Radio Wave Propagation 无线电波传播第八讲电离层中的电波传播 2 垂直传播的几个问题(垂测、电离图分析、顶测) 斜向传播(传输曲线、平面抛物层中的斜传播) 几个概念(哨声、法拉第旋转、电离层闪烁) 二、电离层垂直探测 1、探测原理 1) 点为反射点 0??2) 等量有关 fN,与?3) ?ch2 1'?4) ?fh~'§ 垂直传播中的几个问题 2、频高图的函数曲线称为频高图。?fh~' Ionospheric Station of Gibilmanna Latitude N XXXX Longitude E Istituto Nazionale di Geofisica e Vulcanologia (INGV) This page reports the real time ionograms recorded in Gibilmanna by the new Advanced Ionospheric Sounder (AIS). The critical frequency foF2 and MUF(3000)F2 are scaled by Autoscala program . The AIS and Autoscala were developped at the INGV. This page is updated every 15 minutes . Characteristics ? Each ionospheric layer shows up as an approximately smooth curve, separated from each other by an asymptote at the critical frequency of that layer. ? The upwardly curving sections at the beginning of each layer are due to the transmitted wave being slowed by, but not reflected from, underlying ionisation which has a plasma frequency close to, but not equal to the transmitted frequency. For frequencies approaching the level of maximum plasma frequency in a layer, the virtual height tends to infinity, because the pulse must travel a finite distance at effectively zero speed. ? The frequencies at which this occurs are called the critical frequencies. The critical frequency of each layer is scaled from the asymptote, and the virtual height of each layer is scaled from the lowest point on each curve Ionogram ’s characteristics Bottom profile (post-process) 例: 设电离层中,对于 h > h 0 的高度处的等离子体频率为 f p 2 = ?(h-h 0),?是常数,试计算出电离层的虚高 h‘,真高 h r和相高h p,并比较它们的大小。相高< 真高< 虚高三、垂直电离图分析 1、模型法(比较法) 以抛物模型为例。 2??????????? m m m emY hhN NN 21??????????? m m m eY hhN N或最大电子浓度最大电子浓度对应的高度层的半厚度: : : m m mY h N cff mhh 834 .0' ??由推导的结果可得: 以及) 925 .0('2 1 ) 648 .0('2 1 c m m c m mfhYh fhYh????) 648 .0(') 925 .0(' c c mfhfhY??即
