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Journal Articles Journal of Fluid Mechanics Year : 2022

Coherent magnetic modon solutions in quasigeostrophic shallow water magnetohydrodynamics

Abstract

A class of exact solutions of the magnetohydrodynamic quasi-geostrophic equations (MQG) , which result from rotating shallow water magnetohydrodynamics in the limit of small Rossby and magnetic Rossby numbers is constructed analytically. These solutions are magnetic modons, steady-moving dipolar vortices, which are generalizations of the well-known quasigeostrophic modons. It is shown that various configurations of magnetic modons are possible: with or without external magnetic field, and with or without internal magnetic field trapped inside the dipole. By using the modon solutions as initial conditions for direct numerical simulations of the MQG equations, it is shown that they remain coherent for a long time, running over about a hundred deformation radii without change of form, provided the external and internal magnetic fields are not too strong, and even if a small-amplitude noise is added to initial conditions.
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Dates and versions

hal-03651956 , version 1 (26-04-2022)

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Vladimir Zeitlin, Noé Lahaye. Coherent magnetic modon solutions in quasigeostrophic shallow water magnetohydrodynamics. Journal of Fluid Mechanics, 2022, 941, pp.A15. ⟨10.1017/jfm.2022.289⟩. ⟨hal-03651956⟩
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