THE MEAN ELECTROMOTIVE FORCE RESULTING FROM MAGNETIC BUOYANCY INSTABILITY

Journal Article · Tue Feb 01 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/727/2/112· OSTI ID:21567513

Davies, C R

Motivated both by considerations of the generation of large-scale astrophysical magnetic fields and by potential problems with mean magnetic field generation by turbulent convection, we investigate the mean electromotive force (emf) resulting from the magnetic buoyancy instability of a rotating layer of stratified magnetic field, considering both unidirectional and sheared fields. We discuss why the traditional decomposition into {alpha} and {beta} effects is inappropriate in this case, and that it is only consideration of the entire mean emf that is meaningful. By considering a weighted average of the unstable linear eigenmodes, and averaging over the horizontal plane, we obtain depth-dependent emfs. For the simplified case of isothermal, ideal MHD, we are able to obtain an analytic expression for the emf; more generally, the emf has to be determined numerically. We calculate how the emf depends on the various parameters of the problem, particularly the rotation rate and the latitude of the magnetic layer.

• OSTI ID: 21567513
• Journal Information: Astrophysical Journal, Vol. 727, Issue 2; Other Information: DOI: 10.1088/0004-637X/727/2/112; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CONVECTION
ELECTROMOTIVE FORCE
INSTABILITY
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
ROTATION
SUN
ENERGY TRANSFER
FLUID MECHANICS
HEAT TRANSFER
HYDRODYNAMICS
MAIN SEQUENCE STARS
MASS TRANSFER
MECHANICS
MOTION
STARS