The International Reference Ionosphere (IRI) is the international standard for the specification of ionospheric densities and temperatures. It was developed and is being improved-updated by a joint working group of the International Union of Radio Science (URSI) and the Committee on Space Research (COSPAR). A new version of IRI is scheduled for release in the year 2000. This paper describes the most important changes compared to the current version of IRI: (1) an improved representation of the electron density in the region from the F peak down to the E peak including a better description of the F1 layer occurrence statistics and a more realistic description of the low-latitude bottomside thickness, (2) inclusion of a model for storm-time conditions, (3) inclusion of an ion drift model, (4) two new options for the electron density in the D region, and (5) an improved model for the topside electron temperatures. The outcome of the most recent IRI Workshops (Kuhlungsborn, 1997, and Nagoya, 1998) will be reviewed, and the status of several ongoing task force activities (e.g., efforts to improve the representation of electron and ion densities in the topside ionosphere and the inclusion of a plasmaspheric extension) will be discussed. A few typical IRI applications will be highlighted in section 6.

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International Reference Ionosphere 2000

https://iri.gsfc.nasa.gov/docs/iri_2007_asr.pdf

International Reference Ionosphere 2007: Improvements and new parameters

The paper presents the latest version of the International Reference Ionosphere model (IRI-2016) describing the most important changes and improvements that were included with this version and discussing their impact on the IRI predictions of ionospheric parameters. IRI-2016 includes two new model options for the F2 peak height hmF2 and a better representation of topside ion densities at very low and high solar activities. In addition, a number of smaller changes were made concerning the use of solar indices and the speedup of the computer program. We also review the latest developments toward a Real-Time IRI. The goal is to progress from predicting climatology to describing the real-time weather conditions in the ionosphere.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016SW001593

International Reference Ionosphere 2016: From ionospheric climate to real‐time weather predictions

The International Reference Ionosphere (IRI) project was established jointly by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) in the late sixties with the goal to develop an international standard for the specification of plasma parameters in the Earth’s ionosphere. COSPAR needed such a specification for the evaluation of environmental effects on spacecraft and experiments in space, and URSI for radiowave propagation studies and applications. At the request of COSPAR and URSI, IRI was developed as a data-based model to avoid the uncertainty of theory-based models which are only as good as the evolving theoretical understanding. Being based on most of the available and reliable observations of the ionospheric plasma from the ground and from space, IRI describes monthly averages of electron density, electron temperature, ion temperature, ion composition, and several additional parameters in the altitude range from 60 km to 2000 km. A working group of about 50 international ionospheric experts is in charge of developing and improving the IRI model. Over time as new data became available and new modeling techniques emerged, steadily improved editions of the IRI model have been published. This paper gives a brief history of the IRI project and describes the latest version of the model, IRI-2012. It also briefly discusses efforts to develop a real-time IRI model. The IRI homepage is at http://IRImodel.org.

/pdf/the-international-reference-ionosphere-2012-a-model-of-1o61n09tjl.pdf

The International Reference Ionosphere 2012 – a model of international collaboration

T HE ionosphere is an important source of range and range-rate errors for users of the global positioning system (GPS) satellites who require highaccuracy measurements. At times, the range errors of the troposphere and the ionosphere can be comparable, but the variability of the Earth's ionosphere is much larger than that of the troposphere, and it is more difficult to model. The ionospheric range error can vary from only a few meters, to many tens of meters at the zenith, whereas the tropospheric range error at the zenith is generally between two to three meters. Fortunately, the ionosphere is a dispersive medium; that is, the refractive index is a function of the operating frequency, and twofrequency GPS users can take advantage of this property of the ionosphere to measure and correct for the first-order ionospheric range and range-rate effects directly. Unlike the troposphere, the ionosphere can change rapidly in absolute value. Although the range error of the troposphere generally does not change by more than ±10%, even over long periods of time, the ionosphere frequently changes by at least one order of magnitude during the course of each day. The major effects the ionosphere can have on GPS are the following: 1) group delay of the signal modulation, or absolute range error; 2) carrier phase advance, or relative range error; 3) Doppler shift, or range-rate errors; 4) Faraday rotation of linearly polarized signals; 5) refraction or bending of the radio wave; 6) distortion of pulse waveforms; 7) signal amplitude fading or amplitude scintillation; and 8) phase scintillations. In order to understand the reasons for these potential effects on GPS performance, a brief description of the major characteristics of the ionosphere is necessary.

Ionospheric Effects on GPS

International reference ionosphere — past, present, and future: I. Electron density

Progress in ionospheric informatics based on electron-density profile analysis of ionograms

/pdf/gim-tec-adaptive-ionospheric-weather-assessment-and-forecast-2nx7wecpq1.pdf

GIM-TEC adaptive ionospheric weather assessment and forecast system

[1] Shortcomings of the representation of the topside electron density profile in the International Reference Ionosphere (IRI) model have been noted in comparison with recently analyzed topside sounder data and also with total electron content (TEC) data. Various studies have proposed corrections of the IRI formulas or have introduced a new formalism. This paper reviews the different approaches, their implications for IRI, and their current status. An important challenge for topside modeling is the truthful representation of profiles in the equatorial anomaly (EA) region over the whole range of the EA fountain. This means that the latitudinal representation has to reproduce the merging of the double-peak signature at F region heights into a single peak at the top of the fountain. In this context, special emphasis is given to the coupling between topside and plasmaspheric models.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005RS003370

Improvements of the International Reference Ionosphere model for the topside electron density profile

The planetary ionospheric storm index, Wp, is de- duced from the numerical global ionospheric GPS-IONEX maps of the vertical total electron content, TEC, for more than half a solar cycle, 1999-2008. The TEC values are ex- tracted from the 600 grid points of the map at latitudes 60 N to 60 S with a step of 5 and longitudes 0 to 345 E with a step of 15 providing the data for 00:00 to 23:00 h of lo- cal time. The local effects of the solar radiant energy are filtered out by normalizing of the TEC in terms of the solar zenith angle at a particular time and the local noon value 0. The degree of perturbation, DTEC, is computed as log of TEC relative to quiet reference median for 27 days prior to the day of observation. The W-index map is generated by segmentation of DTEC with the relevant thresholds specified earlier for foF2 so that 1 or 1 stands for the quiet state, 2 or 2 for the moderate disturbance, 3 or 3 for the moder- ate ionospheric storm, and 4 or 4 for intense ionospheric storm at each grid point of the map. The planetary iono- spheric storm Wp index is obtained from the W-index map as a latitudinal average of the distance between maximum positive and minimum negative W-index weighted by the lat- itude/longitude extent of the extreme values on the map. The threshold Wp exceeding 4.0 index units and the peak value Wpmax 6.0 specify the duration and the power of the plan- etary ionosphere-plasmasphere storm. It is shown that the occurrence of the Wp storms is growing with the phase of the solar cycle being twice as much as the number of the magnetospheric storms with Dst 100 nT andAp 100 nT.

/pdf/derivation-of-a-planetary-ionospheric-storm-index-5c0bvcd6r4.pdf

Tamara Gulyaeva

Papers

International reference ionosphere — past, present, and future: I. Electron density

Progress in ionospheric informatics based on electron-density profile analysis of ionograms

GIM-TEC adaptive ionospheric weather assessment and forecast system

Improvements of the International Reference Ionosphere model for the topside electron density profile

Derivation of a planetary ionospheric storm index