A survey of pedestal magnetic fluctuations using gyrokinetics and a global reduced model for microtearing stability

JET Contributors, M. T. Curie, M. Ben Yaala

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

This article presents a global reduced model for slab-like microtearing modes (MTMs) in the H-mode pedestal, which reproduces distinctive features of experimentally observed magnetic fluctuations, such as chirping and discrete frequency bands at noncontiguous mode numbers. Our model, importantly, includes the global variation of the diamagnetic frequencies, which is necessary to reproduce the experimental observations. The key insight underlying this model is that MTM instability is enabled by the alignment of a rational surface with the peak in the profile of the diamagnetic frequency. Conversely, MTMs are strongly stabilized for toroidal mode numbers for which these quantities are misaligned. This property explains the discrete fluctuation bands in several DIII-D and JET discharges, which we survey using our reduced model in conjunction with global gyrokinetic simulations. A fast yet accurate reduced model for MTMs enables rapid interpretation of magnetic fluctuation data from a wide range of experimental conditions to help assess the role of MTM in the pedestal.

Original languageEnglish
Article number042503
JournalPhysics of Plasmas
Volume29
Issue number4
DOIs
Publication statusPublished - 12 Apr 2022

Keywords

  • microtearing stability
  • magnetic fluctuations
  • gyrokinetic simulations

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