Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

I.I. Shagimuratov et al. against them in the auroral ionosphere. As seen on the picture during quit day strong fluctuations were predominated at day time. At storm day the moderate fluctuations were occurred during whole day, maximal intensity took place day time. During next day the TEC fluctuations development is followed with dynamic of the solar- magnetic activity and strong fluctuations were at day time. 6. Oval irregularities Based on the daily GPS measurements from 130-150 high latitude it was created images of the spatial distribution TEC fluctuations (index ROTI) in CGC and MLT coordinates for selected periods. Similarly to the auroral oval, these images demonstrate the irregularity oval [ Shagimuratov et al., 2012, 2013]. The occurrence of the irregularity oval relates with auroral oval, cusp and polar cap. On the Fig. 5 the picture of the irregularity oval development during storm is presented. For quiet day the maximal TEC fluctuation activity took place in evening sector at 68-72° CGL. The developing of fluctuations is begun after 12 MLT. Maximal activity was observed in interval 13-16 MLT on latitudes of 68-70° CGL. During storm the equator edge o f irregularities oval was occurred near 60° CGL. Strong TEC fluctuations were registered in cusp region near 12 MLT. On recovery phase of 12 October 2010 storm the occurrence of TEC fluctuations show distinctly image of irregularity oval. The equator edge of the oval was located near 62-63° at local midnight. In day-side irregularity oval was located higher than 70-75° CGL. Fig. 5 Images of irregularities oval for quiet and storm-time days. 7. Summary The investigations results showed that TEC fluctuation activity in the high latitude ionosphere is depended on geomagnetic conditions. Intensity o f fluctuations essentially increases during geomagnetic storm; maximal effect took place when Bz IMF component for a long time is maintained negative. During geomagnetic disturbed conditions the strong TEC fluctuations were registered at latitudes low than 60-62 °. The occurrence of GPS- TEC fluctuation is very sensitive to solar-geomagnetic changes and can be use to evaluate space weather conditions. Similarly to the auroral oval the spatial distribution of the fluctuations demonstrate the irregularity of oval images. The irregularity oval expands equatorward with increase o f the magnetic activity. The study showed that the operating high-latitudes GPS stations provides opportunity to monitoring of the irregularity oval in near real-time. References Aarons J., GPS system phase fluctuations at auroral latitudes, Journal o f Geophysical Research, 102, A8, 17219- 17231, 1997. Forte B., S. Radicella, Geometrical control of scintillation indices. What happens for GPS satellites, Radio Science, 39, 2004. Chernouss S.A., N.V. Kalitenkov, The dependence of GPS positioning deviation on auroral activity, International Journal o f Remote Sensing, Vol.32, Nol 1, 3005-3017, 2011. Pi X., A.J. Manucci, U.J. Lindqwister, C.M. Ho, Monitoring of global ionosheric irregularities using the worldwide GPS network, Geophysical Research Letters, 24, 2283-2286, 1997. Shagimuratov I.I., I.I. Eflshov, N.Yu. Tepenitsyna, Similarities and Differences of storm time occurrence of GPS phase fluctuations at northern and southern hemispheres, In Proceeding EUCap 2009, (2009). Shagimuratov I.I., A. Krankowski, I. Ephishov, Iu. Cherniak, P. Wielgosz, and I. Zakharenkova, High latitude TEC fluctuations and irregularity oval during geomagnetic storms, Earth Planets Space, Vol. 64, No. 6, 521-529, 2012 . Shagimuratov I.I., Iu.V. Cherniak, I.I. Efishov, A. Krankowski, Space weather monitoring by GPS, In Proceedings International Beacon Satellite Symposium, Bath 2013, 2013. 169