First evidence of Alfvén wave activity in KSTAR plasmas

M. J. Hole; C. M. Ryu; M. H. Woo; J. G. Bak; S. E. Sharapov; M. Fitzgerald

doi:10.1088/0741-3335/55/4/045004

First evidence of Alfvén wave activity in KSTAR plasmas

M. J. Hole^*, C. M. Ryu, M. H. Woo, J. G. Bak, S. E. Sharapov, M. Fitzgerald

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

We report on first evidence of wave activity during neutral beam heating in KSTAR plasmas: 40 kHz magnetic fluctuations with a toroidal mode number of n = 1. Our analysis suggests this a beta-induced Alfvén eigenmode (BAE) resonant with the q = 1 surface. A kinetic analysis, when coupled with electron temperature measurements from electron cyclotron emission and ion/electron temperature ratios from crystallography, enables calculation of the frequency evolution, which is in agreement with observations. Complementary detailed magnetohydrodynamic (MHD) modelling of the magnetic configuration and wave modes supports the BAE conclusion, by locating an n = 1 mode separated from the continuum in the core region. Finally, we have computed the threshold to marginal stability for a range of ion temperature profiles. These suggest the BAE can be driven unstable by energetic ions when the ion temperature radial gradient is sufficiently large. Our findings suggest that mode existence could be used as a form of inference for temperature profile consistency in the radial interval of the mode, thereby extending the tools of MHD spectroscopy.

Original language	English
Article number	045004
Journal	Plasma Physics and Controlled Fusion
Volume	55
Issue number	4
DOIs	https://doi.org/10.1088/0741-3335/55/4/045004
Publication status	Published - Apr 2013

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title = "First evidence of Alfv{\'e}n wave activity in KSTAR plasmas",

abstract = "We report on first evidence of wave activity during neutral beam heating in KSTAR plasmas: 40 kHz magnetic fluctuations with a toroidal mode number of n = 1. Our analysis suggests this a beta-induced Alfv{\'e}n eigenmode (BAE) resonant with the q = 1 surface. A kinetic analysis, when coupled with electron temperature measurements from electron cyclotron emission and ion/electron temperature ratios from crystallography, enables calculation of the frequency evolution, which is in agreement with observations. Complementary detailed magnetohydrodynamic (MHD) modelling of the magnetic configuration and wave modes supports the BAE conclusion, by locating an n = 1 mode separated from the continuum in the core region. Finally, we have computed the threshold to marginal stability for a range of ion temperature profiles. These suggest the BAE can be driven unstable by energetic ions when the ion temperature radial gradient is sufficiently large. Our findings suggest that mode existence could be used as a form of inference for temperature profile consistency in the radial interval of the mode, thereby extending the tools of MHD spectroscopy.",

author = "Hole, {M. J.} and Ryu, {C. M.} and Woo, {M. H.} and Bak, {J. G.} and Sharapov, {S. E.} and M. Fitzgerald",

year = "2013",

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doi = "10.1088/0741-3335/55/4/045004",

language = "English",

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journal = "Plasma Physics and Controlled Fusion",

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T1 - First evidence of Alfvén wave activity in KSTAR plasmas

AU - Hole, M. J.

AU - Ryu, C. M.

AU - Woo, M. H.

AU - Bak, J. G.

AU - Sharapov, S. E.

AU - Fitzgerald, M.

PY - 2013/4

Y1 - 2013/4

N2 - We report on first evidence of wave activity during neutral beam heating in KSTAR plasmas: 40 kHz magnetic fluctuations with a toroidal mode number of n = 1. Our analysis suggests this a beta-induced Alfvén eigenmode (BAE) resonant with the q = 1 surface. A kinetic analysis, when coupled with electron temperature measurements from electron cyclotron emission and ion/electron temperature ratios from crystallography, enables calculation of the frequency evolution, which is in agreement with observations. Complementary detailed magnetohydrodynamic (MHD) modelling of the magnetic configuration and wave modes supports the BAE conclusion, by locating an n = 1 mode separated from the continuum in the core region. Finally, we have computed the threshold to marginal stability for a range of ion temperature profiles. These suggest the BAE can be driven unstable by energetic ions when the ion temperature radial gradient is sufficiently large. Our findings suggest that mode existence could be used as a form of inference for temperature profile consistency in the radial interval of the mode, thereby extending the tools of MHD spectroscopy.

AB - We report on first evidence of wave activity during neutral beam heating in KSTAR plasmas: 40 kHz magnetic fluctuations with a toroidal mode number of n = 1. Our analysis suggests this a beta-induced Alfvén eigenmode (BAE) resonant with the q = 1 surface. A kinetic analysis, when coupled with electron temperature measurements from electron cyclotron emission and ion/electron temperature ratios from crystallography, enables calculation of the frequency evolution, which is in agreement with observations. Complementary detailed magnetohydrodynamic (MHD) modelling of the magnetic configuration and wave modes supports the BAE conclusion, by locating an n = 1 mode separated from the continuum in the core region. Finally, we have computed the threshold to marginal stability for a range of ion temperature profiles. These suggest the BAE can be driven unstable by energetic ions when the ion temperature radial gradient is sufficiently large. Our findings suggest that mode existence could be used as a form of inference for temperature profile consistency in the radial interval of the mode, thereby extending the tools of MHD spectroscopy.

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DO - 10.1088/0741-3335/55/4/045004

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VL - 55

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

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ER -

First evidence of Alfvén wave activity in KSTAR plasmas

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