MARCHENKO_final:Layout 6 Ukrainian geomagnetic repeat station network and results of the field work reduced to the epoch 2005.5 Valentyn Maksymchuk1,*, Myxailo Orlyuk2, Viktor Tregybenko3, Yurij Horodyskyy1, Dmytro Marchenko1 1 Institute of Geophysics NAS of Ukraine, Carpathian Branch, Lviv, Ukraine 2 Institute of Geophysics NAS of Ukraine, Kyiv, Ukraine 3 Ukrainian State Geological Prospecting Institute (UkrDGRI), Kyiv, Ukraine ANNALS OF GEOPHYSICS, 55, 6, 2012; doi: 10.4401/ag-5406 ABSTRACT The results of geomagnetic f ield components of the renewed Ukrainian repeat stations (RS) network are presented. The methods of absolute geomagnetic and astro-geodetic measurements are described. The reduction of geomagnetic field components is carried out to the 2005.5 epoch and a catalogue of RS is created. Maps of magnetic declination for the Ukraine are constructed and compared with results calculated by the IGRF-2005 model. 1. Introduction Investigation of the temporal and spatial structure of the Earth's magnetic field (EMF) is important to solve some fundamental problems in geophysics. One problem is the separation of the Earth magnetic field into contribution from sources of internal and external origin, and the separation of the internal sources into the main (normal) field, arising from the dynamo process in the liquid Earth core and a lithospheric field. To solve this problem it is necessary to have precise data of the absolute values of the magnetic field com- ponents and their time changes. High quality data of the magnetic field components at the Earth's surface can be ob- tained from measurements at magnetic observatories (MO) as well as from the periodic measurements (2-5 years) at re- peat stations (RS) or from space by satellites. These meas- urements are extremely important for the following tasks: – estimation and analysis of the time-spatial dynamics of the EMF, its separation into the various parts and investigations of their nature; – modeling of the Earth magnetic field (for example the IGRF) [Finlay et al. 2010]; – reduction of magnetic surveys and development of maps of the anomalous (lithospheric) magnetic field. For a temporal reduction of the RS measurements a con- tinuous record of the Earth's magnetic field vector BX, BY, BZ, BF, BH, D, I from a MO is needed. Repeated measure- ments of the Earth magnetism elements at the RS network allow to map the secular variations (SV) of the geomagnetic field. Many organizations from the geology, geophysics, ge- odesy and military claim for this type of data. 2. Historical background First general magnetic survey in the Ukraine was accom- plished during the 1930s and 1940s and the second field cam- paign in 1969-1972 with a density of 1 point per 400 km2. At the beginning of 1970 a new repeat station network with 39 points was installed in the Ukrainian region [Krutikhovskaya et al. 1973]. Absolute values of the field strength BF were measured by the proton magnetometer, BH by the quartz H-magnetometer and declination was measured with the fluxgate magnetometer on top of the demagnetized theodo- lite 3T2K. Mean-square errors of the measurements at this RS network for BF component ±2.4 nT, BH ±4.0 nT, BZ ±2.5 nT, D 1.3 minutes of arc. The next magnetic survey at the RS network was done during 1974 and 1975. The components of the geomagnetic field were reduced to 1974.5 by using the data of the magnetic observatories data "Lviv", "Kiev" and "Odessa". This work was used for the mapping of all com- ponents of the geomagnetic field for the territory of the Ukraine and the USSR and for the mapping of the main field for the epoch 1975 year [Krutikhovskaya et al. 1982]. Some of these repeat stations were repeated until the year 1985. After 30 years from the last magnetic survey many points of this network were lost. For this reason, the goal of this work is to analyze the condition, reviving and increasing the existing RS network in Ukraine. In the year 2003 the Carpathian Branch of the Subbotine Institute of Geophysics NAS of Ukraine (CBiGF) and Subbotine Institute of Geo- physics NAS of Ukraine (IGF) started this work. Article history Received September 30, 2011; accepted July 31, 2012. Subject classification: Earth's magnetic field, Repeat station, Secular variation, Magnetic declination. 