Geochronological constraints on Caledonian strike–slip displacement in Svalbard,with implications for the evolution of the Arctic

The timing of Svalbard's assembly in relation to the mid‐Paleozoic Caledonian collision between Baltica and Laurentia remains contentious. The Svalbard archipelago consists of three basement provinces bounded by N–S‐trending strike–slip faults whose displacement histories are poorly understood. Here, we report microstructural and mineral chemistry data integrated with ⁴⁰Ar/³⁹Ar muscovite geochronology from the sinistral Vimsodden‐Kosibapasset Shear Zone (VKSZ, southwest Svalbard) and explore its relationship to adjacent structures and regional deformation within the circum‐Arctic. Our results indicate that strike–slip displacement along the VKSZ occurred in late Silurian–Early Devonian and was contemporaneous with the beginning of the main phase of continental collision in Greenland and Scandinavia and the onset of syn‐orogenic sedimentation in Silurian–Devonian fault‐controlled basins in northern Svalbard. These new‐age constraints highlight possible links between escape tectonics in the Caledonian orogen and mid‐Paleozoic terrane transfer across the northern margin of Laurentia.     

Validation of Galileo orbits using SLR with a focus on satellites launched into incorrect orbital planes

The space segment of the European Global Navigation Satellite System (GNSS) Galileo consists of In-Orbit Validation (IOV) and Full Operational Capability (FOC) spacecraft. The first pair of FOC satellites was launched into an incorrect, highly eccentric orbital plane with a lower than nominal inclination angle. All Galileo satellites are equipped with satellite laser ranging (SLR) retroreflectors which allow, for example, for the assessment of the orbit quality or for the SLR–GNSS co-location in space. The number of SLR observations to Galileo satellites has been continuously increasing thanks to a series of intensive campaigns devoted to SLR tracking of GNSS satellites initiated by the International Laser Ranging Service. This paper assesses systematic effects and quality of Galileo orbits using SLR data with a main focus on Galileo satellites launched into incorrect orbits. We compare the SLR observations with respect to microwave-based Galileo orbits generated by the Center for Orbit Determination in Europe (CODE) in the framework of the International GNSS Service Multi-GNSS Experiment for the period 2014.0–2016.5. We analyze the SLR signature effect, which is characterized by the dependency of SLR residuals with respect to various incidence angles of laser beams for stations equipped with single-photon and multi-photon detectors. Surprisingly, the CODE orbit quality of satellites in the incorrect orbital planes is not worse than that of nominal FOC and IOV orbits. The RMS of SLR residuals is even lower by 5.0 and 1.5 mm for satellites in the incorrect orbital planes than for FOC and IOV satellites, respectively. The mean SLR offsets equal \(-44.9, -35.0\), and \(-22.4\) mm for IOV, FOC, and satellites in the incorrect orbital plane. Finally, we found that the empirical orbit models, which were originally designed for precise orbit determination of GNSS satellites in circular orbits, provide fully appropriate results also for highly eccentric orbits with variable linear and angular velocities.     

Model for prediction of sea dike breaching initiated by breaking wave impact

A computational model system is proposed for the prediction of sea dike breaching initiated from the seaward side by breaking wave impact with the focus on the application of the model system for the estimation failure probability of the defence structure. The described model system is built using a number of existing models for the calculation of grass, clay, and sand erosion. The parameters identified as those having the most significant influence on the estimation of the failure have been described stochastically. Monte Carlo simulations to account for uncertainties of the relevant input parameters and the model itself have been performed and the probabilities of the breach initiation and of the full dike breaching have been calculated. This will form the basis to assess the coastal flood risk due to dike breaching.     

Effects of non-thermal tails in Maxwellian electron distributions on synchrotron and Compton processes

We investigate how the presence of a non-thermal tail beyond a Maxwellian electron distribution affects the synchrotron process as well as Comptonization in plasmas with parameters typical for accretion flows on to black holes. We find that the presence of the tail can significantly increase the net (after accounting for self-absorption) cyclo-synchrotron emission of the plasma, which then provides seed photons for Compton upscattering. Thus, the luminosity in the thermally Comptonized spectrum is enhanced as well. The importance of these effects increases with both increasing Eddington ratio and black hole mass. The enhancement of the Comptonized synchrotron luminosity can be as large as ∼10³ and ∼10⁵ for stellar and supermassive black holes, respectively, when the energy content in the non-thermal tail is 1 per cent.
The presence of the tail only weakly hardens the thermal Comptonization spectrum but it leads to the formation of a high-energy tail beyond the thermal cut-off, which two effects are independent of the nature of the seed photons. Since observations of high-energy tails in Comptonization spectra can constrain the non-thermal tails in the electron distribution and thus the Comptonized synchrotron luminosity, they provide upper limits on the strength of magnetic fields in accretion flows. In particular, the measurement of an MeV tail in the hard state of Cyg X-1 by McConnell et al. implies the magnetic field strength in this source to be at most an order of magnitude below equipartition.     

Analysis and modeling of spatial correlation structure in small-scale rainfall in Central Oklahoma

Spatial correlation structure in small-scale rainfall is analyzed based on a dense cluster of raingauges in Central Oklahoma. This cluster, called the EVAC PicoNet, consists of 53 gauges installed in 25 measurement stations covering an area of about 3 km by 3 km. Two raingauges are placed in 24 stations and five in the central station. Three aspects of the estimated spatial correlation functions are discussed: dependence on time-scale ranging from 1 min to 24 h, inter-storm variability, and dependence on rainfall intensity. The results show a regular dependence of the correlogram parameters on the averaging time-scale, large differences of the correlograms in the individual storms, and the dominance of storms with high spatial variability on the average large sample characteristics. The authors also demonstrate and discuss the ambiguities in correlation estimates conditioned on rainfall intensities. The findings of this study have implications for raingauge network design, rainfall modeling, and conclusive evaluation of radar and satellite estimates of rainfall.