Transient negative turbulent diffusivity induced by fluctuations of the Lorentz force
Prof Krzysztof Mizerski (Institute of Geophysics Polish Academy of Sciences)
Thursday 17th February, 2022 14:00-15:00 Room 110/ZOOM (ID: 981 7560 8906)
Abstract
The turbulent hydro-magnetic dynamo is a process of magnetic field amplification by a chaotic flow of an electrically conducting fluid, responsible for generation of the magnetic fields of planets and stars. Here we demonstrate a curious effect of the Lorentz force, which can act to intensify the magnetic fields, counter intuitively in light of the Lenz law according to which the Lorentz force acts to retard motions and saturate the dynamo-induced magnetic field. However, the net effect of its small-scale fluctuations in a turbulent flow is far from obvious and it is shown that it can lead to temporary amplification rather than saturation of the magnetic energy through creation of transient negative turbulent diffusivity.
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