International Reference Ionosphere (IRI) is a common permanent scientific project of the Committee on Space Research (COSPAR) and the

International Union of Radio Science The International Union of Radio Science (abbreviated ''URSI'', after its French name, ) is one of 26 international scientific unions affiliated to the International Council for Science (ICSU). History and objectives URSI was officially cr ...

(URSI) started 1968/69. It is the international standard empirical model for the terrestrial

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...

since 1999. For a specified geographic location, time, and date, IRI provides average monthly values for electron density, electron temperature and ion temperature, and the molecular composition of the ions in the range of altitudes from 50 km to 2000 km. The latest standard is IRI-2012. A new version, IRI-2016, has since been released. The IRI has been extended to plasmasphere in the IRI-Plas model.

History

Karl Rawer, the 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. Computer source code in

ALGOL ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...

and Fortran followed. In 1986, the code became available on

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, a diskette, or a disk) is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a ...

, and later on the Web. It is improved yearly according to the results obtained at the meetings of the task group, which often occur at COSPAR meetings. Since 1999, IRI has been the "International Standard" for the terrestrial ionosphere.

IRI used (and still has an option to use) an

ITU-R The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communications. Its role is to manage the international radio-frequenc ...

-model that had been developed in respect to

radio propagation Radio propagation is the behavior of radio waves as they travel, or are wave propagation, propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio w ...

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 An ionosonde, or chirpsounder, is a special radar for the examination of the ionosphere. The basic ionosonde technology was invented in 1925 by Gregory Breit and Merle A. Tuve and further developed in the late 1920s by a number of prominent phys ...

s at all ionospheric sounding stations. The authors R. M. Gallet and W. B. Jones had analyzed a wealth of such data from around the world by a method combining Fourier analysis in time with worldwide Legendre analysis of the Fourier coefficients. Meanwhile, regional models are often applied because they reach better local performance. The IRI model specifies monthly averages of electron

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

and ion

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

, and the relative percentage of several different positive ions (O+, H+, He+, N+, NO+, O2+, and Cluster ions). The model can represent variation of these quantities with altitude, latitude, longitude, date, and time of day. It can also make use of solar, ionospheric and geomagnetic indices to refine the model. Vertical total electron content (TEC) may be derived. (A snapshot of model predictions is shown in the latitude vs. longitude map above).

References

Literature

* Bilitza, Dieter; "35 years of International Reference Ionosphere...", ''Advances in Radio Science'', 2, 2004, pp. 283–287 * Hernández-Pajares, Manuel; Juan-Zornoza, José Miguel; Sanz Subirana, Jaume; Bilitza, Dieter; "Combining GPS measurements and IRI model values for

Space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its heliosphere. This includes the effects of the solar wind, especially on the Earth's magnetosphere, ion ...

specification", ''Advances in Space Research'', 29:6, 2002, pp. 949–958, doi 10.1016/S0273-1177(02)00051-0 * Rawer, Karl; Ramakrishnan, Sehadri; Bilitza, Dieter; ''International Reference Ionosphere 1978'',

, Brussels, 1978 * Jones, William B.; Gallet, Roger M.; "The representation of diurnal and geographic variations of ionospheric data by numerical methods", ''ITU Telecommunication Journal'', 29, 1962, pp. 129ff

External links

* {{Official website, http://irimodel.org/ Ionosphere Radio frequency propagation

History

Contents

References

Literature

External links