Catastrophic Catastrophic - - quenching quenching alleviated by alleviated by helicity flux and helicity flux and shear shear Axel Brandenburg ( Axel Brandenburg ( Nordita, Nordita, Copenhagen Copenhagen ) ) Christer Sandin ( Christer Sandin ( Uppsala Uppsala ) ) Collaborators: Eric G Blackman ( Collaborators: Eric G Blackman ( Rochester Rochester ), ), Kandu Subramanian ( Kandu Subramanian ( IUCAA, Pune IUCAA, Pune ), Petri K ), Petri K äpylä äpylä ( ( Oulu Oulu ) )
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Catastrophic a -quenching alleviated by helicity flux and shear
Catastrophic a -quenching alleviated by helicity flux and shear. Axel Brandenburg ( Nordita, Copenhagen ) Christer Sandin ( Uppsala ) Collaborators: Eric G Blackman ( Rochester ), Kandu Subramanian ( IUCAA, Pune ), Petri K äpylä ( Oulu ). Theoretical framework: aW model. Cycle frequency. - PowerPoint PPT Presentation
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Catastrophic Catastrophic -quenching -quenching alleviated by helicity flux alleviated by helicity flux
and shearand shear
Axel Brandenburg (Axel Brandenburg (Nordita, CopenhagenNordita, Copenhagen))
Christer Sandin (Christer Sandin (UppsalaUppsala))Collaborators: Eric G Blackman (Collaborators: Eric G Blackman (RochesterRochester),),
Kandu Subramanian (Kandu Subramanian (IUCAA, PuneIUCAA, Pune), Petri K), Petri Käpylä (äpylä (OuluOulu))
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Theoretical framework: Theoretical framework: model model
•Migration direction
JJBBUB
tt2/1
U k
U
•Cycle frequency
Migration awayfrom equator
031 / bjuω
Penalty to pay for Penalty to pay for
(in practice anisotropic)
meridional circulation
Pouquet, Frisch, Leorat (1976)
0,,31 / pjkpjkijkip bbuu
Brandenburg: helicity flux and shear 3
Internal twist as feedback on Internal twist as feedback on (Pouquet, Frisch, Leorat 1976)(Pouquet, Frisch, Leorat 1976)
031 / bjuω
How can this be used in practice?
Need a closure for <j.b>
Brandenburg: helicity flux and shear 4
Example of bi-helical structureExample of bi-helical structure
Yousef & Brandenburg (2003, A&A)
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Tilt Tilt pol. field regeneration pol. field regeneration