Standard and Non-Standard Solar Models

We summarize the physical input and assumptions commonly adopted in modern standard solar models that also produce good agreement with solar oscillation frequencies. We discuss two motivations for considering non-standard models: the solar neutrino problem and surface lithium abundance problem. We begin to explore the potential for mixed core models to solve the neutrino problem, and compare the structure, neutrino flux, and oscillation frequency predictions for several models in which the inner 25% of the radius is homogenized, taking into account the effects of non-local equilibrium abundances of ³He. The results for the neutrino flux and helioseismic predictions are far from satisfactory, but such models have the potential to reduce the predicted ⁷Be/⁸B neutrino flux ratio, and further studies are warranted. Finally, we discuss how much the neutrino problem can be alleviated in the framework of the standard solar model by using reaction rates, abundances and neutrino capture cross-sections at the limits of their uncertainties, while still satisfying the constraints of helioseismology.     

187Re,recyclingR-process elements through stars,and the age of the Galaxy

The enhanced -decay rate of ionized¹⁸⁷Re in stars has been studied within the context of a detailed numerical model of the production ofr-process elements and their recycling through stars during the course of galactic evolution. It is concluded that the enhanced decay rate does not significantly reduce the Re-Os chronometer age for the Galaxy. Consequently, the¹⁸⁷Re -decay half-life and the neutron cross-section ratio (¹⁸⁶Os)/(¹⁸⁷Os) remain as the significant uncertainties in this chronology. Unlike the uncertainties in other chronologies, both are amenable to laboratory measurements.     

New Early Permian paleomagnetic results from the Brive basin (French Massif Central) and their implications for Late Variscan tectonics

In order to assess the structural evolution of the Brive basin and the Paleozoic activity of surrounding major faults in the French Massif Central, we carried out a paleomagnetic study on Early Permian rocks from this basin. Positive-fold tests and solely reversed polarities indicate that the characteristic remanent magnetization is likely to be primary. Early Permian tilt-corrected site mean declinations vary from 207°–167° indicating that the Brive basin experienced internal vertical-axis rotations. On the contrary, Late Permian paleomagnetic site means exhibit a circular Fisherian distribution showing no relative rotations. Detailed analyses of Permian paleomagnetic data from five contemporaneous basins of the French Massif Central reveal that these basins share the same equatorial paleolatitude with stable Europe throughout the Permian. However, in Early Permian, three of the five basins experienced differential rotations. The Saint-Affrique basin not only suffered internal deformation during the Early Permian, but the basin as a whole underwent a full-scale counterclockwise vertical-axis block rotation with respect to stable Europe. As a consequence, paleomagnetic data from similar late orogenic basins have to be thus carefully considered for establishment of Apparent Polar Wander paths.     

A semi-empirical wind set-up forecasting model for Lake Champlain

The precision of Lake Champlain's water level estimation is a key component in the flood forecasting process for the Richelieu River. Hydrological models do not typically take into consideration the effects of the wind on the water level (also known as the wind set-up). The objective of this study is to create an empirical wind set-up forecast model for Lake Champlain during high wind events. The proposed model uses wind speed and direction across the Lake, as well as wind gusts as inputs. The model is calibrated to a subset of observations and evaluated on an independent sample, considering four wind speed bins. It is tested and compared to a variant of the Zuider Zee equation on 20 wind set-up events that occurred between 2017 and 2019 using hindcast data from five different numerical weather prediction systems (GDPS, RDPS, HRDPS, NOAA and ECMWF). A quantile mapping-based forecast calibration scheme is implemented for each of the forecast products to correct their biases. Results show that events are successfully predicted by the proposed model at least 72 h in advance. These results are better than the other comparative models found in the literature and tested herein. Overall, significant improvements are obtained by including wind speed and wind gusts from different weather stations.