Systematic deviations in source direction estimates of Q-bursts recorded at Nagycenk, Hungary

Q-bursts are globally detectable extremely low frequency (ELF, 3-3000Hz) band wave packets produced by intense lightning discharges. Q-bursts recorded in the Széchenyi István Geophysical Observatory (NCK, 16.7°E, 47.6°N), Hungary, on 1 and 2 August 2012 have been analyzed to find azimuths of their sources. The location of parent lightning strokes of 320 and 205 Q-bursts on the 2days, respectively, have been identified in the records of the World Wide Lightning Location Network (WWLLN) using the detection times at NCK. ELF data-based source azimuths were found to differ systematically from source azimuths obtained from WWLLN lightning locations. The difference between the corresponding azimuth values depends on the azimuth of the source. This variation of the source azimuth error mirrors the symmetry of the conductance of the Earth's crust inferred from magnetotelluric measurements around NCK. After correction for the azimuthal dependence, the variation of the residual error shows a diurnal pattern with positive azimuth deviations occurring near midnight, local time. Füllekrug and Sukhorukov (1999) suggested that the anisotropic conductivity in the Earth's crust below the observatory and the different daytime and nighttime conductivities in the lower ionosphere, respectively, may cause the identified error terms. Our results emphasize the substantial effect of anisotropic conductivity in the Earth's crust around the recording station on the accuracy of ELF direction finding. The need for theoretical approach and more measurements is pointed in understanding the underlying mechanisms quantitatively and in investigating whether ELF observations can be used in geophysical prospecting. © 2016. American Geophysical Union. All Rights Reserved

Tetszőleges alakú, űreszközzel és földi állomáson mérhető elektromágneses jelek terjedésének és gerjesztésének vizsgálata = Investigation of propagation and excitation of arbitrary shaped e.m. signals measured by space vehicles and on ground stations

A 'Tetszőleges alakú, űreszközzel és földi állomáson mérhető elektromágneses jelek terjedésének és gerjesztésének vizsgálata' c. kutatás eredményei a 2002-2005 pályázati időtartam alatt: 1. Sikerült megoldani UWB gerjesztés által létrehozott e.m. jel terjedésének leírását tetszőlegesen erős inhomogenitást tartalmazó előmágnesezett plazmában, továbbá a vákuummal, és előmágnesezett homogén plazmával kitöltött hullámvezetőben. 2. A kifejlesztett elméleti modellekkel anomalisztikus jelenségek azonosítását végeztük el (tweek, spiky whistler, fecskefarkú whistler, X-típus, ferde, valamint ferde és vezetett terjedést mutató whistler-csoportok). A ferdén terjedő jelcsoportok vizsgálata a whistlerek kilépésének új mechanizmusát tárta fel, regisztrátumokból meghatározható a töredék-whistlereknél a műholdhoz viszonyítva az ionoszférába történő belépés helye. 3. A szeizmikus aktivitás és űridőjárási vizsgálatok keretében kifejlesztettük az automata trimpi-detektort. Sikerült megoldani a műholdas távérzékelt adatok georeferálását. Részt veszünk a Demeter-adatok quick-look értékelésében. 4. Sikeresen üzemeltetjük földi műhold-vevő állomásunkat, továbbá elért eredményeink alapján részt veszünk a Demeter-programban, a Kompasz-2 és Vulkan műholdflotta programjában 17 SAS műszerrel és elméleti modellfejlesztéssel, az ISS Obszanovka-1 kísérletében, az ESA-JAXA BepiColombo Merkur misszióban és az ESA Venus Entry Probe misszióban. (szeizmikus aktivitás e.m. jelei és űridőjárás) | Results of the research project titled as 'Investigation of the propagation and excitation of general shaped electromagnetic signals detected by terrestrial and satellite receivers' in the 2002-2005 period: 1. We derived the exact solution of e.m. signals excited UWB sources, that propagate in anisotropic plasma containing arbitrarily strong inhomogeneities. We solved this problem for wave-guides, filled by vacuum, or anisotropic, homogeneous plasma. 2. By the application of our models, we identified and interpreted anomalistic phenomena observed by satellite (tweeks, spiky whistlers, swallow tailed whistlers, 'X'-type, obliquely propagating and ducted oblique signal-groups). In the case of obliquely propagating signal-groups, we verified a new description of the entering and propagation of the whistlers, by that the localization of the entering points of fractional-hop whistlers related to the satellite are determinable. 3. Connecting to the space-weather and seismic activitiy research we developed the automatic trimpi-detector, and an automatic geocoding system for satellite RS data. We participate in the quick-look validation of Demeter-data. 4. We installed and keep in operation our satellite receiver station. We participate in the Demeter-program, the Kompas-2 and Vulkan projects, the ISS Obsztanovka-1 experiment, the ESA-JAXA BepiColombo mission to the Mercury, and the ESA Venus Entry Probe mission, (interplanetary, space weather and seismic e.m. activity research)

