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Title: AN AZIMUTHAL DYNAMO WAVE IN SPHERICAL SHELL CONVECTION

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.
Authors:
; ;  [1] ;  [2]
  1. Physics Department, Gustaf Hällströmin katu 2a, P.O. Box 64, FI-00014 University of Helsinki (Finland)
  2. NORDITA, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
Publication Date:
OSTI Identifier:
22364060
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 780; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; COMPUTERIZED SIMULATION; CONVECTION; DOPPLER EFFECT; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MEAN-FIELD THEORY; PHOTOMETRY; ROTATION; SPHERICAL CONFIGURATION; STARS; TURBULENCE; VELOCITY