2024-09-12T11:25:50Z
https://repo.qst.go.jp/oai
oai:repo.qst.go.jp:00080839
2023-05-15T19:32:22Z
1
Toroidal and slab ETG instability dominance in the linear spectrum of JET-ILW pedestals
F. Parisi, Jason
1002826
I. Parra, Felix
1002827
M. Roach, Colin
1002828
Giroud, Carine
1002829
Dorland, William
1002830
R. Hatch, David
1002831
Barnes, Michael
1002832
C. Hillesheim, Jon
1002833
Aiba, Nobuyuki
1002834
Ball, Justin
1002835
G. Ivanov, Plamen
1002836
Nobuyuki, Aiba
1002837
Local linear gyrokinetic simulations show that electron temperature gradient (ETG) instabilities are the fastest growing modes for kyρi ≳ 0.1 in the steep gradient region for a JET pedestal discharge (92174) where the electron temperature gradient is steeper than the ion temperature gradient. Here, ky is the wavenumber in the direction perpendicular to both the magnetic field and the radial direction, and ρi is the ion gyroradius. At kyρi ≳ 1, the fastest growing mode is often a novel type of toroidal ETG instability. This toroidal ETG mode is driven at scales as large as kyρi ∼ (ρi/ρe)LTe/R0 ∼ 1 and at a sufficiently large radial wavenumber that electron finite Larmor radius effects become important; that is, Kxρe ∼ 1, where Kx is the effective radial wavenumber. Here, ρe is the electron gyroradius, R0 is the major radius of the last closed flux surface, and 1/LTe is an inverse length proportional to the logarithmic gradient of the equilibrium electron temperature. The fastest growing toroidal ETG modes are often driven far away from the outboard midplane. In this equilibrium, ion temperature gradient instability is subdominant at all scales and kinetic ballooning modes are shown to be suppressed by E × B shear. ETG modes are very resilient to E × B shear. Heuristic quasilinear arguments suggest that the novel toroidal ETG instability is important for transport.
journal article
IoP Publishing
2020-10
Nuclear Fusion
12
60
126045
0029-5515
https://repo.qst.go.jp/records/80839
eng
10.1088/1741-4326/abb891
https://iopscience.iop.org/article/10.1088/1741-4326/abb891
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