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Parametric Sensitivity and Constraint of Contrail Cirrus Radiative Forcing in the Atmospheric Component of CNRM-CM6-1
No full textThe impact of aviation on climate change due to CO2 emissions no longer needs to be demonstrated. However, the impact of non-CO2 effects such as those from contrails is still subject to large uncertainties. An often neglected source of uncertainty comes from climate model sensitivity to numerical parameters representing subgrid-scale processes. Here we investigate the sensitivity of contrail radiative forcing due parametric uncertainty based on the atmospheric component of the CNRM-CM6-1 coupled model. A perturbed parameter ensemble is generated from the sampling of twenty-two adjustable parameters involved in convection, cloud microphysics and radiative transfer processes. A surrogate model based on multi-linear regression is used to explore the full range of contrail radiative forcing due to parametric uncertainty. Based on an optimization algorithm and a climatological skill score, we find a constrained range of contrail radiative forcing from equally skillful model versions with different sets of parameters. We find a contrail radiative forcing best-estimate of 56 mW.m-2 with a 5–95 % confidence interval of 38–70 mW.m-2. Finally, a sensitivity analysis shows that model parameters controlling contrail's lifetime play a major role in the estimation of contrail radiative forcing
Inflation at the End of 2025: Constraints on and Using the Latest CMB and BAO Data
No full textInternational audienceInflation elegantly provides initial conditions for the standard model of cosmology, while solving the horizon, flatness, and magnetic monopole problems. Inflationary models make predictions for the tensor-to-scalar ratio and the spectral index of initial density fluctuations. In light of relevant data releases this year, we present constraints on these two parameters using the latest cosmic microwave background (CMB) and baryon acoustic oscillation data (BAO) available. Using data from Planck, the South Pole Telescope, Atacama Cosmology Telescope, and BICEP/Keck experiments, we derive and a 95% upper limit of . This upper limit on is consistent with the official BICEP/Keck result given the numerical precision of the analyses and our choice to impose the self-consistency relation for single field slow-roll inflation on the tensor power spectrum; the constraint is not impacted by the additional CMB data. While adding DESI BAO data to the CMB data has a negligible impact on , the constraint shifts upward to , which favours monomial inflaton potentials with over Starobinsky or Higgs inflation with and , respectively. This shift is caused by marginally significant differences between the CMB and DESI data that remain unexplained in the context of the standard model. We show that a class of polynomial -attractor models can predict the CMB and CMB+DESI results with and , respectively. While future data will improve our sensitivity to , robust constraints are just as crucial to differentiate between inflation models. We make the data needed to reproduce the new CMB and BAO results and visualisation tools for - figures to compare to any inflation model available https://github.com/Lbalkenhol/r_ns_2025
The impact of lunar topography on the 21-cm power spectrum for grid-based arrays : Insights for the Dark-ages EXplorer (DEX)
No full textInternational audienceThe Dark Ages (DA) provides a crucial window into the physics of the infant Universe, with the 21-cm signal offering the only direct probe for mapping out the three-dimensional distribution of matter at this epoch. To measure this cosmological signal, the Dark-ages EXplorer (DEX) has been proposed as a compact, grid-based radio array on the lunar farside. The minimal design consists of a 32 32 array of 3-m dipole antennas, operating in the MHz band. A practical challenge on the lunar surface is that the antennas may get displaced from their intended positions due to deployment imprecisions and non-coplanarity arising from local surface undulations. We present, for the first time, an end-to-end simulation pipeline, called SPADE-21cm, that integrates a sky model with a DA 21-cm signal model simulated in the lunar frame and incorporating lunar topography data. We study the effects of both lateral (xy) and vertical (z) offsets on the two-dimensional power spectra across the MHz and MHz spectral windows, with tolerance thresholds derived only for the latter. Our results show that positional offsets bias the power spectrum by per cent relative to the expected 21-cm power spectrum during DA. Lateral offsets within (at 32.5 MHz) keep the fraction of Fourier modes with strong contamination (> 50 per cent of the signal) to less than 1 per cent, whereas vertical height offsets affect a larger fraction. This conclusion holds for the 21-cm window with cMpc over the range of cMpc
A new constraint on the -distortion with FIRAS: implications for feedback models in galaxy formation and cosmic shear measurements
No full textInternational audienceThe -type distortion of the blackbody spectrum of the cosmic microwave background radiation probes the pressure of the gas trapped in galaxy groups and clusters. We reanalyze archival data of the FIRAS instrument with an improved astrophysical foreground cleaning technique, and measure a mean -distortion of ( at 95% C.L.), a factor of tighter than the original FIRAS results. This measurement directly rules out many models of baryonic feedback as implemented in cosmological hydrodynamical simulations, mostly using information in objects with mass . We discuss its implications for the analysis of cosmic shear and kinetic Sunyaev-Zel'dovich effect data, and future spectral distortion experiments
