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Lookup NU author(s): Dr Andrew BaggaleyORCiD, Professor Anvar ShukurovORCiD, Professor Carlo Barenghi, Kumanan Subramaniam
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We develop a new model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multi-scale flow which models turbulence. Magnetic dissipation occurs only via reconnections of flux ropes. The model is particularly suitable for rarefied plasma, such as the solar corona or galactic halos. We investigate the kinetic energy release into heat, mediated by dynamo action, both in our model and by solving the induction equation with the same flow. We find that the flux rope dynamo is more than an order of magnitude more efficient at converting mechanical energy into heat. The probability density of the magnetic energy released during reconnections has a power-law form with the slope -3, consistent with the solar corona heating by nanoflares. We also present a nonlinear extension of the model. This shows that a plausible saturation mechanism of the fluctuation dynamo is the suppression of turbulent magnetic diffusivity, due to suppression of random stretching at the location of the flux ropes. We confirm that the probability distribution function of the magnetic line curvature has a power-law form suggested by Schekochihin et al. (2002c). We argue, however, using our results that this does not imply a persistent folded structure of magnetic field, at least in the nonlinear stage. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Author(s): Baggaley AW, Shukurov A, Barenghi CF, Subramanian K
Publication type: Article
Publication status: Published
Journal: Astronomische Nachrichten
Year: 2010
Volume: 331
Issue: 1
Pages: 46-62
Print publication date: 01/01/2010
ISSN (print): 0004-6337
ISSN (electronic): 1521-3994
Publisher: Wiley - V C H Verlag GmbH & Co. KGaA
URL: http://dx.doi.org/10.1002/asna.200911298
DOI: 10.1002/asna.200911298
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