Iterative approach to linear ideal MHD modeling of plasma response to 3D magnetic perturbations in tokamaks

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The class of plasma instabilities known as edge-localized modes (ELMs) is of special concern in tokamaks operating in high-confinement mode, such as ASDEX Upgrade and ITER. One strategy for ELM mitigation is the application of resonant magnetic perturbations (RMPs) via external coils. Kinetic modeling accurately describes the plasma response to these RMPs ab initio, particularly the parallel shielding currents at resonant surfaces. Away from resonant surfaces, ideal magnetohydrodynamics (iMHD) is expected to yield sufficiently accurate results, providing a computationally less expensive option that could complement kinetic modeling.

The code MEPHIT has been developed to solve the linearized iMHD equations in a way that is compatible with iterative kinetic modeling approaches. We consider an axisymmetric iMHD equilibrium in realistic tokamak geometry under the influence of a quasi-static non-axisymmetric external perturbation from ELM mitigation coils. The plasma responds to this external magnetic perturbation with a current perturbation, which in turn produces a magnetic field perturbation. The resulting fixed-point equation can be solved in a self-consistent manner by preconditioned iterations in which Ampère's equation and the magnetic differential equations for pressure and current are solved in alternation until convergence is reached. After expansion in toroidal Fourier harmonics, these equations are solved on a triangular mesh in the poloidal plane using finite elements. These results are then benchmarked against established codes.
Original languageEnglish
Article number012014
JournalJournal of Physics: Conference Series
Issue number1
Publication statusPublished - 12 Dec 2022
EventJoint Varenna-Lausanne International Workshop 2022: Theory of Fusion Plasmas - Villa Monastero, Varenna, Italy
Duration: 11 Sept 202216 Sept 2022


  • ideal MHD
  • perturbed equilibrium
  • numerics
  • finite element method
  • preconditioned iterations

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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