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Pietarila Graham, J.; Blackman, E.G.; Mininni, P.D.; Pouquet, A. "Not much helicity is needed to drive large-scale dynamos" (2012) Physical Review E - Statistical, Nonlinear, and Soft Matter Physics. 85(6)
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Abstract:

Understanding the in situ amplification of large-scale magnetic fields in turbulent astrophysical rotators has been a core subject of dynamo theory. When turbulent velocities are helical, large-scale dynamos that substantially amplify fields on scales that exceed the turbulent forcing scale arise, but the minimum sufficient fractional kinetic helicity f h,C has not been previously well quantified. Using direct numerical simulations for a simple helical dynamo, we show that f h,C decreases as the ratio of forcing to large-scale wave numbers k F/k min increases. From the condition that a large-scale helical dynamo must overcome the back reaction from any nonhelical field on the large scales, we develop a theory that can explain the simulations. For k F/k min≥8 we find f h,C3%, implying that very small helicity fractions strongly influence magnetic spectra for even moderate-scale separation. © 2012 American Physical Society.

Registro:

Documento: Artículo
Título:Not much helicity is needed to drive large-scale dynamos
Autor:Pietarila Graham, J.; Blackman, E.G.; Mininni, P.D.; Pouquet, A.
Filiación:Solid Mechanics and Fluid Dynamics (T-3), Center for Nonlinear Studies, Los Alamos National Laboratory MS-B258, Los Alamos, NM 87545, United States
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, United States
Computational and Information Systems Laboratory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000, United States
Departamento de Física, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, 1428 Buenos Aires, Argentina
Palabras clave:Back reaction; Dynamo theories; Helicities; In-situ; Kinetic helicity; Magnetic spectra; Turbulent velocity; Wave numbers; Amplification; Astrophysics; Interactive devices; Magnetic fields; DC generators
Año:2012
Volumen:85
Número:6
DOI: http://dx.doi.org/10.1103/PhysRevE.85.066406
Título revista:Physical Review E - Statistical, Nonlinear, and Soft Matter Physics
Título revista abreviado:Phys. Rev. E Stat. Nonlinear Soft Matter Phys.
ISSN:15393755
CODEN:PLEEE
Registro:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15393755_v85_n6_p_PietarilaGraham

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Citas:

---------- APA ----------
Pietarila Graham, J., Blackman, E.G., Mininni, P.D. & Pouquet, A. (2012) . Not much helicity is needed to drive large-scale dynamos. Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 85(6).
http://dx.doi.org/10.1103/PhysRevE.85.066406
---------- CHICAGO ----------
Pietarila Graham, J., Blackman, E.G., Mininni, P.D., Pouquet, A. "Not much helicity is needed to drive large-scale dynamos" . Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 85, no. 6 (2012).
http://dx.doi.org/10.1103/PhysRevE.85.066406
---------- MLA ----------
Pietarila Graham, J., Blackman, E.G., Mininni, P.D., Pouquet, A. "Not much helicity is needed to drive large-scale dynamos" . Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, vol. 85, no. 6, 2012.
http://dx.doi.org/10.1103/PhysRevE.85.066406
---------- VANCOUVER ----------
Pietarila Graham, J., Blackman, E.G., Mininni, P.D., Pouquet, A. Not much helicity is needed to drive large-scale dynamos. Phys. Rev. E Stat. Nonlinear Soft Matter Phys. 2012;85(6).
http://dx.doi.org/10.1103/PhysRevE.85.066406