Magnetic compressibility and ion-temperature-gradient-driven microinstabilities in magnetically confined plasmas

摘要

The electromagnetic theory of the strongly driven ion-temperature-gradient(ITG) instability in magnetically confined toroidal plasmas is developed.Stabilizing and destabilizing effects are identified, and a critical$\beta_{e}$ (the ratio of the electron to magnetic pressure) for stabilizationof the toroidal branch of the mode is calculated for magnetic equilibriaindependent of the coordinate along the magnetic field. Its scaling is$\beta_{e}\sim L_{Te}/R,$ where $L_{Te}$ is the characteristic electrontemperature gradient length, and $R$ the major radius of the torus. Weconjecture that a fast particle population can cause a similar stabilizationdue to its contribution to the equilibrium pressure gradient. For shearedequilibria, the boundary of marginal stability of the electromagneticcorrection to the electrostatic mode is also given. For a general magneticequilibrium, we find a critical length (for electromagnetic stabilization) ofthe extent of the unfavourable curvature along the magnetic field. This is adecreasing function of the local magnetic shear.