Computer experiments of amplitude‐modulated Langmuir waves: Application to the Geotail observation
Computer experiments of amplitude‐modulated Langmuir waves: Application to the Geotail observation
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DOI：
10.1029/2004ja010703
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发表时间：
2005-06
影响因子：
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通讯作者：
H. Usui;H. Furuya;H. Kojima;H. Matsumoto;Y. Omura
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文献类型：
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作者：
H. Usui;H. Furuya;H. Kojima;H. Matsumoto;Y. Omura
[1]通过粒子模拟实验，研究了电子束相互作用过程中朗缪尔波的振幅调制。在不应用传统的非线性理论如衰减不稳定性和调制不稳定性的情况下，我们证实了在计算机实验中观察到的幅度调制可以用“非线性俘获理论”来解释，该理论解释了静电威尔斯阱中非线性电子俘获调制的空间尺度。为了将非线性俘获理论应用于观测数据，我们对该理论进行了修改，使其适用于时间数据。我们基本上证实了理论估计与计算机实验中观测到的波包时间尺度之间的一致性。我们发现，在计算机实验中获得的时间波形是非常相似的Geotail航天器所观察到的。通过将波包时间尺度的理论估计应用于Geotail波数据，我们发现激发的朗缪尔波的相速度，这是接近电子束速度，可以粗略估计的时间分辨率远高于粒子观测。
[1] We studied the amplitude modulation of Langmuir waves in the process of electron-beam interaction by performing particle-in-cell computer experiments. Without applying the conventional nonlinear theories such as the decay instability and the modulation instability, we confirmed that the amplitude modulation observed in the computer experiments can be accounted for by “nonlinear trapping theory” which explains the spatial scales of the modulation with nonlinear electron trapping in electrostatic wells. In order to apply the nonlinear trapping theory to observational data, we modified the theory to be applicable to temporal data. We basically confirmed the agreement between the theoretical estimate and the temporal scale of wave packets observed in the computer experiments. We found that temporal waveforms obtained in the computer experiments are quite similar to those observed by the Geotail spacecraft. By applying the theoretical estimate of temporal scales of wave packets to the Geotail wave data, we found that the phase velocity of the excited Langmuir waves, which is close to the electron beam velocity, can be roughly estimated with time resolution much higher than the particle observation.