Interacting vorticity waves as an instability mechanism for magnetohydrodynamic shear instabilities

E. Heifetz, J. Mak, J. Nycander, O. M. Umurhan

Research output: Contribution to journalArticlepeer-review

Abstract

The interacting vorticity wave formalism for shear flow instabilities is extended here to the magnetohydrodynamic (MUD) setting, to provide a mechanistic description for stabilising and destabilising shear instabilities by the presence of a background magnetic field. The interpretation relies on local vorticity anomalies inducing a non-local velocity field, resulting in action at a distance. It is shown here that the waves supported by the system are able to propagate vorticity via the Lorentz force, and waves may interact. The existence of instability then rests upon whether the choice of basic state allows for phase locking and constructive interference of the vorticity waves via mutual interaction. To substantiate this claim, we solve the instability problem of two representative basic states, one where a background magnetic field stabilises an unstable flow and the other where the field destabilises a stable flow, and perform relevant analyses to show how this mechanism operates in MHD.

Original languageEnglish
Pages (from-to)199-225
Number of pages27
JournalJournal of Fluid Mechanics
Volume767
Early online date12 Feb 2015
DOIs
Publication statusPublished - Mar 2015

Keywords

  • instability
  • magnetic fluids
  • MUD and electrohydrodynamics
  • PARALLEL MAGNETIC-FIELD
  • BAROCLINIC INSTABILITY
  • JOINT INSTABILITY
  • FLOW
  • PERSPECTIVE
  • STABILITY
  • MAGNETOFLUID
  • DYNAMICS

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