A szeizmikus eseményeket kísérő elektromágneses jelenségek vizsgálata = Investigation of electromagnetic phenomena connecting to seismic events

'A szeizmikus eseményeket kísérő elektromágneses jelenségek vizsgálata'' eredményei a 2002-2005 időszakban: A címben foglalt cél elérése érdekében végzett kutatás eredményei három csoportba foglalhatók: 1) A munka során elért eredmények új képet körvonalaznak a Föld (és más bolygók) ULF-VLF e.m. környezetéről, s ebben nagyon fontos a Demeter (CNES) műhold adatai értékelésével azonosított több, eddig nem ismert e.m. jelenség, valamint az ezek értékeléséhez kifejlesztett új elméleti e.m. hullámterjedési modellek. 2) Sikerült megoldani az e.m. környezet folyamatos monitorozása biztosításához az automatikus whistler detektálást és értékelést (AWDA rendszer), az automatikus trimpi detektálást, továbbá a felszíni hő-infra tranziensek megtalálásához a műholdas távérzékelt adatok automatikus georeferálását és e munkával szimultán egyes felszíni hő-tranizensek vizsgálatát. 3) A Demeter műhold adatai értékelésével felismert új jelenségek közül sikerült megadni az ún. "tüskés" whistlerek (SpW) és egy sajátos, ismétlődő whistler-csoport keletkezési mechanizmusát, az egy földi mérésben (Agra) és a Demeter adataiban talált ún. X-jelenség valószínű keletkezési mechanizmusát és bekapcsolódni a valószínűleg szeizmikus eseményekhez kapcsolódó, zajszerű e.m. kilövelések vizsgálatába. - A munka további következménye az, hogy az itt elért eredmények alapján sikerült bekapcsolódni az ESA-JAXA BepiColombo misszióba, s további kiemelt projektek előkészítésébe is. | The results of the project titled as ""Investigations of electromagnetic phenomena connecting to seismic events"" in the 2002-2005 period: 1) The results of this work produce a new picture of the e.m. environment of the Earth (and other planets), in which the e.m. events, which were found in the data measured by Demeter satellite (CNES) and were unknown earlier, have an important role. The new theoretical e.m. wave propagation models developed for the interpretation of these new e.m. phenomena are important, too. 2) The continuous monitoring of the e.m. environment is the key of this research and application. The following systems were developed: automatic whistler detector and analyser system (the AWDA system), automatic trimpi detector, and for finding of the surface heath-transients an automatic geocoding system of satellite RS data and the investigation of heath-transients were fulfilled. 3) The interpretation of the phenomena were successful in the following cases: the generation of the spiky whistlers (SpW), the generation of a type of whistler groups having special structure, the generation of the X-events appearing in Demeter data and in a single ground based measurement, and to take part in the investigation of a type of noise-like e.m. events which probably have relation to seismic events. - Based on these results it is possible to take part in the ESA-JAXA BepiColombo Mercury-mission and in the preparation of other future core missions

Testing the Robust Yield Estimation Method for Winter Wheat, Corn, Rapeseed, and Sunflower with Different Vegetation Indices and Meteorological Data

