Scaling of up-down asymmetric turbulent momentum flux with poloidal shaping mode number in tokamaks

Justin Ball, Felix I. Parra

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Breaking the up-down symmetry of tokamaks removes a constraint limiting intrinsic momentum transport, and hence toroidal rotation, to be small. Using gyrokinetic theory, we study the effect of different up-down asymmetric flux surface shapes on the turbulent transport of momentum. This is done by perturbatively expanding the gyrokinetic equation in large flux surface shaping mode number. It is found that the momentum flux generated by shaping that lacks mirror symmetry (which is necessarily up-down asymmetric) has a power law scaling with the shaping mode number. However, the momentum flux generated by mirror symmetric flux surface shaping (even if it is up-down asymmetric) decays exponentially with large shaping mode number. These scalings are consistent with nonlinear local gyrokinetic simulations and indicate that low mode number shaping effects (e.g. elongation, triangularity) are optimal for creating rotation. Additionally it suggests that breaking the mirror symmetry of flux surfaces may generate significantly more toroidal rotation.

Original languageEnglish (US)
Article number055016
JournalPlasma Physics and Controlled Fusion
Issue number5
StatePublished - Apr 13 2016
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics


  • gyrokinetics
  • nonlinear simulations
  • plasma turbulence
  • tokamaks
  • transport


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