Detecting the signature of helium reionization through 3HeII 3.46cm line-intensity mapping
No full textInternational audienceHelium reionization is the most recent phase change of the intergalactic medium, yet its timing and main drivers remain uncertain. Among the probes to trace its unfolding, the 3.46 cm hyperfine line of singly-ionized helium opens the study of helium reionization to upcoming radio surveys. We aim to evaluate the detectability of the 3.46,cm signal with radio surveys and the possible constraints it can place on helium reionization, in particular whether it can distinguish between early and late helium reionization scenarios. Moreover, we perform a comprehensive study of the advantages of single-dish vs. interferometric setup. Using hydrodynamical simulations post-processed with radiative transfer, we construct mock data cubes for two models of helium reionization. We compute the power spectrum of the signal and forecast the signal-to-noise ratio for SKA-1 MID, DSA-2000, and a PUMA-like survey, in both observational setups. The two scenarios produce distinct power spectra, but the faintness of the signal, largely caused by weak coupling between the spin temperature and the kinetic temperature in low-density regions of the IGM, combined with high instrumental noise, makes detection very difficult within realistic integration times for current surveys. A PUMA-like survey operating in single-dish mode could, however, detect the 3.46 cm signal with an integrated signal-to-noise ratio of a few in < 1000 h in both scenarios. Distinguishing helium reionization scenarios with 3.46 cm line-intensity mapping therefore remains challenging for current facilities. Our results, however, indicate that next-generation, high-sensitivity surveys with optimized observing strategies, especially when combined with complementary probes of the IGM, could begin to place meaningful constraints on the timing and morphology of helium reionization
MEGATRON: how the first stars create an iron metallicity plateau in the smallest dwarf galaxies
No full textInternational audienceWe study the stellar mass-iron metallicity relation of dwarf galaxies in the new high-resolution MEGATRON cosmological radiation-hydrodynamics simulations. These simulations model galaxy formation up to in a region that will collapse into a Milky-Way-like galaxy at , while self-consistently tracking Population III and II (Pop.~III, Pop.~II) star formation, feedback and chemical enrichment. MEGATRON dwarf galaxies are in excellent agreement with the observed stellar mass-metallicity relation at , including an over-abundance of dwarfs along a flat plateau in metallicity () at low stellar masses (). We tie this feature to the chemical enrichment of dwarf galaxies by Pop.~III pair-instability supernova (PISN) explosions. The strong Lyman-Werner background (LW) from the protogalaxy ensures that PISNe occur in haloes massive enough () to retain their ejecta. We also predict a tail of of iron-deficient () dwarf galaxies. We show that both plateau and tail (i) are robust to large variations in Pop.~II feedback assumptions, and (ii) survive in bound satellites surrounding the central galaxy at
Role of Large‐Scale Traveling Ionospheric Disturbances in the Positive Storm Phase Observed by the Millstone Hill Radar and GNSS TEC Measurements
No full textInternational audienceA moderate geomagnetic storm was driven by high-speed solar wind stream on 14 March 2016. We show that large-scale traveling ionospheric disturbances (LSTIDs) played a significant role in producing the ionospheric storm positive phase at mid-latitudes in the North American sector. The equatorward expansion of the positive storm phase followed the equatorward propagation of the LSTIDs, after which the total electron content (TEC) increased by 11 TECU (42%). Our novel method to estimate Joule heating suggests that sudden increases in Joule heating in the auroral oval triggered the LSTIDs. The effects of the LSTIDs observed by the Millstone Hill radar were sudden uplifts of the ionospheric F region followed by downlifts. The absence of an eastward electric field in the radar measurements rules out the role of electric field in causing the positive storm phase. We suggest that the uplifts of the ionosphere were associated with equatorward neutral wind perturbations carried along with the LSTIDs, whereas the downlifts were associated with poleward winds. During the whole period of the two LSTIDs, the TEC continued to increase. The increase in TEC during the uplift can be explained by the decrease in the recombination rate at higher altitudes under continuous solar photoionization. The maximum in peak-F density during the second downlift can be explained by compression of the plasma. To explain the increase in TEC during the downlift, an additional mechanism is needed, which could be downward plasma flux from the plasmasphere or increase in atomic oxygen due to changes in thermospheric circulation
Mineralogical constraints on carbon deportment in phosphate ores: Implications for decarbonizing ore processing
