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@ARTICLE{PerezvonThun:861833,
      author       = {Perez von Thun, C. and Frassinetti, L. and Horvath, L. and
                      Saarelma, S. and Meneses, L. and de la Luna, E. and
                      Beurskens, M. and Boom, J. and Flanagan, J. and Hillesheim,
                      J. C. and Maggi, C. F. and Pamela, S. J. P. and Solano, E.
                      R.},
      title        = {{L}ong-lived coupled peeling ballooning modes preceding
                      {ELM}s on {JET}},
      journal      = {Nuclear fusion},
      volume       = {59},
      number       = {5},
      issn         = {1741-4326},
      address      = {Vienna},
      publisher    = {IAEA},
      reportid     = {FZJ-2019-02260},
      pages        = {056004 -},
      year         = {2019},
      abstract     = {PaperLong-lived coupled peeling ballooning modes preceding
                      ELMs on JETC. Perez von Thun1,2, L. Frassinetti3, L.
                      Horvath4, S. Saarelma5, L. Meneses6, E. de la Luna7, M.
                      Beurskens8, J. Boom9, J. Flanagan5, J.C. Hillesheim5Show
                      full author listPublished 22 March 2019 • © EURATOM
                      2019Nuclear Fusion, Volume 59, Number 5Download Article
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                      MendeleyArticle informationAbstractIn some JET discharges,
                      type-I edge localised modes (ELMs) are preceded by a class
                      of low-frequency oscillations (Perez et al 2004 Nucl. Fusion
                      44 609). While in many cases the ELM is triggered during the
                      growth phase of this oscillation, it is also observed that
                      this type of oscillation can saturate and last for several
                      tens of ms until an ELM occurs. In order to identify the
                      nature of these modes, a wide pre-ELM oscillation database,
                      including detailed pedestal profile information, has been
                      assembled and analysed in terms of MHD stability parameters.
                      The existence domain of these pre-ELM oscillations and the
                      statistical distribution of toroidal mode numbers (n) up to
                      n  =  16 have been mapped in ballooning alpha () and
                      either edge current density () or pedestal collisionality ()
                      coordinates and compared to linear MHD stability
                      predictions. The pre-ELM oscillations are reliably observed
                      when the ratio is high enough for the pedestal to access the
                      coupled peeling-ballooning (PB) domain (aka stability nose).
                      Conversely, when the pedestal is found to be in or near the
                      high-n ballooning domain (which is at low ratio), ELMs are
                      usually triggered promptly, i.e. with no detectable pre-ELM
                      oscillations, or with pre-ELM oscillations only observable
                      on ECE whose n appears to be too high to be resolved by the
                      magnetics. Individual discharges can sometimes exhibit a
                      fairly wide range of pre-ELM mode numbers, but for a wider
                      database, the statistical n-number domains are found to be
                      well ordered along the stability boundary and behave as
                      expected from PB theory: the higher the ratio, the lower the
                      mode's measured n tends to be. Within the measurement
                      uncertainties, the measured n is usually found to be
                      compatible with the most unstable n predicted by the linear
                      stability code MISHKA1. These results confirm the earlier
                      hypothesis that these modes are coupled peeling-ballooning
                      modes, and extend and generalise to higher-mode numbers the
                      work by Huysmans et al (1998 Nucl. Fusion 38 179), who
                      identified the lowest n modes as pure external kink modes.
                      Since the destabilisation of PB modes is widely accepted to
                      give rise to ELMs, the mode saturation and delayed ELM
                      triggering that is sometimes observed is rather unexpected.
                      Possibilities to reconcile the extended lifetime of these
                      modes with current ELM models are briefly discussed, but
                      will require further investigation.},
      cin          = {IEK-4 / ZEA-2},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IEK-4-20101013 / I:(DE-Juel1)ZEA-2-20090406},
      pnm          = {174 - Plasma-Wall-Interaction (POF3-174)},
      pid          = {G:(DE-HGF)POF3-174},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000462112700001},
      doi          = {10.1088/1741-4326/ab0031},
      url          = {https://juser.fz-juelich.de/record/861833},
}