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The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations

Krankowski A., Shagimuratov I.I., Baran L.W., Yakimova G.

Acta Geophysica

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2007

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Vol. 55, no. 4

490-508

EN

GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm of November 7-12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004) were created. The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50N. In the report, features of the response of TEC to the storm for European and North American sectors are analyzed.

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Features of the ionosphere behavior before the Kythira 2006 earthquake

Zakharenkova I.E., Shagimuratov I.I., Krankowski A.

Acta Geophysica

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2007

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Vol. 55, no. 4

524-534

EN

In this paper we present specific features of TEC (total electron content of the ionosphere) behavior as possible precursors of Kythira (Southern Greece) earthquake of January 8, 2006 (M6.8). For this purpose, we used both the TEC data of GPS-IGS stations nearest to the epicenter, and TEC maps over Europe. The favorable circumstance for this analysis was the quiet geomagnetic situation during the period prior to the earthquake. One day before the earthquake, a characteristic anomaly was found out as the day-time significant increase of TEC at the nearest stations, up to the value of 50% relative to the background condition. To estimate the spatial dimensions of seismo-ionospheric anomaly, the differential mapping method was used. The ionosphere modification as a cloud-like increase of electron concentration situated in the immediate vicinity of the forthcoming earthquake epicenter has been revealed. The amplitude of modification reached the value of 50% relative to the non-disturbed condition and was in existence from 10:00 till 22:00 UT. The area of significant TEC enhancement had a size of about 4000 km in longitude and 1500 km in latitude.

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Impact of tec fluctuations in the Antarctic ionosphere on GPS positioning

Krankowski A., Shagimuratov I. I.

Artificial Satellites : Journal of Planetary Geodesy

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2006

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Vol. 41, No. 1

43--56

EN

With increasing reliance on space-based platforms for global navigation and communication, concerns about the impact of ionospheric scintillation and total electron content fluctuations on these systems have became a high priority. In this paper, GPS transionospheric signals have been used to study the development of ionospheric phase fluctuations observed at Antarctic IGS permanent stations: McMurdo-MCM4, Casey-CAS1, Mawson-MAW1, Sanae-VESL, Syowa-SYOG and Davis-DAV1 in 2001. The use of the multi-station, multi-path observations of the GPS beacons has allowed the study of the time development of irregularities as a function of latitude and longitude of individual geomagnetic storms. The basic storms studied were those of March 19-20, March 31, April 9-11, June 16-17, and September 23, 2001. The rate of TEC (ROT) parameter was used to study the occurrence of TEC fluctuations. The results from studying these storms showed the unique nature of each storm. For the above five storms, data were available from three auroral stations (VESL, SYOG and MAW1) and from 61° to 70° Corrected Geomagnetic Latitude (CGL). In addition, data from three higher latitude polar stations (DAV1, MCM4 and CAS1) near 800 CGL are also analysed. Fluctuation effects, causing dramatic changes in total electron content – TEC, can have a different impact on GPS positioning accuracy (especially during phase ambiguity resolution). Bernese ver.4.2 software was used for the analysis of the GPS permanent data from Antarctic IGS stations. The analyses rely on studying the repeatability of vector co-ordinates. These vectors were investigated during the geomagnetic storms when the intensity of TEC fluctuations was more pronounced. The impact of TEC fluctuations in the high latitude ionosphere on GPS positioning accuracy has been discussed in terms of the total number of observations of doubledifferences (DD) and in the ratio of the total number of all ambiguities to unresolved ones.

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Study of TEC fluctuations in Antarctic ionosphere during storm using GPS observations

Krankowski A., Shagimuratov I.I., Baran L.W., Ephishov I.I.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 2

205-218

EN

GPS observations carried out at Antarctic stations belonging to the IGS network were used to study TEC fluctuations in the high-latitude ionosphere during storms. Dual-frequency GPS phase measurements along individual satellite passes served as raw data. Ionospheric irregularities of a different scale develop in the auroral and polar ionosphere. This is a common phenomenon which causes phase fluctuations of GPS signals. We distinguished TEC variations related to ionospheric structures of a spatial scale bigger than 200-300 km. In the diagram of temporal variations of TEC along satellite passes, the structure of TEC corresponds to a time scale longer than 15-30 min. We attribute the variations in a time scale smaller than 15-30 min to TEC fluctuations related to small-scale ionospheric irregularities. We used the rate of TEC index (ROTI) expressed in TECU/min as a measure of TEC fluctuations. Large-scale ionospheric structures cause an increase in horizontal gradients and difficulties with the carrier phase ambiguity in relative GPS positioning. In turn, the phase fluctuations can cause cycle slips. At polar stations MCM4, CAS1, DAV1 we detected ionospheric structures of TEC enhanced 3-5 times relative to the background, whereas TEC increased to 10-30 TECU in about 10-15 min. The structures were observed during a storm, as well as during moderate geomagnetic activity. The structures can be probably attributed to polar cap patches. During storms the intensity of phase fluctuations increased. The occurrence of phase fluctuations was even detected during the active storm period of 31 March 2001 at a middle-latitude station OHIG (located at 49° corrected geomagnetic lati-tude).

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The fifth year of the activity of the Lamkowko IGS permanent station

Baran L. W., Kapcia J., Krankowski A., Shagimuratov I. I., Wielgosz P.

Geodezja i Kartografia

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1999

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T. 48, z. 3-4

159-167

EN

In the paper, there is presented activity of the Lamkowko Satellite observatory of the Institute of geodesy in regional and global geodynamic programmes. there are shown some results of studies concerning monitoring of the Lamkowko-Borowiec, Lamkowko-Onsala and Lamkowko-Matera vectors and possibilities of the use of the permanent GPS observations to study local ionosphere changes.

PL

Artykuł prezentuje działalność obserwatorium satelitarnego Lamkówko Instytutu Geodezji w ramach programów geodynamicznych regionalnego i globalnego. Przedstawiono wyniki badań monitoringu wektorów Lamkówko-Borowiec, Lamkówko-Onsala i Lamkówko-Matera wraz z możliwościami wykorzystania stałych obserwacji GPS w badaniach miejscowych zmian jonosfery.