ON THE GENERATION OF EQUIPARTITION-STRENGTH MAGNETIC-FIELDS BY TURBULENT HYDROMAGNETIC DYNAMOS

The generation of a mean magnetic field by the action of small-scale t urbulent fluid motions, the alpha-effect, is a fundamental ingredient of mean-held dynamo theory. However, recent mathematical models and nu merical experiments are providing increasingly strong support to the n otion that at high magnetic Reynolds numbers, the alpha-effect is stro ngly impeded long before the mean magnetic held has reached energy equ ipartition with the driving fluid motions. Taken at face value, this r aises serious doubt as to whether the solar magnetic field is produced by a turbulent hydromagnetic dynamo after all, since it is an observe d fact that the Sun does possess a structured, large-scale mean magnet ic field of strength comparable to equipartition. In this Letter we de monstrate that the class of mean-field turbulent hydromagnetic models known as interface dynamos can produce equipartition-strength mean mag netic fields even in the presence of strong alpha-quenching.