Effects of small-scale dynamo and compressibility on the Λ effect

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@article{fb79355d1b2746ee995a120ffd9344cb,
title = "Effects of small-scale dynamo and compressibility on the Λ effect",
abstract = "The Λ effect describes a rotation-induced nondiffusive contribution to the Reynolds stress. It is commonly held responsible for maintaining the observed differential rotation of the Sun and other late-type stars. Here, the sensitivity of the Λ effect to small-scale magnetic fields and compressibility is studied by means of forced turbulence simulations either with anisotropic forcing in fully periodic cubes or in density-stratified domains with isotropic forcing. Effects of small-scale magnetic fields are studied in cases where the magnetic fields are self-consistently generated by a small-scale dynamo. The results show that small-scale magnetic fields lead to a quenching of the Λ effect which is milder than in cases where also a large-scale field is present. The effect of compressibility on the Λ effect is negligible in the range of Mach numbers from 0.015 to 0.8. Density stratification induces a marked anisotropy in the turbulence and a vertical Λ effect if the forcing scale is roughly two times larger than the density scale height.",
keywords = "stars: rotation – sun: rotation – turbulence",
author = "K{\"a}pyl{\"a}, {Petri J.}",
year = "2019",
month = "1",
day = "1",
doi = "10.1002/asna.201913632",
language = "English",
journal = "Astronomische Nachrichten",
issn = "0004-6337",
publisher = "WILEY-VCH VERLAG",

}

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TY - JOUR

T1 - Effects of small-scale dynamo and compressibility on the Λ effect

AU - Käpylä, Petri J.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - The Λ effect describes a rotation-induced nondiffusive contribution to the Reynolds stress. It is commonly held responsible for maintaining the observed differential rotation of the Sun and other late-type stars. Here, the sensitivity of the Λ effect to small-scale magnetic fields and compressibility is studied by means of forced turbulence simulations either with anisotropic forcing in fully periodic cubes or in density-stratified domains with isotropic forcing. Effects of small-scale magnetic fields are studied in cases where the magnetic fields are self-consistently generated by a small-scale dynamo. The results show that small-scale magnetic fields lead to a quenching of the Λ effect which is milder than in cases where also a large-scale field is present. The effect of compressibility on the Λ effect is negligible in the range of Mach numbers from 0.015 to 0.8. Density stratification induces a marked anisotropy in the turbulence and a vertical Λ effect if the forcing scale is roughly two times larger than the density scale height.

AB - The Λ effect describes a rotation-induced nondiffusive contribution to the Reynolds stress. It is commonly held responsible for maintaining the observed differential rotation of the Sun and other late-type stars. Here, the sensitivity of the Λ effect to small-scale magnetic fields and compressibility is studied by means of forced turbulence simulations either with anisotropic forcing in fully periodic cubes or in density-stratified domains with isotropic forcing. Effects of small-scale magnetic fields are studied in cases where the magnetic fields are self-consistently generated by a small-scale dynamo. The results show that small-scale magnetic fields lead to a quenching of the Λ effect which is milder than in cases where also a large-scale field is present. The effect of compressibility on the Λ effect is negligible in the range of Mach numbers from 0.015 to 0.8. Density stratification induces a marked anisotropy in the turbulence and a vertical Λ effect if the forcing scale is roughly two times larger than the density scale height.

KW - stars: rotation – sun: rotation – turbulence

UR - http://www.scopus.com/inward/record.url?scp=85074767558&partnerID=8YFLogxK

U2 - 10.1002/asna.201913632

DO - 10.1002/asna.201913632

M3 - Article

JO - Astronomische Nachrichten

JF - Astronomische Nachrichten

SN - 0004-6337

ER -

ID: 38828169