Evolution of a magnetic blob in a helical flowстатья
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Дата последнего поиска статьи во внешних источниках: 27 мая 2015 г.
Аннотация:A bounded magnetic packet embedded in a helical flow of conducting fluid which can act as a dynamo is studied. It is shown that the magnetized region moves along the jet with a velocity which coincides with the matter velocity at the radius, where the eigenfunction with the maximal growth rate concentrates. The screw dynamo is a slow one and the effective frozenness of the field is unexpected. The growth rate of the magnetic field within the packet can be identified with this maximal possible growth rate. The packet also spreads along the jet axis due to dispersion and magnetic diffusion, leading to growth of the longitudinal width at the velocity which is constant in time and proportional to the square root of the product of magnetic diffusivity and growth rate. Nevertheless, the magnetic packet becomes more concentrated with time due to the exponential growth of the field. The condition under which the passing magnetic packet can magnetize the whole jet is derived.