Magnetic damping of jet flows in quasi-two-dimensional Rayleigh-Bénard convection

Ashna Aggarwal, Jonathan M. Aurnou, and Susanne Horn
Phys. Rev. E 106, 045104 – Published 13 October 2022

Abstract

The mechanism responsible for the damping of the large-scale, azimuthally directed jets observed at Jupiter's surface is not well known, but electromagnetic forces are suspected to play a role as the planet's electrical conductivity increases radially with depth. To isolate the jet damping process, we carry out a suite of direct numerical simulations of quasi-two-dimensional, horizontally periodic Rayleigh-Bénard convection with stress-free boundary conditions in the presence of an external, vertical magnetic field. Jets, punctuated by intermittent convective bursts, develop at Rayleigh numbers (Ra, ratio of buoyancy to diffusion) beyond 105 when the magnetic field is relatively weak. Five primary flow regimes are found by varying 103Ra1010 and the Chandrasekhar number (Ch, ratio of Lorentz to viscosity) 0Ch106: (i) steady convection rolls, (ii) steady magneto-columns, (iii) unsteady to turbulent magneto-plumes, (iv) horizontally drifting magneto-plumes, and (v) jets with intermittent turbulent convective bursts. We parse the parameter space using transitions derived from the interaction parameter (N, ratio of Lorentz to inertia). The transition to the regime dominated by jets has the most immediate applications to the magnetic damping of Jovian jet flows, where the separation between jets and a magnetically constrained system occurs at a jet-based interaction parameter value of NJ1. We approximate the value of the Jovian interaction parameter as a function of depth, and find that the jets may brake at 6000 km below the surface, which is deeper than recent estimates from NASA's Juno mission. This suggests that mechanisms in addition to electromagnetic forces are likely required to fully truncate the jets.

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  • Received 1 March 2022
  • Accepted 12 August 2022

DOI:https://doi.org/10.1103/PhysRevE.106.045104

©2022 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Ashna Aggarwal* and Jonathan M. Aurnou

  • Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, USA

Susanne Horn

  • Centre for Fluid and Complex Systems, Coventry University, Coventry CV1 5FB, United Kingdom

  • *aggarwal01@ucla.edu

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Vol. 106, Iss. 4 — October 2022

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