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The Pannonian basin is an extensional back-arc basin that has undergone neotectonic inversion and is currently shortening. The understanding and quantification of present-day deformation processes during this inversion are still incomplete. To this end, we investigate the active deformation of the Circum-Pannonian region via the interpolation of GNSS-derived velocity field and the derivation of the strain rate fields. For the interpolation of the velocity field, we use ordinary kriging, a strochastic interpolation method. Our results show that estimating a strain rate field that is virtually free of short-wavelength noise requires the scaling of the velocity uncertainties, i.e. assuming a minimum standard deviation of 1 mm/yr in our case. The deformation of the Circum-Pannonian region is defined by the 2–3 mm/yr, NNE-directed motion of the Dinarides, and by the 0.5–1.5 mm/yr, WSW to SSW directed motion of the eastern areas (European foreland, East Carpathians, South Carpathians, Transylvanian basin). These opposite-sense motions define a large-scale, on average NE-SW shortening and transpression-type deformation in the Dinarides as well as in the Pannonian basin, while the East and South Carpathians undergo regional N–S extension. Neotectonic structures generally show good agreement with the strain rate field, for example in the Dinarides, Eastern Alps, or in the western Pannonian basin. However, the presence of fault-parallel shortening or biaxial shortening along sinistral neotectonic structures in the central and eastern Pannonian basin show some discrepancy between current geodetic and observed neotectonic deformation. The vertical velocity field shows dominantly 100 and 1000 km wavelength signals, the former is probably related to the response of the Pannonian lithosphere-asthenosphere system to neotectonic basin inversion, while latter can possibly be explained by far-field subsidence patterns induced by the mantle response to melting of the Fennoscandian ice sheet during the current interglacial period.

A Széchenyi István Geofizikai Obszervatóriumban (SZIGO) már több, mint hat évtizede folyik a felszíni geoelektromos és geomágneses tér megfigyelése. Az Obszervatórium a geomágneses megfigyelő állomásokat tömörítő nemzetközi hálózat, az INTERMAGNET egyik legjobb minősítéssel kitüntetett tagja, melyet a folyamatos és nagy pontosságú adatszolgáltatás révén érdemelt ki (https://www.intermagnet.org/). A geomágneses megfigyelő rendszer nemrégiben újult meg, illetve egészült ki egy redundáns digitalizáló-adatgyűjtő-szerver lánccal, melynek révén a fluxgate magnetométer analóg jelét két független rendszer digitalizálja, rendezi ASCII fájlokba, valamint továbbítja egy-egy adatszerveren telepített SQL adatbázisba. A geomágneses indukció révén az előbbihez szervesen kapcsolódó fizikai mennyiség, a geoelektromos tér mérésére szolgáló rendszer a közeljövőben szintén megújul, melynek eredményeképpen egy nagyobb dinamikatartományt, jobb felbontásban leképező rendszer kerül beüzemelésre. Az alábbiakban az újonnan telepített geomágneses mérőrendszer kerül bemutatásra, valamint néhány, az új rendszerrel, az elmúlt 12 hónapban regisztrált SSC esemény.

Geomagnetic and geoelectric registration has been continuously executed in SZIGO for more than six decades. The Observatory is a member of the global network of the geomagnetic observatories, the so-called INTERMAGNET (https://www.intermagnet.org). The geomagnetic observation system has recently been renewed in all of its components and the organically related geoelectric measurement system is going to be upgraded and improved, too. Present paper provides a short summary of the new geomagnetic observation system and introduces a few SSC events registered in the SZIGO from the last 12 months via the new observation station.

In the last decades, the development of space geodesy methods has allowed much more accurate observations of planetary surface dynamics than before. The various SAR satellites, like global navigation systems, make their observations in different microwave frequency ranges (1-10 GHz). The Earth's atmosphere is transparent to the microwave signal, but the factors affecting wave propagation (propagation direction and velocity) in the medium are time-dependent, the medium is anisotropic, inhomogeneous and, in the case of the ionosphere, dispersive. Without the correction of such atmospheric artifacts the resulting signal delay is evaluated as a displacement during processing, which can be in the order of tens of meters.In order to get information about the actual geophysical processes from the displacement values derived from satellite data, the effects on wave propagation must also be taken into account. Radar interferometric methods are particularly suitable for detecting processes with velocities in the order of a few mm/year, but are limited by the lack of quantitative knowledge of the signal delay in the wave propagation, which is of particular importance for the study of processes on a regional scale.Wave propagation in the neutral atmosphere is mostly distorted by refraction due to water vapour, and the correction is complicated by the dynamic variation of the water vapour content and the inaccurate knowledge of the atmospheric water vapour. In the ionosphere, in addition to Faraday-rotation and electron density dependent refraction, the dispersive nature of the medium is another source of error.Transient atmospheric phenomena (frontal and thunderstorm systems, ionospheric disturbances, sporadic E layers, etc.), which are predominantly inhomogeneous in nature, further complicate the correction of their effects, but also provide an excellent opportunity to study them. The Sentinel-1 satellite images cover an area of 250 km x 250 km with a resolution of 5 m x 20 m. This resolution may prove useful for studying atmospheric inhomogeneities.In radar interferometric processing, virtual displacements generated by atmospheric phenomena can be investigated in areas that are assumed to be geologically stable and contain well-identified objects that provide strong signal reflection. For the latter, corner reflectors points specifically designed for this purpose have already been developed.In the area of Sopron (Hungary), there are 4 such installed permanent artificial reflectors. By including these points and by comparing measurements from the local ionosonde and meteorological station, we have studied the influence of atmospheric phenomena on radar interferometric processing and the applicability of radar interferometry for the study of atmospheric phenomena.