1161 MagNetE workshop 2011 3. Ukrainian RS Network The RS network in Ukraine was renewed and increased during the years 2005-2006. Most of the new points were re- installed at the locations of the destroyed points. But rein- stallation can't give us the same positions of the points as in 1972 to 1973. For this reason measured data at the new Ukrainian RS network during 2006 and 2007 cannot be used for the determination of the secular variations since 1974. This new RS network consists of 52 first order points with a distance between the points of approximately 100-150 km. The density of the RS network is one point per 10,000 km2 with the even distribution in the Ukrainian area. For the as- tronomical gauge azimuth determination, or in general for the bringing of the theodolite horizontal scale to the geo- graphic meridian several methods, we use the classical method of the horary angle of the celestial body [Pandul 1983]. As it was mentioned for the determination of all components of the Earth magnetic field, it is necessary to determined three in- dependent components. Flux-gate magnetometers LEMI-203 [see the website of the Lviv Center of Institute for Space Research: http://www.isr.lviv.ua/products.htm#Flux-gate magnetometers], installed on top of demagnetized theodo- lite 3T2K, can be used for the determination of the angles D and I. Module of the complete vector BF of the magnetic field was measured by the proton magnetometers MINIMAG and MB-01 (proton magnetometers with achieved accuracy 0.01 and 0.1 nT, developed by "Geologorazvedka", St. Pe- tersburg, Russia). In general all recommendations of IAGA was take into account [Newitt et al. 1996] 4. Results The results of the second cycle measurements at Ukrainian RS network were reduced to the epoch 2005.5 [Maksymchuk et al. 2010]. The reduction [Newitt et al. 1996] was based on the data from the magnetic observatories "Kyiv", "Belsk" and "Lviv". In Table 1 all reduced compo- nents are shown. In general, comparison of measured val- ues with the modeled ones show us that differences between the linear components (BX, BY, BZ) can reach several hun- dred nT. Differences in the magnetic declination angles at various regions vary from one minute to half degree. If the analytical model field is very flat without any local (regional) gradients (Figure 1), whereas the real measured field com- posed of big gradient in various area of Ukrainian region. Especially this is visible at the D component. Magnetic dec- lination D in the Ukrainian region fluctuates from 4˚ at the West to 8˚ at the East with the sufficiently complicated spa- tial structure (Figure 2). Strong regional anomalies can be di- vided to the three parts: western part of Ukraine, in the region of the MO "Lviv"; southern part of Ukraine near the MAKSYMCHUK ET AL. 1162 Figure 1. Ukrainian RS Network and magnetic declination D (isogonic counter lines in degree) for the epoch 2005.5. Black stars: RS network; black squares: magnetic observatories. 1163 UKRAINIAN RS NETWORK. EPOCH 2005.5 Nr. RS Name {, Nº m, Eº BX (nT) BY (nT) BZ (nT) Dº 1 Balaklia 49.603 36.500 20465 2839 46377 7.884 2 Bashtanka 47.510 32.107 20977 2257 44673 6.128 3 Berduchiv 50.066 28.590 19788 1769 45647 5.105 4 Beregove 48.234 22.648 20587 1542 44223 4.280 5 Beregomet 48.197 25.378 20700 1610 44515 4.440 6 Bila Cerkva 49.819 29.774 19829 2179 45613 6.265 7 Borynja 49.055 23.059 20337 1665 44540 4.677 8 Verhnjodniprovsk 48.523 34.421 20390 2275 45550 6.362 9 Volnovakha 47.627 37.622 20617 2473 46000 6.829 10 Gadjach 50.476 33.985 19249 2275 46455 6.740 11 Goluba Zatoka 44.422 33.982 22691 2223 42993 5.572 12 Horokhiv 50.580 24.522 19513 1453 45747 4.259 13 Guljaipole 47.778 36.146 20775 2809 45581 7.688 14 Deljatyn 48.549 24.634 20566 1738 44598 4.827 15 Dzergynsk 48.399 37.764 20512 2479 45549 6.883 16 Dymer 50.806 30.274 19242 2103 46308 6.236 17 Dykanka 49.840 34.625 19728 2273 46134 6.571 18 Zhashkiv 49.118 30.015 19763 1900 44764 5.490 19 Zavadiv 50.064 23.390 19771 1716 45381 4.959 20 Kalna 48.953 23.814 20423 1738 44661 4.861 21 Kamjanec 48.578 26.696 20480 1998 44848 5.568 22 Kaniv 49.739 31.386 19704 1841 45433 5.336 23 Kiverci 50.971 25.533 19017 1788 45904 5.374 24 Kirovograd 48.564 32.019 20233 2199 45031 6.198 25 Kovel 51.449 24.758 18818 1532 45811 4.658 26 Kodyma 48.064 29.075 20567 1590 45109 4.412 27 Kurortne 45.904 30.268 22122 2055 43851 5.280 28 Lugansk 48.559 39.696 20253 2645 46353 7.431 29 Luboml 51.267 24.008 18753 1430 45661 4.360 30 Nemuriv 49.008 28.667 20044 2146 44674 6.106 31 Nyzhne Selyshe 48.198 23.456 20703 1597 44083 4.407 32 Nyzhni Sirogozy 46.836 34.411 21333 2047 44529 5.468 33 Ovruch 51.099 28.712 18931 1829 45642 5.521 34 Okunivka 45.364 