The response of toroidal drift modes to profile evolution: A model for small-ELMs in tokamak plasmas?

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We consider a time-dependent linear global electrostatic toroidal fluid ion-temperature gradient (ITG) model to study the evolution of toroidal drift modes in tokamak plasmas as the equilibrium flow-shear varies with time. While we consider the ITG mode as a specific example, the results are expected to be valid for most other toroidal microinstabilities. A key result is that when there is a position in the plasma with a maximum in the instability drive (e.g. ITG), there is a transient burst of stronger growth as the flow-shear evolves through a critical value. This transient burst is expected to drive a filamentary plasma eruption, reminiscent of small-ELMs. The amplitude of the dominant linear mode is initially peaked above or below the outboard midplane, and rotates through it poloidally as the flow-shear passes through the critical value. This theoretical prediction could provide an experimental test of whether this mechanism underlies some classes of small-ELMs.

Original languageEnglish
Article number075011
Pages (from-to)1-13
Number of pages13
JournalPlasma Physics and Controlled Fusion
Issue number7
Publication statusPublished - 3 Jun 2016

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© 2016 IOP Publishing Ltd. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details. Embargo period : 12 months


  • ballooning formalism
  • Floquet modes
  • small ELMs
  • toroidal drift modes

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