International Reference Ionosphere (IRI) is a common permanent scientific project of the

Committee on Space Research The Committee on Space Research (COSPAR) was established on October 3, 1958 by the International Council for Scientific Unions (ICSU). Among COSPAR's objectives are the promotion of scientific research in space on an international level, wi ...

(COSPAR) and the

International Union of Radio Science The International Union of Radio Science (abbreviated ''URSI'', after its French name, french: link=no, Union radio-scientifique internationale) is one of 26 international scientific unions affiliated to the International Council for Science ( ...

(URSI) started 1968/69. It is the international

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object th ...

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 an ...

since 1999. For a specified geographic location, time, and date, IRI provides average monthly values for electron density,

electron temperature Plasma parameters define various characteristics of a plasma, an electrically conductive collection of charged particles that responds ''collectively'' to electromagnetic forces. Plasma typically takes the form of neutral gas-like clouds or char ...

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 The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined by ...

in the IRI-Plas model.

History

Karl Rawer file:Prof. Rawer 2017.jpg, Professor Rawer at his 104th birthday in 2017 Karl Maria Alois Rawer (19 April 1913 – 17 April 2018) was a German specialist in Radio propagation, radio wave propagation and the ionosphere. He developed the analytical co ...

, 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, or a diskette) is an obsolescent 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 w ...

, 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-frequency sp ...

-model that had been developed in respect to

radio propagation Radio propagation is the behavior of radio waves as they travel, or are 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 waves are affecte ...

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 physi ...

s at all

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. T ...

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 substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

and

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

, 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

* D.Bilitza: ''35 years of International Reference Ionosphere...''. Adv.in Radio Science 2,.pp. 283–287 2004 * M.Hernandez-Pajares et al.:''Combining

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

measurements and IRI model values for

Space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the ma ...

specification''. Adv .Space Research 29,pp. 949–958 2002 * K.Rawer et al.:''International Reference Ionosphere 1978''.

,Brussels 1978 * W.B.Jones, R.M.Gallet:Telecomm.J.29, pp. 129ff 1965

External links

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

History

Contents

References

Literature

External links