Tunka-Rex: energy reconstruction with a single antenna station (ARENA 2016)

The Tunka-Radio extension (Tunka-Rex) is a radio detector for air showers in Siberia. From 2012 to 2014, Tunka-Rex operated exclusively together with its host experiment, the air-Cherenkov array Tunka-133, which provided trigger, data acquisition, and an independent air-shower reconstruction. It was shown that the air-shower energy can be reconstructed by Tunka-Rex with a precision of 15\% for events with signal in at least 3 antennas, using the radio amplitude at a distance of 120\,m from the shower axis as an energy estimator. Using the reconstruction from the host experiment Tunka-133 for the air-shower geometry (shower core and direction), the energy estimator can in principle already be obtained with measurements from a single antenna, close to the reference distance. We present a method for event selection and energy reconstruction, requiring only one antenna, and achieving a precision of about 20\%. This method increases the effective detector area and lowers thresholds for zenith angle and energy, resulting in three times more events than in the standard reconstruction

Improved measurements of the energy and shower maximum of cosmic rays with Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is an array of 63 antennas located in the Tunka Valley, Siberia. It detects radio pulses in the 30-80 MHz band produced during the air-shower development. As shown by Tunka-Rex, a sparse radio array with about 200 m spacing is able to reconstruct the energy and the depth of the shower maximum with satisfactory precision using simple methods based on parameters of the lateral distribution of amplitudes. The LOFAR experiment has shown that a sophisticated treatment of all individually measured amplitudes of a dense antenna array can make the precision comparable with the resolution of existing optical techniques. We develop these ideas further and present a method based on the treatment of time series of measured signals, i.e. each antenna station provides several points (trace) instead of a single one (amplitude or power). We use the measured shower axis and energy as input for CoREAS simulations: for each measured event we simulate a set of air-showers with proton, helium, nitrogen and iron as primary particle (each primary is simulated about ten times to cover fluctuations in the shower maximum due to the first interaction). Simulated radio pulses are processed with the Tunka-Rex detector response and convoluted with the measured signals. A likelihood fit determines how well the simulated event fits to the measured one. The positions of the shower maxima are defined from the distribution of chi-square values of these fits. When using this improved method instead of the standard one, firstly, the shower maximum of more events can be reconstructed, secondly, the resolution is increased. The performance of the method is demonstrated on the data acquired by the Tunka-Rex detector in 2012-2014.Comment: Proceedings of the 35th ICRC 2017, Busan, Kore

Towards a cosmic-ray mass-composition study at Tunka Radio Extension (ARENA 2016)

The Tunka Radio Extension (Tunka-Rex) is a radio detector at the TAIGA facility located in Siberia nearby the southern tip of Lake Baikal. Tunka-Rex measures air-showers induced by high-energy cosmic rays, in particular, the lateral distribution of the radio pulses. The depth of the air-shower maximum, which statistically depends on the mass of the primary particle, is determined from the slope of the lateral distribution function (LDF). Using a model-independent approach, we have studied possible features of the one-dimensional slope method and tried to find improvements for the reconstruction of primary mass. To study the systematic uncertainties given by different primary particles, we have performed simulations using the CONEX and CoREAS software packages of the recently released CORSIKA v7.5 including the modern high-energy hadronic models QGSJet-II.04 and EPOS-LHC. The simulations have shown that the largest systematic uncertainty in the energy deposit is due to the unknown primary particle. Finally, we studied the relation between the polarization and the asymmetry of the LDF.Comment: ARENA proceedings, 4 pages, updated reference

First analysis of inclined air showers detected by Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array for the detection of radio emission from cosmic-ray air showers in the frequency band of 30 to 80 MHz and for primary energies above 100 PeV. The standard analysis of Tunka-Rex includes events with zenith angle of up to 50$^\circ$. This cut is determined by the efficiency of the external trigger. However, due to the air-shower footprint increasing with zenith angle and due to the more efficient generation of radio emission (the magnetic field in the Tunka valley is almost vertical), there are a number of ultra-high-energy inclined events detected by Tunka-Rex. In this work we present a first analysis of a subset of inclined events detected by Tunka-Rex. We estimate the energies of the selected events and test the efficiency of Tunka-Rex antennas for detection of inclined air showers.Comment: ARENA2018 proceeding

Palaeoenvironment of the Middle and Upper Neopleistocene at the Gornovo Upper Palaeolithic site (Southern Ural foreland, Russia)