Remote sensing-based crop yield estimation methods rely on vegetation indices, which depend on the availability of the number of observations during the year, influencing the value of the derived crop yield. In the present study, a robust yield estimation method was improved for estimating the yield of corn, winter wheat, sunflower, and rapeseed in Hungary for the period 2000–2020 using 16 vegetation indices. Then, meteorological data were used to reduce the differences between the estimated and census yield data. In the case of corn, the best result was obtained using the Green Atmospherically Resistant Vegetation Index, where the correlation between estimated and census data was R2 = 0.888 before and R2 = 0.968 after the meteorological correction. In the case of winter wheat, the Difference Vegetation Index produced the best result with R2 = 0.815 and 0.894 before and after the meteorological correction. For sunflower, these correlation values were 0.730 and 0.880, and for rapeseed, 0.765 and 0.922, respectively. Using the meteorological correction, the average percentage differences between estimated and census data decreased from 7.7% to 3.9%, from 6.7% to 3.9%, from 7.2% to 4.2%, and from 7.8% to 5.1% in the case of corn, winter wheat, sunflower, and rapeseed, respectively

Lateralized rhythmic acoustic stimulation during daytime NREM sleep enhances slow waves

Slow wave sleep (SWS) is characterized by the predominance of delta waves and slow oscillations, reflecting the synchronized activity of large cortical neuronal populations. Amongst other functions, SWS plays a crucial role in the restorative capacity of sleep. Rhythmic acoustic stimulation (RAS) during SWS has been shown a cost-effective method to enhance slow wave activity. Slow wave activity can be expressed in a region-specific manner as a function of previous waking activity. However, it is unclear whether slow waves can be enhanced in a region-specific manner using RAS. We investigated the effects of unilaterally presented rhythmic acoustic sound patterns on sleep electroencephalographic (EEG) oscillations. Thirty-five participants received during SWS 12-second long rhythmic bursts of pink noise (at a rate of 1 Hz) that alternated with non-stimulated, silent periods, unilaterally delivered into one of the ears of the participants. As expected, RAS enhanced delta power, especially in its low-frequency components between 0.75 and 2.25 Hz. However, increased slow oscillatory activity was apparent in both hemispheres regardless of the side of the stimulation. The most robust increases in slow oscillatory activity appeared during the first 3-4 seconds of the stimulation period. Furthermore, a short-lasting increase in theta and sigma power was evidenced immediately after the first pulse of the stimulation sequences. Our findings indicate that lateralized RAS has a strong potential to globally enhance slow waves during daytime naps. The lack of localized effects suggests that slow waves are triggered by the ascending reticular system and not directly by specific auditory pathways

Solar Cycle-Modulated Deformation of the Earth–Ionosphere Cavity

The Earth–ionosphere cavity resonator is occupied primarily by the electromagnetic radiation of lightning below 100 Hz. The phenomenon is known as Schumann resonances (SR). SR intensity is an excellent indicator of lightning activity and its distribution on global scales. However, long-term measurements from high latitude SR stations revealed a pronounced in-phase solar cycle modulation of SR intensity seemingly contradicting optical observations of lightning from satellite, which do not show any significant solar cycle variation in the intensity and spatial distribution of lightning activity on the global scale. The solar cycle-modulated local deformation of the Earth–ionosphere cavity by the ionization of energetic electron precipitation (EEP) has been suggested as a possible phenomenon that may account for the observed long-term modulation of SR intensity. Precipitating electrons in the energy range of 1–300 keV can affect the Earth–ionosphere cavity resonator in the altitude range of about 70–110 km and modify the SR intensities. However, until now there was no direct evidence documented in the literature supporting this suggestion. In this paper we present long-term SR intensity records from eight stations, each equipped with a pair of induction coil magnetometers: five high latitude (|lat| \u3e 60°), two mid-high latitude (50° \u3c |lat| \u3c 60°) and one low latitude (|lat| \u3c 30°). These long-term, ground-based SR intensity records are compared on the annual and interannual timescales with the fluxes of precipitating 30–300 keV medium energy electrons provided by the POES NOAA-15 satellite and on the daily timescale with electron precipitation events identified using a SuperDARN radar in Antarctica. The long-term variation of the Earth–ionosphere waveguide’s effective height, as inferred from its cutoff frequency, is independently analyzed based on spectra recorded by the DEMETER satellite. It is shown that to account for all our observations one needs to consider both the effect of solar X-rays and EEP which modify the quality factor of the cavity and deform it dominantly over low- and high latitudes, respectively. Our results suggest that SR measurements should be considered as an alternative tool for collecting information about and thus monitoring changes in the ionization state of the lower ionosphere associated with EEP