Observations of magnetic helicity

The first observational signature of magnetic helicity in the solar atmosphere (sunspot whirls) was discovered 77 years ago. Since then, the existence of a cycle-invariant hemispheric helicity pattern has been firmly established through current helicity and morphological studies. During the last yea...

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Detalles Bibliográficos
Publicado: 2003
Materias:
Clouds
Earth atmosphere
Magnetohydrodynamics
Magnetic helicity
Space research
magnetic field
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_02731177_v32_n10_p1855_vanDrielGesztelyi
http://hdl.handle.net/20.500.12110/paper_02731177_v32_n10_p1855_vanDrielGesztelyi
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_02731177_v32_n10_p1855_vanDrielGesztelyi
record_format dspace
spelling paper:paper_02731177_v32_n10_p1855_vanDrielGesztelyi2023-06-08T15:25:31Z Observations of magnetic helicity Clouds Earth atmosphere Magnetohydrodynamics Magnetic helicity Space research magnetic field The first observational signature of magnetic helicity in the solar atmosphere (sunspot whirls) was discovered 77 years ago. Since then, the existence of a cycle-invariant hemispheric helicity pattern has been firmly established through current helicity and morphological studies. During the last years, attempts were made to estimate/measure magnetic helicity from solar and interplanetary observations. Magnetic helicity (unlike current helicity) is one of the few global quantities that is conserved even in resistive magnetohydrodynamics (MHD) on a timescale less than the global diffusion timescale, thus magnetic helicity studies make it possible to trace helicity as it emerges from the sub-photospheric layers to the corona and then is ejected via coronal mass ejections (CMEs) into the interplanetary space reaching the Earth in a magnetic cloud. We give an overview of observational studies on the relative importance of different sources of magnetic helicity, i.e. whether photospheric plasma motions (photospheric differential rotation and localized shearing motions) or the twist of the emerging flux tubes created under the photosphere (presumably by the radial shear in the differential rotation in the tachocline) is the dominant helicity source. We examine the sources of errors present in these early results and try to judge how realistic they are. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved. 2003 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_02731177_v32_n10_p1855_vanDrielGesztelyi http://hdl.handle.net/20.500.12110/paper_02731177_v32_n10_p1855_vanDrielGesztelyi
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Clouds
Earth atmosphere
Magnetohydrodynamics
Magnetic helicity
Space research
magnetic field
spellingShingle Clouds
Earth atmosphere
Magnetohydrodynamics
Magnetic helicity
Space research
magnetic field
Observations of magnetic helicity
topic_facet Clouds
Earth atmosphere
Magnetohydrodynamics
Magnetic helicity
Space research
magnetic field
description The first observational signature of magnetic helicity in the solar atmosphere (sunspot whirls) was discovered 77 years ago. Since then, the existence of a cycle-invariant hemispheric helicity pattern has been firmly established through current helicity and morphological studies. During the last years, attempts were made to estimate/measure magnetic helicity from solar and interplanetary observations. Magnetic helicity (unlike current helicity) is one of the few global quantities that is conserved even in resistive magnetohydrodynamics (MHD) on a timescale less than the global diffusion timescale, thus magnetic helicity studies make it possible to trace helicity as it emerges from the sub-photospheric layers to the corona and then is ejected via coronal mass ejections (CMEs) into the interplanetary space reaching the Earth in a magnetic cloud. We give an overview of observational studies on the relative importance of different sources of magnetic helicity, i.e. whether photospheric plasma motions (photospheric differential rotation and localized shearing motions) or the twist of the emerging flux tubes created under the photosphere (presumably by the radial shear in the differential rotation in the tachocline) is the dominant helicity source. We examine the sources of errors present in these early results and try to judge how realistic they are. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.
title Observations of magnetic helicity
title_short Observations of magnetic helicity
title_full Observations of magnetic helicity
title_fullStr Observations of magnetic helicity
title_full_unstemmed Observations of magnetic helicity
title_sort observations of magnetic helicity
publishDate 2003
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_02731177_v32_n10_p1855_vanDrielGesztelyi
http://hdl.handle.net/20.500.12110/paper_02731177_v32_n10_p1855_vanDrielGesztelyi
_version_ 1768546539848859648

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