© 2015 Elsevier Ltd and INQUAComplex biostratigraphical methods and radiocarbon dates were used to reconstruct the Middle (late Middle Pleistocene) and Late Neopleistocene (Late Pleistocene) palaeoenvironments covering the Palaeolithic period in the western foreland of the Urals. The Gornovo Palaeolithic settlement is located on the lowest terrace of the Belaya River. From the base to the top, this terrace consists of fluvial and lacustrine deposits of the Belaya horizon (Middle Neopleistocene; 427–364 ka), alluvial and lacustrine deposits of the Larevka horizon (Middle Neopleistocene; 364–334 ka), fluvial and lacustrine deposits of the Tabulda horizon (Late Neopleistocene; 57–24 ka), water-slope deposits of the Kudashevo horizon (Late Neopleistocene; 24–11 ka) and chernozem soil of the Holocene. The small and large mammals, insects, molluscs, and ostracods discovered in the deposits complete the palaeoecological characteristics of these periods. A diverse herbaceous steppe vegetation dominated during the Belaya Interglacial (a mixed coniferous forests with broad-leaved trees occurred in wet areas). The ostracoda species clearly indicate a cooling at the end of this time span. Molluscs inhabited the rivers and shores of freshwater ponds. The large mammals belong to the Middle Pleistocene fauna complex. During Larevka time span vegetation and fauna indicate cold climate conditions. The cold steppe communities typical of the beginning of this period changed gradually into communities that show an increasing role of the taiga. The ostracoda species confirm these cold conditions. Forest-steppe landscapes dominated during the second part of the Tabulda time span. Numerous ostracods as well as molluscs populated the lakes and floodplain basins. Entomological data show that the palaeoenvironment conditions were somewhat cooler than modern environment existing in the Southern Ural foreland. The large mammals of the Gornovo site belong to the Late Palaeolithic complex with the specific presence of Camelus sp. The Gornovo forest-steppe small mammalian fauna developed in cool continental climate conditions when coniferous forests grew in the river valleys and when forest-steppe landscapes dominated in the water interfluves. The artefacts are characteristic of the beginning of the Late Palaeolithic (32–24 ka). The Kudashevo time is correlated with the late Valdai (late Late Pleistocene; 24–11 ka). The herbage-Artemisia-Chenopodiaceae grassland-steppe association covered most of the territory and a Picea forest with Betula and a small quantity of broad-leaved trees grew in wet depressions. The climate at the end of this period became colder. Freshwater and terrestrial molluscs were represented by rare widespread species while the ostracoda species indicate cold conditions

Signal recognition and background suppression by matched filters and neural networks for Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array, which measures the radio emission of the cosmic-ray air-showers in the frequency band of 30-80 MHz. Tunka-Rex is co-located with TAIGA experiment in Siberia and consists of 63 antennas, 57 of them are in a densely instrumented area of about 1 km\textsuperscript{2}. In the present work we discuss the improvements of the signal reconstruction applied for the Tunka-Rex. At the first stage we implemented matched filtering using averaged signals as template. The simulation study has shown that matched filtering allows one to decrease the threshold of signal detection and increase its purity. However, the maximum performance of matched filtering is achievable only in case of white noise, while in reality the noise is not fully random due to different reasons. To recognize hidden features of the noise and treat them, we decided to use convolutional neural network with autoencoder architecture. Taking the recorded trace as an input, the autoencoder returns denoised trace, i.e. removes all signal-unrelated amplitudes. We present the comparison between standard method of signal reconstruction, matched filtering and autoencoder, and discuss the prospects of application of neural networks for lowering the threshold of digital antenna arrays for cosmic-ray detection.Comment: ARENA2018 proceeding

Current Status and New Challenges of The Tunka Radio Extension

The Tunka Radio Extension (Tunka-Rex) is an antenna array spread over an area of about 1~km$^2$. The array is placed at the Tunka Advanced Instrument for cosmic rays and Gamma Astronomy (TAIGA) and detects the radio emission of air showers in the band of 30 to 80~MHz. During the last years it was shown that a sparse array such as Tunka-Rex is capable of reconstructing the parameters of the primary particle as accurate as the modern instruments. Based on these results we continue developing our data analysis. Our next goal is the reconstruction of cosmic-ray energy spectrum observed only by a radio instrument. Taking a step towards it, we develop a model of aperture of our instrument and test it against hybrid TAIGA observations and Monte-Carlo simulations. In the present work we give an overview of the current status and results for the last five years of operation of Tunka-Rex and discuss prospects of the cosmic-ray energy estimation with sparse radio arrays.Comment: Proceedings of E+CRS 201

