Minimal perturbation flows that trigger mean field dynamos in shear flows - Laboratoire Interdisciplinaire des Sciences du Numérique Access content directly
Journal Articles Journal of Plasma Physics Year : 2018

Minimal perturbation flows that trigger mean field dynamos in shear flows

Abstract

Using a variational optimization method we find the smallest flow perturbations that can trigger kinematic dynamo action in Kolmogorov flow. In comparison to previous work, a second-order mean field dynamo model is used to track down the optimal dynamos in the high magnetic Reynolds number limit ( $Rm$ ). The magnitude of minimal perturbation flows decays inversely proportional to the magnetic Reynolds number. We reveal the asymptotic high- $Rm$ structure of the optimal flow perturbation and the magnetic eigenmode. We identify the optimal dynamo as of $\unicode[STIX]{x1D6FC}{-}\unicode[STIX]{x1D6FA}$ type, with magnetic fluctuations that localize on a critical layer.

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Dates and versions

hal-04466147 , version 1 (19-02-2024)

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Wietze Herreman. Minimal perturbation flows that trigger mean field dynamos in shear flows. Journal of Plasma Physics, 2018, 84 (3), pp.735840305. ⟨10.1017/S0022377818000508⟩. ⟨hal-04466147⟩
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