity 56 Ni, as inferred from the observed [Fe II] line profiles. The advantage of the binary merger progenitor model for the matter mixing is the flat and less extended ρ r 3 profile of the C+O core and the helium layer, which may be characterized by the small helium core mass. From the best explosion model, the direction of the bipolar explosion axis (the strongest explosion direction), the neutron star (NS) kick velocity, and its direction are predicted. Other related implications and future prospects are also given.

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Section: Issues In Stellar Evolution Models and Impacts Of Possible Lmentioning

confidence: 99%

Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-star and Binary Merger Progenitor Models for SN 1987A

Ono

Nagataki

Ferrand

et al. 2020

ApJ

104

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“…In recent years, simulations using the fully compressible hydromagnetics equations with, e.g., the Pencil Code (Brandenburg andDobler 2002, Brandenburg 2003), have gained popularity (e.g. Käpylä et al 2012, Masada et al 2013, Hotta et al 2014). The acoustic time step issue has been dealt with either by increasing the star's luminosity (e.g.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity to luminosity, centrifugal force, and boundary conditions in spherical shell convection

Käpylä

Gent²,

Olspert³

et al. 2019

Geophysical & Astrophysical Fluid Dynamics

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We test the sensitivity of hydrodynamic and magnetohydrodynamic turbulent convection simulations with respect to Mach number, thermal and magnetic boundary conditions, and the centrifugal force. We find that varying the luminosity, which also controls the Mach number, has only a minor effect on the largescale dynamics. A similar conclusion can also be drawn from the comparison of two formulations of the lower magnetic boundary condition with either vanishing electric field or current density. The centrifugal force has an effect on the solutions, but only if its magnitude with respect to acceleration due to gravity is by two orders of magnitude greater than in the Sun. Finally, we find that the parameterisation of the photospheric physics, either by an explicit cooling term or enhanced radiative diffusion, is more important than the thermal boundary condition. In particular, runs with cooling tend to lead to more anisotropic convection and stronger deviations from the Taylor-Proudman state. In summary, the fully compressible approach taken here with the Pencil Code is found to be valid, while still allowing the disparate timescales to be taken into account.

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“…However, these simulations are local in the sense that they cannot study the effects of the global dynamo-generated large-scale field on the small-scale field. Very recently, Hotta et al (2014Hotta et al ( , 2015 have studied small-scale dynamo action in the Sun using high-resolution MHD simulations. Again, however, these simulations did not consider the large-scale dynamo.…”

Section: Introductionmentioning

confidence: 99%

Is the Small-Scale Magnetic Field Correlated With the Dynamo Cycle?

Karak

Brandenburg

2015

ApJ

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The small-scale magnetic field is ubiquitous at the solar surface-even at high latitudes. From observations we know that this field is uncorrelated (or perhaps even weakly anticorrelated) with the global sunspot cycle. Our aim is to explore the origin, and particularly the cycle dependence, of such a phenomenon using three-dimensional dynamo simulations. We adopt a simple model of a turbulent dynamo in a shearing box driven by helically forced turbulence. Depending on the dynamo parameters, large-scale (global) and small-scale (local) dynamos can be excited independently in this model. Based on simulations in different parameter regimes, we find that, when only the large-scale dynamo is operating in the system, the small-scale magnetic field generated through shredding and tangling of the large-scale magnetic field is positively correlated with the global magnetic cycle. However, when both dynamos are operating, the small-scale field is produced from both the small-scale dynamo and the tangling of the large-scale field. In this situation, when the large-scale field is weaker than the equipartition value of the turbulence, the small-scale field is almost uncorrelated with the large-scale magnetic cycle. On the other hand, when the large-scale field is stronger than the equipartition value, we observe an anticorrelation between the smallscale field and the large-scale magnetic cycle. This anticorrelation can be interpreted as a suppression of the smallscale dynamo. Based on our studies we conclude that the observed small-scale magnetic field in the Sun is generated by the combined mechanisms of a small-scale dynamo and tangling of the large-scale field.

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High-Resolution Calculations of the Solar Global Convection With the Reduced Speed of Sound Technique. I. The Structure of the Convection and the Magnetic Field Without the Rotation

Cited by 70 publications

References 42 publications

Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-star and Binary Merger Progenitor Models for SN 1987A

Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-star and Binary Merger Progenitor Models for SN 1987A

Sensitivity to luminosity, centrifugal force, and boundary conditions in spherical shell convection

Is the Small-Scale Magnetic Field Correlated With the Dynamo Cycle?

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