Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

ОМ. Barkhatova etal. ApriL 1975 June, 1982 Time, h Tim#, h Fig. 3. Examples of index IAI variations for April IAI 1975 and June 1982 (top panel); synchronized variation of index Dst (middle panel); synchronized variations of index AE (lower panel). Gray color indicates increased values of index IAI observed within the intense magnetic storms and auroral disturbances Thus during the development of magnetic storms which are accompanied by intense substorms in the auroral region, high negative values of index IAI are observed and it is evidence of mid-latitude ionospheric concentration decreasing within these periods. 5. Conclusions In the present study the "cleared" critical frequencies (CCF) values of the ionospheric F2 layer are analyzed over the station Moscow in minimum (1975) and maximum (1982) Solar activity years. Comparison of CCF variations for each season for two years with index Kp*10 variations shows their co-ordination. It observed simultaneous increase CCF and Kp*10 in minimum as with in maximum Solar activity year. This means that CCF variations adequately reflect the state of midlatitude ionosphere in various heliogeophysical conditions. The study of average values of CCF variations in international undisturbed and disturbed days for 1975 and 1982 allowed picking out five classes of ionospheric disturbances which correspond to the quiet state of ionosphere, the state of the ionosphere with a small, increased, high and extreme disturbance. On the basis o f this classes created an index of ionospheric activity IAI which ranges from 0 to ± 4 depending on the level of ionospheric disturbance. Analysis of received IAI index values for minimum and maximum Solar activity years shows that the increase in the absolute index values is usually accompanied by increase in global geomagnetic and/or auroral disturbances. This demonstrates the validity of developed index to characterize the ionospheric activity independently of the season. In addition by the sign of IAI index can judge the drop or increase concentration of ionospheric layer F2 since the index values correspond to real variations of the critical frequency midlatitude ionosphere. Acknowledgements. This work is executed at partial support under grant of the RFBR 09-05-00495, and also program Ministry of Education and Science «Development of higher school scientific potential (2009-2011 project N 10266)». References Kutiev, I. and Muchtarov, P. Modeling of midlatitude F-region response to geomagnetic activity // J Geophys Res, 106, 15 501- 15 509,2001. Bremer, J , Cander, Lj. R , Mielich, J , and Stamper, R : Derivation and test o f ionospheric activity indices from real­ time ionosonde observations in the European region. // J. Atmos. Sol.-Terr. Phy., 68, 2075-2090,2006. Gulyaeva T. L , Stanislwska I , Tomasik M. Ionospheric weather: cloning missed foF2 observations for derivation of variability index. // Ann. Geophys, 26, 315-321, 2008. Janowski B.M. Terrestrial Magnetism, L. 1978, 592 p. 128