The helicity constraint in spherical shell dynamos
نویسندگان
چکیده
RE PR INT The helicity constraint in spherical shell dynamos A. Brandenburg, P. J. Käpylä, D. Mitra, D. Moss, and R. Tavakol 1 NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden 2 Observatory, University of Helsinki, PO Box 14, FI-00014 University of Helsinki, Finland 3 School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK 4 School of Mathematics, University of Manchester, Oxford Road, Manchester M13 9PL, UK
منابع مشابه
Magnetic helicity in stellar dynamos: new numerical experiments
The theory of large scale dynamos is reviewed with particular emphasis on the magnetic helicity constraint in the presence of closed and open boundaries. In the presence of closed or periodic boundaries, helical dynamos respond to the helicity constraint by developing small scale separation in the kinematic regime, and by showing long time scales in the nonlinear regime where the scale separati...
متن کاملAdvances in Theory and Simulations of Large-Scale Dynamos
Recent analytical and computational advances in the theory of large-scale dynamos are reviewed. The importance of the magnetic helicity constraint is apparent even without invoking mean-field theory. The tau approximation yields expressions that show how the magnetic helicity gets incorporated into mean-field theory. The test-field method allows an accurate numerical determination of turbulent ...
متن کاملNumerical modeling of the geodynamo' of field generation and equilibration Mechanisms
Numerical calculations of fluid dynamos powered by thermal convection in a rotating, electrically conducting spherical shell are analyzed. We find two regimes of nonreversing, strong field dynamos at Ekman number 10 -4 and Rayleigh numbers up to 11 times critical. In the strongly columnar regime, convection occurs only in the fluid exterior to the inner core tangent cylinder, in the form of nar...
متن کاملMagnetic helicity in galactic dynamos
Magnetic fields correlated on kiloparsec scales are seen in spiral galaxies. Their origin could be due to amplification of a small seed field by a turbulent galactic dynamo. We review the current status of the galactic dynamo, especially the constraints imposed by magnetic helicity conservation. We estimate the minimal strength of the large-scale magnetic field which could arise inspite of the ...
متن کاملMagnetic Helicity Evolution
The term “dynamo” means different things to the laboratory fusion plasma and astrophysical plasma communities. To alleviate the resulting confusion and to facilitate interdisciplinary progress, we pinpoint conceptual differences and similarities between laboratory plasma dynamos and astrophysical dynamos. We can divide dynamos into three types: 1. magnetically dominated helical dynamos which su...
متن کامل