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Mean electromotive force in turbulent shear flow
1A. F. Ioffe Institute of Physics and Technology, 194021 St. Petersburg, Russia.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|February 28, 2002
Summary
Turbulent shear flow can generate large-scale magnetic fields by stretching magnetic field lines. This process, distinct from the alpha effect, leads to mean field instability and dynamo action in astrophysical bodies.
Area of Science:
- Plasma physics
- Astrophysical fluid dynamics
- Magnetohydrodynamics
Background:
- Turbulent shear flows are prevalent in astrophysical environments.
- Understanding the generation of large-scale magnetic fields is crucial for astrophysics.
- The alpha effect is a known mechanism for dynamo action, but may not fully explain shear-driven generation.
Purpose of the Study:
- To investigate the generation of mean electromotive force in turbulent shear flow.
- To analyze the role of magnetic field line stretching by the mean flow.
- To explore mechanisms for large-scale magnetic field generation beyond the alpha effect.
Main Methods:
- Analysis of mean electromotive force in turbulent shear flow.
- Incorporation of magnetic field line stretching by the mean flow.
- Investigation of magnetohydrodynamics-turbulence properties under shear.
Main Results:
- Mean flow can alter magnetohydrodynamics-turbulence, enabling dynamo action.
- Shear's contribution to mean electromotive force is not described by the alpha effect.
- Sufficiently strong shear induces mean field instability, with growth rates dependent on field length scale.
Conclusions:
- A novel mechanism for large-scale magnetic field generation in turbulent shear flows is identified.
- This mechanism may explain magnetic field generation in galaxies, accretion discs, and jets.
- The findings extend our understanding of astrophysical dynamos.