Biostratigraphy of the early Middle Pleistocene of the Southern Fore-Urals

© 2015 Elsevier Ltd and INQUA. A summary of published and unpublished data on the stratigraphy of the early Middle Pleistocene of the Southern Urals region is presented in this paper. It follows previous reviews about the characteristics of the Pleistocene deposits of the easternmost part of Europe. Deposits of different origin, which constitute the regional stratigraphic units, are characterized. Mammalian data form the base for the (bio)stratigraphical subdivision. Fossil mollusca, ostracoda, mammals and pollen are used for the reconstruction of the palaeoenvironmental conditions and the stratigraphical position of the main localities is discussed.The beginning of the early Middle Pleistocene (Minzitarovo time) coincides with a stabilization of the hydrographic network. Palaeontological remains from that period are rare. Pinus-Picea forests with small admixture of broad-leaved species were spread at the beginning of this interval. Later, the role of forests decreased and the role of herbs and Chenopodiaceae increased. Palynological data indicate that the climate was cool during that time. The landscapes of the Baza time were dominated by herbaceous-Artemisia associations and small birch forests with an admixture of broadleaved and coniferous trees and the terminal time was characterized by the wide development of taiga. Ostracods and molluscs are known from those deposits. Ecological composition of the small mammalian faunas indicates forest-steppe conditions for the southern part of this natural zone. Small mammals of that time belong to the Tiraspol faunal assemblage. The climate was warm and dry. The initial Tanyp time was characterized by the development of herbaceous-Artemisia-Chenopodiaceae steppes and broadleaved birch forests, which were subsequently replaced by a dominance of taiga associations, which tolerate cold climatic conditions. Molluscs are represented by rare terrestrial and freshwater species. The assemblage of freshwater ostracods includes cold-resistant species. In the Atasevo time, broadleaved birch forests and meadow-steppes characterized the landscape. The presence of stenothermic-thermophilic ostracods species indicates warm climatic conditions. Molluscs are represented by terrestrial and numerous freshwater species. The small mammalian fauna is characterized by the smaller percentage of Mimomys voles; it post-dates the Baza fauna. The Atasevo fauna is unique because of the occurrence of Arvicola mosbachensis Schmidtgen among the typical early Middle Pleistocene species.At the end of this period during the Chusovskoi timespan, the herbaceous-Artemisia-Chenopodiaceae steppes, which covered spacious open areas, were subsequently replaced by coniferous-birch forests with an admixture of broadleaved trees. Fossil remains are rare. Ostracods represent cold-resistant species indicating that the climate was cold

Biostratigraphy of the early Middle Pleistocene of the Southern Fore-Urals

© 2015 Elsevier Ltd and INQUAA summary of published and unpublished data on the stratigraphy of the early Middle Pleistocene of the Southern Urals region is presented in this paper. It follows previous reviews about the characteristics of the Pleistocene deposits of the easternmost part of Europe. Deposits of different origin, which constitute the regional stratigraphic units, are characterized. Mammalian data form the base for the (bio)stratigraphical subdivision. Fossil mollusca, ostracoda, mammals and pollen are used for the reconstruction of the palaeoenvironmental conditions and the stratigraphical position of the main localities is discussed. The beginning of the early Middle Pleistocene (Minzitarovo time) coincides with a stabilization of the hydrographic network. Palaeontological remains from that period are rare. Pinus–Picea forests with small admixture of broad-leaved species were spread at the beginning of this interval. Later, the role of forests decreased and the role of herbs and Chenopodiaceae increased. Palynological data indicate that the climate was cool during that time. The landscapes of the Baza time were dominated by herbaceous-Artemisia associations and small birch forests with an admixture of broadleaved and coniferous trees and the terminal time was characterized by the wide development of taiga. Ostracods and molluscs are known from those deposits. Ecological composition of the small mammalian faunas indicates forest-steppe conditions for the southern part of this natural zone. Small mammals of that time belong to the Tiraspol faunal assemblage. The climate was warm and dry. The initial Tanyp time was characterized by the development of herbaceous–Artemisia–Chenopodiaceae steppes and broadleaved birch forests, which were subsequently replaced by a dominance of taiga associations, which tolerate cold climatic conditions. Molluscs are represented by rare terrestrial and freshwater species. The assemblage of freshwater ostracods includes cold-resistant species. In the Atasevo time, broadleaved birch forests and meadow-steppes characterized the landscape. The presence of stenothermic–thermophilic ostracods species indicates warm climatic conditions. Molluscs are represented by terrestrial and numerous freshwater species. The small mammalian fauna is characterized by the smaller percentage of Mimomys voles; it post-dates the Baza fauna. The Atasevo fauna is unique because of the occurrence of Arvicola mosbachensis Schmidtgen among the typical early Middle Pleistocene species. At the end of this period during the Chusovskoi timespan, the herbaceous–Artemisia–Chenopodiaceae steppes, which covered spacious open areas, were subsequently replaced by coniferous-birch forests with an admixture of broadleaved trees. Fossil remains are rare. Ostracods represent cold-resistant species indicating that the climate was cold