  We report the finding 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. Observational results both from
photometry and Doppler imaging have revealed persistent drifts of spots for
several rapidly rotating stars, but, although an azimuthal dynamo wave has been
proposed as a possible mechanism responsible for this behavior, it has been
judged as unlikely, as practical evidence for such waves from DNS has been
lacking. The large-scale magnetic field in our DNS, which is due to
self-consistent dynamo action, is dominated by 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 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.
