Mesospheric anomalous diffusion during noctilucent clouds

The Andenes specular meteor radar shows meteor-trail diffusion rates increasing on average by ~ 20% at times and locations where a lidar observes noctilucent clouds (NLCs). This high-latitude effect has been attributed to the presence of charged NLC but this study shows that such behaviors result predominantly from thermal tides. To make this claim, the current study evaluates data from three stations, at high-, mid-, and low-latitudes, for the years 2012 to 2016, comparing diffusion to show that thermal tides correlate strongly with the presence of NLCs. This data also shows that the connection between meteor-trail diffusion and thermal tide occurs at all altitudes in the mesosphere, while the NLC influence exists only at high-latitudes and at around peak of NLC layer. This paper discusses a number of possible explanations for changes in the regions with NLCs and leans towards the hypothesis that relative abundance of background electron density plays the leading role. A more accurate model of the meteor trail diffusion around NLC particles would help researchers determine mesospheric temperature and neutral density profiles from meteor radars.Public versio

Combining Sources of Description for Approximating Music Similarity Ratings

In this paper, we compare the effectiveness of basic acoustic features and genre annotations when adapting a music similarity model to user ratings. We use the Metric Learning to Rank algorithm to learn a Mahalanobis metric from comparative similarity ratings in in the MagnaTagATune database. Using common formats for feature data, our approach can easily be transferred to other existing databases. Our results show that genre data allow more effective learning of a metric than simple audio features, but a combination of both feature sets clearly outperforms either individual set

Hydrochemical properties of deep carbonate aquifers in the SW German Molasse basin

Background The Upper Jurassic (Malm) limestone and the Middle Triassic Muschelkalk limestone 18 are the major thermal aquifers in the southwest German alpine foreland. The aquifers 19 are of interest for production of geothermal energy and for balneological purposes. Methods Hydrochemical data from several hundred wells within two deep limestone aquifers in the Molasse basin of SW Germany have been compiled, examined, validated, and analyzed with the aim to characterize the fluids and to investigate the origin of the fluid properties. Results The hydrochemical properties of the two aquifers differ in several aspects. The total amounts of dissolved solids (TDS) are much higher within the Upper Muschelkalk aquifer than within the Upper Jurassic. Water composition data reflect the origin and hydrochemical evolution of deep water. Rocks and their minerals control the chemical signature of the water. With increasing depth, the total of dissolved solids increases. In both aquifers, the water evolves to a NaCl-dominated fluid regardless of the aquifer rock. Discussion The salinity of the aquifers has different sources. In the case of the Upper Muschelkalk, it is linked to deep circulation systems, while the hydrochemical properties in the Upper Jurassic developed due to changing overburden and hydraulic potential

Criteria and geological setting for the generic geothermal underground research laboratory, GEOLAB

High flow rate injection and related hydromechanical interaction are the most important factors in reservoir development of Enhanced Geothermal Systems (EGS). GeoLaB, a new generic geothermal underground research laboratory (URL), is proposed for controlled high flow rate experiments (CHFE) to address limited comprehension of coupled processes connected to EGS reservoir flow conditions. As analogue for typical EGS development, CHFE require specific hydromechanical conditions including a connected fracture network in crystalline basement rock, sufficient hydraulic fracture transmissivities, a strike-slip to normal faulting tectonic regime, controllable hydraulic boundary conditions, and hydrothermal alteration fracture fillings that improve conditions for hydromechanical interaction. With the aim to identify most appropriate areas for future site selection, four criteria have been established based on the EGS reference site of Soultz. Two URLs in crystalline basement worldwide approximate the requirements of a new generic GeoLaB and may be used for accompanying experimentation. Besides favourable geological, hydraulic, and stress conditions, the vicinity to long-term EGS production favours the southern Black Forest as potential region for GeoLaB. Therefore, an exemplary site assessment has been carried out at “Wilhelminenstollen” in the southern Black Forest (Germany). New remote sensing, hydrochemical, and geophysical analyses as well as reactivation potential, and stress modelling were added to complement existing geological and hydrogeological information. At this site, reactivation potential analysis reveals two local maxima prone for shear reactivation as strike-slip faults. The highest lineament density is observed for the N110°E strike direction that is associated with both slip and dilation tendency maxima. Clay minerals occur in fractures and the matrix. Local, partly water-bearing fractures, when partly filled with ore minerals, were connected to veins in the tunnel using shallow geophysical methods. Hydrochemical data reveal infiltration of the tunnel water from at least 500 m above the tunnel. The results suggest a crystalline basement with a fracture network that is regionally connected and water-conducting. Hydraulic conductivity in the southern Black Forest granite is estimated to amount to about 4.5·10−8 m s−1 at 500 m depth. The hydraulic boundary conditions exclude unknown drainage. Analyses of the influence of topography on orientation and magnitude of the maximum stress indicate a minimum overburden of about 500 m for regional reactivation to be valid. In conclusion, the southern Black Forest and in particular “Wilhelminenstollen” offers favourable condition for CHFE. Final decision on the GeoLaB site is to be drawn from forthcoming exploration wells

