Magnetic helicity and fluxes in an inhomogeneous alpha squared dynamo. (arXiv:1901.07552v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Brandenburg_A/0/1/0/all/0/1">A. Brandenburg</a> (Nordita)
Much work on turbulent three-dimensional dynamos has been done using triply
periodic domains, in which there are no magnetic helicity fluxes. Here we
present simulations where the turbulent intensity is still nearly homogeneous,
but now there is a perfect conductor boundary condition on one end and a
vertical field or pseudo-vacuum condition on the other. This leads to migratory
dynamo waves. Good agreement with a corresponding analytically solvable alpha^2
dynamo is found. Magnetic helicity fluxes are studied in both types of models.
It is found that at moderate magnetic Reynolds numbers, most of the magnetic
helicity losses occur at large scales. Whether this changes at even larger
magnetic Reynolds numbers, as required for alleviating the catastrophic dynamo
quenching problem, remains still unclear.
Much work on turbulent three-dimensional dynamos has been done using triply
periodic domains, in which there are no magnetic helicity fluxes. Here we
present simulations where the turbulent intensity is still nearly homogeneous,
but now there is a perfect conductor boundary condition on one end and a
vertical field or pseudo-vacuum condition on the other. This leads to migratory
dynamo waves. Good agreement with a corresponding analytically solvable alpha^2
dynamo is found. Magnetic helicity fluxes are studied in both types of models.
It is found that at moderate magnetic Reynolds numbers, most of the magnetic
helicity losses occur at large scales. Whether this changes at even larger
magnetic Reynolds numbers, as required for alleviating the catastrophic dynamo
quenching problem, remains still unclear.
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