Nonlinear Mode Couplings in a Cylindrical Magnetized Plasma

抄録

Nonlinear mode couplings in plasma turbulence generate mesoscale global structures, such as zonal flows and streamers. A streamer is a poloidally localized structure that is radially elongated. In the Large Mirror Device-Upgrade, a streamer structure was observed in the ion saturation-current fluctuation measured with a 64-channel poloidal Langmuir probe array. The bunching of waves was poloidally localized and rotated slowly in the ion diamagnetic direction. The frequency and poloidal mode number of its envelope corresponded to one particular mode, which was strongly coupled with many other modes. By calculating the radial biphase profile of three pronounced modes, including the particular mode, the streamer structure was confirmed to be radially elongated.