A summary of methods yielding information about the generation and configuration of the geomagnetic main field is presented with special focus on complications concerning these methods. A global source model constructed with the help of machine learning (and deep learning) is proposed to mitigate these issues, in particular the uncertainties caused by vigorous convection and small scale fields.

There are potentially dangerous areas where InSAR technology cannot be applied routinely in the absence of proper persistent or distributed scatterers. Here, we planned and investigated the use of truncated trihedral triangle corner reflectors (CRs) oriented to ascending and descending directions for Sentinel-1 orbit, which were mounted on the optimal concrete basement including an additional global navigation satellite system (GNSS) adapter. These integrated benchmarks were designed to produce a signal-to-clutter ratio of about 100 (i.e., 20 dB). The mechanical design allows optimal orientation of the reflectors and resistance against dynamic effects. We investigated 1:5 models of the CRs and integrated benchmarks in an anechoic chamber to estimate the effects of truncation and the interference of the twin reflectors. The main effect of the interference is the asymmetric monostatic radar cross section, which can be neglected. The integrated benchmarks were also investigated in two recent landslide areas in Hungary using Sentinel-1 single look complex (SLC) scenes, which confirmed that the preliminary requirements can be met.

The Széchenyi István Geophysical Observatory, also known as the Nagycenk Geophysical Observatory (NCK), was established in 1957. It has been the only measurement site in Hungary where observations of various parameters of the atmospheric global electric circuit are made in the framework of organized research under the umbrella of the Hungarian Academy of Sciences (MTA). Measurements of the atmospheric electrical potential gradient (PG) and Schumann resonances (SRs) running quasi-continuously in the observatory for decades provide an invaluable source of information for geophysical research. This paper gives an overview on the history of the observatory and particularly on various atmospheric electricity (AE) measurements on-site to commemorate the efforts and excellence of the people who served atmospheric sciences by dedicating their lives to obtaining high-quality, reliable data and scientific achievements at the highest possible level.

Summary of the long term data taking, related to one of the proposed next generation ground-based gravitational detector's location is presented here. Results of seismic and infrasound noise, electromagnetic attenuation and cosmic muon radiation measurements are reported in the underground Matra Gravitational and Geophysical Laboratory near Gy\"ongy\"osoroszi, Hungary. The collected seismic data of more than two years is evaluated from the point of view of the Einstein Telescope, a proposed third generation underground gravitational wave observatory. Applying our results for the site selection will significantly improve the signal to nose ratio of the multi-messenger astrophysics era, especially at the low frequency regime., Comment: 47 pages, 37 figures

The past decade has seen a great number of studies dealing with magmatic water contents and how these could be retrieved by the nominally anhydrous minerals’ (NAMs) trace structural hydroxyl (water) contents. Constraints have been made to magmatic hygrometry with clinopyroxene and plagioclase. Although results suggest that the method is more flexible and reliable than melt inclusion studies, they also indicate that the trace hydroxyl contents could still be overprinted by syn- and post-eruptive processes. Clinopyroxenes can hold more structural hydroxyl than plagioclases. A comprehensive review is presented with the inclusion of all published results so far to compile the available pieces of information. As a case study, micro-FTIR measurements are made of a representative set of plagioclase phenocrysts from the Börzsöny Mts. (Carpathian–Pannonian Region). The samples were selected to represent the progress of the volcanic activity in time and space, considering the petrologic and geochemical evolution of volcanic products in well-defined volcanostratigraphic positions. The syn- and post-eruptive cooling rate seems to have the greatest effect on water retention. This means that the systematic investigation of water in volcanic phenocrysts can contribute to distinguish the slowly and rapidly cooling parts of the volcanostratigraphic units.

