International Reference Ionosphere (IRI) Workshop 2011

Report/ Dieter Bilitza

The 2011 IRI Workshop was hosted by the Space Science Directorate of the South African National Space Agency (SANSA), SANSA Space Science, formerly the Hermanus Magnetic Observatory (HMO), in Hermanus, South Africa. The meeting took place from October 10 to 14, 2011 and was attended by 60 participants representing 20 countries including a sizable group of attendees from African countries (16 representing 7 countries). The special emphasis of the 2011 workshop was on improving IRI over the African Region. The 65 presentations were grouped into sessions on IRI in the African Sector: Topside Ionosphere: Storm-Time and Real-Time IRI; F Peak Height and Density; TEC and related Parameters; The Ionosphere and IRI During the Recent Solar Minimum; Lower Ionosphere; Inputs for IRI; IRI Applications; and Final Discussions. The workshop has received financial support from COSPAR, URSI, NSF, SANSA, Cape Town Routes Unlimited, and the Overstrand Municipality.

The meeting provided an excellent opportunity to review the many IRI-related science and educational activities in Africa and to focus on shortcomings of the IRI model over this large and important longitude sector. Most of the research activities reported at this meeting were based on ionospheric parameters deduced from ionosonde and GPS measurements. But there were also important contributions that relied on satellite sounder and in situ measurements including data from the older Alouette and ISIS topside sounders and from the more recent TIMED and C/NOFS satellites. It became quite clear that additional work is needed to more accurately represent the African zone and particular the Equatorial Ionization Anomaly (EIA) region in IRI.

An important event during this workshop was the presentation of the latest version of the IRI model, IRI-2012 (Bilitza, USA). This new version includes several improvements and new additions: (1) A better representation of the bottomside electron density profile based on the work of Altadill, Blanch, and Torta (Spain) with a large volume of worldwide ionosonde data; (2) A better representation of the profile of molecular ion composition in the bottomside ionosphere based on normalizing the photochemistry from the FLIP model with the IRI electron density (Richards and Bilitza, USA); A new model for the electron temperature that now accounts also for solar activity variations based on a large volume of insitu measurements (Truhlik, Bilitza, and Triskova, Czech Republic and USA); Inclusion of auroral boundaries and their movement with magnetic activity based on the TIMED/GUVI model of Zhang and Paxton (USA); Adding a model describing storm effects in the E region based on TIMED/SABER data (Mertens, USA); Using the latest model version for the Earth’s magnetic field (International Geomagnetic Reference Field, IGRF-11) and the Earth’s atmosphere (NRL-MSIS-00 model of Picone and Drob, USA); Inclusion of Corrected Geomagnetic Coordinates (CGM) (Papitashvili, USA) and of several additional solar indices: F10.7 daily, 81-day, 12-month running mean, and PF10.7. Workshop participants received a beta version of the IRI-2012 Fortran code and will help to test the new code before it is officially released later in the year.

Storm-time conditions and the quality of IRI predictions were studied in a number presentations based on ionosonde measurements (Buresova, Czech Republic; Oyeyemi, Nigeria; Pietrella, Italy; Pezzopane, Italy; Ngwira, South Africa; Cherniak, Ukraine). The need for a Real-Time IRI (IRI-RT) becomes very clear from these presentations. A possible approach was presented by Galkin (USA) assimilating data from the digisonde network into IRI (GIRO). But most storm-modeling is so far limited to the F2 peak density, although it is clear that the peak height (hmF2) is also severely affected by the storm (Buresova; Ngwira). A first step towards a better representation of hmF2 in IRI was presented by Altadill (Spain) who introduced a global model for the quiet-time hmF2 based on a large volume of values scaled from ionograms. This is an important improvement because in the current IRI hmF2 is obtained indirectly through its relationship with the propagation factor M(3000)F2 also scaled from ionograms.

