High-n collisionless ballooning modes in axisymmetric toroidal plasmas

C. Z. Cheng

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33 Citations (Scopus)


A collisionless kinetic ballooning-mode equation which includes the full ion finite-Larmorradius (FLR) the magnetic-drift and the trapped-electron effects is derived and investigated for a largeaspect- ratio circular-flux-surface equilibrium in the frequency regime ωbiωti< ω < ωbeωteThe finite-Larmor-radius effects can reduce the growth rate but do not stabilize the ballooning modes due to the destabilizing influence of the ion-magnetic-drift resonances. It is in general incorrect to simulate the FLR effects by employing the often used FLR-modified MHD model for (kθρi)2≳ 0.1 and ϵn≳ 0.1 where kθρiis the ion FLR parameter and ϵn= Ln/R measures the magnetic-drift frequency. The trapped electrons have a stabilizing effect due to the reduction of the destabilizing circulating-electron parallel-current perturbation. For a typical tokamak aspect ratio the critical β can be improved by 40%.

Original languageEnglish
Pages (from-to)773-785
Number of pages13
JournalNuclear Fusion
Issue number6
Publication statusPublished - 1982 Jun

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics


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