Update on the Activities of the URSI/COSPAR Working Group on the International Reference Ionosphere (IRI)

[Dieter Bilitza, IRI Steering Group Executive Secretary, Vice-Chair of Panel on Capacity Building, and Vladimir Truhlik, Chair of URSI/COSPAR Working Group on IRI]

The URSI/COSPAR IRI Working Group is a team of 68 members from 29 countries. The Figure below lists the names and shows the global distribution of the current working group roster. The working group was initiated in 1969 with the goal of establishing an internationally accepted standard for the description of the most important parameters of Earth’s ionosphere.

"COSPAR and URSI requested a model that would be primarily based on experimental evidence"

By charter the model should be primarily based on experimental evidence using all available ground and space data sources and should not depend on the evolving theoretical understanding of ionospheric processes. COSPAR and URSI requested a model that would be primarily based on experimental evidence using all available ground and space data sources and that should not depend on the evolving theoretical understanding of ionospheric processes. This is similar to other widely used and internationally accepted standard models for other parts of geospacer, like the Mass Spectrometer and Incoherent Scatter (MSIS) model for Earth’s atmosphere and the International Geomagnetic Reference Field (IGRF) model for the Earth magnetic field.

It describes the global variation of electron density, electron temperature, ion temperature and ion composition in Earth’s ionosphere (50 km – 2000 km) and in addition, vertical ionospheric total electron content (vITEC), equatorial vertical ion drift, auroral boundaries, and occurrence probability of spread-F and F1 layer. This brief report gives an update on recent activities of the IRI Working Group.

Working group meetings are an essential ingredient for the success of the IRI project because they provide a venue for discussing new data sources, model shortcomings and improvements, for highlighting model applications, and most importantly for helping to initiate collaborations between group members on ionospheric modelling projects. The working group organized a session during the COSPAR Scientific Assembly in Athens, Greece in July 2022 on the topic of "Real-time and retrospective ionosphere modelling with in-situ and GNSS satellite data". The 1.5-day session was well attended and presented a number of different approaches to improving the quality of real-time forecasts with the help of data assimilation into the background IRI model. The primary data sources were GNSS TEC observations, ionosonde recordings, as well as COSMIC radio occultation data. The IRI Working Group held a business meeting at the end of the conference week and decided on several organizational changes and model improvements. The group thanked David Altadill for his eight years (the maximum allowed due to COSPAR rules) of service as Working Group Chair and elected Vladimir Truhlik as new IRI Chair. Andrezj Krankowski was re-elected as COSPAR Vice-Chair and Ivan Galkin as URSI Vice-Chair. The IRI Working Group has two Vice-Chairs because it is an Inter-Union Working Group. Sessions on IRI improvements, validations and usage have been proposed for the 2023 URSI General Assembly in Sapporo, Japan (https://www.ursi-gass2023.jp/) on and for the 2024 COSPAR Scientific Assembly in Busan, South Korea (https://www.cospar2024.org/). Both sessions have been accepted and organizational preparations are underway.

The IRI Working Group held an IRI-related COSPAR Capacity Building Workshop entitled "Improved Real-time Ionospheric Predictions with Data from Space-borne Sensors and GNSS" in Daejeon, South Korea on May 6 - 19, 2023 (see report in this issue on page 70).

Models for the D-region electron density, ion temperature and the equatorial ion drift have been replaced

The latest version of the IRI model was released during the 2022 COSPAR General Assembly and includes several important IRI improvements and additions. The models for the D-region electron density, the ion temperature, and the equatorial ion drift have been replaced by newer, better ones and significant improvements were implemented for the topside electron density profile. For the first time an extension of the electron density profile to plasmaspheric altitudes was included directly in the model code. These and additional smaller changes are described in detail in a recent article by Bilitza et al. (2022) which also provides a good introduction for users who are interested in a deeper understanding of the data base and mathematical framework of the model.

The performance of the IRI model has been assessed and evaluated in many independent multimodel studies and the model has been always found to be one of the most reliable models. In 2014 IRI was elected to become the ISO (International Standardization Organization) standard for the ionosphere and was re-affirmed in 2021. The wide application of the IRI model for the description of Earth’s ionosphere is documented in the list of different journals in which IRI has been referenced and in the percentage of JGR, RS, and SW papers that have used IRI each year (see figures).

The IRI FORTRAN code can be downloaded from the IRI homepage at irimodel.org. The page also provides access to the online computation of IRI parameters at the CCMC and other websites. Here an IRI user will also find information about past and upcoming IRI workshops and about IRI-related publications.

Recent Publications:

Bilitza D, B. Reinisch (eds.), International Reference Ionosphere – Progress and New Inputs, Advances in Space Research, Volume 68, Issue 5, pp. 2057-2256, 1 Sep 2021.

Truhlík, Vladimír, Dieter Bilitza, Dmytro Kotov, Maryna Shulha, and Ludmila Třísková. 2021. «A Global Empirical Model of the Ion Temperature in the Ionosphere for the International Reference Ionosphere» Atmosphere 12, no. 8: 1081. https://doi.org/10.3390/atmos12081081

Bilitza, D., Pezzopane, M., Truhlik, V., Altadill, D., Reinisch, B. W., & Pignalberi, A. (2022). The International Reference Ionosphere model: A review and description of an ionospheric benchmark. Reviews of Geophysics, 60, e2022RG000792. https://doi.org/10.1029/2022RG000792