Physics of auroral phenomena : proceedings of the 38th annual seminar, Apatity, 2-6 march, 2015 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Издательство Кольского научного центра РАН, 2015. - 189 с. : ил., табл.

"Physics o f Auroral P henom ena", Proc. XXXVIII A nnual Seminar, A patity, pp. 107-110, 2 0 1 5 © Kola Science Centre, Russian Academy o f Science, 2015 Polar Geophysical Institute OCCURRENCE OF GPS SIGNALS PHASE FLUCTUATIONS DURING AURORAL ACTIVITY I.I. Shagimuratov1, S.A.Chemouss 2 ,1.1. Efishov1, M.V.Filatov2, N.Y.Tepenitsyna1, G.A. Yakimova1, E.M. Koltunenko1, M.V. Shvec 2 1 West Department o f IZM1RAN, RAS, Kaliningrad, Russia 2Polar Geophysical Institute o f KSC RAS, Apatity, Russia Abstract. We present the result of investigations of GNSS signal phase fluctuations occurrence during the geomagnetic storm on October 2, 2013. During this space weather event the intense phase fluctuations have been registrated at the permanent GNSS stations located not only in auroral and subauroral regions but even over midlatitude stations. In combination with optical and geomagnetic measurements this fact confirms the expansion of the auroral oval towards the equator. Introduction A trans-ionospheric radio wave propagating through electron density irregularities may experience phase and amplitude fluctuations. Such fluctuations are appeared due to irregularities with different scales that presents in the polar ionopsphere. Ionospheric irregularities can be structured with latitude and their intensity differ in the high- latitude ionosphere at subauroral, auroral, polar and cusp regions. In accordance with this, the fluctuation activity varies considerably with latitude and space weather's conditions.The small irregularities with scale lees than 1 km cause fast fluctuations it is usually called scintillations. The medium and large scale ionospheric irregularities are responsible for slow fluctuations. The low frequency GPS phase fluctuations may be directly due to electron density changes along the radio ray path, or the total electron content (TEC) changes. Strong TEC fluctuations can complicate phase ambiguity resolution; increase the number of undetected and uncorrected cycle slips and loss of signal lock in GPS navigation[l-3]. and positioning errors [4] Figure 1. Ae and Dst variations for September 30 - October 4, 2013 Data and Geomagnetic conditions 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 [5, 6 ]. RINEX-derived dual-frequency GPS observation with 30 sec sampling rate were processed to obtain the information about occurrence of the ionospheric irregularities. The TEC measurements for individual satellite passes served as raw data. During active phase of storm we used magnetometer data of chaim of the Scandinavian network. 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 2 October 2013. The storm was rather moderate with active phase started 2 October 2013 after midnight. On the Fig. 1, the geomagnetic conditions for September 30 - October 4, 2013 are presented, including data of subauroral magnetometers. 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. Standard GPS 107