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Abstract: Magnetic field embedded in a perfectly conducting fluid preserves itstopology for all time. Although ionized astrophysical objects, like stars andgalactic disks, are almost perfectly conducting, they show indications ofchanges in topology, `magnetic reconnection-, on dynamical time scales.Reconnection can be observed directly in the solar corona, but can also beinferred from the existence of large scale dynamo activity inside stellarinteriors. Solar flares and gamma ray busts are usually associated withmagnetic reconnection. Previous work has concentrated on showing howreconnection can be rapid in plasmas with very small collision rates. Here wepresent numerical evidence, based on three dimensional simulations, thatreconnection in a turbulent fluid occurs at a speed comparable to the rmsvelocity of the turbulence, regardless of the value of the resistivity. Inparticular, this is true for turbulent pressures much weaker than the magneticfield pressure so that the magnetic field lines are only slightly bent by theturbulence. These results are consistent with the proposal by Lazarian andVishniac 1999 that reconnection is controlled by the stochastic diffusion ofmagnetic field lines, which produces a broad outflow of plasma from thereconnection zone. This work implies that reconnection in a turbulent fluidtypically takes place in approximately a single eddy turnover time, with broadimplications for dynamo activity and particle acceleration throughout theuniverse. In contrast, the reconnection in 2D configurations in the presence ofturbulence depends on resistivity, i.e. is slow.

Author: A. Lazarian, G. Kowal, E. Vishniac, K. Kulpa-Dubel, K. Otmianowska-Mazur

Source: https://arxiv.org/


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