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Title: Global gyrokinetic nonlinear simulations of kinetic infernal modes in reversed shear tokamaks
Authors: Ishida, Y.
Ishizawa, A.
Imadera, K.
Kishimoto, Y.
Nakamura, Y.
Author's alias: 石澤, 明宏
中村, 祐司
Issue Date: Sep-2020
Publisher: AIP Publishing
Journal title: Physics of Plasmas
Volume: 27
Issue: 9
Thesis number: 092302
Abstract: The nonlinear evolution of electromagnetic instabilities in reversed shear plasmas is investigated by means of global gyrokinetic simulations. It is found that the kinetic infernal mode (KIM), which is a pressure-driven instability with low to intermediate toroidal mode number excited in a region of low magnetic shear, is unstable at high β, while the ion temperature gradient mode is unstable at low β, where β is the ratio of the plasma kinetic pressure to the magnetic pressure. The β threshold of the KIM is much lower than that of the kinetic ballooning mode (KBM) appearing in a normal shear plasma, while both the KIM and KBM are strong at the unfavorable curvature region, and the KIM has the same parity as the KBM. Nonlinear simulations show that the KIM gets saturated by exciting strong zonal flows and fluctuations of low toroidal mode number. The amplitude of the KIM turbulence is similar to that of the KBM turbulence in spite of the fact that the linear growth rate of the KIM is much higher than that of the KBM. This is because the excitation of zonal flows and fluctuations at low toroidal mode number is stronger in the reversed shear plasma than that of the normal shear plasma. On the other hand, the energy flux and particle flux due to the KIM turbulence are about two or three times larger than those by the KBM turbulence.
Rights: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Physics of Plasmas 27, 092302 (2020) and may be found at https://doi.org/10.1063/5.0013349.
The full-text file will be made open to the public on 1 September 2021 in accordance with publisher's 'Terms and Conditions for Self-Archiving'.
URI: http://hdl.handle.net/2433/255548
DOI(Published Version): 10.1063/5.0013349
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