|
内容記述 |
The relationship between the amplitude and frequency of magnetic fluctuations driven by MHD instabilities in toroidal magnetically confined plasmas has been investigated. In LHD and JT-60U, it has previously been observed that, prior to mode locking, the amplitude–frequency relationship follows a unique trajectory, which can be reproduced by the force balance model between the electromagnetic braking force and the viscous driving force. In contrast, new phenomena have been observed in which the trajectory differs between the frequency-decreasing and frequency-increasing phases, which cannot be explained by the conventional model. Furthermore, in LHD, a new behaviour was observed in which the lower limit of the frequency after the decrease is restricted to approximately half of its pre-decrease value. These new behaviours have been successfully explained by an extended model that incorporates the dependence of the plasma response field to the external magnetic field on the plasma rotation frequency and the influence of the diamagnetic drift. |