Hydrochemical characterisation of a Major central European heat flux anomaly: the Bürchau geothermal spring system, Southern Black Forest, Germany

Background: The possible signature of deep fluids originating from processes occurring during infiltration or circulation in a remote valley in the Black Forest (Germany), a typical infiltration area in the crystalline basement which represents a possible recharge zone of one of the major heat flux density anomalies in central Europe, has been hydrochemically characterised. Chemical and isotopic compositions of two warm springs and several cold springs in Bürchau as well as water from the Badenweiler Spa were sampled three times during June and October 2013. Methods: A number of 70 water samples were taken at natural outlet conditions and analysed for major and trace elements, water H/O-isotope ratios and sulphur isotope ratios of dissolved sulfate. A chlorofluorocarbon (CFC) analysis was conducted to determine the underground residence time of the thermal water. To assess water-rock interactions seven rock samples representing the occurring lithological units of the study area were prepared to thin sections for polarization microscopic analysis. Results: The main spring in Bürchau discharging water with a temperature up to T = 18.1°C at flow rates of approximately 0.2 L s$^{-1}$ is Na-Ca-HCO$_{3}$-dominated and generally low mineralised (total dissolved solids (TDS) of about 150 mg L$^{-1}$). Even lower mineralisation and temperature of a nearby spring indicates further dilution with shallow groundwater. With respect to cold springs in the vicinity, the thermal water in Bürchau is slightly enriched in Cl, B, Li, Rb and Cs. In nearby granites, sericitisation of plagioclase and oxidation of pyrite to goethite have been identified. The stable isotope composition of H and O suggests meteoric origin of the water. Chlorofluorocarbon (CFC) analyses indicate that 30% to 40% of the thermal water in Bürchau is younger than 60 to 70 years. Reservoir temperatures have been estimated to 40°C to 80°C using sulphate and quartz geothermometers. Conclusions: Thus, the circulation time of the other 60% to 70% of the thermal water is longer than 70 years. Estimated reservoir temperatures in a range of 40°C to 80°C correspond to an infiltration depth of about 1,600 to 1,800 m

Experimental evidence of magnetic flux pumping in ASDEX upgrade

In high-β scenarios with on-axis co-current electron cyclotron current drive, which normally lowers q 0 below unity, the absence of sawteeth suggests the involvement of an additional current redistribution mechanism beyond neoclassical current diffusion. This is supported by imaging motional Stark effect diagnostic measurements, which indicate that q 0 remains consistently around 1. This phenomenon is observed in the presence of a 1/1 mode, indicating its potential role in the current redistribution. It is shown that the mode’s ability to modify the central current and suppress sawteeth increases with plasma pressure. These findings align with a recent theoretical model, which predicts a pressure threshold for sawtooth avoidance by a 1/1 quasi-interchange mode and where this threshold increases with the strength of inward current diffusion. Moreover, the advantages of the flux pumping scenario for future machines are highlighted.</p