The finite-difference time-domain (FDTD) method has been used for a long time to compute the propagation of very low frequency (VLF) and low frequency (LF) radio waves in the Earth-Ionosphere waveguide. In previously published FDTD schemes, only the electronic density of the ionosphere was accounted for, since in usual natural conditions the effect of the ion density can be neglected. In the present paper, the FDTD scheme is extended to the case where one or several ion species must be accounted for, which may occur in special natural conditions or in such artificial conditions as after high altitude nuclear bursts. The conditions that must hold for the effect of the ions not to be negligible are discussed, the FDTD scheme with ions is derived, and numerical experiments are provided to show that the effect of the ions may be significant when the ionosphere is disturbed by incident flows of γ or β rays.

中文翻译：

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在地球电离层波导中存在离子的情况下，VLF-LF波的FDTD传播

有限差分时域（FDTD）方法已被使用很长时间了，以计算极低频（VLF）和低频（LF）无线电波在地球电离层波导中的传播。在以前发布的FDTD方案中，仅考虑了电离层的电子密度，因为在通常的自然条件下，可以忽略离子密度的影响。在本文中，FDTD方案扩展到必须考虑一种或几种离子种类的情况，这种情况可能发生在特殊的自然条件下或在人工条件下，例如在高空核爆炸之后。讨论了使离子的影响不可忽略的必要条件，得出了带有离子的FDTD方案，