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电阻率型m≥2的撕裂模在线性不稳定性阈值附近的非线性演化方程可以表示为 ?-Q2A+K2/2A2à-Q2(δ△1e)/(△1e)A3=0。这里A为模的幅值,Q为线性增长率,K为模的波矢,△e为线性模匹配计算中的外区解的对数微分差,δ△1e为非线性效应对于对数微分差的贡献。本文除在拟线性近似下推导出该方程外,还仔细讨论了该模的非线性行为。在对称电流分布sheet pinch模型的特例下,可以证明δ△1e=0,不存在新的平衡点。The nonlinear evolution equation of the resistive m≥2 tearing modes near their linear thresholds is derived as ?-Q2A+K/2A2à-Q2(δ△1e)/(△1e)A3=0 where the quasilinear approximation has been used; A is the mode amplitude; Q and K are the dimensionless linear growth rate and wave vector; △e and δ△1e are the linear and nonlinear discontinuities of the logarithmic derivatives. The nonlinear time evolutions of the modes are discussed in detail. No bifurcation solution exists for a symmetrical sheet pinch model.
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