Moskva, Russian Federation
The International Reference Ionosphere (IRI) imports global effective ionospheric IG12 index based on ionosonde measurements of the critical frequency foF2 as a proxy of solar activity. Similarly, the global electron content (GEC), smoothed by the sliding 12-months window (GEC12), is used as a solar proxy in the ionospheric and plasmaspheric model IRI-Plas. GEC has been calculated from global ionospheric maps of total electron content (TEC) since 1998 whereas its productions for the preceding years and predictions for the future are made with the empirical model of the linear dependence of GEC on solar activity. At present there is a need to re-evaluate solar and ionospheric indices in the ionospheric models due to the recent revision of sunspot number (SSN2) time series, which has been conducted since July 1, 2015 [Clette et al., 2014]. Implementation of SSN2 instead of the former SSN1 series with the ionospheric model could increase model prediction errors. A formula is proposed to transform the smoothed SSN212 series to the proxy of the former basic SSN112=R12 index, which is used by the IRI and IRI-Plas models for long-term ionospheric predictions. Regression relationships are established between GEC12, the sunspot number R12, and the proxy solar index of 10.7 cm microwave radio flux, F10.712. Comparison of calculations by the IRI-Plas and IRI models with observations and predictions for Moscow during solar cycles 23 and 24 has shown the advantage of implementation of GEC12 index with the IRI-Plas model.
Global electron content, Sunspot number, Solar radio flux, Ionosphere · Plasmasphere, Models IRI, IRI-Plas
1. Afraimovich E.L., Perevalova N.P. GPS-Monitoring verkhnej atmosfery Zemli [GPS-Monitoring of the Upper Atmosphere of the Earth]. Irkutsk: ISTP SB RAS, 2006, 480 p. (In Russian).
2. Afraimovich E.L., Astafyeva E.I., Oinats A.V., Yasukevich Yu.V., Zhivetiev I.V. Global electron content: a new conception to track solar activity. Ann. Geophys. 2008, vol. 26, no. 2, pp. 335-344.
3. Ahluwalia H.S. The descent of the solar cycle 24 and future space weather. Adv. Space Res. 2016, vol. 57, iss. 2, pp. 710-714. DOI:https://doi.org/10.1016/j.asr.2015.11.015.
4. Bilitza D., Sheikh N.M., Eyfrig R. A global model for the height of the F2 peak using M3000 values from the CCIR. Telecomm. J. 1979, vol. 46, pp. 549-553.
5. Bilitza D., McKinnell L.A., Reinisch B., Fuller-Rowell T. The international reference ionosphere today and in the future. J. Geodesy. 2011. vol. 85, pp. 909-920. DOI:https://doi.org/10.1007/s00190-010-0427-x.
6. Bilitza D., Brown S.A., Wang M.Y., Souza J.R., Roddy P.A. Measurements and IRI model predictions during the recent solar minimum. J. Atmos. Solar-Terr. Phys. 2012, vol. 86, pp. 99-106. DOI:https://doi.org/10.1016/j.jastp.2012.06.010.
7. Bilitza D. The International Reference Ionosphere - Status 2013. Adv. Space Res. 2015, vol. 55, iss. 8, pp. 1914-1927. DOI: 10.1016.j.asr.2014.07.032.
8. CCIR Atlas of Ionospheric Characteristics. Comite Consultatif International des Radio Communications Rep. 340. Geneve, International Telecommunication Union, 1983.
9. Chasovitin Yu.K., Shirochkov A.V., Besprozvannaya A.S., Gulyaeva T.L., Denisenko P.F., Armenskaya O.A., Ivanova S.E., Kashirin A.I., Klueva N.M., Koryakina E.A., Mironova L.S., Sykilinda T.N., Shushkova V.B., Vodolazkin V.I., Sotsky V.V., Sheidakov N.E. An empirical model for the global distribution of density, temperature and effective collision frequency of electrons in the ionosphere. Adv. Space Res. 1987, vol. 7, iss. 6, pp. 49-52.
10. Clette F., Svalgaard L., Vaquero J.M., Cliver E.W. Revisiting the sunspot number: a 400-year perspective on the solar cycle. Space Sci. Rev. 2014, vol. 186, iss. 1, pp. 35-103.
11. Gulyaeva T.L., Bilitza D. Towards ISO Standard Earth Ionosphere and Plasmasphere Model. New Developments in the Standard Model. Nova Science Publishers Inc., 2012, рр. 1-39. Available at https://www.novapublishers.com/catalog/product_ info.php?products_id=35812 (accessed September 1, 2016).
12. Gulyaeva T.L., Veselovsky I.S. Imaging Global Electron Content backwards in time more than 160 years ago. Adv. Space Res. 2014, vol. 53, iss. 3, pp. 403-411. DOI:https://doi.org/10.1016/j.asr. 2013.11.036.
13. Deminov M.G. Solar activity index for long-term ionospheric forecasts. Cosmic Research. 2016, vol. 54, no. 1, pp. 1-7. DOI:https://doi.org/10.1134/S0010952516010068.
14. Hao Y.Q., Shi H., Xiao Z., Zhang D.H. Weak ionization of the global ionosphere in solar cycle 24. Ann. Geophys. 2014, vol. 32. pp. 809-816. DOI:https://doi.org/10.5194/angeo-32-809-2014.
15. Jones W.B., Gallet R.M. Representation of diurnal and geographical variations of ionospheric data by numerical method. Telecomm. J. 1962, vol. 29, p. 129; 1965, vol. 32, p. 18.
16. Liu R., Smith P., King J. A new solar index which leads to improved foF2 prediction using the CCIR atlas. Telecomm. J. 1983, vol. 50, pp. 408-414.
17. Lukianova R., Mursula K. Changed relation between sunspot numbers, solar UV/EUV radiation and TSI during the declining phase of solar cycle 23. J. Atmos. Solar-Terr. Phys. 2011, vol. 73, iss. 2-3, pp. 235-240. DOI:https://doi.org/10.1016/j.jastp.2010.04.002.
18. Maruyama T. Solar proxies pertaining to empirical ionospheric total electron content models. J. Geophys. Res. 2010, vol. 115, A04306. DOI:https://doi.org/10.1029/2009JA014890.
19. Nava B., Coisson P., Radicella S.M. A new version of the NeQuick ionosphere electron density model. J. Atmosph. Solar-Terr. Phys. 2008, vol. 70, iss. 15, pp. 1856-1862. DOI: 10.1016/ j.jastp. 2008.01.015.
20. Ratovsky K.G., Oinats A.V., Medvedev A.V. Similarities and differences between regular variations of F2-layer parameters of the polar and midlatitude ionosphere in East Siberian sector. Solnechno-zemnaya fizika [Solar-Terr. Phys.]. 2015, vol. 1, no. 2, pp.70-79. DOI:https://doi.org/10.12737/7832. (In Russian).
21. URL: http://sidc.oma.be/silso/ (accessed September 1, 2016).
22. URL: ftp://ftp.geolab.nrcan.gc.ca/data/solar_flux/daily_flux_ values/ (accessed September 1, 2016).
23. URL: http://www.izmiran.ru/ services/iweather/ (accessed September 1, 2016).
24. URL: ftp://sideshow.jpl.nasa.gov/pub/iono_daily/ (accessed September 1, 2016).
25. URL: http://irimodel.org/indices/ accessed September 1, 2016).
26. URL: http://ftp.izmiran.ru/pub/ izmiran/SPIM/ (accessed September 1, 2016).
27. URL: http://www.ionolab. org/ (accessed September 1, 2016).
