Helical coronal ejections and their role in the solar cycle

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dc.creatorBrandenburg, Axel
dc.creatorSandin, Christer
dc.creatorKäpylä, Petri J.
dc.date2004-07-29
dc.date.accessioned2026-07-07T02:14:09Z
dc.date.available2026-07-07T02:14:09Z
dc.descriptionThe standard theory of the solar cycle in terms of an alpha-Omega dynamo hinges on a proper understanding of the nonlinear alpha effect. Boundary conditions play a surprisingly important role in determining the magnitude of alpha. For closed boundaries, the total magnetic helicity is conserved, and since the alpha effect produces magnetic helicity of one sign in the large scale field, it must simultaneously produce magnetic helicity of the opposite sign. It is this secondary magnetic helicity that suppresses the dynamo in a potentially catastrophic fashion. Open boundaries allow magnetic helicity to be lost. Simulations are presented that allow an estimate of alpha in the presence of open or closed boundaries, either with or without solar-like differential rotation. In all cases the sign of the magnetic helicity agrees with that observed at the solar surface (negative in the north, positive in the south), where significant amounts of magnetic helicity can be ejected via coronal mass ejections. It is shown that open boundaries tend to alleviate catastrophic alpha quenching. The importance of looking at current helicity instead of magnetic helicity is emphasized and the conceptual advantages are discussed.
dc.description8 pages, 7 figs, IAU Symp. 223, In: Multi-Wavelength Investigations of Solar Activity. Eds: A.V. Stepanov, E.E. Benevolenskaya & A.G. Kosovichev
dc.identifierhttps://arxiv.org/abs/astro-ph/0407598
dc.identifierhttp://arxiv.org/abs/astro-ph/0407598
dc.identifierIAU Symp. 223 (2004) 57-64
dc.identifierdoi:10.1017/S1743921304005101
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/8007
dc.subjectAstrophysics
dc.titleHelical coronal ejections and their role in the solar cycle
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