Causes and consequences of magnetic cloud expansion

Autores
Démoulin, P.; Dasso, S.
Año de publicación
2009
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
Context. A magnetic cloud (MC) is a magnetic flux rope in the solar wind (SW), which, at 1 AU, is observed ∼2-5 days after its expulsion from the Sun. The associated solar eruption is observed as a coronal mass ejection (CME).Aims. Both the in situ observations of plasma velocity distribution and the increase in their size with solar distance demonstrate that MCs are strongly expanding structures. The aim of this work is to find the main causes of this expansion and to derive a model to explain the plasma velocity profiles typically observed inside MCs.Methods. We model the flux rope evolution as a series of force-free field states with two extreme limits: (a) ideal magneto-hydrodynamics (MHD) and (b) minimization of the magnetic energy with conserved magnetic helicity. We consider cylindrical flux ropes to reduce the problem to the integration of ordinary differential equations. This allows us to explore a wide variety of magnetic fields at a broad range of distances to the Sun.Results. We demonstrate that the rapid decrease in the total SW pressure with solar distance is the main driver of the flux-rope radial expansion. Other effects, such as the internal over-pressure, the radial distribution, and the amount of twist within the flux rope have a much weaker influence on the expansion. We demonstrate that any force-free flux rope will have a self-similar expansion if its total boundary pressure evolves as the inverse of its length to the fourth power. With the total pressure gradient observed in the SW, the radial expansion of flux ropes is close to self-similar with a nearly linear radial velocity profile across the flux rope, as observed. Moreover, we show that the expansion rate is proportional to the radius and to the global velocity away from the Sun.Conclusions. The simple and universal law found for the radial expansion of flux ropes in the SW predicts the typical size, magnetic structure, and radial velocity of MCs at various solar distances. © 2009 ESO.
Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fuente
Astron. Astrophys. 2009;498(2):551-566
Materia
interplanetary medium
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Boundary pressure
Coronal mass ejection
Cylindrical flux ropes
Expansion rate
Flux ropes
Force free fields
In-situ observations
interplanetary medium
Magnetic clouds
Magnetic energies
Magnetic flux ropes
Magnetic helicity
Plasma velocity
Radial distributions
Radial expansions
Radial velocity
Self-similar
Solar eruption
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Astrophysics
Boundary layer flow
Energy conservation
Expansion
Fluid dynamics
Magnetic fields
Magnetic flux
Magnetic structure
Magnetohydrodynamics
Ordinary differential equations
Pressure gradient
Solar wind
Sun
Velocity
Velocity distribution
Solar energy
Nivel de accesibilidad
acceso abierto
Condiciones de uso
http://creativecommons.org/licenses/by/2.5/ar
Repositorio
Biblioteca Digital (UBA-FCEN)
Institución
Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
OAI Identificador
paperaa:paper_00046361_v498_n2_p551_Demoulin

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oai_identifier_str paperaa:paper_00046361_v498_n2_p551_Demoulin
network_acronym_str BDUBAFCEN
repository_id_str 1896
network_name_str Biblioteca Digital (UBA-FCEN)
spelling Causes and consequences of magnetic cloud expansionDémoulin, P.Dasso, S.interplanetary mediumSun: coronal mass ejections (CMEs)Sun: magnetic fieldsBoundary pressureCoronal mass ejectionCylindrical flux ropesExpansion rateFlux ropesForce free fieldsIn-situ observationsinterplanetary mediumMagnetic cloudsMagnetic energiesMagnetic flux ropesMagnetic helicityPlasma velocityRadial distributionsRadial expansionsRadial velocitySelf-similarSolar eruptionSun: coronal mass ejections (CMEs)Sun: magnetic fieldsAstrophysicsBoundary layer flowEnergy conservationExpansionFluid dynamicsMagnetic fieldsMagnetic fluxMagnetic structureMagnetohydrodynamicsOrdinary differential equationsPressure gradientSolar windSunVelocityVelocity distributionSolar