α -effect dynamos with zero kinetic helicity
Abstract
A simple explicit example of a Roberts-type dynamo is given in which the α effect of mean-field electrodynamics exists in spite of pointwise vanishing kinetic helicity of the fluid flow. In this way, it is shown that α -effect dynamos do not necessarily require nonzero kinetic helicity. A mean-field theory of Roberts-type dynamos is established within the framework of the second-order correlation approximation. In addition, numerical solutions of the original dynamo equations are given that are independent of any approximation of that kind. Both theory and numerical results demonstrate the possibility of dynamo action in the absence of kinetic helicity.
- Publication:
-
Physical Review E
- Pub Date:
- February 2008
- DOI:
- 10.1103/PhysRevE.77.026405
- arXiv:
- arXiv:0801.0602
- Bibcode:
- 2008PhRvE..77b6405R
- Keywords:
-
- 52.65.Kj;
- 52.75.Fk;
- 47.65.-d;
- Magnetohydrodynamic and fluid equation;
- Magnetohydrodynamic generators and thermionic convertors;
- plasma diodes;
- Magnetohydrodynamics and electrohydrodynamics;
- Astrophysics
- E-Print:
- 6 pages, 3 figures, accepted for PRE