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We study the magneto-rotational instability (MRI) driven dynamo in a geometrically thin disc ($H/R\ll 1$) using stratified zero net flux (ZNF) shearing box simulations. We find that mean fields and EMFs oscillate with a primary frequency…

高能天体物理现象 · 物理学 2024-07-22 Prasun Dhang , Abhijit Bendre , Kandaswamy Subramanian

Magnetorotational instability (MRI) has been suggested to lead a rapid growth of the magnetic field in core collapse supernovae and produce departures from spherical syymmetry that can be important in determining the explosion mechanism. We…

太阳与恒星天体物理 · 物理学 2015-05-14 V. Urpin

Magnetars are highly magnetized neutron stars that can produce X-ray and soft gamma-ray emissions and that have a dipole of $10^{14}$ G to $10^{15}$ G. A promising mechanism for explaining magnetar formation is magnetic field amplification…

高能天体物理现象 · 物理学 2022-09-22 Alexis Reboul-Salze , Jérôme Guilet , Raphaël Raynaud , Matteo Bugli

Numerical simulations of the magnetorotational instability (MRI) with zero initial net flux in a non-stratified isothermal cubic domain are used to demonstrate the importance of magnetic boundary conditions.In fully periodic systems the…

高能天体物理现象 · 物理学 2011-07-08 Petri J. Käpylä , Maarit J. Korpi

We investigated the impacts of magnetorotational instability (MRI) on the dynamics of weakly magnetized, rapidly rotating core-collapse by conducting high resolution MHD simulations in axisymmetry with simplified neutrino transfer. We found…

高能天体物理现象 · 物理学 2015-06-18 Hidetomo Sawai , Shoichi Yamada

The local properties of turbulence driven by the magnetorotational instability (MRI) in rotating, shearing flows are studied in the framework of a shearing-box model. Based on numerical simulations, we propose that the MRI-driven turbulence…

太阳与恒星天体物理 · 物理学 2015-12-14 Justin Walker , Geoffroy Lesur , Stanislav Boldyrev

The initial magnetic field of previous magnetorotational instability (MRI) simulations has always included a significant system-scale component, even if stochastic. However, it is of conceptual and practical interest to assess whether the…

高能天体物理现象 · 物理学 2017-10-13 Pallavi Bhat , Fatima Ebrahimi , Eric G. Blackman , Kandaswamy Subramanian

In the presence of strong density stratification, turbulence can lead to a large-scale instability of a horizontal magnetic field if its strength is in a suitable range (within a few percent of the turbulent equipartition value). This…

太阳与恒星天体物理 · 物理学 2014-04-28 Sarah Jabbari , Axel Brandenburg , Nathan Kleeorin , Dhrubaditya Mitra , Igor Rogachevskii

Simulations of the magnetorotational instability (MRI) in a homogeneous shearing box have shown that the asymptotic strength of the magnetic field declines steeply with increasing resolution. Here I model the MRI driven dynamo as a large…

高能天体物理现象 · 物理学 2011-02-11 Ethan T. Vishniac

The magneto-rotational instability (MRI) is considered to be a promising mechanism to amplify the magnetic field in fast rotating protoneutron stars. In contrast to accretion disks, radial buoyancy driven by entropy and lepton fraction…

高能天体物理现象 · 物理学 2015-06-23 Jerome Guilet , Ewald Mueller

Helioseismology provides important constraints for the solar dynamo problem. However, the basic properties and even the depth of the dynamo process, which operates also in other stars, are unknown. Most of the dynamo models suggest that the…

太阳与恒星天体物理 · 物理学 2014-02-11 Alexander G. Kosovichev , Valery V. Pipin , Junwei Zhao

We analyze the linear growth of the magnetorotational instability (MRI) in the short time limit using nonmodal methods. Our findings are quite different to standard results, illustrating that shearing wave energy can grow at the maximum MRI…

等离子体物理 · 物理学 2014-12-01 Jonathan Squire , Amitava Bhattacharjee

The interaction between weak magnetic fields and rotation can lead to instabilities that transport angular momentum (AM) and chemical elements affecting the evolution of massive stars. We explore the effects of the magneto-rotational…

太阳与恒星天体物理 · 物理学 2022-09-28 A. Griffiths , G. Meynet , P. Eggenberger , F. Moyano , M. A. Aloy

The negative effective magnetic pressure instability operates on scales encompassing many turbulent eddies and is here discussed in connection with the formation of active regions near the surface layers of the Sun. This instability is…

太阳与恒星天体物理 · 物理学 2013-09-10 Koen Kemel , Axel Brandenburg , Nathan Kleeorin , Dhrubaditya Mitra , Igor Rogachevskii

The magnetorotational instability (MRI) is a shear instability and thus its sensitivity to the shear parameter $q = - d\ln\Omega/d\ln r $ is of interest to investigate. Motivated by astrophysical disks, most (but not all) previous MRI…

太阳与恒星天体物理 · 物理学 2015-06-22 Farrukh Nauman , Eric G. Blackman

The magnetorotational instability (MRI) plays a key role in the formation of stars and black holes, by enabling outward angular momentum transport in accretion disks. The use of combined axial and azimuthal magnetic fields allows the…

Helioseismology has provided unprecedented information about the internal rotation of the Sun. One of the important achievements was the discovery of two radial shear layers: one near the bottom of the convection zone (the tachocline) and…

太阳与恒星天体物理 · 物理学 2015-06-23 Atefeh Barekat , Jesper Schou , Laurent Gizon

The magnetorotational instability (MRI) has been suggested to have an important role on the dynamics of accretion disks. We investigate MRI as an alternative way for guiding the plasma from the disk to the funnel flow at the…

高能天体物理现象 · 物理学 2012-10-08 S. Dogan , E. R. Pekunlu

Despite the importance of the magnetorotational instability (MRI) as a fundamental mechanism for angular momentum transport in magnetized accretion disks, it has yet to be demonstrated in the laboratory. A liquid sodium alpha-omega dynamo…

天体物理学 · 物理学 2009-11-07 K. Noguchi , V. I. Pariev , S. A. Colgate , J. Nordhaus , H. F. Beckley

Recent analysis of the helioseismic observations indicate that the previously observed surface torsional oscillations extend significantly downwards into the solar convection zone. In an attempt to understand these oscillations, we study…

天体物理学 · 物理学 2007-05-23 Eurico Covas , Reza Tavakol , David Moss , Andrew Tworkowski