Lightning‐induced electron precipitation events observed at L ∼ 2.4 as phase and amplitude perturbations on subionospheric VLF signals
Lightning‐induced electron precipitation events observed at L ∼ 2.4 as phase and amplitude perturbations on subionospheric VLF signals
复制标题
在 L 〜 2.4 观测到的闪电诱发电子降水事件，作为亚电离层 VLF 信号的相位和幅度扰动
DOI：
10.1029/ja092ia04p03293
复制
发表时间：
1987
影响因子：
--
通讯作者：
D. L. Carpenter
中科院分区：
文献类型：
--
作者：
U. Inan;D. L. Carpenter
利用Trimpi效应研究了闪电诱导的电子沉淀(LEP)事件，其中低电离层(D区)的降水引起的电离增强引起了亚电离层VLF信号的快速扰动。1983年，在南极帕尔默(L-2.4)测量了夏威夷的NPM发射机(23.4千赫)和阿根廷的欧米茄发射机(12.9千赫)的信号的相位和幅度，以及磁层哨声背景。这两个震源的长基线和海上大圆路径使观测到的扰动可以用单波导模理论来解释。解析表达式用于将相位扰动的大小与沿传播路径的一段电离层反射高度的差异变化联系起来。将预测的两个不同信号上的相对扰动大小之间的关系与测量结果进行了比较。根据这一信息，哨声感生通量水平在10/sup-4/-10/sup-2/erg cm/sup-2/S/sup-1/范围内，降水区大致呈圆形，而不是沿L壳拉长。正如单模理论所预期的那样，测量的幅度变化往往很小(-0.5dB)和负，但同时幅度和相位扰动的比率比理论预测的略大，可能是由于附加模式的影响(S)。对幅度相对于相位扰动的相对可检测性的评估有利于相位扰动-10分贝，而与所使用的检测方案无关。版权所有美国地球物理联盟1987年
Lightning-induced electron precipitation (LEP) events are studied using the Trimpi effect, in which the precipitation-induced ionization enhancements in the lower ionosphere (D region) give rise to rapid perturbations of subionospheric VLF signals. In 1983,the phase and amplitude of signals from the NPM transmitter in Hawaii (23.4 kHz) and the Omega transmitter in Argentina (12.9 kHz) were measured at Palmer, Antarctica (L-2.4), together with the magnetospheric whistler background. The long baseline and over-sea great circle paths from these two sources make it possible for the observed perturbations to be interpreted using a single waveguide mode theory. Analytical expressions are used to relate the magnitude of the phase perturbations to differential changes in ionospheric reflection height along a segment of the propagation path. The predicted relationship between relative perturbation sizes on the two different signals is compared with measurements. From this information, the whistler-induced flux levels are inferred to be in the 10/sup -4/--10/sup -2/ erg cm/sup -2/ s/sup -1/ range and the precipitation regions are inferred to be roughly ''circular'' in shape, rather than elongated along L shells. Measured amplitude changes tended to be small (--0.5 dB) and negative, as expected from a single-mode theory, but the ratios of simultaneous amplitudemore » and phase perturbations were slightly larger than the theory predicts, probably due to the effects of an additional mode(s). An assessment of the relative detectability of amplitude versus phase perturbations favors phase perturbations by -- 10 dB, irrespective of the detection scheme used. copyright American Geophysical Union 1987« less