No full textInternational audienceThe release of CO2 from carbon-bearing minerals during phosphate ore processing contributes to industrial emissions but remains poorly quantified. This study examines the Bouchane phosphate deposit, part of the Gantour Basin in Morocco, which consists of Upper Cretaceous–Paleogene sedimentary phosphates. The objective is to constrain the proportions and deportment of carbon within its mineral phases and assess their contribution to CO2 release during beneficiation and acidulation. For this purpose, 20 representative samples from a stratigraphic section of the deposit were analyzed for petrographic composition, bulk mineralogy by X-ray diffraction, bulk geochemistry by inductively coupled plasma optical emission spectroscopy (ICP-OES), and total carbon by induction furnace, complemented by in-situ microanalyses using an electron probe micro-analyzer (EPMA) and quantitative automated mineralogy with a TESCAN Integrated Mineral Analyzer (TIMA). Moreover, the modal composition of the studied samples was determined using various approaches such as quantitative X-ray diffraction (QXRD), quantitative automated mineralogy (QAM), element-to-mineral conversion (EMC), and total inversion (TI). The studied samples were predominantly composed of phosphatic coated grains, peloids, coprolites, and skeletal particles. The chemistry of these sediments varied along the stratigraphic section, marked by a dominance of inorganic carbon compared to organic carbon, with a mean content of 11.38 ± 4.58 wt% and 0.68 ± 0.03 wt%, respectively. The developed calculated mineralogy techniques (EMC, TI) proved successful in accurate quantification of the modal composition of the phosphate sediments. Automated mineralogy by TIMA provided a quantification of the percentage of problematic locked carbonates within phosphatic grains, with values below 3 %. These grains were predicted to hold 11 % of the CO2 in carbonate fluorapatite (CFA), and 0.3 % and 0.1 % in calcite and dolomite, respectively. The remaining carbonate phases are removed during washing and flotation. This study shows that adopting holistic approaches in phosphate mining is efficient for developing rapid, low-cost techniques for mineralogical characterization (EMC, TI) and indicates that phosphate rock processing results in limited in situ CO2 release from carbonate minerals
Culturable macroplastic-associated potential human pathogens in coral reef lagoons, Madagascar
No full textInternational audiencePotentially human pathogenic bacteria (PHPBs) have been detected in plastic-associated marine microbiomes, primarily through DNA-based methods. However, data on their culturability and concentrations on plastics remain limited, yet are essential to assess actual health risks. To address this gap, 70 floating macroplastic and 20 seawater samples were collected from two human-impacted reef lagoons in southwestern Madagascar (AtsimoAndrefana region). PHPBs were cultured from their microbiomes using selective media and quantified. Macroplastics were predominantly polypropylene (34 %) and polyamide (31 %). In increasing order of concentration, four culturable PHPBs, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Vibrio Harveyi clade species, were identified on both macroplastics and in seawater, across all sites and polymer types. Notably, 52 % of macroplastic samples harbored two PHPB species simultaneously, while only 7 % were PHPB-free. Concentrations of all PHPBs were consistently and significantly higher on macroplastics than in seawater, regardless of the measurement unit or polymer type, with the Vibrio Harveyi clade being the most abundant. No significant correlations were observed among PHPB species concentrations, suggesting limited interaction and independent colonization. These findings indicate that floating macroplastics may serve as reservoirs and fomites for viable PHPBs. However, their potential impacts on ecosystems and human health should be interpreted cautiously. We emphasize the need to contextualize PHPB concentration data by considering factors such as exposure pathways, environmental persistence, and bacterial virulence, rather than relying solely on concentration-based comparisons, which may lead to misinterpretatio
An energy-based dual phase-field model for shear cracking patterns in heterogeneous geomaterials
No full textInternational audienceThe phase field method (PFM) enables natural crack initiation and complex propagation by minimizing the system’s potential energy, eliminating the need for predefined failure criteria. While advantageous, this energy-driven approach can be limiting in scenarios where specific fracture criteria or control over crack direction and timing are essential, particularly in heterogeneous materials or those exhibiting tension–compression asymmetry. To overcome these limitations, we propose a dual-phase field model incorporating material heterogeneity and distinct evolution equations for mode-I and mode-II fractures. A directional weighting parameter is introduced to calibrate shear crack paths, allowing for controlled crack directionality from an energetic standpoint. Simulation results reveal that shear crack inclination increases as the weight parameter decreases, highlighting a strong correlation between this parameter and crack trajectory. The stress–strain response shows brittle behavior, with more pronounced softening and a shift toward ductile characteristics as the weight parameter increases. Material heterogeneity significantly influences both crack patterns and strength: weak zones foster localized, symmetric fractures, whereas strong zones produce more complex, asymmetric failures. Increased heterogeneity leads to irregular crack paths, lower peak strength, and reduced structural stability. Overall, the proposed model enhances predictive accuracy and flexibility in simulating mixed-mode fracture in heterogeneous geomaterials, offering valuable insights for engineering applications such as slope stability assessment and fracture risk mitigation