energyContext. A magnetic cloud (MC) is a magnetic flux rope in the solar wind (SW), which, at 1 AU, is observed ∼2-5 days after its expulsion from the Sun. The associated solar eruption is observed as a coronal mass ejection (CME).Aims. Both the in situ observations of plasma velocity distribution and the increase in their size with solar distance demonstrate that MCs are strongly expanding structures. The aim of this work is to find the main causes of this expansion and to derive a model to explain the plasma velocity profiles typically observed inside MCs.Methods. We model the flux rope evolution as a series of force-free field states with two extreme limits: (a) ideal magneto-hydrodynamics (MHD) and (b) minimization of the magnetic energy with conserved magnetic helicity. We consider cylindrical flux ropes to reduce the problem to the integration of ordinary differential equations. This allows us to explore a wide variety of magnetic fields at a broad range of distances to the Sun.Results. We demonstrate that the rapid decrease in the total SW pressure with solar distance is the main driver of the flux-rope radial expansion. Other effects, such as the internal over-pressure, the radial distribution, and the amount of twist within the flux rope have a much weaker influence on the expansion. We demonstrate that any force-free flux rope will have a self-similar expansion if its total boundary pressure evolves as the inverse of its length to the fourth power. With the total pressure gradient observed in the SW, the radial expansion of flux ropes is close to self-similar with a nearly linear radial velocity profile across the flux rope, as observed. Moreover, we show that the expansion rate is proportional to the radius and to the global velocity away from the Sun.Conclusions. The simple and universal law found for the radial expansion of flux ropes in the SW predicts the typical size, magnetic structure, and radial velocity of MCs at various solar distances. © 2009 ESO.Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.2009info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfhttp://hdl.handle.net/20.500.12110/paper_00046361_v498_n2_p551_DemoulinAstron. Astrophys. 2009;498(2):551-566reponame:Biblioteca Digital (UBA-FCEN)instname:Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturalesinstacron:UBA-FCENenginfo:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by/2.5/ar2025-09-29T13:42:57Zpaperaa:paper_00046361_v498_n2_p551_DemoulinInstitucionalhttps://digital.bl.fcen.uba.ar/Universidad públicaNo correspondehttps://digital.bl.fcen.uba.ar/cgi-bin/oaiserver.cgiana@bl.fcen.uba.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:18962025-09-29 13:42:59.049Biblioteca Digital (UBA-FCEN) - Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturalesfalse
dc.title.none.fl_str_mv Causes and consequences of magnetic cloud expansion
title Causes and consequences of magnetic cloud expansion
spellingShingle Causes and consequences of magnetic cloud expansion
Démoulin, P.
interplanetary medium
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Boundary pressure
Coronal mass ejection
Cylindrical flux ropes
Expansion rate
Flux ropes
Force free fields
In-situ observations
interplanetary medium
Magnetic clouds
Magnetic energies
Magnetic flux ropes
Magnetic helicity
Plasma velocity
Radial distributions
Radial expansions
Radial velocity
Self-similar
Solar eruption
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Astrophysics
Boundary layer flow
Energy conservation
Expansion
Fluid dynamics
Magnetic fields
Magnetic flux
Magnetic structure
Magnetohydrodynamics
Ordinary differential equations
Pressure gradient
Solar wind
Sun
Velocity
Velocity distribution
Solar energy
title_short Causes and consequences of magnetic cloud expansion
title_full Causes and consequences of magnetic cloud expansion
title_fullStr Causes and consequences of magnetic cloud expansion
title_full_unstemmed Causes and consequences of magnetic cloud expansion
title_sort Causes and consequences of magnetic cloud expansion
dc.creator.none.fl_str_mv Démoulin, P.
Dasso, S.
author Démoulin, P.
author_facet Démoulin, P.
Dasso, S.
author_role author
author2 Dasso, S.