32.751 22110 2071 43446 5.338 35 Orelka 48.956 35.794 19956 2419 45901 6.905 36 Orlovka 46.661 36.106 21531 2405 44877 6.355 37 Pervomaisk 48.041 30.747 20635 1623 44637 4.487 38 Pryluki 50.589 32.146 19263 2330 46169 6.895 39 Reni 45.338 28.441 22307 1932 43032 4.925 40 Rogatyn 49.454 24.589 20111 1580 45199 4.492 41 Sarnu 51.237 26.759 18959 2012 46164 6.062 42 Starobelsk 49.118 38.868 20242 2638 46608 7.418 43 Stepanivka 46.777 30.900 21246 1326 44222 3.554 44 Sumy 51.000 35.101 19063 2814 46419 8.397 45 Urzuf 46.886 37.061 21354 2374 44513 6.328 46 Kherson 46.777 33.116 21344 2080 44475 5.562 47 Cherkasy 49.406 32.670 19943 2261 45457 6.465 48 Chernigiv 51.512 31.443 18571 1829 46767 5.628 49 Chortkiv 48.999 25.927 20424 1697 45023 4.741 50 Shepetivka 49.938 27.247 20003 1709 45270 4.881 51 Shostka 51.803 33.402 18676 2769 46800 8.435 52 Jastrubivka 45.516 34.127 22097 2202 43647 5.688 Table 1. RS catalogue of components of the geomagnetic field for the epoch 2005.5. MAKSYMCHUK ET AL. 1164 Figure 2. Magnetic declination D (degree) based on IGRF-2005 model. Figure 3. Anomalous magnetic field in Ukrainian area (nT) [Orlyuk and Romenets 2005]. 1165 MO "Odessa" and eastern part near the Ukrainian–Russian border. The structure of the magnetic declination in general agreed with the anomalous magnetic field (Figure 3). Anom- alous values of the declination in the western Ukraine coin- cide with the Lviv regional magnetic anomaly, in the South with the Odessa regional magnetic anomaly, and in the East with the western fork of the Kursk magnetic anomaly. This demonstrates their common nature. 5. Conclusions During 2003 and 2004, 52 repeat stations were renewed and installed at the Ukrainian RS network taking into ac- count the condition of the RS network after 1972. These points are located almost uniformly on the Ukrainian area. Comparison of measured components with modeled ones from IGRF model demonstrates important differences; it is especially the case of magnetic declination D. To estimate with higher accuracy the real field feature and to improve ex- isting maps of the anomalous magnetic field is necessary to densify RS network during next cycle of repeat measure- ments. Results of geomagnetic measurements will be ap- plied to the adjustment of normal magnetic field model for the Ukrainian territory and for future research of secular variations of the Earth magnetic field. Acknowledgements. The authors would like to thank the anony- mous reviewers and the editor, Dr. Gerald Duma, for their significant com- ments which led to improvements in the presentation and discussion of these results. References Finlay, C.C., S. Maus, C.D. Beggan, T.N. Bondar, A. Chambo- dut, T.A. Chernova, A. Chulliat, V.P. Golovkov, B. Hamil- ton, M. Hamoudi, R. Holme, G. Hulot, W. Kuang, B. Langlais, V. Lesur, F. J. Lowes, H. Lühr, S. Macmillan, M. Mandea, S. McLean, C. Manoj, M. Menvielle, I. Michaelis, N. Olsen, J. Rauberg, M. Rother, T. J. Sabaka, A. Tangborn, L. Tøffner-Clausen, E. Thébault, A.W.P. Thomson, I. Wardinski, Z. Wei and T.I. Zvereva (2010). International Geomagnetic Reference Field: the eleventh generation, Geophysical Journal International, 183, 1216-1230. Krutikhovskaya, Z.A., I.K. Pashkevich and I.M. Silina (1982). Magnetic model and the structure of the Earth crust of the Ukrainian Shield, Kyiv, Naykova dumka, 216 pp. (in Russian). Krutixovskaya, Z.A., I.K. Pashkevich, O.M. Rusakov and V.D. Solovjov (1973). Ground absolute magnetic survey of the Ukrainian SSR, Visnyk AN URSR, 9. 101-102 (in Ukrainian). Maksymchuk, V.Yu., M.I. Orlyuk, V.I. Tregybenko, Yu.M. Horodyskyy, V.P. Mjasoedov and E.F. Nakalov (2010). Ground absolute magnetic survey at the Ukrainian RS network for the epoch 2005, Geophysical Journal, Kyiv, 32, (5), 102-166 (in Ukrainian). Newitt, L.R., C.E. Barton and J.U. Bitterly (1996). Guide for magnetic repeat station surveys, IAGA, Boulder, 112. Orlyuk, M.I., and A.A. Romenets (2005). New criterion of the Earth's magnetic field disturbance and some aspects of its use, Geophysical Journal, Kyiv, 27, (6), 1012-1023 (in Russian). Pandul, I.S. (1983). Astro-geodetic determinations on Sun for geographers, geologists and surveyors, Moscow, Nedra, 128. *Corresponding author: Valentyn Maksymchuk, Institute of Geophysics NAS of Ukraine, Carpathian Branch, Lviv, Ukraine; email: vmaksymchuk@cb-igph.lviv.ua. © 2012 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved. UKRAINIAN RS NETWORK. 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