The Solar Dynamo and Planetary Dynamo

A dynamo driven by flows of differential rotation and global convection in a rotating sphere is reviewed as a model of the solar and planetary dynamos. The flows can amplify a magnetic field from an infinitesimal level and thus can generate a magnetic field. The flows periodically reverse the polarity of the field and force the generated field system to propagate along iso-rotation surface in the sphere in form of a wave during the generation process. The flows can also generate the field without reversing its polarity depending on the structure of the flows of the differential rotation. The basic dynamo process with and without polarity reversals is explained in terms of topological deformation of field lines by the flows in the sphere. The oscillatory and steady dynamos are interpreted as corresponding to the solar and planetary dynamos respectively.