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Large scale dynamos with ambipolar diffusion nonlinearity

Axel Brandenburg·Kandaswamy Subramanian
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Abstract

It is shown that ambipolar diffusion as a toy nonlinearity leads to very similar behaviour of large scale turbulent dynamos as full MHD. This is demonstrated using both direct simulations in a periodic box and a closure model for the magnetic correlation functions applicable to infinite space. Large scale fields develop via a nonlocal inverse cascade as described by the alpha-effect. However, because magnetic helicity can only change on a resistive timescale, the time it takes to organize the field into large scales increases with magnetic Reynolds number.

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Axel Brandenburg, Kandaswamy Subramanian. 2000-07-28. Large scale dynamos with ambipolar diffusion nonlinearity. https://arxiv.org/abs/astro-ph/0007450

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