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Nordita Astrophysics seminars

Intense bipolar structures from stratified helical dynamos

by Dhrubaditya Mitra

122:026 ()


We perform direct numerical simulations of the equations of magnetohydrodynamics with external random forcing and in the presence of gravity. The domain is a divided in two parts, in the bottom layer the forcing is helical whereas in the top layer the helicity of the forcing is zero with a smooth transition in the middle. At early times, a large-scale helical dynamo develops in the bottom layer. At late times the dynamo saturates, but the vertical magnetic flux continues to develop and rises to form dynamic bipolar structures at the top, which later dis- appear and reappear again. Their field strength can exceed three times the equipartition value of the turbulence. This is the first example of self-consistent generation of bipolar magnetic structures from a dynamo simulation.