IRI Updates - IRIWeb, Model Software and Solar/Magnetic Indices

By Dieter Bilitza and Natalia Papitashvili, Code 633

The IRIWeb interface at http://nssdc.gsfc.nasa.gov/space/models/iri.html was upgraded to the latest version of the IRI (International Reference Ionosphere) model. IRIWeb lets users compute, list, and plot IRI parameters online. In addition to the traditional IRI parameters (Ne, Te, Ti, Ni, TEC) users can now also compute the equatorial vertical ion drift, the storm to quiet time ratio for the F2 peak plasma frequency (a parameter proportional to the F2 peak density), and the occurrence probability for an F1 layer. The ion drift is a critical parameter for the understanding and description of the equator anomaly phenomenon (latitudinal maxima in density on both sides of the magnetic equator) and the F1 occurrence probability was included to help HF (high frequency) radio wave propagation studies and applications. IRIWeb now also provides several new input options: (i) the user can specify the sunspot number (R) and the ionospheric global index (IG), (ii) the STORM model can be turned on and off, (iii) for the topside electron temperature the new model of Trsikova et al. (Institute of Atmospheric Physics,  Prague, Czech Republic) can be used, (iv) for the D-region electron density the new model of Friedrich et al. (Graz, Austria) can be used, (v) for the F1 occurrence probability the user can choose between three model options.

Several corrections and improvements were made to the IRI code and the newest version of the program files were posted at ftp://nssdcftp.gsfc.nasa.gov/models/ionospheric/iri/iri2001/fortran_code/ in early March. These corrections are based on the feedback from IRI users who pointed out specific problems and often helped resolving them: David Simpson, GSFC, Code 692/582; Cemil B Erol, Turkey; Daniel Heynderickx, BIRA, Brussel, Belgium; Richard E. Denton, Dartmouth College, Hanover, New Hampshire; Kevin Jennings, SwRI, Texas; Bill Taylor, Raytheon ITSS, Lanham, Maryland; Minakishi Chamua, Dibrugarh University, Assam, India. Specific corrections are listed with dates and short explanations in the comment field at the top of the Fortran program files.

Regular updates are made to the IRI solar and magnetic indices files based on the indices data that are available from the National Geophysical Data Center (NGDC) in Boulder, Colorado, the Ionospheric Prediction Service (IPS) in Sydney, Australia and the World Data Center C1 (WDC-C1) in Chilton, U.K. For the solar indices the file also includes predicted values and extends to December 2005. The most recent update (Feb 2003) resulted in increased R12 predictions (e.g., July 2002: from 90 to 103) and decreased  IG12 predictions (July 2002: from 145 to 135).

The IRI homepage is located at http://nssdc.gsfc.nasa.gov/space/model/ionos/iri.html