An Azimuthal dynamo wave in spherical shell convection

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2014
Major/Subject
Mcode
Degree programme
Language
en
Pages
6
Series
ASTROPHYSICAL JOURNAL LETTERS, Volume 780, issue 2
Abstract
We report the discovery of an azimuthal dynamo wave of a low-order (m = 1) mode in direct numerical simulations (DNS) of turbulent convection in spherical shells. Such waves are predicted by mean-field dynamo theory and have been obtained previously in mean-field models. An azimuthal dynamo wave has been proposed as a possible explanation for the persistent drifts of spots observed on several rapidly rotating stars, as revealed through photometry and Doppler imaging. However, this has been judged unlikely because evidence for such waves from DNS has been lacking. Here we present DNS of large-scale magnetic fields showing a retrograde m = 1 mode. Its pattern speed is nearly independent of latitude and does not reflect the speed of the differential rotation at any depth. The extrema of magnetic m = 1 structures coincide reasonably well with the maxima of m = 2 structures of the temperature. These results provide direct support for the observed drifts being due to an azimuthal dynamo wave.
Description
VK: resolve; Karhunen, J.; ReSoLVE
Keywords
Astrophysics - Solar and Stellar Astrophysics
Other note
Citation
Cole , E , Käpylä , P J , Mantere , M J & Brandenburg , A 2014 , ' An Azimuthal dynamo wave in spherical shell convection ' , Astrophysical Journal Letters , vol. 780 , no. 2 , L22 . https://doi.org/10.1088/2041-8205/780/2/L22