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Abstract: The magnetic Reynolds number R M, is defined as the product of acharacteristic scale and associated flow speed divided by the microphysicalmagnetic diffusivity. For laminar flows, R M also approximates the ratio ofadvective to dissipative terms in the total magnetic energy equation, but forturbulent flows this latter ratio depends on the energy spectra and approachesunity in a steady state. To generalize for flows of arbitrary spectra we definean effective magnetic dissipation number, R {M,e}, as the ratio of theadvection to microphysical dissipation terms in the total magnetic energyequation, incorporating the full spectrum of scales, arbitrary magnetic Prandtlnumbers, and distinct pairs of inner and outer scales for magnetic and kineticspectra. As expected, for a substantial parameter range R {M,e}\sim {O}1 <>1 highlights that, just as inhydrodynamic turbulence,energy dissipation of large scale structures inturbulent flows via a cascade can be much faster than the dissipation of largescale structures in laminar flows. This illustrates that the rate of energydissipation by magnetic reconnection is much faster in turbulent flows, andmuch less sensitive to microphysical reconnection rates compared to laminarflows.

Autor: Eric G. Blackman, George B. Field

Fuente: https://arxiv.org/

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