Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

“Physics o f Auroral Phenomena”, Proc. XXXVII Annual Seminar, Apatity, pp. 90-93, 2014 © Kola Science Centre, Russian Academy of Science, 2014 Polar Geophysical Institute CASE STUDY OF TEC FLUCTUATION DURING AURORAL DISTURBANCES I. Shagimuratov1, S. Chernouss2,1. Efishov1, M. Shvec2, Y. Cherniak1, L. Koltunenko1, M. Filatov2 1West Department oflZM IRAN , Kaliningrad 2Polar Geophysical Institute o fK SC RAS, Apatity- Murmansk Abstract. In the paper there are presented occurrence of TEC fluctuations in high latitudes ionosphere during September 2011 events. The simultaneously GPS observations from more than 130 stations provided to obtain, similarly auroral oval, irregularity oval. It is shown that irregularity oval very sensitive to changes of solar- geomagnetic activity and can use as indicator space weather conditions. Introduction The scintillations of trans-ionospheric radio signals is very well known indicator space weather condition. The electron density irregularities presented in high latitude ionosphere may experience phase and amplitude fluctuations of GPS signals. The information about TEC fluctuations may be obtained using the regular GPS observations provided by the International GPS Service (IGS). The world wide and numerous network GPS stations are very opportunely to monitor the spatial distribution of ionospheric irregularities in planetary scale (Shagimuratov et al, 2009). In this report GPS measurements of global IGS network were used to study the storm time occurrence of phase fluctuations (TEC changes) in the high latitude ionosphere during September 2011 events. The GPS stations with geomagnetic coordinates higher than 55°N and different longitudes were involved in this investigation. Dual­ frequency GPS measurements for individual satellite passes served as raw data. As a measure of fluctuation activity the rate of TEC (ROT, in the unit of TECU/min, 1 TECU=1016 electron/m2) at 1 min. interval was used (Aarons 1997), as the measure intensity of TEC fluctuations do index ROTI( Pi et al., 1997). Solar and geomagnetic conditions In September 2011 took place three moderate geomagnetic storms-9, 17 and 26 September. The development of the storms was rather similar. On recovery phase of 9 and 26 September substorm activity took place In Fig. 1. Dst, Kp, AE indices and Bz component of IMF during September 2011 are presented. Over Europe all storms started in daytime. It will be noted the increased auroral activity was observed on the beginning September on background of low geomagnetic disturbances. On the Fig. 2 is presented development TEC fluctuation over subauroral NNVN station. In the quit conditions of 8 September the fluctuations were very low, indicating that the station located outside auroral oval. During driven phase of storm (9 September) strong fluctuations were observed in 15-19 MLT. In this time sharply increase also AE index, the development TEC fluctuations next days were occurred according with development substorm activity on recovery phase storm. 0 4в ее 144 182 240 288 336 384 432 480 628 576 624 672 720 1 2 3 4 5 6 7 8 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Figure 1. The solar and geomagnetic conditions during September 2011 90