Summary Electromagnetic variation’s amplitude decreases exponentially in conducting media. Higher conductance results higher attenuation of the electromagnetic variations vs. depth. In this presentation an investigation is introduced which aims to estimate the electromagnetic attenuation coefficient and mean resistivity of the near surface rocky layers of the Matra mountains, Hungary. The whole investigation consists of a confirmation, based on high frequency magnetotelluric sounding, too. The direct estimation of the attenuation coefficient is performed by means of a signal excited by the global thunderstorm activity in the ground-ionosphere cavity, the so called Schumann resonance. The method basis on the direct determination of the ELF signal’s amplitude decay between a surface and the corresponding subsurface site. In case of parallel recording at the two sites, the attenuation could basically be computed from the rate of the variation’s spectral amplitude at certain frequencies. As the surface and the subsurface observation could not be performed at the same time due technical reasons, an ELF reference observation site had been involved in the investigation. The attenuation can then be estimated by comparison of the transfer functions related to the ‘subsurface station - reference site’ and the ‘reference site – surface station’ relation.

Rocksalt has remarkable mechanical properties and a high economic importance, however, this strength of salt compared to other rocks makes it a rather vulnerable material. Human activities could lead to acceleration of the dissolution of soluble rocksalt and collapse of subsurface caverns. Although sinkhole development can be considered local geological disaster regarding the characteristic size of surface depressions the deformations can result in catastrophic events. In this study we report the spatiotemporal evolution of surface deformation in Solotvyno salt mine area in Ukraine based on Sentinel-1 interferometric synthetic aperture radar measurements. Although the mining operations were finished in 2010 several sinkholes have been opened up since then. Our results show that even though the enormous risk managing efforts the sinkholes continue to expand with a maximum line-of-sight deformation rate of 5 cm/yr. The deformation time series show a rather linear feature and unfortunately no slowdown of the processes can be recognized based on the investigated 4.5 year-long data set. We utilized both ascending and descending satellite passes to discriminate the horizontal and vertical deformations and our results revealed that vertical deformation is much more dominant in the area. With the 6-day repetition time of Sentinel-1 observations the evolution of surface changes can be detected in quasi real-time which can facilitate disaster response and recovery.

The Carpathian bend is amongst the tectonically most active areas in Europe where intraplate subduction triggers sub-crustal earthquakes releasing significant amount of seismic energy in a well-defined seismic zone. To constrain the deep processes by exploiting their linkage to the surface processes an accurate knowledge of surface deformations is required. Detection of small-magnitude tectonic processes with high reliability is a challenge in which the recent space geodetic techniques may bright a breakthrough. In this study we used the archive ENVISAT data set of the European Space Agency to investigate the feasibility limit of detecting crustal deformations in the region of the south Carpathian bend, where past geodetic observations failed to unravel the tectonic processes with high details. Despite the inherent limitations of radar interferometry our results show that coherent velocity field can be estimated with a magnitude of few mm/year. The vertical displacement field suggests subsidence in the Brasov basin which is in agreement with former studies, however radar interferometry can provide a more detailed picture.

Apart from the lithosphere-asthenosphere boundary (LAB), mid-lithospheric discontinuities (MLDs) in thick and old continental lithospheres appear to play an important role in global plate tectonics. Initiation of intra-continental subduction, delamination of the lower continental lithospheric mantle and removal of cratonic roots are likely to occur along MLDs. Here we introduce the ‘pargasosphere’ hypothesis which could account for the origin of both boundaries. The observation that pargasitic amphibole is stable even at very low bulk ‘water’ concentration (~a few hundreds ppm wt.) implies that the solidus of the shallow upper mantle (

In the first part of the paper a brief introduction is given (a) to the magnetotelluric (MT) and magnetovariation (MV) soundings, (b) to electrical resistivity of minerals and rocks, and their dependence on temperature and fluid content. The basic geoelectric model in the Pannonian Basin is a (linear) tectonic zone (“dike”) and a series of dikes. In the second part the main crustal and mantle conductivity anomalies observed in the Pannonian Basin (PB) are summarized: (a) deep conductive crustal fractures and their relation to the occurrence of the earthquakes, boundary of the megablock(s) etc., (b) middle crustal conductors as indicators of decrease in stress and seismic activity depending on thermal regime, (c) the conductive asthenosphere and its lateral change in the PB in connection with the heat flow and tectonics. The general relation between the depth of the conductive asthenosphere and the regional heat flow is also presented, (d) MT anisotropy of the resistivity distribution in the PB and its tectonic explanation based on Haas’s tectonic map (2001, Fig. 1). All these observations and conclusions are considered as results for further investigations.

