Weak magnetohydrodynamic turbulence and intermittency

2015 ◽  
Vol 770 ◽  
Author(s):  
R. Meyrand ◽  
K. H. Kiyani ◽  
S. Galtier
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Three Dimensional ◽  
Leading Order ◽  
Magnetohydrodynamic Turbulence ◽  
Asymptotic Regime ◽  
Resonant Interactions ◽  
Vector Separation ◽  
Parallel Current

Three-dimensional numerical simulation is used to investigate intermittency in incompressible weak magnetohydrodynamic turbulence with a strong uniform magnetic field $\boldsymbol{b}_{\mathbf{0}}$ and zero cross-helicity. At leading order, this asymptotic regime is achieved via three-wave resonant interactions with the scattering of a wave on a 2D mode for which $k_{\Vert }=0$. When the interactions with the 2D modes are artificially reduced, we show numerically that the system exhibits an energy spectrum with $k_{\bot }^{-3/2}$, whereas the expected exact solution with $k_{\bot }^{-2}$ is recovered with the full nonlinear system. In the latter case, strong intermittency is found when the vector separation of structure functions is taken transverse to $\boldsymbol{b}_{\mathbf{0}}$. This result may be explained by the influence of the 2D modes whose regime belongs to strong turbulence. In addition to shedding light on the origin of this intermittency, we derive a log-Poisson law, ${\it\zeta}_{p}=p/8+1-(1/4)^{p/2}$, which fits the data perfectly and highlights the important role of parallel current sheets.

scholarly journals The Development of a Split-tail Heliosphere and the Role of Non-ideal Processes: A Comparison of the BU and Moscow Models

2021 ◽  
Vol 923 (2) ◽  
pp. 179
Author(s):  
M. Kornbleuth ◽  
M. Opher ◽  
I. Baliukin ◽  
M. Gkioulidou ◽  
J. D. Richardson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Magnetic Field ◽  
Three Dimensional ◽  
Magnetic Field Effects ◽  
The North ◽  
Mhd Instabilities ◽  
North And South ◽  
Numerical Treatments ◽  
Numerical Approaches

Abstract Global models of the heliosphere are critical tools used in the interpretation of heliospheric observations. There are several three-dimensional magnetohydrodynamic (MHD) heliospheric models that rely on different strategies and assumptions. Until now only one paper has compared global heliosphere models, but without magnetic field effects. We compare the results of two different MHD models, the BU and Moscow models. Both models use identical boundary conditions to compare how different numerical approaches and physical assumptions contribute to the heliospheric solution. Based on the different numerical treatments of discontinuities, the BU model allows for the presence of magnetic reconnection, while the Moscow model does not. Both models predict collimation of the solar outflow in the heliosheath by the solar magnetic field and produce a split tail where the solar magnetic field confines the charged solar particles into distinct north and south columns that become lobes. In the BU model, the interstellar medium (ISM) flows between the two lobes at large distances due to MHD instabilities and reconnection. Reconnection in the BU model at the port flank affects the draping of the interstellar magnetic field in the immediate vicinity of the heliopause. Different draping in the models cause different ISM pressures, yielding different heliosheath thicknesses and boundary locations, with the largest effects at high latitudes. The BU model heliosheath is 15% thinner and the heliopause is 7% more inwards at the north pole relative to the Moscow model. These differences in the two plasma solutions may manifest themselves in energetic neutral atom measurements of the heliosphere.

THE EINSTEIN–BRILLOUIN–KELLER ACTION QUANTIZATION FOR DIRAC FERMIONS

2011 ◽  
Vol 25 (08) ◽  
pp. 537-549 ◽  
Author(s):  
P. ONORATO
Keyword(s):  
Magnetic Field ◽  
Carbon Nanostructures ◽  
Uniform Magnetic Field ◽  
Graphene Nanoribbons ◽  
Maslov Index ◽  
Transverse Magnetic ◽  
Dirac Fermions ◽  
Integral Calculus ◽  
Classical Trajectories

The Einstein–Brillouin–Keller semiclassical quantization and the topological Maslov index are used to compute the electronic structure of carbon based nanostructures with or without transverse magnetic field. The calculation is based on the Dirac Fermions approach in the limit of strong coupling for the pseudospin. The electronic bandstructure for carbon nanotubes and graphene nanoribbons are discussed, focusing on the role of the chirality and of the unbonded edges configuration respectively. The effects of a transverse uniform magnetic field are analyzed, the different kinds of classical trajectories are discussed and related to the corresponding energies. The development is concise, transparent, and involves only elementary integral calculus and provides a conceptual and intuitive introduction to the quantum nature of carbon nanostructures.

scholarly journals CONFORMAL MODELS OF MAGNETOHYDRODYNAMIC TURBULENCE

1996 ◽  
Vol 11 (29) ◽  
pp. 5261-5277 ◽  
Author(s):  
OMDUTH COCEAL ◽  
STEVEN THOMAS
Keyword(s):  
Three Dimensional ◽  
Approximate Solutions ◽  
Velocity Fields ◽  
Point Of View ◽  
Three Dimensions ◽  
Finite Conductivity ◽  
Magnetohydrodynamic Turbulence ◽  
Infinite Conductivity ◽  
Conformal Models

