Magnetic cloud models with bent and oblate cross-section boundaries

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Context. Magnetic clouds (MCs) are formed by magnetic flux ropes that are ejected from the Sun as coronal mass ejections. These structures generally have low plasma beta and travel through the interplanetary medium interacting with the surrounding solar wind. Thus, the dynamical evolution of the int...

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Autores principales:	Démoulin, P., Dasso, S.
Formato:	Artículo publishedVersion
Lenguaje:	Inglés
Publicado:	2009
Materias:	Interplanetary medium Sun: coronal mass ejections (CMEs) Sun: magnetic fields Arbitrary cross section Boundary shapes Coronal mass ejection Cylindrical models Cylindrical symmetry Dynamical evolution Field strengths Flux ropes Global quantities Helicities In-situ data In-situ observations Internal structure Large anisotropy Magnetic clouds Magnetic configuration Magnetic field orientations Magnetic field profile Magnetic field strengths Magnetic flux ropes Magnetic models Minimum variance Solar source Sun: coronal mass ejection Sun: magnetic field Theoretical models Time evolutions Total pressure Aspect ratio Astrophysics Boundary layer flow Interplanetary spacecraft Magnetic fields Magnetic flux Magnetic structure Planetary surface analysis Solar wind Sun Semiconductor counters
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_00046361_v507_n2_p969_Demoulin
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paperaa:paper_00046361_v507_n2_p969_Demoulin
record_format	dspace
spelling	paperaa:paper_00046361_v507_n2_p969_Demoulin2023-06-12T16:40:50Z Magnetic cloud models with bent and oblate cross-section boundaries Astron. Astrophys. 2009;507(2):969-980 Démoulin, P. Dasso, S. Interplanetary medium Sun: coronal mass ejections (CMEs) Sun: magnetic fields Arbitrary cross section Boundary shapes Coronal mass ejection Cylindrical models Cylindrical symmetry Dynamical evolution Field strengths Flux ropes Global quantities Helicities In-situ data In-situ observations Internal structure Interplanetary medium Large anisotropy Magnetic clouds Magnetic configuration Magnetic field orientations Magnetic field profile Magnetic field strengths Magnetic flux ropes Magnetic models Minimum variance Solar source Sun: coronal mass ejection Sun: magnetic field Theoretical models Time evolutions Total pressure Aspect ratio Astrophysics Boundary layer flow Interplanetary spacecraft Magnetic fields Magnetic flux Magnetic structure Planetary surface analysis Solar wind Sun Semiconductor counters Context. Magnetic clouds (MCs) are formed by magnetic flux ropes that are ejected from the Sun as coronal mass ejections. These structures generally have low plasma beta and travel through the interplanetary medium interacting with the surrounding solar wind. Thus, the dynamical evolution of the internal magnetic structure of a MC is a consequence of both the conditions of its environment and of its own dynamical laws, which are mainly dominated by magnetic forces.Aims. With in-situ observations the magnetic field is only measured along the trajectory of the spacecraft across the MC. Therefore, a magnetic model is needed to reconstruct the magnetic configuration of the encountered MC. The main aim of the present work is to extend the widely used cylindrical model to arbitrary cross-section shapes.Methods. The flux rope boundary is parametrized to account for a broad range of shapes. Then, the internal structure of the flux rope is computed by expressing the magnetic field as a series of modes of a linear force-free field.Results. We analyze the magnetic field profile along straight cuts through the flux rope, in order to simulate the spacecraft crossing through a MC. We find that the magnetic field orientation is only weakly affected by the shape of the MC boundary. Therefore, the MC axis can approximately be found by the typical methods previously used (e.g., minimum variance). The boundary shape affects the magnetic field strength most. The measurement of how much the field strength peaks along the crossing provides an estimation of the aspect ratio of the flux-rope cross-section. The asymmetry of the field strength between the front and the back of the MC, after correcting for the time evolution (i.e., its aging during the observation of the MC), provides an estimation of the cross-section global bending. A flat or/and bent cross-section requires a large anisotropy of the total pressure imposed at the MC boundary by the surrounding medium.Conclusions. The new theoretical model developed here relaxes the cylindrical symmetry hypothesis. It is designed to estimate the cross-section shape of the flux rope using the in-situ data of one spacecraft. This allows a more accurate determination of the global quantities, such as magnetic fluxes and helicity. These quantities are especially important for both linking an observed MC to its solar source and for understanding the corresponding evolution. © 2009 ESO. Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2009 info:eu-repo/semantics/article info:ar-repo/semantics/artículo info:eu-repo/semantics/publishedVersion application/pdf eng info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00046361_v507_n2_p969_Demoulin
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language	Inglés
orig_language_str_mv	eng