International audience; The structural hydroxyl content of the nominally anhydrous minerals (olivine and pyroxenes) in the upper mantle is among the important attributes that influence the physical and chemical features of the upper mantle. In this study, we provide detailed Fourier-transform infrared (FTIR) data on 63 petrographically and geochemically well-defined upper mantle xenoliths from the Nograd-Gomor Volcanic Field (Pannonian Basin, Central Europe). These xenoliths show extremely low average structural hydroxyl contents (similar to 0, 31 and 185 ppm for olivine, orthopyroxene and clinopyroxene, respectively) compared to values reported regionally and worldwide. The studied xenoliths have anomalous types of FTIR spectra and high structural hydroxyl ratios between clinopyroxenes and orthopyroxenes (an average of similar to 8). Furthermore, there is usually no correlation between the structural hydroxyl content and other physical or chemical properties of the xenoliths. These specific FTIR characteristics suggest that the Nograd-Gomor upper mantle xenoliths were exposed to significant modification of their structural hydroxyl contents, which may be linked to pre- and post-eruptive processes. Decompression during extension leads to lower 'water' activity, which is most likely to have played a key role. However, pre-eruptive mantle metasomatism with an agent having low water activity cannot be excluded either. The post-eruptive cooling can be significant as well, as suggested by the higher structural hydroxyl content in xenoliths hosted in more rapidly cooled volcanic facies (i.e. pyroclastics). Our study reveals how FTIR characteristics may evolve in continental rift settings in young extensional basins. Furthermore, novel applications of our study are the diagnostic features that indicate significant changes in structural hydroxyl properties. This contributes to distinguishing low structural hydroxyl contents linked to the pre-eruptive (i.e., low structural hydroxyl content in pyroxenes, anomalous partitioning and anomalous band characteristic in pyroxenes) or the post-eruptive (completely 'dry' olivines) periods.

SUMMARYWe infer seismic azimuthal anisotropy from ambient-noise-derived Rayleigh waves in the wider Vienna Basin region. Cross-correlations of the ambient seismic field are computed for 1953 station pairs and periods from 5 to 25 s to measure the directional dependence of interstation Rayleigh-wave group velocities. We perform the analysis for each period on the whole data set, as well as in overlapping 2°-cells to regionalize the measurements, to study expected effects from isotropic structure, and isotropic–anisotropic trade-offs. To extract azimuthal anisotropy that relates to the anisotropic structure of the Earth, we analyse the group velocity residuals after isotropic inversion. The periods discussed in this study (5–20 s) are sensitive to crustal structure, and they allow us to gain insight into two distinct mechanisms that result in fast orientations. At shallow crustal depths, fast orientations in the Eastern Alps are S/N to SSW/NNE, roughly normal to the Alps. This effect is most likely due to the formation of cracks aligned with the present-day stress-field. At greater depths, fast orientations rotate towards NE, almost parallel to the major fault systems that accommodated the lateral extrusion of blocks in the Miocene. This is coherent with the alignment of crystal grains during crustal deformation occurring along the fault systems and the lateral extrusion of the central part of the Eastern Alps.

Long period magnetotelluric (MT) data were collected at 14 locations along a ~50 km long NNW-SSE profile in the Nograd-Gomor Volcanic Field (NGVF), which is one of the five mantle xenolith bearing Neogene alkali basalt locations in the Carpathian-Pannonian region. As a result, a low resistivity anomaly (

At present, the satellite SAR persistent scatterer interferometry can already estimate surface changes with a near to 1 mm theoretical precision limit. However, the ascending and descending acquisitions of available SAR services cannot provide three-dimensional changes routinely, though the slow deformation processes are basically three-dimensional (3D). In this paper the geometric features of ascending and descending SAR data and possible fusion with geodetic data are summarised. All the geometric equations are introduced, which are necessary to derive the two characteristic changes in the observation plain defined by ascending and descending unit vectors pointing to SAR satellite positions. The unambiguously derivable characteristic changes can be transformed into vertical and east changes, but they may be biased by possible north displacement. The geometric features of symmetric and asymmetric acquisitions are also investigated. Monte-Carlo simulation is used to investigate the precision of two estimated components. It is experienced that the precisions are not sensitive to one degree standard deviations of positional angles. The Gauss–Markov model of least square adjustment method is used to derive only the statistical properties of reasonable data fusion which can contribute to the 3D applications. Although complementary satellites, which are already proposed in the literature, could provide precise autonomous solutions, in the practise GNSS and levelling data can be used for direct data fusion. Whereas, even errorless levelled high changes cannot contribute to the proper estimation of northern components, GNSS derived changes are the best candidates, which can be interpolated or measured directly. Moreover, these two techniques can properly compensate the weaknesses of each other. The interferometric SAR techniques are not sensitive enough to the north changes, but can contribute to the precision of height estimation, which are the weakest components of the GNSS technique. This statement is valid if the standard deviations of combined data are comparable. For test computations the geometric parameters of available Sentinel-1A images are used, which cover the area of the Szechenyi Istvan Geophysical Observatory, where experimental integrated geodetic benchmark is located combining ascending and descending backscatterers with the possibility of the GNSS, gravimetric and traditional geodetic measurements, as well.