author2_role author
dc.subject.none.fl_str_mv interplanetary medium
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Boundary pressure
Coronal mass ejection
Cylindrical flux ropes
Expansion rate
Flux ropes
Force free fields
In-situ observations
interplanetary medium
Magnetic clouds
Magnetic energies
Magnetic flux ropes
Magnetic helicity
Plasma velocity
Radial distributions
Radial expansions
Radial velocity
Self-similar
Solar eruption
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Astrophysics
Boundary layer flow
Energy conservation
Expansion
Fluid dynamics
Magnetic fields
Magnetic flux
Magnetic structure
Magnetohydrodynamics
Ordinary differential equations
Pressure gradient
Solar wind
Sun
Velocity
Velocity distribution
Solar energy
topic interplanetary medium
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Boundary pressure
Coronal mass ejection
Cylindrical flux ropes
Expansion rate
Flux ropes
Force free fields
In-situ observations
interplanetary medium
Magnetic clouds
Magnetic energies
Magnetic flux ropes
Magnetic helicity
Plasma velocity
Radial distributions
Radial expansions
Radial velocity
Self-similar
Solar eruption
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Astrophysics
Boundary layer flow
Energy conservation
Expansion
Fluid dynamics
Magnetic fields
Magnetic flux
Magnetic structure
Magnetohydrodynamics
Ordinary differential equations
Pressure gradient
Solar wind
Sun
Velocity
Velocity distribution
Solar energy
dc.description.none.fl_txt_mv Context. A magnetic cloud (MC) is a magnetic flux rope in the solar wind (SW), which, at 1 AU, is observed ∼2-5 days after its expulsion from the Sun. The associated solar eruption is observed as a coronal mass ejection (CME).Aims. Both the in situ observations of plasma velocity distribution and the increase in their size with solar distance demonstrate that MCs are strongly expanding structures. The aim of this work is to find the main causes of this expansion and to derive a model to explain the plasma velocity profiles typically observed inside MCs.Methods. We model the flux rope evolution as a series of force-free field states with two extreme limits: (a) ideal magneto-hydrodynamics (MHD) and (b) minimization of the magnetic energy with conserved magnetic helicity. We consider cylindrical flux ropes to reduce the problem to the integration of ordinary differential equations. This allows us to explore a wide variety of magnetic fields at a broad range of distances to the Sun.Results. We demonstrate that the rapid decrease in the total SW pressure with solar distance is the main driver of the flux-rope radial expansion. Other effects, such as the internal over-pressure, the radial distribution, and the amount of twist within the flux rope have a much weaker influence on the expansion. We demonstrate that any force-free flux rope will have a self-similar expansion if its total boundary pressure evolves as the inverse of its length to the fourth power. With the total pressure gradient observed in the SW, the radial expansion of flux ropes is close to self-similar with a nearly linear radial velocity profile across the flux rope, as observed. Moreover, we show that the expansion rate is proportional to the radius and to the global velocity away from the Sun.Conclusions. The simple and universal law found for the radial expansion of flux ropes in the SW predicts the typical size, magnetic structure, and radial velocity of MCs at various solar distances. © 2009 ESO.
Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
description Context. A magnetic cloud (MC) is a magnetic flux rope in the solar wind (SW), which, at 1 AU, is observed ∼2-5 days after its expulsion from the Sun. The associated solar eruption is observed as a coronal mass ejection (CME).Aims. Both the in situ observations of plasma velocity distribution and the increase in their size with solar distance demonstrate that MCs are strongly expanding structures. The aim of this work is to find the main causes of this expansion and to derive a model to explain the plasma velocity profiles typically observed inside MCs.Methods. We model the flux rope evolution as a series of force-free field states with two extreme limits: (a) ideal magneto-hydrodynamics (MHD) and (b) minimization of the magnetic energy with conserved magnetic helicity. We consider cylindrical flux ropes to reduce the problem to the integration of ordinary differential equations. This allows us to explore a wide variety of magnetic fields at a broad range of distances to the Sun.Results. We demonstrate that the rapid decrease in the total SW pressure with solar distance is the main driver of the flux-rope radial expansion. Other effects, such as the internal over-pressure, the radial distribution, and the amount of twist within the flux rope have a much weaker influence on the expansion. We demonstrate that any force-free flux rope will have a self-similar expansion if its total boundary pressure evolves as the inverse of its length to the fourth power. With the total pressure gradient observed in the SW, the radial expansion of flux ropes is close to self-similar with a nearly linear radial velocity profile across the flux rope, as observed. Moreover, we show that the expansion rate is proportional to the radius and to the global velocity away from the Sun.Conclusions. The simple and universal law found for the radial expansion of flux ropes in the SW predicts the typical size, magnetic structure, and radial velocity of MCs at various solar distances. © 2009 ESO.
publishDate 2009
dc.date.none.fl_str_mv 2009
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/20.500.12110/paper_00046361_v498_n2_p551_Demoulin
url http://hdl.handle.net/20.500.12110/paper_00046361_v498_n2_p551_Demoulin
dc.language.none.fl_str_mv eng
language eng
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/2.5/ar
eu_rights_str_mv openAccess
rights_invalid_str_mv http://creativecommons.org/licenses/by/2.5/ar
dc.format.none.fl_str_mv application/pdf
dc.source.none.fl_str_mv Astron. Astrophys. 2009;498(2):551-566
reponame:Biblioteca Digital (UBA-FCEN)
instname:Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
instacron:UBA-FCEN
reponame_str Biblioteca Digital (UBA-FCEN)
collection Biblioteca Digital (UBA-FCEN)
instname_str Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
instacron_str UBA-FCEN
institution UBA-FCEN
repository.name.fl_str_mv Biblioteca Digital (UBA-FCEN) - Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
repository.mail.fl_str_mv ana@bl.fcen.uba.ar
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score 13.070432