无线电波传播2电离层中的电波传播.ppt

§
二、电离层垂直探测
1、探测原理
1)=0点为反射点
2)1与N,f等量有关
3)h
CT
4)h~f
2、频高图
h~f的函数曲线称为频高图
以小测力
题况级
Ionospheric Station of Gibilmanna
Latitude 37 9N XXXX Longitude 140E
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 fo F2 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.
Gibilmanna DATE: 2UUd 03 23- TIHE IUT 09: 15
4 MH2


234567891011121314MHz5
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 be
eginning of eac
ayer are due to the transmitted wave being slowed by
but not reflected from underlying ionisation which has a
lasma 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
600
IoF
200
foE
9 MHz 10
例:设电离层中,对于h
>h0的高度处的等离子
体频率为fp2=ah-h),
是常数,试计算出电离
层的虚高h,真高h和相
高hn,并比较它们的大
图65垂测史每
因分析
相高<真高<虚高
垂直电离图分析
1、模型法(比较法)
以抛物模型为例。
Nm-Nehm-h
N
或
h -h
Nn:最大电子浓度
最大电子浓度对应的高度
y:层的半厚度
由推导的结果可得
f=
以及
Yn=h()
(F
n+Ym=h'(
图6?n和Y的确是
h()-h()
2、直接积分法
(1)积分反演表达式
h'(f)= u'dh(f)
(6-38)
h(f)=h1+。(-1)dh(fn)
(6-39)
可将的主要特性表示为
M
N
(6-40)
N
通常M=1,这时,方程(6-38)是阿贝尔方
程,其解是
h(f
h'(. sin Q2)dQ2 (6-41)
arcsin