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Titolo:
Astrophysical significance of the anisotropic kinetic alpha effect
Autore:
Brandenburg, A; von Rekowski, B;
Indirizzi:
Univ Newcastle Upon Tyne, Dept Math, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England Univ Newcastle Upon Tyne Newcastle Upon Tyne Tyne & Wear England NE1 7RU NORDITA, DK-2100 Copenhagen O, Denmark NORDITA Copenhagen Denmark ONORDITA, DK-2100 Copenhagen O, Denmark
Titolo Testata:
ASTRONOMY & ASTROPHYSICS
fascicolo: 3, volume: 379, anno: 2001,
pagine: 1153 - 1160
SICI:
1432-0746(200112)379:3<1153:ASOTAK>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
LACKING PARITY-INVARIANCE; LARGE-SCALE STRUCTURES; NON-LINEAR EVOLUTION; TURBULENT CONVECTION; INVERSE CASCADES; MAGNETIC-FIELDS; FLOW; SIMULATION; GENERATION; ROTATION;
Keywords:
MHD; turbulence;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: Brandenburg, A Univ Newcastle Upon Tyne, Dept Math, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England Univ Newcastle Upon Tyne Newcastle Upon Tyne Tyne & Wear England NE1 7RU
Citazione:
A. Brandenburg e B. von Rekowski, "Astrophysical significance of the anisotropic kinetic alpha effect", ASTRON ASTR, 379(3), 2001, pp. 1153-1160

Abstract

The generation of large scale flows by the anisotropic kinetic alpha (AKA)effect is investigated in simulations with a suitable time-dependent space- and time-periodic anisotropic forcing lacking parity invariance. The forcing pattern moves relative to the fluid, which leads to a breaking of the Galilean invariance as required for the AKA effect to exist. The AKA effect is found to produce a clear large scale ow pattern when the Reynolds number, R, is small as only a few modes are excited in linear theory. In this case the non-vanishing components of the AKA tensor are dynamically independent of the Reynolds number. For larger values of R, many more modes are excited and the components of the AKA tensor are found to decrease rapidly with increasing value of R. However, once there is a magnetic field (imposed andof sufficient strength, or dynamo-generated and saturated) the field begins to suppress the AKA effect, regardless of the value of R. It is argued that the AKA effect is unlikely to be astrophysically significant unless the magnetic field is weak and R is small.

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Documento generato il 12/08/20 alle ore 21:04:30