Geomagnetically induced currents (GICs) in power systems, which can lead to transformer damage over the short and the long term, are a result of space weather events and geomagnetic variations. For a long time, only high-latitude areas were considered to be at risk from these currents, but recent studies show that considerable GICs also appear in midlatitude and equatorial countries. In this paper, we present initial results from a GIC model using a thin-sheet approach with detailed surface and subsurface conductivity models to compute the induced geoelectric field. The results are compared to measurements of direct currents in a transformer neutral and show very good agreement for short-period variations such as geomagnetic storms. Long-period signals such as quiet-day diurnal variations are not represented accurately, and we examine the cause of this misfit. The modelling of GICs from regionally varying geoelectric fields is discussed and shown to be an important factor contributing to overall model accuracy. We demonstrate that the Austrian power grid is susceptible to large GICs in the range of tens of amperes, particularly from strong geomagnetic variations in the east–west direction.

The Ciomadul is the youngest volcano of the Carpathian–Pannonian region, which erupted last time at 32 ka. It produced high-K dacitic lava domes and pumiceous pyroclastic rocks. The dacite is crystal-rich and contains plagioclase, amphibole in addition to biotite, titanite, apatite, zircon and occasionally quartz, K-feldspar as well as olivine, clinopyroxene and orthopyroxene. There are two groups of amphiboles, characterized by low-Al and high-Al, respectively. They occur in the same samples and also as different zones of the same crystals. Thermobarometric calculations suggest that the low-Al amphiboles were formed from a low temperature (

A new array type, the γ11n arrays are introduced in this paper, in which the sequence of the current(C) and potential (P) electrodes is CPCP and the distance between the last two electrodes is n times the distance between the first two ones and that of the second and third one. These arrays are called quasi null arrays because they are – according to their array and behaviour – between the traditional and null arrays. It is shown by numerical modelling that in detection of small-effect inhomogeneities these configurations may be more effective than the traditional ones including the optimised Stummer configuration. Certain γ11n configurations – especially the γ112, γ113 and γ114 – produced better results both in horizontal and vertical resolution investigations. On the basis of the numerical studies, the γ11n configurations seem to be very promising in problems where the anomalies are similar to the numerically investigated ones, that is they can detect and characterise, for example,tunnels, caves, cables, tubes, abandoned riverbeds or discontinuity in a clay layer with greater efficacy than those of the traditional configurations. γ11n measurements need less data than traditional configurations therefore also the time demand of electrical resistivity tomography (ERT) measurements can be shortened by their use.

The so-called Transdanubian Conductivity Anomaly (TCA) of the Hungarian part of the NW Pannonian Basin has been well known for more than five decades. The exceptionally low resistivity (i.e. 1–2 Ωm) zone has a very large areal extent (on the order a few thousand km2) and it is an entirely subsurface anomaly occurring at depth between circa 3–15 km, with no corresponding outcrops. Various geological explanations of this enigmatic crustal-scale geophysical anomaly range from invoking sub-horizontal Alpine nappe contacts to sub-vertical dikes with graphite and/or saline fluid content. Only one possible analogue outcrop area was considered for the high conductivity anomaly so far, namely the Drauzug/Gailtal area of the Eastern Alps in Austria, some 300 km to the West from the TCA area. Previous attempts to find correspondence between the TCA and prominent seismic reflectors seen on 2D seismic reflection profiles were based on data acquired by research institutions. This study systematically correlates, for the first time, the TCA with 2D industry seismic reflection data in the same area. Our new results show a very strong correlation between the subsurface extent and location of the TCA with various sub-horizontally oriented Cretaceous Alpine nappe surfaces. In addition, we draw on the latest structural correlation of the Alpine nappe stack of the Transdanubian Range with its proper tectonic counterpart in the Eastern Alps.At the southern edge of the Upper Austroalpine units in northern Styria, in the Veitsch Nappe of the Greywacke Zone, numerous graphite localities are known historically. These laterally extensive graphite units in NW Styria formed as the result of greenschist-grade metamorphism of a Carboniferous coal sequence during the Cretaceous. For the first time, we describe here one well penetration of possibly age-equivalent graphitic units in NW Hungary. Correlation of the magnetotelluric anomaly with the distinct reflection seismic signature suggests that the same Palaeozoic graphitebearing Upper Austroalpine units should be present at 3–15 km depth in our study area.Therefore we propose that the best explanation for the observed extent and geometry of the TCA is the presence of graphite in subhorizontal, tectonically thinned detachment surfaces at the base of the Upper Austroalpine nappe edifice of NW Hungary