topic	Interplanetary medium Sun: coronal mass ejections (CMEs) Sun: magnetic fields Arbitrary cross section Boundary shapes Coronal mass ejection Cylindrical models Cylindrical symmetry Dynamical evolution Field strengths Flux ropes Global quantities Helicities In-situ data In-situ observations Internal structure Interplanetary medium Large anisotropy Magnetic clouds Magnetic configuration Magnetic field orientations Magnetic field profile Magnetic field strengths Magnetic flux ropes Magnetic models Minimum variance Solar source Sun: coronal mass ejection Sun: magnetic field Theoretical models Time evolutions Total pressure Aspect ratio Astrophysics Boundary layer flow Interplanetary spacecraft Magnetic fields Magnetic flux Magnetic structure Planetary surface analysis Solar wind Sun Semiconductor counters
spellingShingle	Interplanetary medium Sun: coronal mass ejections (CMEs) Sun: magnetic fields Arbitrary cross section Boundary shapes Coronal mass ejection Cylindrical models Cylindrical symmetry Dynamical evolution Field strengths Flux ropes Global quantities Helicities In-situ data In-situ observations Internal structure Interplanetary medium Large anisotropy Magnetic clouds Magnetic configuration Magnetic field orientations Magnetic field profile Magnetic field strengths Magnetic flux ropes Magnetic models Minimum variance Solar source Sun: coronal mass ejection Sun: magnetic field Theoretical models Time evolutions Total pressure Aspect ratio Astrophysics Boundary layer flow Interplanetary spacecraft Magnetic fields Magnetic flux Magnetic structure Planetary surface analysis Solar wind Sun Semiconductor counters Démoulin, P. Dasso, S. Magnetic cloud models with bent and oblate cross-section boundaries
topic_facet	Interplanetary medium Sun: coronal mass ejections (CMEs) Sun: magnetic fields Arbitrary cross section Boundary shapes Coronal mass ejection Cylindrical models Cylindrical symmetry Dynamical evolution Field strengths Flux ropes Global quantities Helicities In-situ data In-situ observations Internal structure Interplanetary medium Large anisotropy Magnetic clouds Magnetic configuration Magnetic field orientations Magnetic field profile Magnetic field strengths Magnetic flux ropes Magnetic models Minimum variance Solar source Sun: coronal mass ejection Sun: magnetic field Theoretical models Time evolutions Total pressure Aspect ratio Astrophysics Boundary layer flow Interplanetary spacecraft Magnetic fields Magnetic flux Magnetic structure Planetary surface analysis Solar wind Sun Semiconductor counters
description	Context. Magnetic clouds (MCs) are formed by magnetic flux ropes that are ejected from the Sun as coronal mass ejections. These structures generally have low plasma beta and travel through the interplanetary medium interacting with the surrounding solar wind. Thus, the dynamical evolution of the internal magnetic structure of a MC is a consequence of both the conditions of its environment and of its own dynamical laws, which are mainly dominated by magnetic forces.Aims. With in-situ observations the magnetic field is only measured along the trajectory of the spacecraft across the MC. Therefore, a magnetic model is needed to reconstruct the magnetic configuration of the encountered MC. The main aim of the present work is to extend the widely used cylindrical model to arbitrary cross-section shapes.Methods. The flux rope boundary is parametrized to account for a broad range of shapes. Then, the internal structure of the flux rope is computed by expressing the magnetic field as a series of modes of a linear force-free field.Results. We analyze the magnetic field profile along straight cuts through the flux rope, in order to simulate the spacecraft crossing through a MC. We find that the magnetic field orientation is only weakly affected by the shape of the MC boundary. Therefore, the MC axis can approximately be found by the typical methods previously used (e.g., minimum variance). The boundary shape affects the magnetic field strength most. The measurement of how much the field strength peaks along the crossing provides an estimation of the aspect ratio of the flux-rope cross-section. The asymmetry of the field strength between the front and the back of the MC, after correcting for the time evolution (i.e., its aging during the observation of the MC), provides an estimation of the cross-section global bending. A flat or/and bent cross-section requires a large anisotropy of the total pressure imposed at the MC boundary by the surrounding medium.Conclusions. The new theoretical model developed here relaxes the cylindrical symmetry hypothesis. It is designed to estimate the cross-section shape of the flux rope using the in-situ data of one spacecraft. This allows a more accurate determination of the global quantities, such as magnetic fluxes and helicity. These quantities are especially important for both linking an observed MC to its solar source and for understanding the corresponding evolution. © 2009 ESO.
format	Artículo Artículo publishedVersion
author	Démoulin, P. Dasso, S.
author_facet	Démoulin, P. Dasso, S.
author_sort	Démoulin, P.
title	Magnetic cloud models with bent and oblate cross-section boundaries
title_short	Magnetic cloud models with bent and oblate cross-section boundaries
title_full	Magnetic cloud models with bent and oblate cross-section boundaries
title_fullStr	Magnetic cloud models with bent and oblate cross-section boundaries
title_full_unstemmed	Magnetic cloud models with bent and oblate cross-section boundaries
title_sort	magnetic cloud models with bent and oblate cross-section boundaries
publishDate	2009
url	http://hdl.handle.net/20.500.12110/paper_00046361_v507_n2_p969_Demoulin
work_keys_str_mv	AT demoulinp magneticcloudmodelswithbentandoblatecrosssectionboundaries AT dassos magneticcloudmodelswithbentandoblatecrosssectionboundaries
_version_	1769810258239160320

Magnetic cloud models with bent and oblate cross-section boundaries

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