Nonlinear magnetohydrodynamic dynamo
- 1 December 1995
- journal article
- research article
- Published by AIP Publishing in Physics of Plasmas
- Vol. 2 (12), 4455-4461
- https://doi.org/10.1063/1.871002
Abstract
The self‐consistent nonlinear evolution and saturation of the dynamo, including the back reaction of the magnetic field on the flow through the Lorentz J×B force, is investigated via simulation of the fully compressible magnetohydrodynamic (MHD) equations. The saturated state is found to be highly turbulent. The energy in the saturated magnetic field is only a small fraction of the kinetic energy in the flow which drives the dynamo. However, as the collision frequency decreases and the Reynolds number R increases, the ratio of magnetic to kinetic energy in the saturated state increases gradually. The nonlinear viscosity generated by the turbulent fluctuations rises rapidly relative to the collisional viscosity as R increases, such that the total transport of momentum remains virtually unchanged as the collisional viscosity is reduced. The scale lengths of the magnetic and velocity fluctuations both decrease as R increases, so that the scale size of the magnetic field remains comparable to the scale size of the flow.Keywords
This publication has 22 references indexed in Scilit:
- Construction of fast dynamos using unsteady flows and maps in three dimensionsGeophysical & Astrophysical Fluid Dynamics, 1988
- Chaotic flows and fast magnetic dynamosPhysics of Fluids, 1988
- Chaotic flows and magnetic dynamosPhysical Review Letters, 1988
- Fast dynamo action in unsteady flows and maps in three dimensionsPhysical Review Letters, 1987
- Fast dynamo action in a steady flowJournal of Fluid Mechanics, 1987
- A high magnetic Reynolds number dynamoPhysics of Fluids, 1987
- Dynamo action in a family of flows with chaotic streamlinesGeophysical & Astrophysical Fluid Dynamics, 1986
- Topological constraints associated with fast dynamo actionJournal of Fluid Mechanics, 1985
- Kinematic dynamo in random flowSoviet Physics Uspekhi, 1985
- Alpha-effect in flux ropes and sheetsPhysics of the Earth and Planetary Interiors, 1979