Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas

K. Ida, T. Kobayashi, M. Yoshinuma, Y. Suzuki, Y. Narushima, T. E. Evans, S. Ohdachi, H. Tsuchiya, Inagaki Shigeru, K. Itoh

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Bifurcation physics of a magnetic island was investigated using the heat pulse propagation technique produced by the modulation of electron cyclotron heating. There are two types of bifurcation phenomena observed in a large helical device (LHD) and DIII-D. One is a bifurcation of the magnetic topology between nested and stochastic fields. The nested state is characterized by the bi-directional (inward and outward) propagation of the heat pulse with slow propagation speed. The stochastic state is characterized by the fast propagation of the heat pulse with electron temperature flattening. The other bifurcation is between the magnetic island with larger thermal diffusivity and that with smaller thermal diffusivity. The damping of toroidal flow is observed at the O-point of the magnetic island both in helical plasmas and in tokamak plasmas during a mode locking phase with strong flow shears at the boundary of the magnetic island. Associated with the stochastization of the magnetic field, the abrupt damping of toroidal flow is observed in LHD. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that this flow damping is due to the change in the non-diffusive term of momentum transport.

Original languageEnglish
Article number092001
JournalNuclear Fusion
Volume56
Issue number9
DOIs
Publication statusPublished - Jul 29 2016

Fingerprint

magnetic islands
toroidal plasmas
heat
physics
propagation
damping
thermal diffusivity
pulses
shear flow
electron cyclotron heating
flattening
decay
ion temperature
locking
temperature gradients
topology
electron energy
momentum
modulation
magnetic fields

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Ida, K., Kobayashi, T., Yoshinuma, M., Suzuki, Y., Narushima, Y., Evans, T. E., ... Itoh, K. (2016). Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas. Nuclear Fusion, 56(9), [092001]. https://doi.org/10.1088/0029-5515/56/9/092001

Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas. / Ida, K.; Kobayashi, T.; Yoshinuma, M.; Suzuki, Y.; Narushima, Y.; Evans, T. E.; Ohdachi, S.; Tsuchiya, H.; Shigeru, Inagaki; Itoh, K.

In: Nuclear Fusion, Vol. 56, No. 9, 092001, 29.07.2016.

Research output: Contribution to journalArticle

Ida, K, Kobayashi, T, Yoshinuma, M, Suzuki, Y, Narushima, Y, Evans, TE, Ohdachi, S, Tsuchiya, H, Shigeru, I & Itoh, K 2016, 'Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas', Nuclear Fusion, vol. 56, no. 9, 092001. https://doi.org/10.1088/0029-5515/56/9/092001
Ida, K. ; Kobayashi, T. ; Yoshinuma, M. ; Suzuki, Y. ; Narushima, Y. ; Evans, T. E. ; Ohdachi, S. ; Tsuchiya, H. ; Shigeru, Inagaki ; Itoh, K. / Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas. In: Nuclear Fusion. 2016 ; Vol. 56, No. 9.
@article{e217d23776854c12a5902e3efc4fd46d,
title = "Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas",
abstract = "Bifurcation physics of a magnetic island was investigated using the heat pulse propagation technique produced by the modulation of electron cyclotron heating. There are two types of bifurcation phenomena observed in a large helical device (LHD) and DIII-D. One is a bifurcation of the magnetic topology between nested and stochastic fields. The nested state is characterized by the bi-directional (inward and outward) propagation of the heat pulse with slow propagation speed. The stochastic state is characterized by the fast propagation of the heat pulse with electron temperature flattening. The other bifurcation is between the magnetic island with larger thermal diffusivity and that with smaller thermal diffusivity. The damping of toroidal flow is observed at the O-point of the magnetic island both in helical plasmas and in tokamak plasmas during a mode locking phase with strong flow shears at the boundary of the magnetic island. Associated with the stochastization of the magnetic field, the abrupt damping of toroidal flow is observed in LHD. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that this flow damping is due to the change in the non-diffusive term of momentum transport.",
author = "K. Ida and T. Kobayashi and M. Yoshinuma and Y. Suzuki and Y. Narushima and Evans, {T. E.} and S. Ohdachi and H. Tsuchiya and Inagaki Shigeru and K. Itoh",
year = "2016",
month = "7",
day = "29",
doi = "10.1088/0029-5515/56/9/092001",
language = "English",
volume = "56",
journal = "Nuclear Fusion",
issn = "0029-5515",
publisher = "IOP Publishing Ltd.",
number = "9",

}

TY - JOUR

T1 - Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas

AU - Ida, K.

AU - Kobayashi, T.

AU - Yoshinuma, M.

AU - Suzuki, Y.

AU - Narushima, Y.

AU - Evans, T. E.

AU - Ohdachi, S.

AU - Tsuchiya, H.

AU - Shigeru, Inagaki

AU - Itoh, K.

PY - 2016/7/29

Y1 - 2016/7/29

N2 - Bifurcation physics of a magnetic island was investigated using the heat pulse propagation technique produced by the modulation of electron cyclotron heating. There are two types of bifurcation phenomena observed in a large helical device (LHD) and DIII-D. One is a bifurcation of the magnetic topology between nested and stochastic fields. The nested state is characterized by the bi-directional (inward and outward) propagation of the heat pulse with slow propagation speed. The stochastic state is characterized by the fast propagation of the heat pulse with electron temperature flattening. The other bifurcation is between the magnetic island with larger thermal diffusivity and that with smaller thermal diffusivity. The damping of toroidal flow is observed at the O-point of the magnetic island both in helical plasmas and in tokamak plasmas during a mode locking phase with strong flow shears at the boundary of the magnetic island. Associated with the stochastization of the magnetic field, the abrupt damping of toroidal flow is observed in LHD. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that this flow damping is due to the change in the non-diffusive term of momentum transport.

AB - Bifurcation physics of a magnetic island was investigated using the heat pulse propagation technique produced by the modulation of electron cyclotron heating. There are two types of bifurcation phenomena observed in a large helical device (LHD) and DIII-D. One is a bifurcation of the magnetic topology between nested and stochastic fields. The nested state is characterized by the bi-directional (inward and outward) propagation of the heat pulse with slow propagation speed. The stochastic state is characterized by the fast propagation of the heat pulse with electron temperature flattening. The other bifurcation is between the magnetic island with larger thermal diffusivity and that with smaller thermal diffusivity. The damping of toroidal flow is observed at the O-point of the magnetic island both in helical plasmas and in tokamak plasmas during a mode locking phase with strong flow shears at the boundary of the magnetic island. Associated with the stochastization of the magnetic field, the abrupt damping of toroidal flow is observed in LHD. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that this flow damping is due to the change in the non-diffusive term of momentum transport.

UR - http://www.scopus.com/inward/record.url?scp=84986888094&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84986888094&partnerID=8YFLogxK

U2 - 10.1088/0029-5515/56/9/092001

DO - 10.1088/0029-5515/56/9/092001

M3 - Article

VL - 56

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 9

M1 - 092001

ER -