MHD dynamo in a Dean-like flow inside a torus

2016 ◽  
Vol 52 (1-2) ◽  
pp. 15-24
Author(s):  
A. Chupin
Keyword(s):  
Mhd Dynamo

MHD dynamo in a Dean-like flow inside a torus

2016 ◽  
Vol 52 (1) ◽  
pp. 15-24
Author(s):  
A. Chupin ◽  
Keyword(s):  
Mhd Dynamo

Comparison of Stellar Oscillations and Activity Data to Infer Internal Rotation

1993 ◽  
Vol 137 ◽  
pp. 675-678
Author(s):  
Gaetano Belvedere
Keyword(s):  
Active Regions ◽  
The Sun ◽  
Acoustic Oscillations ◽  
Activity Data ◽  
Surface Distribution ◽  
Stellar Oscillations ◽  
Mhd Dynamo ◽  
Latitude Distribution ◽  
Stellar Interiors ◽  
Angular Velocity Profile

AbstractRecently it has beeen suggested that the latitude distribution of the main surface features of solar activity is intimately related to the angular velocity profile inside the Sun through the working of a MHD dynamo in the boundary layer between the convective and the radiative zones (Belvedere et al. 1991).Although the present observational capabilities are not very encouraging, here we want to point out, in the framework of the analogy to the Sun (solar-stellar connection), that space observations of surface distribution and latitudinal migration of active regions on stellar surfaces, which could be carried out in this decade with more sophisticated techniques, may conversely allow us to infer the rotation profile, and consequently the angular momentum distribution, in stellar interiors. This methodology may in principle be considered alternate or complementary to the classical one based on observation of acoustic oscillations.

scholarly journals General relativistic magnetic perturbations and dynamo effects in extragalactic radiosources

2010 ◽  
Vol 6 (S274) ◽  
pp. 393-397
Author(s):  
L. C. Garcia de Andrade
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Magnetic Fluctuations ◽  
Dynamo Action ◽  
Magnetic Contrast ◽  
Mhd Dynamo ◽  
Curvature Energy ◽  
Induction Equation ◽  
The Universe ◽  
The Magnetic Field

AbstractBy making use of the MHD self-induction equation in general relativity (GR), recently derived by Clarkson and Marklund (2005), it is shown that when Friedmann universe possesses a spatial section whose Riemannian curvature is negative, the magnetic energy bounds computed by Nuñez (2002) also bounds the growth rate of the magnetic field given by the strain matrix of dynamo flow. Since in GR-MHD dynamo equation, the Ricci tensor couples with the universe magnetic field, only through diffusion, and most ages are highly conductive the interest is more theoretical here, and only very specific plasma astrophysical problems can be address such as in laboratory plasmas. Magnetic fields and the negative curvature of some isotropic cosmologies, contribute to enhence the amplification of the magnetic field. Ricci curvature energy is shown to add to strain matrix of the flow, to enhance dynamo action in the universe. Magnetic fluctuations of the Clarkson-Marklund equations for a constant magnetic field seed in highly conductive flat universes, leads to a magnetic contrast of ≈ 2, which is well within observational limits from extragalactic radiosources of ≈ 1.7. In the magnetic helicity fluctuations the magnetic contrast shows that the dynamo effects can be driven by these fluctuations.

scholarly journals Magnetohydrodynamic drift equations: from Langmuir circulations to magnetohydrodynamic dynamo?

2012 ◽  
Vol 698 ◽  
pp. 51-61 ◽  
Author(s):  
V. A. Vladimirov
Keyword(s):  
Magnetic Field ◽  
Mathematical Structure ◽  
Mhd Equations ◽  
Reynolds Stresses ◽  
Oscillating Flows ◽  
Averaged Equations ◽  
Mhd Dynamo ◽  
Leading Term ◽  
Langmuir Circulations ◽  
Advection Velocity

AbstractWe derive the closed system of averaged magnetohydrodynamic (MHD) equations for general oscillating flows. The used small parameter of our asymptotic theory is the dimensionless inverse frequency, and the leading term for a velocity field is chosen to be purely oscillating. The employed mathematical approach combines the two-timing method and the notion of a distinguished limit. The properties of commutators are used to simplify calculations. The derived averaged equations are similar to the original MHD equations, but surprisingly (instead of the commonly expected Reynolds stresses) a drift velocity plays a part of an additional advection velocity. In the special case of a vanishing magnetic field $\mathbi{h}\equiv 0$, the averaged equations produce the Craik–Leibovich equations for Langmuir circulations (which can be called ‘vortex dynamo’). We suggest that, since the mathematical structure of the full averaged equations for $\mathbi{h}\not = 0$ is similar to those for $\mathbi{h}\equiv 0$, these full equations could lead to a possible mechanism of MHD dynamo, such as the generation of the magnetic field of the Earth.

scholarly journals The spontaneous magnetic field direction in an anisotropic MHD dynamo

2012 ◽  
Vol 28 (5) ◽  
pp. 225-231 ◽  
Author(s):  
B. A. Shakhov ◽  
M. Jurcisin ◽  
E. Jurcisinova ◽  
M. Stehlik
Keyword(s):  
Magnetic Field ◽  
Field Direction ◽  
Magnetic Field Direction ◽  
Mhd Dynamo

Effects of boundary layers on magnetic field behavior in an MHD dynamo model

2001 ◽  
Vol 128 (1-4) ◽  
pp. 149-161 ◽  
Author(s):  
F. Takahashi ◽  
J.S. Katayama ◽  
M. Matsushima ◽  
Y. Honkura
Keyword(s):  
Magnetic Field ◽  
Boundary Layers ◽  
Dynamo Model ◽  
Field Behavior ◽  
Mhd Dynamo

scholarly journals Generation of coupled global and local magnetic fields by a cellular MHD dynamo

2006 ◽  
Vol 2 (S239) ◽  
pp. 482-487
Author(s):  
A. V. Getling ◽  
R. D. Simitev ◽  
F. H. Busse
Keyword(s):  
Magnetic Fields ◽  
Stationary Regime ◽  
Polar Regions ◽  
Magnetic Structures ◽  
Local Structures ◽  
First Case ◽  
Mhd Dynamo ◽  
Electromagnetic Processes ◽  
Background Fields ◽  
Global And Local

AbstractThe convection-driven MHD dynamo in a rotating spherical shell is simulated numerically. Convection cells are regarded as a connecting link between the global and local electromagnetic processes. Local (in many cases, bipolar) magnetic structures are regularly produced by convection cells. Dynamo regimes in “thick” and “thin” shells are discussed. In the first case, the “general” magnetic field maintained by the dynamo has a sign-alternating dipolar component, which varies cyclically, although not periodically. The local structures, as they disintegrate, change into background fields, which drift toward the poles. From time to time, reversals of the magnetic fields in the polar regions occur, as “new” background fields expel the “old” fields. In the second case, the system settles down to a nearly stationary regime without polarity reversals.

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