One of the Penninic Nappes is the Kőszeg-Rechnitz (K-R) tectonic window at the Eastern end of the Eastern Alps. It has a complicated metamorphic history from the Jurassic time. The organic material of the Penninic Ocean was transformed to electrically conductive meta-anthracite. Its amount in the chalcophyllite is estimated by geochemists to 0.2 per cent. Taking this conducting structure as a test area pilot deep magnetotelluric (MT) soundings have been carried out and we determined

Matra Gravitational and Geophysical Laboratory (MGGL) has been established near Gy\"ongy\"osoroszi, Hungary in 2015, in the cavern system of an unused ore mine. The Laboratory is located at 88~m below the surface, with the aim to measure and analyse the advantages of the underground installation of third generation gravitational wave detectors. Specialized instruments have been installed to measure seismic, infrasound, electromagnetic noise, and the variation of the cosmic muon flux. In the preliminary (RUN-0) test period, March-August 2016, data collection has been accomplished. In this paper we describe the research potential of the MGGL, list the installed equipments and summarize the experimental results of RUN-0. Here we report RUN-0 data, that prepares systematic and synchronized data collection of the next run period., Comment: 24 pages, 16 figures, accepted version

In connection with the EURISGIC WP2 project the authors present those procedures which have been used to construct a map in cells on the electrical resistivity distribution in Europe at least till to the asthenosphere. The data are based on the deep magnetotelluric soundings published in the international literature. This map is the basis of the calculation of the induction risk endangering the electric network and communication systems.

The paper describes research in geomagnetism and aeronomy carried out in the framework of a project organized by the Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences. It includes the development of the instrumentation of the Nagycenk Geophysical Observatory (geomagnetic measuring systems, ionosonde), moreover other instrumental and methodological developments, too. Observatory data are available in a database. Based on results of the Nagycenk and Tihany observatories and on data of permanent and temporal networks, long-term trends of different electromagnetic parameters were investigated. Thus geomagnetic activity was found secularly increasing, a decrease of the atmospheric electric potential gradient and a 11-year modulation of the winter/December attenuation of the geomagnetic pulsation activity were confirmed. Several possibilities (pulsations, whistlers, modelling) were used to improve knowledge about structure and parameters of the magnetosphere. Electromagnetic precursors of earthquakes were looked for. A significant increase of understanding was obtained in connection with Schumann resonances and electromagnetic transients caused by lightning. It was shown that see-coasts influence characteristically changes in ionospheric trends (hmF2). When looking for the effect of the global climate changes in the subsurface electric resistivity, an example was discovered for the decrease of the resistivity due to infiltrating water from precipitation. Electromagnetic exploration of tectonically conditioned weak zones was continued, too.

Ground based observations of the “Szechenyi Istvan” Geophysical Observatory of the Hungarian Academy of Sciences (Nagycenk) offer a unique opportunity for investigation of the complex processes of Earth’s environment and of its effect on radio wave propagation. High temporal resolution recording of variations of the geomagnetic field, vertical incidence sounding of the ionosphere and observation of whistlers enable determination of plasma density profiles in the inner magnetosphere (plasmasphere) and their changes. Study of ionospheric processes and their effects in the upper atmosphere (thermosphere) is supported by a permanent GPS station. Both DC and AC fields of lightning discharges are also recorded in the Observatory. Measurement of the DC field is related to the atmospheric electric circuit, where the global thunderstorm activity is the generator and fine weather areas play the role of loading. Loading of the atmospheric electric field depends on rate of ionization, ionization being caused by galactic cosmic rays. However, galactic cosmic rays are modulated by solar activity. Similarly amplitude of Schumann resonances depend on thunderstorm activity and its distance from the recording site. Resonance frequencies occurring at wave-lengths approximating dimensions of the Earth-ionosphere waveguide are affected by conductivity variations of the upper boundary of the cavity resonator and thus, by changes of thickness of the cavity resonator.

Firstly a short introduction is given about the theory of the g11n configurations which belong to the group of the geoelectrical quasi null arrays. On the basis of our numerical investigations the application of these arrays seem to be rather perspective. Their field application is however difficult because of the complexity of the inversion of the data of these arrays. These arrays have very large geometric factor, they may change their sign and they can produce very sharp changes. Using an own developed code we inverted field data. The very first results show the field applicability of these configurations.

Geoelectrical null and quasi arrays have been studied since very long time, but they have not been introduced in the practice. Its reason is that their application was rather difficult and that the inversion of the data of the arrays whose application is simpler has not been solved. We studied the theory of these arrays and developed a code to invert their data. In the presentation a short introduction will be given in their theory and the very first field experiments will be shown.

