International Reference Ionosphere
Encyclopedia
International Reference Ionosphere (IRI) is a common permanent scientific project of the Committee on Space Research and the International Union of Radio Science
International Union of Radio Science
The International Union of Radio Science is one of 26 international scientific unions affiliated to the International Council for Science.- History and objectives :...

 started 1968/69. It is the international standard
Standard (metrology)
In the science of measurement, a standard is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. Standards are the fundamental reference for a system of weights and measures, against which all other measuring devices are compared...

 for the terrestrial ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

 since 1999.

History

Karl Rawer
Karl Rawer
Karl Rawer is a German specialist in radio wave propagation and the ionosphere who developed the analytical code to determine suitable frequency ranges for short wave communication by which the German forces successfully built-up their long distance communications during World War II.After studies...

, first chairman of the URSI/COSPAR Task group on the IRI (1968-`84) specified as goal of the IRI to establish a (monthly) average model of the terrestrial ionosphere based on reliably measured data obtained with ground- and space-based methods. Contradictions between these had to be resolved in critical discussions. After a decade filled with data collection a first set of tables was given out in 1978. PC-codes in ALGOL
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...

 and Fortran
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...

 followed. 1986 the code became available on Floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...

, later in the Web. It is yearly improved according to the results obtained at the meetings of the task group.Since 1999 the IRI is "International Standard" for ionosphere.

Contents

The IRI used (and yet uses as an option) an ITU-R
ITU-R
The ITU Radiocommunication Sector is one of the three sectors of the International Telecommunication Union and is responsible for radio communication....

-model that had been developed in respect to Radio propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...

 via the ionosphere, specifying two parameters of which one is narrowly related to the peak electron density and the other to the peak altitude of the ionosphere. Both have been and are regularly determined from Ionogram
Ionogram
An ionogram is a display of the data produced by an ionosonde. It is a graph of the virtual height of the ionosphere plotted against frequency. Ionograms are often converted into electron density profiles...

s at all Ionospheric sounding
Ionospheric sounding
In telecommunication and radio science, an ionospheric sounding is a technique that provides real-time data on high-frequency ionospheric-dependent radio propagation, using a basic system consisting of a synchronized transmitter and receiver....

 stations. The authors R.M.Gallet and W.B.Jones had world-wide analyzed a wealth of such data by a method combining Fourier
Fourier
Fourier most commonly refers to Joseph Fourier , French mathematician and physicist, or the mathematics, physics, and engineering terms named in his honor for his work on the concepts underlying them:In mathematics:...

- analysis in time with world-wide Legendre-analysis of the Fourier-coefficients. Meanwhile regional models are often applied because they reach better local performance.

The IRI-model specifies vertical profiles of electron density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

, Electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

 and Ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

 temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 and the relative share of the different positive ions. Vertical Electron content may be derived (A snapshot is shown in the (latitude vs. longitude) map) aside).


Literature

  • D.Bilitza: 35 years of International Reference Ionosphere.... Adv.in Radio Science 2,.pp. 283–287 2004

  • M.Hernandez-Pajares et al.:Combining GPS measurements and IRI model values for Space weather
    Space weather
    Space weather is the concept of changing environmental conditions in near-Earth space or thespace from the Sun's atmosphere to the Earth's atmosphere. It is distinct from the concept ofweather within the Earth's planetary atmosphere...

     specification
    . Adv .Space Ressearch 29,pp. 949–958 2002

  • K.Rawer et al.:International Reference Ionosphere 1978. International Union of Radio Science
    International Union of Radio Science
    The International Union of Radio Science is one of 26 international scientific unions affiliated to the International Council for Science.- History and objectives :...

    ,Brussels 1978

  • W.B.Jones, R.M.Gallet:Telecomm.J.29, pp. 129ff 1965
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