Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

“P hysics o f Auroral P henom ena ”, Proc. XXXIII A n nua l Sem inar, Apatity, pp. 151 -154 , 2011 © Kola Science Centre, Russian Academy of Science, 2011 Polar Geophysical Institute CON JUGATE A N D INTER -HEM ISPHER IC OCCURRENCE OF GPS TEC FLUCTUAT ION S IN HIGH LAT ITUDE IONOSPHERE I. Shagimuratov1, S. Chemouss2,1. Ephishov1, N. Tepenitsyna1, and L. Koltunenko1 1. West Department o f Institute o f Terrestrial Magnetism, Ionosphere and Radiowaves Propagation, Kaliningrad, Russia 2. Polar Geophysical Institute KSC RAS, Apatity, Murmansk region, Russia Abstract. In the given report we present storm-time effects of TEC fluctuations in the polar ionosphere and discuss the similarities and differences of some features of their development in northern and southern hemisphere using GPS measurements at the geomagnetic conjugated stations. In paper relation between TEC fluctuations occur and auroral oval parameters are discussed. Data source GPS observations carried at the Antarctic and Arctic IGS stations were used to study the development of TEC fluctuations in the high latitude ionosphere In Table 1 the geomagnetic conjugated stations and their geographic and Corrected Geomagnetic coordinates use in this study are presented. Estimation technique For the analysis of TEC fluctuations we used high- precision dual-frequency GPS phase measurements of individual satellites passes. As measure of phase fluctuation activity we used the rate of TEC (ROT) on 1 min interval: ROT = 9.53 ((Ф1 - 02)ti+l - (Ф1 - 02)1, ) where Ф1 and Ф2 [m] denote the measured differential carrier phase observable of LI and L2. A scaling factor 9.53 converts the differential ionospheric delay to units of electrons/m2. The rate of TEC characterizes relative spatial changes of TEC along satellite passes. When using ROT we avoid the problem of phase ambiguities. As a measure of TEC fluctuation activity we used also the Rate of TEC Index (ROTI) based on standard deviation of ROT:ROTI has been estimated at 10-min interval Data and analysis Some authors studied the dependence of the TEC fluctuations on the magnetic and auroral activity mostly during great planetary storms (Shagimuratov, 2008; Afraymovich and Perevalova 2006; Aarons et a l, 2000). This method of attack was applied because planetary storms produce affects on GPS signals not only in high but also in middle latitudes. Our paper devoted to the conjugacy of these phenomena. Fig. 1 (a,b,c) presents the development of TEC fluctuations during the geomagnetic activity period of 23-27 July 2004. Pictures illustrate the occurrence of TEC fluctuations for all satellite passes observed over a 24 hour interval. At all stations located at different longitude occurrence TEC fluctuations took place at the same UT. The intensity of fluctuations essentially increases during active phase o f storm. Maximal effect was observed while Bz was negative. At polar stations MCM4 and RESO intensity TEC fluctuations are differed, it is probably season effect. At auroral stations MAC1/FAIR the storm-time development TEC fluctuations is rather similar At subauroral stations KRG/JOEN TEC fluctuations are clearly seen during the most disturbed days, when Bz is strong negative. The picture of TEC fluctuations at both hemispheres was very similar. The TEC fluctuations are caused by the presence of medium and large-scale irregularities in the ionosphere. To evaluate the intensity of TEC fluctuations and accordingly the ionospheric irregularities we used the index ROTI. As well as auroral oval the spatial and temporal occurrence of the irregularities can be visually presented in coordinates- Geomagnetic local time and Corrected geomagnetic latitude. As example Fig. 2 shows the pictures o f TEC fluctuations over polar cap geomagnetic conjugate stations of MCM4/RESO and auroral stations DAV1/NYAL for quiet day of 21 July and the most disturbed day o f 27 July 2004. Stations Geographic Coordinates Corrected Geomagnetic Coordinates latitude longitude latitude longitude MCM4 -77.50 166.40 -79.99 322.95 RESO 74.41 -94.53 83.10 320.28 MAC1 -54.30 158.56 -64.18 247.29 FAIR 64.58 -147.30 64.95 264.67 WHIT 60.45 -135.13 63.29 278.64 KERG -49.21 70.15 -58.29 123.33 JOEN 62.23 30.05 58.36 108.44 DAV1 -68.34 77.58 -74.67 102.29 NYAL 78.55 11.52 75.77 111.78 Table 1. Geographic and corrected geomagnetic coordinates o f Antarctic and Arctic IGS stations 151