Gyrokinetic investigations on entropy modes in dipole magnetic field confined plasmas with an anisotropic temperature

Abstract

Entropy modes are typical instabilities particularly seen in dipole field confined plasmas. In this paper, linear gyrokinetic calculations, together with the integral dispersion relation method, are applied to study the electrostatic entropy mode in such plasmas with an anisotropic temperature. The numerical approach is verified for certain typical conditions with previous studies. We then further focus on the anisotropic temperature effect on the entropy mode. Basic characteristics of the entropy mode are obtained with the effect. The results show that the entropy mode has a peak growth rate at kρi ∼ 1, and the mode is shifted from the ion to the electron diamagnetic regimes at small k⊥ρi. This work can be applied for various dipole magnetic field confined plasmas as well as certain other configurations, such as Z-pinch and field reversed configurations.