Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections

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In situ data provide only a one-dimensional sample of the plasma velocity along the spacecraft trajectory crossing an interplanetary coronal mass ejection (ICME). Then, to understand the dynamics of ICMEs it is necessary to consider some models to describe it. We derive a series of equations in a hi...

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Autores principales: Nakwacki, Maria Soledad, Dasso, Sergio Ricardo, Mandrini, Cristina Hemilse
Publicado: 2008
Materias:
Coronal mass ejections, interplanetary
Magnetic fields, interplanetary
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00380938_v250_n2_p347_Demoulin
http://hdl.handle.net/20.500.12110/paper_00380938_v250_n2_p347_Demoulin
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_00380938_v250_n2_p347_Demoulin2023-06-08T15:02:42Z Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections Nakwacki, Maria Soledad Dasso, Sergio Ricardo Mandrini, Cristina Hemilse Coronal mass ejections, interplanetary Magnetic fields, interplanetary In situ data provide only a one-dimensional sample of the plasma velocity along the spacecraft trajectory crossing an interplanetary coronal mass ejection (ICME). Then, to understand the dynamics of ICMEs it is necessary to consider some models to describe it. We derive a series of equations in a hierarchical order, from more general to more specific cases, to provide a general theoretical basis for the interpretation of in situ observations, extending and generalizing previous studies. The main hypothesis is a self-similar expansion, but with the freedom of possible different expansion rates in three orthogonal directions. The most detailed application of the equations is though for a subset of ICMEs, magnetic clouds (MCs), where a magnetic flux rope can be identified. The main conclusions are the following ones. First, we obtain theoretical expressions showing that the observed velocity gradient within an ICME is not a direct characteristic of its expansion, but that it depends also on other physical quantities such as its global velocity and acceleration. The derived equations quantify these dependencies for the three components of the velocity. Second, using three different types of data we show that the global acceleration of ICMEs has, at most, a small contribution to the in situ measurements of the velocity. This eliminates practically one contribution to the observed velocity gradient within ICMEs. Third, we provide a method to quantify the expansion rate from velocity data. We apply it to a set of 26 MCs observed by Wind or ACE spacecrafts. They are typical MCs, and their main physical parameters cover the typical range observed in MCs in previous statistical studies. Though the velocity difference between their front and back includes a broad range of values, we find a narrow range for the determined dimensionless expansion rate. This implies that MCs are expanding at a comparable rate, independently of their size or field strength, despite very different magnitudes in their velocity profiles. Furthermore, the equations derived provide a base to further analyze the dynamics of MCs/ICMEs. © 2008 Springer Science+Business Media B.V. Fil:Nakwacki, M.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Mandrini, C.H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2008 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00380938_v250_n2_p347_Demoulin http://hdl.handle.net/20.500.12110/paper_00380938_v250_n2_p347_Demoulin
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Coronal mass ejections, interplanetary
Magnetic fields, interplanetary
spellingShingle Coronal mass ejections, interplanetary
Magnetic fields, interplanetary
Nakwacki, Maria Soledad
Dasso, Sergio Ricardo
Mandrini, Cristina Hemilse
Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
topic_facet Coronal mass ejections, interplanetary
Magnetic fields, interplanetary
description In situ data provide only a one-dimensional sample of the plasma velocity along the spacecraft trajectory crossing an interplanetary coronal mass ejection (ICME). Then, to understand the dynamics of ICMEs it is necessary to consider some models to describe it. We derive a series of equations in a hierarchical order, from more general to more specific cases, to provide a general theoretical basis for the interpretation of in situ observations, extending and generalizing previous studies. The main hypothesis is a self-similar expansion, but with the freedom of possible different expansion rates in three orthogonal directions. The most detailed application of the equations is though for a subset of ICMEs, magnetic clouds (MCs), where a magnetic flux rope can be identified. The main conclusions are the following ones. First, we obtain theoretical expressions showing that the observed velocity gradient within an ICME is not a direct characteristic of its expansion, but that it depends also on other physical quantities such as its global velocity and acceleration. The derived equations quantify these dependencies for the three components of the velocity. Second, using three different types of data we show that the global acceleration of ICMEs has, at most, a small contribution to the in situ measurements of the velocity. This eliminates practically one contribution to the observed velocity gradient within ICMEs. Third, we provide a method to quantify the expansion rate from velocity data. We apply it to a set of 26 MCs observed by Wind or ACE spacecrafts. They are typical MCs, and their main physical parameters cover the typical range observed in MCs in previous statistical studies. Though the velocity difference between their front and back includes a broad range of values, we find a narrow range for the determined dimensionless expansion rate. This implies that MCs are expanding at a comparable rate, independently of their size or field strength, despite very different magnitudes in their velocity profiles. Furthermore, the equations derived provide a base to further analyze the dynamics of MCs/ICMEs. © 2008 Springer Science+Business Media B.V.
author Nakwacki, Maria Soledad
Dasso, Sergio Ricardo
Mandrini, Cristina Hemilse
author_facet Nakwacki, Maria Soledad
Dasso, Sergio Ricardo
Mandrini, Cristina Hemilse
author_sort Nakwacki, Maria Soledad
title Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
title_short Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
title_full Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
title_fullStr Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
title_full_unstemmed Expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
title_sort expected in situ velocities from a hierarchical model for expanding interplanetary coronal mass ejections
publishDate 2008
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00380938_v250_n2_p347_Demoulin
http://hdl.handle.net/20.500.12110/paper_00380938_v250_n2_p347_Demoulin
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AT dassosergioricardo expectedinsituvelocitiesfromahierarchicalmodelforexpandinginterplanetarycoronalmassejections
AT mandrinicristinahemilse expectedinsituvelocitiesfromahierarchicalmodelforexpandinginterplanetarycoronalmassejections
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