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An azimuthal dynamo wave in spherical shell convection
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
2014 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 780, no 2, L22- p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2014. Vol. 780, no 2, L22- p.
Keyword [en]
convection, dynamo, magnetohydrodynamics (MHD), stars: activity, stars: late-type, turbulence
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-140368DOI: 10.1088/2041-8205/780/2/L22ISI: 000328993700008ScopusID: 2-s2.0-84891597048OAI: diva2:690470
Swedish Research Council, 621-2011-5076 2012-5797EU, European Research Council, 227952

QC 20140123

Available from: 2014-01-23 Created: 2014-01-23 Last updated: 2014-01-23Bibliographically approved

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Käpylä, Petri J.Brandenburg, Axel
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