A hot flow anomaly (HFA) like event was observed by the Solar TErrestrial RElations Observatory (STEREO) in the night side magnetosheath in the far tail in February-March 2007. The magnetic signature of the tangential discontinuity was visible, but the resolution of the plasma ion data is not sufficient for our analysis, so a method is given to identify HFAs without solar wind velocity measurements. The event observed in the night side magnetosheath in the far tail might be the remnant of an HFA event, a not-so-active current sheet. This observation suggests that the lifetime of the HFAs might be several 10 minutes, much longer than the expected several minutes., accepted on January 23, 2015 to Journal of Atmospheric and Solar-Terrestrial Physics. 5 pages, 2 figures

The Nograd-Gomor Volcanic Field (NGVF) is one of the five mantle xenolith bearing alkaline basalt locations in the Carpathian Pannonian Region. This allows us to constrain the structure and properties (e.g. composition, current deformation state, seismic anisotropy, electrical conductivity) of the upper mantle, including the lithosphere-asthenosphere boundary (LAB) using not only geophysical, but also petrologic and geochemical methods. For this pilot study, eight upper mantle xenoliths have been chosen from Barna-Nagykő, the southernmost location of the NGVF. The aim of this study is estimating the average seismic properties of the underlying mantle. Based on these estimations, the thickness of the anisotropic layer causing the observed average SKS delay time in the area was modelled considering five lineation and foliation end-member orientations. We conclude that a 142–333 km thick layer is required to explain the observed SKS anisotropy, assuming seismic properties calculated by averaging the properties of the eight xenoliths. It is larger than the thickness of the lithospheric mantle. Therefore, the majority of the delay time accumulates in the sublithospheric mantle. However, it is still in question whether a single anisotropic layer, represented by the studied xenoliths, is responsible for the observed SKS anisotropy, as it is assumed beneath the Bakony–Balaton Highland Volcanic Field (Kovacs et al. 2012), or the sublithospheric mantle has different layers. In addition, the depths of the Moho and the LAB ( $$25\,\pm \,5, 65\,\pm \,10\,\hbox {km}$$ , respectively) were estimated based on S receiver function analyses of data from three nearby permanent seismological stations.

This is a summary of the activities of the Geophysics Department of the Geodetic and Geophysical Institute in the framework of the Scientific School Earth Electromagnetism. Ten reports cover the most important topics and emphasize interconnections between the different phenomena. The topics include interplanetary space, magnetosphere and ionosphere, electromagnetic waves in a wide spectrum, and electromagnetic induction, also within a wide range of frequencies and applications. Geomagnetism, especially the Szechenyi Istvan Geophysical Observatory Nagycenk with a lot of different recordings of electromagnetic parameters play important roles in most topics.

Firstly the authors give an overview on the geological, geophysical and tectonical features of the Diosjenő dislocation belt (or zone, according to some authors) around the river Ipoly near the Hungarian-Slovak border among great structural units: Vepor, Gemericum and formations of the Mid Hungarian Mts. The longest magnetic anomaly of the Pannonian Basin lies in this belt. It is assumed that it is due to ultrabasic magmatite of greenschist facies. The near-surface geoelectric soundings did not find any conductivity increase near Diosjenő (western part of the zone), but there are graphitic micaschists in the boreholes around Szecseny. There is some earthquake activitiy in the region with hypothetical depth of 7-8 km. Two deep magnetotelluric (MT) profiles cross the dislocation zone. The resistivity distribution from the surface to the conductive asthenosphere along these profiles was obtained by using instruments, operating in two different period ranges. After processing the measured data by 1D/2D inve...

Electrical potential differences between electrodes inserted in eight selected sites of the trunk of a Turkey oak (Quercus cerris) and the ground have been recorded continuously since November 1997. The mean amplitudes of daily electric variations were determined for time intervals when the meteorological and atmospheric electricity conditions were undisturbed. It was found that the mean daily amplitudes show a characteristic annual fluctuation. Both in 1998 and in 1999 two peaks were observed: the first maximum appears suddenly about the end of March, and the second one was seen in late June, July. Between November and March the mean amplitudes were smaller by about one order of magnitude.

International audience; 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. Key words: acceleration of particles – plasmas – shock waves – supernovae: general – waves Online-only material: color figures

This work presents ground based Ultra Low Frequency (ULF) magnetic field measurements in the frequency range from 10–15 mHz from 1 January 2008 to 14 April 2009. In this time period a strong earthquake series hit the Italian Abruzzo region around L'Aquila with the main stroke of magnitude M = 6.3 on 6 April 2009. In the frame of the South European Geomagnetic Array (SEGMA), a European collaboration runs ULF fluxgate instruments providing continuously magnetic field data recorded in mid- and south Europe. The main scientific objective is the investigation of signal variations due to seismic activity and the discrimination between other natural and human influences. The SEGMA station closest to the L'Aquila earthquake epicenter is L'Aquila observatory located in the epicenter region. For the scientific analysis we extract the nighttime period from 22:00–02:00 UT and determine the power spectral density (PSD) of the horizontal (H) and vertical (Z) magnetic field components and the standardized polarization ratio (Z) over (H). To discriminate local emissions from global geomagnetic effects, data from three SEGMA stations in distances up to 630 km from the epicenter region are analyzed and further compared to the independent global geomagnetic ∑ Kp index. Apart from indirect ionospheric effects, electromagnetic noise could be originated in the lithosphere due to tectonic mechanisms in the earthquake focus. To estimate the amplitude of assumed lithospheric electromagnetic noise emissions causing anomalies in the PSD of the (Z) component, we consider magnetotelluric calculations of the electric crust conductivity in the L'Aquila region. Results found at L'Aquila observatory are interpreted with respect to the lithosphere electrical conductivity in the local observatory region, the ∑ Kp index, and further in a multi station analysis. Possible seismic related ULF anomalies occur ~2 weeks before the main stroke.