The talks presented at this meeting made use of a number of data sources including ionosondes, GPS, COSMIC, ISIS, ISS-b, Hinotori, CHAMP, C/NOFS, TIMED, Demeter, and DMSP. Like in earlier workshops ionosondes were the prime data sources including data from African stations (McKinnell, Mbambo, Sessanga, South Africa; Oyeyemi, Nigeria; Ahoua, Ivory Coast), European stations (Buresova; Altadill; Pietrella; Mosert; Bilitza), Argentine and Antarctic stations (Mosert; Gularte), Chinese stations (Wang; Shi), Indian stations (Srinivas), Brazilian stations (de Souza and Bilitza) and Thai stations (Wichaipanich; Kenpankho). Studies of spread-F occurrence over Thailand (Wichaipanich) and over China (Shi) are bearing promise for a future extension of the IRI spread-F model from currently the Brazilian longitude sector to a global model. Another widely used data source were GPS-TEC measurements including data from ground receivers located in China (Wang; Shi), Argentina (Mosert), Russia (Zakharenkova) and in several African countries (Olwendo, Kenya; Ochieng, Kenya; Okoh, Nigeria; Mbambo, South Africa; Cilliers, South Africa). The data were used to evaluate IRI over the respective region and to point out times and regions were improvements are needed. Tomographic techniques have evolved to the point were they can help to get information for the IRI peak and profile models (Chartier, UK). The IGS IONO group continues its role as main liaison between the GPS and IRI community and as producer of the definitive GPS TEC maps and new products like the ROTI index (Krankowski, Poland). New initiatives in Argentina bear great potential for future inputs to IRI modeling (Gularte, Argentina) including the Argentine Network for the Study of the Upper Atmosphere (RAPEAS) and the Argentina Ionospheric Radar Experiment Station (AIRES).

An important topic was the investigation of IRI performance during the recent very low and extended solar maximum using ionosonde data (Fuller-Rowell; Bilitza; Buresova), C/NOFS data (Klenzing, USA), and GPS TEC (Cherniak; Cilliers). Since there is good agreement at the F-peak, the discrepancy found above the peak with C/NOFS and CHAMP satellite measurements must be due to an overestimation in IRI of hmF2 and/or the topside shape. CHAMP and C/NOFS data will help to introduce the required improvements into IRI.

The IRI team continues its involvement and support of international science unions.

The International Telecommunication Union (ITU) and the International Union of Radio Science (URSI) have asked the IRI team to help facilitate the science transfer from URSI studies to ITU recommendations. IRI was invited to present the IRI F-peak mapping status and plans at the ITU-R meeting in Genève in October 17-21, 2011 (Reinisch, USA). IRI is also actively involved in efforts by the International Standardization Organization (ISO) to establish ISO standards for the Near-Earth space environment. The IRI-ISO standard document has now been sent out to the international ionosphere community for review (Bilitza, USA and Gulyaeva, Russia).

Papers from the 2009 IRI Workshop in Kagoshima, Japan have now been published in a first issue of Earth, Planets, and Space (EPS, Volume 63, Number 4, 2011) and a second special EPS issue will be published soon. A special issue of Advances in Space Research is in preparation with the presentation from the IRI session during the 2010 Scientific Assembly of the Committee on Space Research (COSPAR). The IRI group has submitted a session proposal for the 2012 COSPAR meeting in Mysore, India (July 16-21), which now has been approved. The session will be on ‘Global and Regional Representation of Ionospheric Peak Parameters for Space Weather Applications’. For its 2013 Workshop the IRI community has been invited to the University of Warmia and Mazury in Olsztyn, Poland with A. Krankowski as the local organizer. Two new members were elected to join the IRI Working Group: Patrick Sibanda (University of Zambia, Lusaka, Zambia), and Jiankui Shi (Center for Space Science and Applied Research, CAS, Beijing, China).

The workshop was expertly organized by the SANSA team led by Lee-Anne McKinnell; John Bosco Habarulema deserves a special mention for his untiring support of participants’ needs before and throughout the workshop week from pick-up at the airport to drop-off. The little seaside town of Hermanus fully lived up to its title as one of the world’s prime location for whale sightings. An excursion to the Hemel en Aarde Valley near Hermanus with food pairing and dinner at local wineries convinced the attendees that the valley carries its name rightfully, “Heaven on Earth”. The Executive Mayor of the Overstrand Municipality Nicolle Botha-Guthrie and SANSA CEO Dr. Sandile Malinga welcomed the delegates at the dinner reception.