science

International Reference Ionosphere

International Reference Ionosphere is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand International Reference Ionosphere rather than just read about it. In short: International Reference Ionosphere (IRI) is a common permanent scientific project of the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) started 1968/69. It is the international standard empirical model for the terrestrial ionosphere since 1999.

Key takeaways

International Reference Ionosphere belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect International Reference Ionosphere to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of International Reference Ionosphere from memory before moving on to harder problems.

Reference excerpt

International Reference Ionosphere (IRI) is a common permanent scientific project of the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) started 1968/69. It is the international standard empirical model for the terrestrial ionosphere 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 and Fortran followed. In 1986, the code became available on floppy disk, 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.

Contents IRI used (and still has an option to use) an ITU-R-model that had been developed in respect to radio propagation 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 ionograms 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, electron and ion temperature, 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 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, International Union of Radio Science, 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

Illustrations

Worked examples

Example 1 — a first encounter with International Reference Ionosphere

Start with the simplest possible case. Write down what International Reference Ionosphere claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to International Reference Ionosphere before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about International Reference Ionosphere ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of International Reference Ionosphere

In research: International Reference Ionosphere appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses International Reference Ionosphere in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: International Reference Ionosphere is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ionosphere, Radio frequency propagation, so understanding it makes those chapters shorter.
In everyday life: Look for International Reference Ionosphere outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study International Reference Ionosphere in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what International Reference Ionosphere means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain International Reference Ionosphere out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is International Reference Ionosphere in simple terms?

Why does International Reference Ionosphere matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study International Reference Ionosphere?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on International Reference Ionosphere.