We present the analysis of a Pc 3 geomagnetic pulsation event observed simultaneously by CHAMP and by the South European GeoMagnetic Array SEGMA (1.56 < L < 1.88) during the conjunction of July 6, 2002. Both compressional and transverse oscillations were identified in CHAMP magnetic measurements. A close correspondence between the compressional component and the ground signals is observed. At the same time the joint analysis of space and ground observations clearly indicates the occurrence of a field line resonance at L ✠ 1.6. A direct confirmation of the well known 90° rotation of the ULF wave polarization ellipse through the ionosphere is also provided.

[1] During June–July 2002 the low-altitude (h ∼ 400 km) Challenging Minisatellite Payload (CHAMP) satellite passed approximately every 2nd day close to the South European Geomagnetic Array (SEGMA, 1.56 < L < 1.88) during daytime hours. We present here the analysis of a Pc3 geomagnetic pulsation event observed simultaneously in space and at the ground array during the conjunction of 6 July 2002. Both compressional and transverse oscillations were identified in CHAMP magnetic measurements. A close correspondence between the compressional component and the ground signals is observed. The behavior of the CHAMP azimuthal component shows evidence for the occurrence of a field line resonance at L ≅ 1.6. The frequency of these azimuthal oscillations is ∼20% higher than the frequency of both the compressional oscillation and the ground pulsations. Such a difference is explained in terms of a sort of Doppler shift caused by the fast movement of the satellite across the resonance region where the phase signal changes rapidly. A further analysis verifies for the first time by space measurements the theoretical pattern of the wave polarization sense in the resonance region. The comparison with corresponding SEGMA measurements also provides an unprecedented direct confirmation of the well-known 90° rotation of the ULF wave polarization ellipse through the ionosphere.

We present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths crust considering an average electrical conductivity of =10−3 S/m and a certain distance of the observatory to the earthquake epicenter.

We present an analysis of ULF geomagnetic field fluctuations at low latitudes during the first CAWSES campaign (29March-3April 2004). During the whole campaign, mainly in the prenoon sector, a moderate Pc3-4 pulsation activity is observed, clearly related to interplanetary upstream waves. On 3April, in correspondence to the Earth's arrival of a coronal mass ejection, two SIs are observed whose waveforms are indicative of a contribution of the high-latitude ionospheric currents to the low-latitude ground field. During the following geomagnetic storm, low frequency (Pc5) waves are observed at discrete frequencies. Their correspondence with the same frequencies detected in the radial components of the interplanetary magnetic field and solar wind speed suggests that Alfvénic solar wind fluctuations may act as direct drivers of magnetospheric fluctuations. A cross-phase analysis, using different pairs of stations, is also presented for identifying field line resonant frequencies and monitoring changes in plasmaspheric mass density. Lastly, an analysis of ionospheric vertical soundings, measured at the Rome ionosonde station (41.8° N, 12.5° E), and vertical TEC measurements deduced from GPS signals within an European network shows the relation between the ULF resonances in the inner magnetosphere and thermal plasma density variations during geomagnetically quiet conditions, in contrast to various storm phases at the end of the CAWSES campaign.

Mechanically weak zones may arise e.g. due to rock realignment in the subsurface having an effect to the near surface-, or even to the surface sediments. If they are not directly seen from the surface a new method, the so-called pressure probe (Pre-P) method may be used to detect and characterise them. This method is presented on the example of the investigation of the fracture system of a landslide. Repeatability of the Pre-P measurements, adequate sampling distance, resolution of the method and the possible data processing steps are also investigated. We know from these investigations that: 1. there are consolidated zones on the slope side of the fractures whose broadness correlates with the broadness of the given fracture; 2. both the large and the small fractures follow each other periodically; 3. even the structure inside the blocks which belong to the large fractures can be well seen which refers to the very good resolution of the method. The here presented Pre-P method seems to be the most favourable tool to map the fracture system of such kind of landslides according to its resolution capacity, speed, simplicity of its application, the interpretation of the data and its costs.