2024-09-19T00:06:34Z
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
I. Parra, Felix
M. Roach, Colin
Giroud, Carine
Dorland, William
R. Hatch, David
Barnes, Michael
C. Hillesheim, Jon
Aiba, Nobuyuki
Ball, Justin
G. Ivanov, Plamen
Nobuyuki, Aiba
metadata only access
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.
IoP Publishing
2020-10
eng
journal article
https://repo.qst.go.jp/records/80839
10.1088/1741-4326/abb891
https://iopscience.iop.org/article/10.1088/1741-4326/abb891
0029-5515
Nuclear Fusion
60
12
126045