Not much helicity is needed to drive large-scale dynamos

Autores
Pietarila Graham, Jonathan; Blackman, Eric G.; Mininni, Pablo Daniel; Pouquet, Annick
Año de publicación
2012
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
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.
Fil: Pietarila Graham, Jonathan. Los Alamos National Laboratory; Estados Unidos
Fil: Blackman, Eric G.. University Of Rochester; Estados Unidos
Fil: Mininni, Pablo Daniel. Universidad de Buenos Aires; Argentina. National Center for Atmospheric Research; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina
Fil: Pouquet, Annick. National Center for Atmospheric Research; Estados Unidos
Materia
Magnetic Fields
Dynamo Theory
Helicity
Nivel de accesibilidad
acceso abierto
Condiciones de uso
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repositorio
CONICET Digital (CONICET)
Institución
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identificador
oai:ri.conicet.gov.ar:11336/56652
Acceder
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network_acronym_str CONICETDig
repository_id_str 3498
network_name_str CONICET Digital (CONICET)
spelling Not much helicity is needed to drive large-scale dynamosPietarila Graham, JonathanBlackman, Eric G.Mininni, Pablo DanielPouquet, AnnickMagnetic FieldsDynamo TheoryHelicityhttps://purl.org/becyt/ford/1.3https://purl.org/becyt/ford/1Understanding 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.Fil: Pietarila Graham, Jonathan. Los Alamos National Laboratory; Estados UnidosFil: Blackman, Eric G.. University Of Rochester; Estados UnidosFil: Mininni, Pablo Daniel. Universidad de Buenos Aires; Argentina. National Center for Atmospheric Research; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Pouquet, Annick. National Center for Atmospheric Research; Estados UnidosAmerican Physical Society2012-06info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfapplication/pdfhttp://hdl.handle.net/11336/56652Pietarila Graham, Jonathan; Blackman, Eric G.; Mininni, Pablo Daniel; Pouquet, Annick; Not much helicity is needed to drive large-scale dynamos; American Physical Society; Physical Review E: Statistical, Nonlinear and Soft Matter Physics; 85; 6; 6-2012; 6632001-66320131539-3755CONICET DigitalCONICETenginfo:eu-repo/semantics/altIdentifier/url/http://pre.aps.org/abstract/PRE/v85/i6/e066406info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevE.85.066406info:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by-nc-sa/2.5/ar/reponame:CONICET Digital (CONICET)instname:Consejo Nacional de Investigaciones Científicas y Técnicas2025-09-29T10:31:31Zoai:ri.conicet.gov.ar:11336/56652instacron:CONICETInstitucionalhttp://ri.conicet.gov.ar/Organismo científico-tecnológicoNo correspondehttp://ri.conicet.gov.ar/oai/requestdasensio@conicet.gov.ar; lcarlino@conicet.gov.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:34982025-09-29 10:31:31.625CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicasfalse
dc.title.none.fl_str_mv Not much helicity is needed to drive large-scale dynamos
title Not much helicity is needed to drive large-scale dynamos
spellingShingle Not much helicity is needed to drive large-scale dynamos
Pietarila Graham, Jonathan
Magnetic Fields
Dynamo Theory
Helicity
title_short Not much helicity is needed to drive large-scale dynamos
title_full Not much helicity is needed to drive large-scale dynamos
title_fullStr Not much helicity is needed to drive large-scale dynamos
title_full_unstemmed Not much helicity is needed to drive large-scale dynamos
title_sort Not much helicity is needed to drive large-scale dynamos
dc.creator.none.fl_str_mv Pietarila Graham, Jonathan
Blackman, Eric G.
Mininni, Pablo Daniel
Pouquet, Annick
author Pietarila Graham, Jonathan
author_facet Pietarila Graham, Jonathan
Blackman, Eric G.
Mininni, Pablo Daniel
Pouquet, Annick
author_role author
author2 Blackman, Eric G.
Mininni, Pablo Daniel
Pouquet, Annick
author2_role author
author
author
dc.subject.none.fl_str_mv Magnetic Fields
Dynamo Theory
Helicity
topic Magnetic Fields
Dynamo Theory
Helicity
purl_subject.fl_str_mv https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
dc.description.none.fl_txt_mv 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.
Fil: Pietarila Graham, Jonathan. Los Alamos National Laboratory; Estados Unidos
Fil: Blackman, Eric G.. University Of Rochester; Estados Unidos
Fil: Mininni, Pablo Daniel. Universidad de Buenos Aires; Argentina. National Center for Atmospheric Research; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina
Fil: Pouquet, Annick. National Center for Atmospheric Research; Estados Unidos
description 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.
publishDate 2012
dc.date.none.fl_str_mv 2012-06
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/11336/56652
Pietarila Graham, Jonathan; Blackman, Eric G.; Mininni, Pablo Daniel; Pouquet, Annick; Not much helicity is needed to drive large-scale dynamos; American Physical Society; Physical Review E: Statistical, Nonlinear and Soft Matter Physics; 85; 6; 6-2012; 6632001-6632013
1539-3755
CONICET Digital
CONICET
url http://hdl.handle.net/11336/56652
identifier_str_mv Pietarila Graham, Jonathan; Blackman, Eric G.; Mininni, Pablo Daniel; Pouquet, Annick; Not much helicity is needed to drive large-scale dynamos; American Physical Society; Physical Review E: Statistical, Nonlinear and Soft Matter Physics; 85; 6; 6-2012; 6632001-6632013
1539-3755
CONICET Digital
CONICET
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/url/http://pre.aps.org/abstract/PRE/v85/i6/e066406
info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevE.85.066406
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
eu_rights_str_mv openAccess
rights_invalid_str_mv https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.format.none.fl_str_mv application/pdf
application/pdf
dc.publisher.none.fl_str_mv American Physical Society
publisher.none.fl_str_mv American Physical Society
dc.source.none.fl_str_mv reponame:CONICET Digital (CONICET)
instname:Consejo Nacional de Investigaciones Científicas y Técnicas
reponame_str CONICET Digital (CONICET)
collection CONICET Digital (CONICET)
instname_str Consejo Nacional de Investigaciones Científicas y Técnicas
repository.name.fl_str_mv CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicas
repository.mail.fl_str_mv dasensio@conicet.gov.ar; lcarlino@conicet.gov.ar
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score 13.070432

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