Evolution of magnetic clouds in the inner heliosphere

Magnetic clouds (MCs) are objects in expansion during their travel through the heliosphere. In situ observations indicate that their front travel faster than their back, showing a clear empirical signature of expansion. With the aim of quantifying the expansion rate of MCs in the inner heliosphere (...

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Autores principales:	Gulisano, Adriana María, Dasso, Sergio Ricardo, Ruiz, Maria Emilia
Publicado:	2010
Materias:	Interplanetary physics Magnetic clouds Solar Wind
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0094243X_v1216_n_p391_Gulisano http://hdl.handle.net/20.500.12110/paper_0094243X_v1216_n_p391_Gulisano
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_0094243X_v1216_n_p391_Gulisano
record_format	dspace
spelling	paper:paper_0094243X_v1216_n_p391_Gulisano2025-07-30T17:48:50Z Evolution of magnetic clouds in the inner heliosphere Gulisano, Adriana María Dasso, Sergio Ricardo Ruiz, Maria Emilia Interplanetary physics Magnetic clouds Solar Wind Magnetic clouds (MCs) are objects in expansion during their travel through the heliosphere. In situ observations indicate that their front travel faster than their back, showing a clear empirical signature of expansion. With the aim of quantifying the expansion rate of MCs in the inner heliosphere (0.3 to 1 AU), we present here a statistical study of events observed by the spacecraft Helios 1 and 2, during their complete period of operations. From the analysis of the profile of the MC magnetic field components in its local frame, which is obtained from a rotation of the observed magnetic field vectors to a system of reference oriented as the main axis of the flux rope, we revise a list of events identified in previous works and redefine improved MC boundaries/orientation for each event. We then split the sample into two subsets according to the characteristics of their velocity profiles, (a) those MCs with a significantly perturbed velocity profile due to the interaction with their surrounding solar wind (i.e. overtaken by streams) and (b) those that are not perturbed. We compute the dimensionless local expansion rate (ζ) for MCs defined by several works [e.g. Démoulin et al., Solar Phys, 250, 347-374 (2008)]. We find significantly different distribution of values for ζ when perturbed and non perturbed events are considered. Non perturbed MCs expand at rates ζ consistent with the expected value from the global pressure decay in the surrounding solar wind for increasing helio-distances, while perturbed ones may present strong departures from that global rule. We interpret these departures of ζ for perturbed MCs as a consequence of interaction with streams on their expansion. © 2010 American Institute of Physics. Fil:Gulisano, A.M. 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:Ruiz, M.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2010 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0094243X_v1216_n_p391_Gulisano http://hdl.handle.net/20.500.12110/paper_0094243X_v1216_n_p391_Gulisano
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Interplanetary physics Magnetic clouds Solar Wind
spellingShingle	Interplanetary physics Magnetic clouds Solar Wind Gulisano, Adriana María Dasso, Sergio Ricardo Ruiz, Maria Emilia Evolution of magnetic clouds in the inner heliosphere
topic_facet	Interplanetary physics Magnetic clouds Solar Wind
description	Magnetic clouds (MCs) are objects in expansion during their travel through the heliosphere. In situ observations indicate that their front travel faster than their back, showing a clear empirical signature of expansion. With the aim of quantifying the expansion rate of MCs in the inner heliosphere (0.3 to 1 AU), we present here a statistical study of events observed by the spacecraft Helios 1 and 2, during their complete period of operations. From the analysis of the profile of the MC magnetic field components in its local frame, which is obtained from a rotation of the observed magnetic field vectors to a system of reference oriented as the main axis of the flux rope, we revise a list of events identified in previous works and redefine improved MC boundaries/orientation for each event. We then split the sample into two subsets according to the characteristics of their velocity profiles, (a) those MCs with a significantly perturbed velocity profile due to the interaction with their surrounding solar wind (i.e. overtaken by streams) and (b) those that are not perturbed. We compute the dimensionless local expansion rate (ζ) for MCs defined by several works [e.g. Démoulin et al., Solar Phys, 250, 347-374 (2008)]. We find significantly different distribution of values for ζ when perturbed and non perturbed events are considered. Non perturbed MCs expand at rates ζ consistent with the expected value from the global pressure decay in the surrounding solar wind for increasing helio-distances, while perturbed ones may present strong departures from that global rule. We interpret these departures of ζ for perturbed MCs as a consequence of interaction with streams on their expansion. © 2010 American Institute of Physics.
author	Gulisano, Adriana María Dasso, Sergio Ricardo Ruiz, Maria Emilia
author_facet	Gulisano, Adriana María Dasso, Sergio Ricardo Ruiz, Maria Emilia
author_sort	Gulisano, Adriana María
title	Evolution of magnetic clouds in the inner heliosphere
title_short	Evolution of magnetic clouds in the inner heliosphere
title_full	Evolution of magnetic clouds in the inner heliosphere
title_fullStr	Evolution of magnetic clouds in the inner heliosphere
title_full_unstemmed	Evolution of magnetic clouds in the inner heliosphere
title_sort	evolution of magnetic clouds in the inner heliosphere
publishDate	2010
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0094243X_v1216_n_p391_Gulisano http://hdl.handle.net/20.500.12110/paper_0094243X_v1216_n_p391_Gulisano
work_keys_str_mv	AT gulisanoadrianamaria evolutionofmagneticcloudsintheinnerheliosphere AT dassosergioricardo evolutionofmagneticcloudsintheinnerheliosphere AT ruizmariaemilia evolutionofmagneticcloudsintheinnerheliosphere
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Evolution of magnetic clouds in the inner heliosphere

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