Ionogram
An ionogram is the representation of the time of flight of a signal emitted by an ion probe and reflected by the ionosphere over frequency . They are used to measure the degree of ionization and the height of the ionospheric layers.
principle
The ion probe, a measuring station that works according to the radar principle, sends a signal that hits the ionosphere perpendicularly, which usually runs through a frequency range of 0.1 to 30 MHz, and measures the transit time of the received echo, from which the height of the reflection is determined .
With increasing frequency, the signal is broken back less strongly and penetrates deeper into the ionosphere before it is reflected. The deeper penetration increases the measured height of the layer, which is also called the virtual height. If the probe is above the ionosphere (satellite), the virtual height is reduced. When the so-called critical frequency is exceeded , the ionosphere is no longer able to reflect the signal.
An ionogram is helpful in determining the most favorable operating frequency for radio links in the shortwave range .
Measured values in ionograms
The International Union of Radio Science (URSI) defines or standardizes the measurable parameters of the ionosphere in the context of the evaluation of ionograms in its Handbook of Ionogram Interpretation and Reduction published by WRPiggott and K.Rawer . The main ones are as follows:
abbreviation | meaning | abbreviation | meaning |
---|---|---|---|
foF2 | critical (maximum) frequency of the F 2 layer | h'F | the minimum, virtual height of the F-layer as a whole |
foF1 | critical (maximum) frequency of the F 1 layer | h'F2 | the minimum, virtual height of the charge maximum of the F-layer |
foE | critical (maximum) frequency of the E-layer | h'E | the minimum, virtual height of the E-layer as a whole |
fxI | Spread F Index | hmF2 | Height of the maximum of the F 2 layer |
fmin | minimum frequency from which a reflection occurs | hmF1 | Height of the maximum of the F 1 layer |
hmE | Height of the maximum of the E-layer |
More ionograms
Web links
- Current ionogram from the Sodankylä Geophysical Observatory of the University of Oulu