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在平板模型下,所谓普适模是绝对稳定的。对于圆柱形等离子体,情形又如何呢?两者的主要差别在于:代替平板模型下的外行波边条件,在柱模型下则在r=0和r=∞处都没有波能外流。这可有效地改变模的稳定性。假设了指数型密度和电流分布,本文导出了漂移波的积分本征方程。在模径向慢变的情形下,它可变为二阶微分方程。对此方程作了数值计算,结果表明确实存在不稳定模。对两种模型(平板模型与柱模型)作了比较。In the slab model the so-called universal modes are absolutly stable. How about the cylindrical plasma? The main difference is that instead of the out-going boundary condition in the slab mode, in the cylindrical plasma there is not any wave energy outgoing at r=0 and r=∞. This may change the stabilities of the modes effectively.Assuming exponential plasma density and current profiles, the integral eigen-equa-tion of drift wave has been derived. In the ease of slow radial variation, it can be converted into a second order differential equation. The equation has been solved numerically. The results show that the unstable modes do exist. The comparison between the two models (cylindrical one and slab one) has been made.
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