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Podor A.,Óbuda 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.

Kovacs P.,Geological and Geophysical Institute of Hungary | Facsko G.,Finnish Meteorological Institute | Facsko G.,Geodetic and Geophysical Institute | Dandouras I.,CNRS Institute for research in astrophysics and planetology
Planetary and Space Science | Year: 2014

In this paper the turbulent dynamics of a hot flow anomaly (HFA) event is investigated. The HFAs are transient plasma disturbances generated by the interaction of the bow shock (BS) and a tangential discontinuity (TD) embedded in the solar wind. The typical changes of the plasma parameters inside HFAs (increased plasma temperature, low bulk velocity, increased magnetic fluctuations, etc.) have been thoroughly interpreted by the records of space missions (e.g. Cluster). It is shown that the level of the turbulent intermittency inside the HFA cavity can be monitored in terms of space and time by the fourth statistical moment of the temporal differences of the time-series, i.e. by their flatness. With the multi-spacecraft observations the intermittency in the plasma fluctuations can be revealed not only in temporal but also in spatial scales. However, in the analysis, it must be taken into account that the dynamics of the foreshock region and the HFAs is governed not only by turbulent fluctuations but also by regular wave phenomena. In many cases the wave activities are more energetic than the turbulent processes, therefore the periodic signal components considerably modify the power-law behaviour of the turbulent spectra and determine the probability density functions and structure functions of the magnetic records exhibiting turbulent intermittency. On the other hand, while the wave phenomena are tight to certain time-scales, the turbulent character appears in a wide range of temporal scales. For this reason, it is argued that with the use of a dynamical high-pass filtering, the wave-like and turbulent-like components of the HFA magnetic signal can be discriminated. In our work the high-pass filtering is carried out with the use of continuous wavelet transformation. It is shown that the high-frequency components of HFA magnetic fluctuations exhibit strong intermittency referring to turbulent dynamics. It is also suggested that in the low-frequency regime, the turbulent dynamics is hidden by the wave activities. © 2014 Elsevier Ltd.

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 Pécs
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.

Antel C.,University of Cape Town | Collier A.B.,Exegetic Analytics | Collier A.B.,University of KwaZulu - Natal | Lichtenberger J.,Eötvös Loránd 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.

Viljanen A.,Finnish Meteorological Institute | Pirjola R.,Finnish Meteorological Institute | Pirjola R.,Natural Resources Canada | Pracser E.,Geodetic and Geophysical Institute | And 3 more authors.
Space Weather | Year: 2013

We consider the model of the Finnish high-voltage power grid in 1978-1979, for which the accurate parameters are available for calculating geomagnetically induced currents (GIC). Moving the grid at different locations across Europe gives estimates of GIC levels in this region. For calculating the geoelectric field driving GIC, we use different layered models of the ground conductivity and 1 min geomagnetic data of the year 2003. The results show a clear concentration of large GIC in north Europe, where the peak values are about 3-5 times larger than in Central and South Europe, being up to about 200 A in this specific power grid. There are two factors contributing to this finding. First, geomagnetic variations are generally stronger in the north. Second, there are regions in the north with clearly smaller ground conductivities than typically at other areas. Both of these reasons lead to larger electric fields in the north. A very similar behavior of GIC is found in the case when a single-layered ground conductivity model is assumed everywhere. We also show that the geographic characteristics of GIC are quite insensitive to the details of the power grid model by modifying various parameters of the Finnish grid. ©2013. American Geophysical Union. All Rights Reserved.

Kis A.,Geodetic and Geophysical Institute | Kis A.,French National Center for Scientific Research | Agapitov O.,French National Center for Scientific Research | Agapitov O.,Taras Shevchenko National University | And 5 more authors.
Astrophysical Journal | Year: 2013

It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population. © 2013. The American Astronomical Society. All rights reserved.

Balassa G.,Budapest University of Technology and Economics | Bencze P.,Geodetic and Geophysical Institute | Dobrowiecki T.,Budapest University of Technology and Economics
13th IMEKO TC10 Workshop on Technical Diagnostics 2014: Advanced Measurement Tools in Technical Diagnostics for Systems' Reliability and Safety | Year: 2014

This paper describes the error treatment of REXUS rocket-borne measurements of ion density in the middle atmosphere, using so called Gerdien condenser. The main challenge is that measurements in the range of 25-85 km can be carried out only with a sounding rockets or balloons. Therefore not only the measurement time is limited but a lot of noise distorts the data. Another problem is that the measurement model cannot be validated accurately due to the hard accessibility, so apart from a few exceptions we had to rely on probabilistic estimates. Uncertainties and the influencing effects distorting the measurement or endangering the device were estimated, with special attention to environmental effects like shock waves, radiation, photoelectric effect, etc. Finally a full error propagation model has been established and validated through simulations. Copyright© (2014) by the International Measurement Confederation (IMEKO).

Ujvari G.,Geodetic and Geophysical Institute | Klotzli U.,University of Vienna
International Journal of Earth Sciences | Year: 2015

Loess sediments in Austria deposited ca. 30–20 ka ago yield different zircon age signatures for samples collected around Krems (SE Bohemian Massif; samples K23 and S1) and Wels (halfway between the Bohemian Massif and the Eastern Alps; sample A16). Cathodoluminescence (CL) imaging reveals both old, multistage zircons with complex growth histories and inherited cores, and young, first-cycle magmatic zircons. Paleoproterozoic ages between 2,200 and 1,800 Ma (K23 and S1), an age gap of 1,800–1,000 Ma for S1 and abundant Cadomian grains, indicate NW African/North Gondwanan derivation of these zircons. Also, A16 yields ages between 630 and 600 Ma that can be attributed to “Pan-African” orogenic processes. Significant differences are seen for the <500 Ma part of the age spectra with major age peaks at 493–494 and 344–335 Ma (K23 and S1), and 477 and 287 Ma (A16). All three samples show negative initial ɛHf signatures (−25 to −10, except one grain with +9.4) implying zircon crystallization from magmas derived by recycling of older continental crust. Hf isotopic compositions of 330- to 320-Ma-old zircons from S1 and K23 preclude a derivation from Bavarian Forest granites and intermediate granitoids. Rather, all the data suggest strong contributions of eroded local rocks (South Bohemian pluton, Gföhl unit) to loess material at the SE edge of the Bohemian Massif (K23 and S1) and sourcing of zircons from sediment donor regions in the Eastern Alps for loess at Wels (A16). We tentatively infer primary fluvial transport and secondary eolian reworking and re-deposition of detritus from western/southwestern directions. Finally, our data highlight that loess zircon ages are fundamentally influenced by fluvial transport, its directions, the interplay of sediment donor regions through the mixing of detritus and zircon fertility of rocks, rather than Paleowind directions. © 2015, Springer-Verlag Berlin Heidelberg.

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