参量激励过程中三波耦合的一般色散关系（Ⅱ）一般色散关系以及泵场阈值和增长率
doi: 10.11728/cjss2005.01.20050503 cstr: 32142.14.cjss2005.01.20050503
General Dispersion Relation for the Three-Wave Process of Parametric Excitation(Ⅱ) The Basic Formula, the Field Threshold and the Growing Rate
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摘要: 本文讨论了各向同性的均匀有耗电离层背景下激励参量不稳定性的三波耦合过程.首先推导有耗情况下参量激励过程中的一般色散关系,然后针对文献[1]得出的两种频率和波矢匹配条件计算激励参量不稳定性所需要的泵波阈值场强和受激励的等离子体波的增长率.结果表明,过密加热时泵场阈值与电子碰撞频率和离子碰撞频率的乘积成正比,不同于以前的一些理论模型得到的泵场阈值与碰撞频率的一次方成正比的结论;欠密加热比过密加热需要能量更高的高频泵波来激励参量不稳定性.Abstract: Three-wave coupling process in parametric excitation is further studied under an isotropic,homogenous and collisional ionospheric background.A general dispersive equation is firstly derived to describe the excitation of waves for a collisional ionosphere.Then,to start with this dispersive equation as well as the two kinds of wave frequencies and vectors matching conditions obtained in the paper [1],the threshold fields of pump waves to trigger overdense and underdense parametric instabilities and the growing rates of the excited plasma waves are obtained and compared with each other.The results show that in the case of overdense heating the threshold value is proportional to both ion and electron collisional frequency,which is much different from the previous results that the threshold only holds a proportional relation with electron collisional frequency.It is also concluded that more powerful HF waves are required to give rise to parametric instability for underdense heating than overdense heating.
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Key words:
- Parametric instability /
- Dispersive relation /
- Threshold value /
- Plasma wave
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