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Viljanen A.,Finnish Meteorological Institute | Pirjola R.,Finnish Meteorological Institute | Pirjola R.,Natural Resources Canada | Pracser E.,Geodetic and Geophysical Institute | And 2 more authors.
Journal of Space Weather and Space Climate | Year: 2014

Statistics of geomagnetically induced currents (GIC) in the European high-voltage power grids based on 1-min geomagnetic recordings in 1996-2008 and on 1-D models of the ground conductivity have been derived in the EURISGIC project (European Risk from Geomagnetically Induced Currents). The simplified yet realistic power grid model indicates that large GIC can occur anywhere in Europe. However, geomagnetic variations are clearly larger in North Europe, so it is the likely region of significant GIC events. Additionally, there are areas in the North with especially low ground conductivities, which further tend to increase GIC. The largest modelled GIC values at single substations in 1996-2008 are about 400 A in the Nordic Countries, about 100 A in the British Isles, about 80 A in the Baltic Countries, and less than 50 A in Central and South Europe. The largest GIC event in the period studied is the Halloween storm on 29-30 October 2003, and the next largest ones occurred on 15 July 2000 and 9 November 2004. © A. Viljanen et al., Published by EDP Sciences 2014.

Ujvari G.,Hungarian Academy of Sciences | Ujvari G.,Geodetic and Geophysical Institute | Kok J.F.,University of California at Los Angeles | Varga G.,Hungarian Academy of Sciences | Kovacs J.,University of Pecs
Earth-Science Reviews | Year: 2016

Loess deposits are recorders of aeolian activity during past glaciations. Since the size distribution of loess deposits depends on distance to the dust source, and environmental conditions at the source, during transport, and at deposition, loess particle size distributions and derived statistical measures are widely used proxies in Quaternary paleoenvironmental studies. However, the interpretation of these proxies often only considers dust transport processes. To move beyond such overly simplistic proxy interpretations, and toward proxy interpretations that consider the range of environmental processes that determine loess particle size distribution variations we provide a comprehensive review on the physics of dust particle mobilization and deposition. Furthermore, using high-resolution bulk loess and quartz grain size datasets from a last glacial/interglacial sequence, we show that, because grain size distributions are affected by multiple, often stochastic processes, changes in these distributions over time allow multiple interpretations for the driving processes. Consequently, simplistic interpretations of proxy variations in terms of only one factor (e.g. wind speed) are likely to be inaccurate. Nonetheless using loess proxies to understand temporal changes in the dust cycle and environmental parameters requires (i) a careful site selection, to minimize the effects of topography and source distance, and (ii) the joint use of bulk and quartz grain size proxies, together with high resolution mass accumulation rate calculations if possible. © 2016 Elsevier B.V.

Podor A.,Obuda University | Kiszely M.,Geodetic and Geophysical Institute
Geodesy and Cartography | Year: 2014

The aim of the study is to find possible solutions to represent earthquake catalogue data and design maps which can help non-professionals to identify those places where earthquakes occurred frequently. The goal is to visualize all available catalogue data sets in a complex way on a single map, displaying the long-term recurrence times of earthquakes. Therefore, raw data and aggregated data were combined with different cartographic visualization techniques to test the applicability of earthquake maps. Preliminary research demonstrates that aggregation can improve the process of retrieving information from earthquake maps and 3D visualization is useful to find the places of earthquakes of highest magnitude. A second result is that 3D visualization is not effective in the comparison of quantities of released energy and the number of earthquakes. © 2014 Vilnius Gediminas Technical University (VGTU) Press.

Gordeev E.,Saint Petersburg State University | Facsko G.,Finnish Meteorological Institute | Facsko G.,Geodetic and Geophysical Institute | Sergeev V.,Saint Petersburg State University | And 5 more authors.
Journal of Geophysical Research: Space Physics | Year: 2013

Global magnetohydrodynamic (MHD) modeling is a powerful tool in space physics research. There are several advanced and still developing global MHD codes that are widely used to simulate plasma processes in solar wind magnetosphere-ionosphere system. The verification of global simulation codes is an important but a difficult problem. We present an approach for systematic and quantitative testing of code performance based on statistical empirical dependencies of the key magnetospheric parameters obtained from observations. We demonstrate the applicability of the method by testing the Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) global MHD model. A large set of nearly stationary solutions (162 runs altogether) with different stationary interplanetary magnetic field (IMF) and solar wind inputs were generated for different dipole tilts and levels of solar EUV radiation. As key parameters, we use the large-scale characteristics of the magnetosphere, including the magnetopause size and shape, geometry of the tail neutral sheet, magnetotail plasma pressure, tail lobe magnetic field, and cross-polar cap electric potential. We found that the GUMICS-4 stationary solutions generally fit the statistical relations, however, with some discrepancies. Particularly, position of the subsolar magnetopause, neutral sheet shape and position, and the plasma sheet pressure during northward IMF agree well with statistical models. At the same time, the size of the tail magnetopause and the lobe magnetic field magnitude appear to be systematically lower compared to their empirical values. Furthermore, the ionospheric potential is smaller in magnitude compared to empirical relations. These results provide an important starting point in the further development of the GUMICS simulation. Key Points New approach to verify GMHD code performance GUMICS-4 model verification based on comparison with empirical relations Magnetospheric large-scale structure in GUMICS-4 fits to empirical models ©2013. American Geophysical Union. All Rights Reserved.

Antel C.,University of Cape Town | Collier A.B.,Exegetic Analytics | Collier A.B.,University of KwaZulu - Natal | Lichtenberger J.,Eotvos Lorand University | And 2 more authors.
Geophysical Research Letters | Year: 2014

Whistlers detected at Dunedin, New Zealand are an anomaly: there is little lightning around Dunedin's conjugate point yet whistlers appear in relatively large numbers. These surplus whistlers have consequently inspired investigations into their origins. Dunedin's lightning-sparse conjugate point lies in the Aleutian Islands, a region populated with active volcanoes. Their presence has allowed us to perform a novel analysis: the correlation of whistlers to volcanic lightning. We report on our investigation, which successfully yielded the first observations of "volcanic whistlers." It was found that the single July 2008 Mount Okmok eruption had an impressive effect on the number of whistlers at Dunedin. The eruptions at Mount Redoubt in 2009 also caused a sporadic flow of whistlers in Dunedin. Key Points A new method is used to deduce location and time of whistler lightning source Volcanic lightning can generate whistlers Volcanic lightning strokes have been individually linked to whistlers ©2014. American Geophysical Union. All Rights Reserved.

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