5 Conclusion

This paper demonstrates that merging full-disk helioseismological data provided by different instruments is possible, and significantly rewarding. Merging IRIS, Mark-1 and LOWL into the IRIS⁺⁺ data base provides 11 years of reasonably good quality full-disk data, with sufficient duty cycles so that the sidelobe structure becomes only marginally visible. This is certainly the longest data base publicly available, and the only one to cover a complete solar cycle at the date of writing this paper. The annual duty cycles are of the order of 60%, reaching sometimes 90% in summer on a monthly basis, and over 95% on a 4-month basis after the partial gap filling method.

If, in the opinion of the authors, there is extremely little chance to detect g-modes from the ground with this present generation of observational methods and instruments, the p-mode study can, to a very large extent, be completely made from the ground, and only a relatively small international effort, in manpower and financial supports, is required to maintain such a network alive for many more years, or even decades. The detailed behaviour of the p-mode parameter changes with solar activity has only started to be addressed, and it may very well be that it will provide the key to final understanding the magnetic cycle. The 11 years time series of this IRIS⁺⁺ data bank must be exploited with these questions in mind: evolution of frequencies, linewidths, amplitudes, and also other parameters, at various timescales across the solar cycle, correlation with activity indexes and also with other relevant solar data such as irradiance and radius. Such a long time series can also be exploited for extremely high accuracy measurement of the rotational splitting of the low frequency p-modes (much less sensitive to the surface disturbances, and thus providing better access to the solar core rotation). There is no doubt that a good exploitation of this data bank will finally raise more questions than it will provide answers, and that as always, more observations of better quality will be necessary.

Acknowledgements

Data from the IRIS network depends on the coordinated efforts of many people from several nations. The authors wish to thank those who have conceived the instrument: E. Fossat and G. Grec; those who have contributed to build and maintain all instruments on site: B. Gelly, J. F. Manigault, G. Rouget, J. Demarcq, G. Galou, A. Escobar, J. M. Robillot; those who have operated the observing sites: M. Baijumamov, S. Ehgamberdiev, S. Ilyasov, S. Khalikov, I. Khamitov, G. Menshikov, S. Raubaev, T. Hoeksema, Z. Benkhaldoun, M. Lazrek, S. Kadiri, H. Touma, M. Anguera, A. Jimenez, P. L. Palle, A. Pimienta, C. Regulo, T. Roca Cortes, L. Sanchez, F. X. Schmider; R. Luckhurst, those who have developed the analysis software: S. Ehgamberdiev, S. Khalikov, E. Fossat, B. Gelly, M. Lazrek, P. L. Palle, L. Sanchez, E. Gavryuseva, V. Gavryusev; and those who have contributed to the success of the IRIS project in other critical ways: P. Delache, D. Gough, I. Roxburgh, F. Hill, T. Roca-Cortes, G. Zatsepin, T. Yuldashbaev, L. Woltjer, H. Van der Laan, D. Hofstadt, J. Kennewell, D. Cole, P. H. Scherrer, F. Sanchez, J. P. Veziant. The IRIS group is grateful to BISON, IAC and HAO for sharing the Mark-1 and LOWL data and acknowledges the LOWL observers Eric Yasukawa and Darryl Koon.
The uzbek contribution has been supported by the Intas 97-31198 and SCOPES 7UZPJ065728.01/1 grants, and the cooperation between the IRIS group and LOWL has been supported by the CNRS/NSF cooperation.