弱縱向外電場對磁化等離子體中哨聲波的影響
EFFECT OF A WEAK LONGITUDINAL ELECTRIC FIELD ON WHISTLER WAVES
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摘要: 本文以等離子體動力論為基礎(chǔ)討論存在縱向外電場時磁化等離子體的哨聲波。由于外電場的影響,等離子體偏離平衡態(tài)。取電子穩(wěn)態(tài)分布函數(shù)為局域的麥克斯韋分布,用沿?zé)o擾軌道積分方法求出系統(tǒng)的介電張量,并分別用介電張量的厄米部份和反厄米部份分析哨聲的色散關(guān)系和增長率。對于波矢在以電場方向為軸頂角為2c錐角范圍內(nèi)的哨聲,外電場的作用使波增長;波矢在此錐角范圍之外,外電場的作用使其衰減。波的增長率隨頻率增高而增大,隨波矢傾角增大而減小。ee時,波矢與外電場平行對應(yīng)的最大增長率與等離子體密度成正比,與磁場強(qiáng)度成反比。文中還給出了以電離層F層作背景參數(shù)的數(shù)值計算結(jié)果。
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關(guān)鍵詞:
- 等離子體; 縱向電場; 哨聲波; 增長率
Abstract: The effect of a longitudinal electric field on whistlers is studied based on kinetic theory. A local Maxwellian distribution is taken as steady distribution function of electrons which departs from equilibrium due to the applied electric field. The dielectric tensor is derived by integrating along orbits of the particles in the unperturbed field. Dispersion relation and growth rate are analyzed from Hermitian and anti-Hermtian part of this tensor respectively. It is found that the waves are growing when the angle between wave vector and electric field is in the range of c, otherwise the whistler waves are damping. The growth rate increases with the wave frequency and decreases with the angle between wave vector and applied field. In case ee, the maximum of growth rate, which is at =0, is proportional to the plasma density and anti-proportional to the magnetic field intensity. Some computed results for parameters at top of F layer are given. -
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