Shearing box simulations in the Rayleigh unstable regime

TY - JOUR

T1 - Shearing box simulations in the Rayleigh unstable regime

AU - Nauman, Farrukh

AU - Blackman, Eric G.

PY - 2017/5/1

Y1 - 2017/5/1

N2 - We study the stability properties of Rayleigh unstable flows both in the purely hydrodynamic and magnetohydrodynamic (MHD) regimes for two different values of the shear q = 2.1, 4.2 (q = -dln Ω/dln r) and compare it with the Keplerian case q = 1.5. We find that the q > 2 regime is unstable both in the hydrodynamic and in the MHD limit (with an initially weak magnetic field). In this regime, the velocity fluctuations dominate the magnetic fluctuations. In contrast, in the q < 2 [magnetorotational instability (MRI)] regime, the magnetic fluctuations dominate. This highlights two different paths to MHD turbulence implied by the two regimes, suggesting that in the q > 2 regime, the instability produces primarily velocity fluctuations that causemagnetic fluctuations, with the causality reversed for the q < 2MRI unstable regime.We also find that the magnetic field correlation is increasingly localized as the shear is increased in the Rayleigh unstable regime. In calculating the time evolution of spatial averages of different terms in the MHD equations, we find that the q > 2 regime is dominated by terms that are non-linear in the fluctuations, whereas for q < 2, the linear terms play a more significant role.

AB - We study the stability properties of Rayleigh unstable flows both in the purely hydrodynamic and magnetohydrodynamic (MHD) regimes for two different values of the shear q = 2.1, 4.2 (q = -dln Ω/dln r) and compare it with the Keplerian case q = 1.5. We find that the q > 2 regime is unstable both in the hydrodynamic and in the MHD limit (with an initially weak magnetic field). In this regime, the velocity fluctuations dominate the magnetic fluctuations. In contrast, in the q < 2 [magnetorotational instability (MRI)] regime, the magnetic fluctuations dominate. This highlights two different paths to MHD turbulence implied by the two regimes, suggesting that in the q > 2 regime, the instability produces primarily velocity fluctuations that causemagnetic fluctuations, with the causality reversed for the q < 2MRI unstable regime.We also find that the magnetic field correlation is increasingly localized as the shear is increased in the Rayleigh unstable regime. In calculating the time evolution of spatial averages of different terms in the MHD equations, we find that the q > 2 regime is dominated by terms that are non-linear in the fluctuations, whereas for q < 2, the linear terms play a more significant role.

KW - Astrophysics - Solar and Stellar Astrophysics

KW - Physics - Plasma Physics

U2 - 10.1093/mnras/stx209

DO - 10.1093/mnras/stx209

M3 - Journal article

SN - 0035-8711

VL - 467

SP - 1652

EP - 1660

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

IS - 2

ER -