IRI'96 Workshop Report

COSPAR'96, Birmingham, U.K., July 14-21, 1996
C4.2 Quantitative Description of Ionospheric Storm Effects and Irregularities
Convenor: Dieter Bilitza, USA

The current International Reference Ionosphere model, IRI 95, does not
include ionospheric storm effects. This two-day symposium was addressing
the need of incorporating ionospheric storm effects in the IRI model.
In addition the session continued IRI efforts to include occurrence
statistics for irregularities (e.g. Spread-F) in the model. 
Seven subsessions dealt with specific aspects of the modeling problem.

The "Coordinated Storm Studies" session reviewed specific storm events that
had been the topic of coordinated studies like CEDAR (Buonsanto, MIT; Richards,
U. Alabama) and PRIME (Bradley, UK; Pavlov, Russia; Tulunay, Turkey). The 
"Theoretical Storm Studies" session started with overviews by Anderson 
(Phillips Lab.) and Schunk (Utah State U.). Manifestation of storm effects 
were presented in the session on "Storm-related Data Studies" by Reinisch 
(UML; Digisonde observation), by Werner and Proelss (Germany; trough model), 
Rishbeth (UK; 30 years of ionosonde data), Oyama (Japan; Akebono and
Hinotori data), Truhlik (Czech R.; IK-19 and Magion data). Potential methods 
of representing storm effects in IRI were presented in the session on
"Stormtime Updating" by Kishcha (Russia) and Fuller-Rowell (UK/USA). 
The session on "Spread-F and Irregularities" included reviews by Abdu (Brazil;
Spread-F) and Fejer (Utah State U.; ion drift).

In describing ionospheric strom effects IRI needs to represent the following 
effects observed during magnetic storms: polar cap expansion, auroral oval 
expansion, large changes in F peak density and height, large changes in ion 
composition, elevated plasma temperatures, and anisotropic ion temperature. 
The next version of IRI will include a representation of the Feldstein
auroral ovals for different levels of magnetic activity and also the 
subauroral updating algorithm for the F peak height and density that 
was developed by Kishcha (Russia) and colleagues. Very prosiming for 
future improvements of stromtime updating in IRI are the efforts 
described in the talks by Kishcha (Russia), Fuller-Rowell (NOAA) and 
Rishbeth (UK). All three model studies are based on the long ionosonde data 
record and all three describe first order effects in terms of the neutral 
density ratios. The IZMIRAN method that is now scheduled to become part of 
IRI-96 also allows updating with measured peak and electron content data. 
Fuller-Rowell used his theoretical model to come up with an empirical 
description that also includes the effects of the neutral wind field. 
Updating might also benefit from the study of Tulunay (Turkey) who reported 
a direct correlation between IMF direction and auroral foF2, although 
season-specific studies with more data are needed to confirm this results.

Very interesting in terms of the IRI ion composition model were the
presentations by Triskova (Czech R.) and Lathuiller (France) that 
showed the dependence of the ion transition heights (lower and upper)
on magnetic activity based on Active and Apex data, and EISCAT data,

Papers by Scotto (Italy) and by Gonzalez (Argentina) presented improvements 
of the IRI F1 region model that resulted from the ongoing work of the IRI 
F1/Bottomside Task Force Activity at the International Center of Theoretical 
Physics (ICTP) in Trieste, Italy. Mahajan (India) described an improved 
representation of the E-F valley parameters for IRI.

The poster session consisted of 14 posters. It included several contributions 
by Zherebtsov, Shubin,and Depuev (Russia) dealing with the variation of peak
parameters during disturbances, and two application-oriented papers reporting 
on the use of IRI for altimeter data analysis (Shum, UTD; Bilitza, HSTX/NSSDC).

Selected papers of this two-day session will be published in  Advances in Space
Research (ASR).

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