Le Spèctre des Terres Rares de la Fluorine en Tant Que Marqueur des Propriétés du Milieu de Dépôt et des Interactions Entre Solutions Minéralisantes et Roches Sources. Exemple Pris dans le District de la Marche Occidentale (France)

Partitioning of lanthanides between solution and fluorspar is characterised by high partition coefficients in favor of fluorite, the coefficients growing slightly from La to Lu. On the example of the fluorite's district of the Western Marche France, we show how this property may be used as a geochemical criterion, to study the genesis of fluorspar. We find that two geochemical systems with different compositions and physicochemical properties have coexisted in the district. The first system deposited Chatenet and Charbonnière fluorite, the other one Rossignol fluorite. The chondrite normalised R. E. E. distribution of Rossignol fluorite shows a positive anomaly in europium, the origin of which is discussed. We propose that this anomaly (as well as the pattern of the various R. E. E. distributions analysed) are inherited from surrounding rocks by alteration processes rather than being the result of oxydoreduction phenomena. We suggest that, in general, coexistence of barite and of over-abundant europium fluorite is due to alteration of feldspars (or feldspar-rich rocks) which provides a possible source of barium.     

Non-stationary one-dimensional probabilistic radiative transfer in a bounded medium

Monochromatic time-dependent diffusion of a photon in a homogeneous bounded medium is considered as a one-dimensional probabilistic process in a medium with absorbing boundaries. Simple and intuitive relations are shown to exist between Laplace transforms of time-dependent distributions of photons in infinite medium and inside a bounded medium, as well as for the corresponding emerging intensities. One obtains in particular an explicit and exact expression for the original time-dependent distribution inside a bounded one-dimensional medium.     

Turbulent Heating in the Accelerating Region Using a Multishell Model

Solar energetic particles (SEPs) are released into the heliosphere by solar flares and coronal mass ejections (CMEs). They are mostly protons, with smaller amounts of heavy ions from helium to iron, and lesser amounts of species heavier than iron. The spectra of heavy ions have been previously studied mostly by using the fluence of the particles in an event-integrated spectrum in a small number of spectral snapshots. In this article, we analyze the temporal evolution of the heavy-ion spectra using two large SEP events (27 January 2012 and 7 January 2014) from the Solar TErrestrial Relations Observatory (STEREO) era using Advanced Composition Explorer (ACE) Solar Isotope Spectrometer (SIS) and Ultra Low Energy Isotope Spectrometer (ULEIS), Energetic Particles: Acceleration, Composition and Transport (EPACT) onboard Wind, and the STEREO-A (Ahead) and -B (Behind) Low-Energy Telescope (LET) and Suprathermal Ion Telescope (SIT) instruments, taking a large number of snapshots covering the temporal evolution of the event. We find large differences in the spectra of the ions after the main flux enhancement in terms of the grouping of similar species, but also in terms of the location of the instruments. Although it is somewhat less noticeable than in the case of the temporal evolution of protons (Doran and Dalla, Solar Phys. 291, 2071, 2016), we observe a wave-like pattern travelling through the heavy ion spectra from the highest energies to the lowest, creating an “arch” structure that later straightens into a power law after 18 to 24 hours.