Global Hall-MHD simulations of magnetorotational instability in a plasma Couette flow experiment

Observations of proton density fluctuations of the solar wind at 1 au have shown the presence of a decade-long transition region of the density spectrum above sub-ion scales, characterized by a flattening of the spectral slope. We use the proton density fluctuations data collected by the BMSW instrument on-board the Spektr-R satellite in order to delimit the plasma parameters under which the transition region can be observed. Under similar plasma conditions to those in observations, we carry out 3D compressible magnetohydrodynamics (MHD) and Hall-MHD numerical simulations and find that Hall physics is necessary to generate the transition region. The analysis of the kω power spectrum in the Hall-MHD simulation indicates that the flattening of the density spectrum is associated with fluctuations having frequencies smaller than the ion cyclotron frequency.

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8.10. Three-dimensional global MHD simulations of jet formation in active galactic nuclei

Symposium - International Astronomical Union ◽

10.1017/s0074180900085235 ◽

1998 ◽

Vol 184 ◽

pp. 363-364

Author(s):

R. Matsumoto ◽

K. Shibata

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Three Dimensional ◽

Galactic Nuclei ◽

Equatorial Region ◽

Astrophysical Jets ◽

Magnetorotational Instability ◽

Jet Formation ◽

Mhd Simulations ◽

Avalanche Flow

Magnetically driven jets from accretion disks are considered to be the most promising models of astrophysical jets. Uchida & Shibata (1985) and Shibata & Uchida (1986) first carried out two-dimensional nonlinear MHD simulations of jet formation from a magnetized disk. Matsumoto et al. (1996) applied the Uchida-Shibata model to a gas torus in active galactic nuclei and showed that the surface layer of the torus accretes faster than the equatorial region like an avalanche because magnetic braking most effectively extracts angular momentum from that layer. A magnetized torus subjects to global non-axisymmetric instabilities (Curry & Pudritz 1996) and local magnetorotational instability (Balbus & Hawley 1991). We carried out three-dimensional global MHD simulations to show the non-axisymmetric effects on the torus, avalanche flow and jet formation.

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Karman-Howarth-Monin equation for compressible Hall MHD turbulence: 2D and 3D Hall MHD simulations

10.5194/egusphere-egu21-11106 ◽

2021 ◽

Author(s):

Victor Montagud-Camps ◽

Petr Hellinger ◽

Andrea Verdini ◽

Simone Landi ◽

Emanuele Papini ◽

...

Keyword(s):

Three Dimensional ◽

Structure Functions ◽

Real Space ◽

Energy Cascade ◽

Mhd Equations ◽

Order Structure ◽

Mhd Simulations ◽

Turbulence Anisotropy ◽

Basic Fluid ◽

Hall Mhd

<p>Turbulence in the solar wind is developed along a vast range of scales, generally under weakly compressible and strong magnetic field plasma conditions. <br>The effects of weakly and moderate compressibility (Mach &#8804;1) and turbulence anisotropy on the energy transfer rate are investigated at MHD and Hall MHD scales. For this purpose, the results of two and three-dimensional compressible Hall MHD simulations are analyzed using a new form of the Karman-Howarth-Monin (KHM) equations that accounts for compressible effects down to Hall MHD scales.<br>The KHM are dynamic equations directly derived from the basic fluid equations that describe the plasma, such as the Hall MHD equations. They provide a relation between the two-point cross-correlations in real space or II-order structure functions, the III-order structure functions and the energy cascade rate of turbulence. These relations depend upon turbulence anisotropy. The effects of compressibility and the Hall term on anisotropy and the estimation of the energy cascade rate via the KHM equations are discussed.</p>

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