Temporal and spatial variability of space weather driven telluric fields in Northwestern Russiaтезисы доклада

Дата последнего поиска статьи во внешних источниках: 21 мая 2019 г.

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1. Полный текст 24EMIW_GIC_Abstract_2_DOI.docx 30,3 КБ 25 декабря 2018 [SokolovaElena]
2. Полный текст GICs_poster_EMWS-2018_1008.ppt 2,1 МБ 10 ноября 2018 [SokolovaElena]

[1] Temporal and spatial variability of space weather driven telluric fields in northwestern russia / D. Epishkin, V. Pilipenko, E. Y. Sokolova et al. // Abstracts of 24th EM Induction Workshop. — Vol. 3. — Helsingor, Denmark, 2018. — P. 107–107. Permanently changing state of the Sun interiors is responsible for variations in solar electromagnetic environment. Intensive disturbances are often accompanied by coronal mass injections and acceleration of the solar wind stream up to 1000 km/s. Reaching the Earth they can produce global magnetic storms or sub-storms - the strongest space-born magnetospheric-ionospheric events, which have a potential to cause serious damage for space- and ground-based technological objects. In sub-polar regions, in particular, inside the auroral oval, the amplitudes of anomalous disturbances attain the highest levels. Russian territories to the north from the Polar Circle are intensively developed in nowadays. The investigations of space weather effects in these areas are of great importance for mitigation possible risks connected first of all with threats to electric power supply infrastructure caused by geomagnetically induced currents (GIC). The permanent observations of the transient geomagnetic field in northern Europe are carried out by international research community already rather long time and mostly in relation to magnetospheric and ionospheric studies. Constantly operating geomagnetic array IMAGE serves as the main ground-base source of information. Due to these observations the solid knowledge has been already cumulated regarding the character of anomalous space weather effects on geomagnetic field variations, while thorough studies of GICs still are not so common and need more consolidated efforts. Moving in this direction we assume, that before a regional network of GIC measurements will be arranged, for estimation of possible scales and dynamic character of GICs one can analyse electric fields induced in the ground during intensive space weather events, because telluric fields being responsible for total currents in the electric circuit “ground-electric power grid” are strongly correlated with GICs. The paper presents our approaches and the first experience of the analyses of temporal and spatial variability of telluric electric fields in the eastern Fennoscandia and their comparison with available GIC measurement in electric power grids of Kola Peninsular and Karelia. We mostly analyse “synthetic” telluric fields calculated on IMAGE geomagnetic records via impedance tensors estimated in sounding sites of the deep electromagnetic array BEAR deployed over the Shield 20 years ago. In our investigations we also use some MT data and GIC measurement in vicinity of important infrastructure objects in northwestern Russia. The elaborated algorithm of telluric E(t) field synthesis for a geomagnetic field event H(t) uses frequency domain relationship of the natural electric and magnetic fields via complex impedance tensor Z(f) (basic plane wave approximation of the external field). FFT procedure is applied for magnetic time record in a running window W(Ƭ) to produce a set of spectral estimates H(f) and corresponding E(f)= Z(f) H(f). Inverse Fourier transform performed for each running window position results in estimation of E(Ƭ+dt (i), i=0,n), where dt(i) is a time shift from the beginning of the record. Thus for a specific moment of time we have several electric field estimates, which are averaged to get final synthetic electric field series E(t). The smaller shift of the window more stable averaging is achieved. The program was successfully tested on the totally synthetic magnetic and electric fields of COMDAT project, connected by known Z(f). The presented current results include: (1) the analyses of E-field variations (intensity, dynamics, polarization) at a particular location in dependence of space weather conditions (on example of E-fields synthesized for LOZ station of IMAGE network via local impedance tensor of BEAR array and natural geomagnetic events of different intensity) in correlation with synchronous measurements of GICs at Kola Peninsula; b) analyses of induced telluric field dependence on the local geoelecrical structure: comparison of a set of E-field events synthesized for specific geomagnetic record via a range of impedances specific for Eastern Fennoscandian Shield with its complicated deep conductivity pattern; c) analyses of telluric field spatial variability over Eastern Fennoscandia: E-fields synthesized for IMAGE station from Kola Peninsula to southern Finland for a strong sub-storm via local impedances and compared with GIC measurement in close sites and mid-latitude telluric field observatories in Alexandrovka; d) analyses of Е-field/GIC dependency on the local and regional geoelectrical strike and electric power grid spatial orientation. Keywords: synthesis of telluric fields, Eastern Fennoscandian Shield, GIC, space weather Acknowledgements: Colleagues from geomagnetic observatories IMAGE, BEAR WG, RFBR grants 15-05-00543.

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