ICTP'94 IRI Task Force Activity

IRI charts new waters at ICTP, Trieste, Italy
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During the month of July a special task force activity at the
International Center for Theoretical Physics (ICTP) in Trieste
Italy explored new ways of improving critical elements of the
International Reference Ionosphere (IRI) model. ICTP is an
science center funded by the International Atomic Energy Agency
(IAEA), UNESCO, and the Italian government, that has as its main
objectives the support of advanced studies
and research in physical and mathematical sciences, especially in
the developing countries and to provide an international forum for
scientific contacts between scientists from all countries.

Following an invitation of Prof. Sandro Radicella, the Director of
ICTP's Atmospheric Physics and Radiopropagation Laboratory (APRL),
a dozen scientists, half and half from developing and developed
countries, convened at ICTP to focus on the modelling of F1 layer
characteristics in the IRI model. Improved global maps for these 
parameters will benefit studies and application that require ray-
tracing through the middle ionosphere. The F1 height marks 
the transition from molecular to atomic ions and/or the
transition from the E-region chemical photoequilibrium (solar
control) to the more dynamic F-region regime (controlled by the
magnetic field geometry). 

To accomplish the set task the IRI team decided to test an approach 
different from the traditional meeting and workshop format. A small 
group of modellers and data provider met in front of computer terminals 
and blackboards to discuss and resolve a specific IRI modelling problem.
The first week of the 3-week effort was primarily used for software, 
hardware and science preparations and also as a time-buffer for getting the
arriving scientist familiarized with the computer systems. 
The F1-region modelling problem was sub-divided into six well-defined
well-focussed science questions. These topics were than tackled
(one a day) during the second week with all participants present:
  1 - Validation of the Ducharme et al. formulas; 
  2 - IRI model treatment when F1 is not present; 
  3 - Comparison of IRI-hmF1 with measurements; 
  4 - Validation of the hmF1-NmF1 relationship; 
  5 - Relation of F1 appearance/variability to ion 
      transition height and dynamics
During round-table discussions and presentations in the morning,
a strategy was developed for testing and exploring particular
modelling issues and assumptions and this was than followed in the
afternoon with 2-3 person teams in front of computer terminals with
access to ICTP's computer power and network connectivity. The last
week was reserved for following up on the issues that had not been 
resolved during the previous week and also to polish-up plots and
tables created during the workshop activity for later-date publication.

The task force activity was very successful and resulted in several
recommendations for improvements of the IRI model and of ionogram
data reduction in general. Most importantly, it was recommend that
global maps should be established for the following parameters: the
gradient at the F1 point, the density at a fixed height of 170km
and/or 180 km (these last parameters are especially important during
times when F1 is not present). It was also shown that the current 
limitation of F1 appearance to none-winter month is to restrictive 
and should be removed. The activity was strongly endorsed by the
IRI Working Group during its COSPAR meeting and ICTP was encouraged
to continue and possibly expand this type of activity. There was a
general sense of accomplishment shared by all the participants.
The effort showed what can be accomplished by a small group of 
scientists with a very focussed ionospheric modelling problem and
with access to computers and networks.

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