Extension of geodesic acoustic mode theory to helical systems
Extension of geodesic acoustic mode theory to helical systems
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DOI：
10.1063/1.1922807
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发表时间：
2005-05
影响因子：
2.2
通讯作者：
T. Watari;Y. Hamada;A. Fujisawa;K. Toi;K. Itoh
中科院分区：
文献类型：
--
作者：
T. Watari;Y. Hamada;A. Fujisawa;K. Toi;K. Itoh
本文将目前应用于托卡马克装置的测地声模（GAM）振荡理论推广到螺旋系统。利用三维平衡的漂移动力学方程，得到了包含朗道阻尼的广义色散关系。振荡频率由磁通量坐标表示的磁场强度的傅立叶分量的平方和获得。通过微扰法求解色散关系，得到了GAM无碰撞阻尼率的解析形式。结果表明，螺旋系统中的GAM频率比托卡马克中的高，多螺旋度磁位形中的阻尼率增加。然而，阻尼率预计将是小的，如果电子的温度高于离子的温度。
The present paper extends the theory of geodesic acoustic mode (GAM) oscillation, which so far has been applied to tokamaks, to helical systems. By using drift kinetic equations for three-dimensional equilibriums, a generalized dispersion relation is obtained including Landau damping. The oscillation frequency is obtained in terms of the squared sum of Fourier components of the magnetic field intensity expressed by means of magnetic flux coordinates. An analytic form of the collisionless damping rate of GAM is obtained by solving the dispersion relation perturbatively. It is found that the GAM frequency is higher in helical systems than in tokamaks and that damping rate is enhanced in multi-helicity magnetic configurations. However, damping rates are predicted to be small if the temperature of electrons is higher than that of ions.