磁尾宽频带静电噪声的一种新的激发机制

本文提出了磁尾宽频带静电噪声强谱段的一种新的激发机制。在等离子体片边界层中存在着瞬时的局域性的晨昏电场。电子和离子对该电场的响应不同:在电场存在的区域内,电子作回旋漂移运动,而离子轨道在的时间尺度内可视为直线。由于等离子体片边界层中等离子体是非均匀的,这就导致了电荷分离的产生,从而可激发静电不稳定性。本文通过求解含电场的Vlasov方程,计算了由此产生的不稳定波的频率和增长率,考察了波矢方向。上述计算结果均与强谱段静电噪声的观测特征一致。

THE GENERATION OF BEN BY THE LOCAL AND TRANSIENT DAWN-DUSK ELECTRIC FIELD IN THE MAGNETOTAIL

A new mechanism for exciting the Broadband Electrostatic Noise （BEN） in the strong spectrum branch （ω - ω_eh） has been proposed in this paper. Satellite observations show that the local and transient dawn-dusk electric fields （LTEF） are often present in the plasma sheet boundary region of the magnetotail. Because the motion of the electrons in LTEF is adiabatic in the time scale τ （τ~ω_eh^1-）, while the orbits of ions may approximately be regarded as straight lines. The electron and ions will suffer different response to the LTEF, causing the appearence of charge seperation between electrons and ions in the plasma sheet boundary region where the plasma is inhomogenous. A new kind of plasma instability will thus be excited which can lead to the generation of the BEN in its strong spectrum branch.