Early/fast VLF events produced by electron density changes associated with sprite halos
Early/fast VLF events produced by electron density changes associated with sprite halos
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DOI：
10.1029/2002ja009816
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发表时间：
2003-10
影响因子：
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通讯作者：
R. C. Moore;C. Barrington-Leigh;U. Inan;T. Bell
中科院分区：
文献类型：
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作者：
R. C. Moore;C. Barrington-Leigh;U. Inan;T. Bell
[1]早期/快速甚低频（VLF）的事件期间观察到的13个紧密间隔（1065公里）的网站的散射场的幅度进行比较与预期的精灵晕扰动使用的数值模型内的波传播的地球电离层波导。使用三种不同的夜间环境低电离层电子密度分布分析了三种不同的早期/快速事件的不同幅度。与精灵晕事件的电子密度扰动确定使用全波电磁（FWEM）模型。观察到的散射场振幅的典型（VLF振幅变化为0.2 dB-1 dB）被发现是在一个因素内的7个原因的闪电的峰值电流的基础上NLDN。然而，在以前的研究中，一些精灵产生的闪电表现出大的慢尾成分，表明大量的持续电流，并意味着电荷去除高达2-3倍，从NLDN报告的峰值电流推断。对于本文中讨论的情况下，散射场计算使用的干扰所造成的2-3倍大的电荷去除被发现是在两个测量值的一个因素。因此，与精灵晕相关的电子密度变化引起的VLF散射似乎是观测到的至少一些早期/快速事件的VLF扰动的根本原因。
[1] The magnitudes of scattered fields produced during early/fast very low frequency (VLF) events observed at 13 closely spaced (∼65 km) sites are compared with those expected for sprite halo disturbances using a numerical model of wave propagation within the Earth-ionosphere waveguide. Three different early/fast events of varying magnitudes are analyzed using three different nighttime ambient lower ionospheric electron density profiles. The electron density disturbances associated with sprite-halo events are determined using a full-wave electromagnetic (FWEM) model. Observed scattered field amplitudes of typical (VLF amplitude changes of 0.2 dB 1 dB) are found to be within a factor of seven for peak currents of causative lightning based on NLDN. However, in previous studies, some sprite-producing lightning flashes have exhibited large slow-tail components, indicating substantial continuing currents and implying charge removal up to 2–3 times larger than that inferred from the peak current reported by NLDN. For the cases discussed in this paper, scattered field calculations using disturbances caused by 2–3 times larger charge removal are found to be within a factor of two of the measured values. VLF scattering from electron density changes associated with sprite halos thus appear to be the underlying cause of at least some of the VLF perturbations observed as early/fast events.