Following the previous work of Ferretti and Yang on the role of magnetic fields in the theory of conformal turbulence, we show that nonunitary minimal model solutions to two-dimensional magnetohydrodynamics (MHD) obtained by dimensional reduction from three dimensions exist under different (and more restrictive) conditions. From a three-dimensional point of view, these conditions are equivalent to perpendicular flow, in which the magnetic and velocity fields are orthogonal. We extend the analysis to the finite conductivity case and present some approximate solutions, whose connection with the exact ones of the infinite conductivity case is also discussed.

Liquid-metal flow in a system of electrically coupled U-bends in a strong uniform magnetic field

1995 ◽  
Vol 299 ◽  
pp. 73-95 ◽  
Author(s):  
Sergei Molokov ◽  
Robert Stieglitz
Keyword(s):  
Magnetic Field ◽  
Pressure Drop ◽  
Liquid Metal ◽  
Uniform Magnetic Field ◽  
Flow Direction ◽  
Metal Flow ◽  
Three Dimensional ◽  
Recirculatory Flow ◽  
The Magnetic Field ◽  
Very High

Liquid-metal magnetohydrodynamic flow in a system of electrically coupled U-bends in a strong uniform magnetic field is studied. The ducts composing the bends are electrically conducting and have rectangular cross-sections. It has been anticipated that very strong global electric currents are induced in the system, which modify the flow pattern and produce a very high pressure drop compared to the flow in a single U-bend. A detailed asymptotic analysis of flow for high values of the Harmann number (in fusion blanket applications of the order of 103−104) shows that circulation of global currents results in several types of peculiar flow patterns. In ducts parallel to the magnetic field a combination of helical and recirculatory flow types may be present and vary from one bend to another. The magnitude of the recirculatory motion may become very high depending on the flow-rate distribution between the bends in the system. The recirculatory flow may account for about 50% of the flow in all bends. In addition there are equal and opposite jets at the walls parallel to the magnetic field, which are common to any two bends. The pressure drop due to three-dimensional effects linearly increases with the number of bends in a system and may significantly affect the total pressure drop. To suppress this and some other unwelcome tendencies either the ducts perpendicular to the magnetic field should be electrically separated, or the flow direction in the neighbouring ducts should be made opposite, so that leakage currents cancel each other.

ON THE APPLICATION OF PLASMA KINETIC THEORY TO IONIC SOUND-WAVE EXPERIMENTS IN MAGNETIC FIELDS

1965 ◽  
Vol 43 (10) ◽  
pp. 1750-1765 ◽  
Author(s):  
M. J. Haggerty
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Critical Frequency ◽  
Magnetic Field Intensity ◽  
Sound Waves ◽  
Cyclotron Radius ◽  
The Mean ◽  
The Magnetic Field ◽  
Theoretical Results

The kinetic theoretical results for a homogeneous plasma in a uniform magnetic field are discussed qualitatively. The role of the mean cyclotron radius as a natural long-range cutoff is clarified. A relationship between a critical frequency for ionic sound waves and the magnetic-field intensity is predicted.

scholarly journals The three-dimensional Ising spin glass in an external magnetic field: the role of the silent majority

2014 ◽  
Vol 2014 (5) ◽  
pp. P05014 ◽  
Author(s):  
M Baity-Jesi ◽  
R A Baños ◽  
A Cruz ◽  
L A Fernandez ◽  
J M Gil-Narvion ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Spin Glass ◽  
Three Dimensional ◽  
Ising Spin Glass ◽  
Silent Majority ◽  
Ising Spin

Inverse cascades in incompressible fluid and magnetofluid turbulence

1996 ◽  
Vol 56 (3) ◽  
pp. 467-491
Author(s):  
Murshed Hossain
Keyword(s):  
Magnetic Field ◽  
Incompressible Fluid ◽  
Uniform Magnetic Field ◽  
Spatial Scales ◽  
Three Dimensional ◽  
Self Organization ◽  
Anisotropic Fluid ◽  
Uniform Rotation ◽  
Fluid Turbulence ◽  
Turbulent Fluctuations

Absolute equilibrium statistical theory and numerical simulations are reviewed in the context of inverse cascades in two- and three-dimensional incompressible fluid and magnetofluid turbulence. Turbulent fluctuations of physically interesting quantities undergo inverse cascade to larger spatial scales, leading to self-organization under certain circumstances. In particular, most systems with more than one quadratic ideal invariant, or, having some kind of imposed anisotropy, exhibit inverse cascades. Anisotropic fluid turbulence in the presence of a uniform rotation and magnetofluid turbulence in the presence of a uniform magnetic field are considered.

Sign in / Sign up

Export Citation Format

Share Document