scholarly journals The Twists and Turns of the Dynamo Effect

Physics ◽  
2012 ◽  
Vol 5 ◽  
Author(s):  
Andreas Tilgner
Keyword(s):  
Dynamo Effect

scholarly journals Filaments and the Solar Dynamo

1998 ◽  
Vol 167 ◽  
pp. 406-414
Author(s):  
N. Seehafer
Keyword(s):  
Mean Field ◽  
Decisive Role ◽  
Dynamo Theory ◽  
Simultaneous Generation ◽  
Alpha Effect ◽  
Generation Region ◽  
The Mean ◽  
Numerical Bifurcation ◽  
Dynamo Effect

AbstractFilaments are a global phenomenon and their formation, structure and dynamics are determined by magnetic fields. So they are an important signature of the solar magnetism. The central mechanism in traditional mean-field dynamo theory is the alpha effect and it is a major result of this theory that the presence of kinetic or magnetic helicities is at least favourable for the effect. Recent studies of the magnetohydrodynamic equations by means of numerical bifurcation-analysis techniques have confirmed the decisive role of helicity for a dynamo effect. The alpha effect corresponds to the simultaneous generation of magnetic helicities in the mean field and in the fluctuations, the generation rates being equal in magnitude and opposite in sign. In the case of statistically stationary and homogeneous fluctuations, in particular, the alpha effect can increase the energy in the mean magnetic field only under the condition that also magnetic helicity is accumulated there. Generally, the two helicities generated by the alpha effect, that in the mean field and that in the fluctuations, have either to be dissipated in the generation region or to be transported out of this region. The latter may lead to the appearance of helicity in the atmosphere, in particular in filaments, and thus provide valuable information on dynamo processes inaccessible to in situ measurements.

scholarly journals Angular Momentum Transport and Dynamo Effect in Kepler Disks

2001 ◽  
Vol 200 ◽  
pp. 410-414
Author(s):  
Günther Rüdiger ◽  
Udo Ziegler
Keyword(s):  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Spherical Model ◽  
Momentum Transport ◽  
Rotational Instability ◽  
Jet Formation ◽  
Angular Momentum Transport ◽  
Dynamo Effect ◽  
Background Shear

Properties have been demonstrated of the magneto-rotational instability for two different applications, i.e. for a global spherical model and a box simulation with Keplerian background shear flow. In both nonlinear cases a dynamo operates with a negative (positive) α-effect in the northern (southern) disk hemisphere and in both cases the angular momentum transport is outwards. Keplerian accretion disks should therefore exhibit large-scale magnetic fields with a dipolar geometry of the poloidal components favoring jet formation.

Non-Riemannian generalizations of the Born–Infeld model and the meaning of the cosmological term

2017 ◽  
Vol 14 (07) ◽  
pp. 1750108 ◽  
Author(s):  
Diego Julio Cirilo-Lombardo
Keyword(s):  
Type Equation ◽  
Field Equations ◽  
Dynamical Equations ◽  
Primordial Magnetic Fields ◽  
Suitable Form ◽  
Theory Of Gravitation ◽  
Affine Action ◽  
Dynamo Effect ◽  
The Einstein Formula

Theory of gravitation based on a non-Riemannian geometry with dynamical torsion field is geometrically analyzed. To this end, the simplest Lagrangian density is introduced as a measure (reminiscent of a sigma model) and the dynamical equations are derived. Our goal is to rewrite this generalized affine action in a suitable form similar to the standard Born–Infeld (BI) Lagrangian. As soon as the functional action is rewritten in the BI form, the dynamical equations lead the trace-free GR-type equation and the field equations for the torsion, respectively: both equations emerge from the model in a sharp contrast with other attempts where additional assumptions were heuristically introduced. In this theoretical context, the Einstein [Formula: see text], Newton [Formula: see text] and the analog to the absolute [Formula: see text]-field into the standard BI theory all arise from the same geometry through geometrical invariant quantities (as from the curvature [Formula: see text]). They can be clearly identified and correctly interpreted both physical and geometrically. Interesting theoretical and physical aspects of the proposed theory are given as clear examples that show the viability of this approach to explain several problems of actual interest. Some of them are the dynamo effect and geometrical origin of [Formula: see text] term, origin of primordial magnetic fields and the role of the torsion in the actual symmetry of the standard model. The relation with gauge theories, conserved currents, and other problems of astrophysical character is discussed with some detail.

Dynamo Effect With Inertial Modes in a Spherical Shell?

2001 ◽  
pp. 271-277
Author(s):  
M. Rieutord ◽  
L. Valdettaro
Keyword(s):  
Spherical Shell ◽  
Dynamo Effect

The Dynamo Effect in Stars

2000 ◽  
pp. 1-8 ◽  
Author(s):  
Axel Brandenburg
Keyword(s):  
Dynamo Effect

Dynamo Effect of the Earth and the Formation of Oil

2010 ◽  
Author(s):  
G.V. Tarasenko ◽  
G.V. Tarasenko
Keyword(s):  
The Earth ◽  
Dynamo Effect

THE DYNAMO EFFECT

2003 ◽  
pp. 1-66 ◽  
Author(s):  
S. FAUVE ◽  
F. PETRELIS
Keyword(s):  
Dynamo Effect

Planetary Magnetic Dynamo Effect on Atmospheric Protection of Early Earth and Mars

2007 ◽  
pp. 279-300 ◽  
Author(s):  
V. Dehant ◽  
H. Lammer ◽  
Y. N. Kulikov ◽  
J. -M. Grießmeier ◽  
D. Breuer ◽  
...  
Keyword(s):  
Early Earth ◽  
Dynamo Effect
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