The role of COST Actions in unifying the European ionospheric community in the transition between the two millennia

This paper consists of a review of the important contributions of four COST (European Co-operation
in Science and Technology) Actions in the period 1991–2009 to terrestrial ionospheric research, with applications
in modern communication and navigation systems. Within this context, new ionospheric studies were initiated,
leading to the development of a number of models, algorithms for prediction, forecasting, and real-time specification,
as well as numerical programs. These were successfully implemented in different collaborative projects
within EU instruments, promoting co-operation between scientists and researchers across Europe. A further outcome
was to bring together more than a hundred researchers from around 40 scientific institutions, agencies, and
academia in about 25 countries worldwide. They collaborated with enthusiasm in research, as briefly described
in this paper, forming a lively ionospheric community and presenting a strong intellectual response to the rapidly
growing contemporary challenge of space weather research