The magnetic helicity budget of a CME-prolific active region

Coronal mass ejections (CMEs) are thought to be the way by which the solar corona expels accumulated magnetic helicity which is injected into the corona via several methods. DeVore (2000) suggests that a significant quantity is injected by the action of differential rotation, however Démoulin et al....

Descripción completa

Guardado en:
Detalles Bibliográficos
Publicado: 2002
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00380938_v208_n1_p43_Green
http://hdl.handle.net/20.500.12110/paper_00380938_v208_n1_p43_Green
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_00380938_v208_n1_p43_Green
record_format dspace
spelling paper:paper_00380938_v208_n1_p43_Green2023-06-08T15:02:37Z The magnetic helicity budget of a CME-prolific active region Coronal mass ejections (CMEs) are thought to be the way by which the solar corona expels accumulated magnetic helicity which is injected into the corona via several methods. DeVore (2000) suggests that a significant quantity is injected by the action of differential rotation, however Démoulin et al. (2002b), based on the study of a simple bipolar active region, show that this may not be the case. This paper studies the magnetic helicity evolution in an active region (NOAA 8100) in which the main photospheric polarities rotate around each other during five Carrington rotations. As a result of this changing orientation of the bipole, the helicity injection by differential rotation is not a monotonic function of time. Instead, it experiences a maximum and even a change of sign. In this particular active region, both differential rotation and localized shearing motions are actually depleting the coronal helicity instead of building it. During this period of five solar rotations, a high number of CMEs (35 observed, 65 estimated) erupted from the active region and the helicity carried away has been calculated, assuming that each can be modeled by a twisted flux rope. It is found that the helicity injected by differential rotation (≈ -7 × 1042 Mx2) into the active region cannot provide the amount of helicity ejected via CMEs, which is a factor 5 to 46 larger and of the opposite sign. Instead, it is proposed that the ejected helicity is provided by the twist in the sub-photospheric part of the magnetic flux tube forming the active region. 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00380938_v208_n1_p43_Green http://hdl.handle.net/20.500.12110/paper_00380938_v208_n1_p43_Green
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description Coronal mass ejections (CMEs) are thought to be the way by which the solar corona expels accumulated magnetic helicity which is injected into the corona via several methods. DeVore (2000) suggests that a significant quantity is injected by the action of differential rotation, however Démoulin et al. (2002b), based on the study of a simple bipolar active region, show that this may not be the case. This paper studies the magnetic helicity evolution in an active region (NOAA 8100) in which the main photospheric polarities rotate around each other during five Carrington rotations. As a result of this changing orientation of the bipole, the helicity injection by differential rotation is not a monotonic function of time. Instead, it experiences a maximum and even a change of sign. In this particular active region, both differential rotation and localized shearing motions are actually depleting the coronal helicity instead of building it. During this period of five solar rotations, a high number of CMEs (35 observed, 65 estimated) erupted from the active region and the helicity carried away has been calculated, assuming that each can be modeled by a twisted flux rope. It is found that the helicity injected by differential rotation (≈ -7 × 1042 Mx2) into the active region cannot provide the amount of helicity ejected via CMEs, which is a factor 5 to 46 larger and of the opposite sign. Instead, it is proposed that the ejected helicity is provided by the twist in the sub-photospheric part of the magnetic flux tube forming the active region.
title The magnetic helicity budget of a CME-prolific active region
spellingShingle The magnetic helicity budget of a CME-prolific active region
title_short The magnetic helicity budget of a CME-prolific active region
title_full The magnetic helicity budget of a CME-prolific active region
title_fullStr The magnetic helicity budget of a CME-prolific active region
title_full_unstemmed The magnetic helicity budget of a CME-prolific active region
title_sort magnetic helicity budget of a cme-prolific active region
publishDate 2002
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00380938_v208_n1_p43_Green
http://hdl.handle.net/20.500.12110/paper_00380938_v208_n1_p43_Green
_version_ 1768543221011447808

Ejemplares similares