scholarly journals Numerical simulations of the magnetorotational instability in protoneutron stars – I. Influence of buoyancy

2015 ◽  
Vol 450 (2) ◽  
pp. 2153-2171 ◽  
Author(s):  
Jérôme Guilet ◽  
Ewald Müller
Keyword(s):  
Numerical Simulations ◽  
Magnetorotational Instability ◽  
Protoneutron Stars

scholarly journals Magnetically driven jets and winds from weakly magnetized accretion discs

2019 ◽  
Vol 490 (3) ◽  
pp. 3112-3133 ◽  
Author(s):  
J Jacquemin-Ide ◽  
J Ferreira ◽  
G Lesur
Keyword(s):  
Numerical Simulations ◽  
Energy Content ◽  
Initial Energy ◽  
Accretion Discs ◽  
Analytical Models ◽  
Magnetorotational Instability ◽  
New Class ◽  
Analytical Criterion ◽  
First Time

Abstract Semi-analytical models of disc outflows have successfully described magnetically driven, self-confined super-Alfvénic jets from near-Keplerian accretion discs. These jet-emitting discs (JEDs) are possible for high levels of disc magnetization μ defined as μ = 2/β, where beta is the usual plasma parameter. In near-equipartition JEDs, accretion is supersonic and jets carry away most of the disc angular momentum. However, these solutions prove difficult to compare with cutting-edge numerical simulations, for the reason that numerical simulations show wind-like outflows but in the domain of small magnetization. In this work, we present for the first time self-similar isothermal solutions for accretion–ejection structures at small magnetization levels. We elucidate the role of magnetorotational instability-like (MRI) structures in the acceleration processes that drive this new class of solutions. The disc magnetization μ is the main control parameter: Massive outflows driven by the pressure of the toroidal magnetic field are obtained up to μ ∼ 10−2, while more tenuous centrifugally driven outflows are obtained at larger μ values. The generalized parameter space and the astrophysical consequences are discussed. We believe that these new solutions could be a stepping stone in understanding the way astrophysical discs drive either winds or jets. Defining jets as self-confined outflows and winds as uncollimated outflows, we propose a simple analytical criterion based on the initial energy content of the outflow, to discriminate jets from winds. We show that jet solution is achieved at all magnetization levels, while winds could be obtained only in weakly magnetized discs that feature heating.

scholarly journals How to form a millisecond magnetar? Magnetic field amplification in protoneutron stars

2017 ◽  
Vol 12 (S331) ◽  
pp. 119-124 ◽  
Author(s):  
Jérôme Guilet ◽  
Ewald Müller ◽  
Hans-Thomas Janka ◽  
Tomasz Rembiasz ◽  
Martin Obergaulinger ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Gamma Ray ◽  
Core Collapse ◽  
Magnetorotational Instability ◽  
Strong Magnetic Fields ◽  
Physical Conditions ◽  
Field Amplification ◽  
Magnetic Prandtl Number ◽  
Protoneutron Stars

AbstractExtremely strong magnetic fields of the order of 1015G are required to explain the properties of magnetars, the most magnetic neutron stars. Such a strong magnetic field is expected to play an important role for the dynamics of core-collapse supernovae, and in the presence of rapid rotation may power superluminous supernovae and hypernovae associated to long gamma-ray bursts. The origin of these strong magnetic fields remains, however, obscure and most likely requires an amplification over many orders of magnitude in the protoneutron star. One of the most promising agents is the magnetorotational instability (MRI), which can in principle amplify exponentially fast a weak initial magnetic field to a dynamically relevant strength. We describe our current understanding of the MRI in protoneutron stars and show recent results on its dependence on physical conditions specific to protoneutron stars such as neutrino radiation, strong buoyancy effects and large magnetic Prandtl number.

scholarly journals Numerical simulations of the Princeton magnetorotational instability experiment with conducting axial boundaries

2016 ◽  
Vol 94 (6) ◽  
Author(s):  
Xing Wei ◽  
Hantao Ji ◽  
Jeremy Goodman ◽  
Fatima Ebrahimi ◽  
Erik Gilson ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Magnetorotational Instability

Magnetorotational instability: recent developments

2010 ◽  
Vol 368 (1916) ◽  
pp. 1607-1633 ◽  
Author(s):  
Keith Julien ◽  
Edgar Knobloch
Keyword(s):  
Angular Momentum ◽  
Numerical Simulations ◽  
Theoretical Approach ◽  
Laboratory Experiments ◽  
Accretion Disc ◽  
Nonlinear Processes ◽  
Magnetorotational Instability ◽  
Recent Developments ◽  
The Subject

The magnetorotational instability is believed to play an important role in accretion disc physics in extracting angular momentum from the disc and allowing accretion to take place. For this reason the instability has been the subject of numerous numerical simulations and, increasingly, laboratory experiments. In this review, recent developments in both areas are surveyed, and a new theoretical approach to understanding the nonlinear processes involved in the saturation of the instability is outlined.

Sign in / Sign up

Export Citation Format

Share Document