Finite-time Response of Dynamo Mean-field Effects in Magnetorotational Turbulence

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Accretion disk turbulence along with its effect on large-scale magnetic fields plays an important role in understanding disk evolution in general, and the launching of astrophysical jets in particular. Motivated by enabling a comprehensive subgrid description for global long-term simulations of accretions disks, we aim to further characterize the transport coefficients emerging in local simulations of magnetorotational disk turbulence. For the current investigation, we leverage a time-dependent version of the test-field method, which is sensitive to the turbulent electromotive force (EMF) generated as a response to a set of pulsating background fields. We obtain Fourier spectra of the transport coefficients as a function of oscillation frequency. These are well approximated by a simple response function, describing a finite-time buildup of the EMF as a result of a time-variable mean magnetic field. For intermediate timescales (i.e., slightly above the orbital frequency), we observe a significant phase lag of the EMF compared to the causing field. Augmented with our previous result on a nonlocal closure relation in space, and incorporated into a suitable mean-field description that we briefly sketch out here, the new framework will allow us to drop the restrictive assumption of scale separation.

Original languageEnglish
Article number118
JournalAstrophysical Journal
Volume928
Issue number2
Number of pages7
ISSN0004-637X
DOIs
Publication statusPublished - 1 Apr 2022

    Research areas

  • ROTATING MAGNETOCONVECTION, SHEARING BOX, IMPLEMENTATION, SIMULATIONS, INSTABILITY, SATURATION, PATTERNS, I.

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