On the spherical-axial transition in supernova remnants

A new law of motion for supernova remnant (SNR) which introduces the quantity of swept matter in the thin layer approximation is introduced. This new law of motion is tested on 10 years observations of SN1993J. The introduction of an exponential gradient in the surrounding medium allows to model an aspherical expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR, SN1987a, are modeled. In the case of SN1987a the three observed rings are simulated.Comment: 19 figures and 14 pages Accepted for publication in Astrophysics & Space Science in the year 201

The Physics of turbulent and dynamically unstable Herbig-Haro jets

The overall properties of the Herbig-Haro objects such as centerline velocity, transversal profile of velocity, flow of mass and energy are explained adopting two models for the turbulent jet. The complex shapes of the Herbig-Haro objects, such as the arc in HH34 can be explained introducing the combination of different kinematic effects such as velocity behavior along the main direction of the jet and the velocity of the star in the interstellar medium. The behavior of the intensity or brightness of the line of emission is explored in three different cases : transversal 1D cut, longitudinal 1D cut and 2D map. An analytical explanation for the enhancement in intensity or brightness such as usually modeled by the bow shock is given by a careful analysis of the geometrical properties of the torus.Comment: 17 pages, 10 figures. Accepted for publication in Astrophysics & Spac

Gas injection in a liquid saturated porous medium. Influence of pressurization effects and liquid films

We study numerically and experimentally the displacement of a liquid by a gas in a two-dimensional model porous medium. In contrast with previous pore-network studies on drainage in porous media, the gas compressibility is fully taken account. The influence of the gas injection rate on the displacement pattern, breakthrough time and the evolution of the pressure in the gas phase due in part to gas compressibility are investigated. A good agreement is found between the simulations and the experiments as regards the invasion patterns. The agreement is also good on the drainage kinetics when the dynamic liquid films are taken into account

Time-Dependent Models for a decade of SN 1993J

A classical and a relativistic law of motion for a supernova remnant (SNR) are deduced assuming an inverse power law behavior for the density of the interstellar medium and applying the thin layer approximation. A third equation of motion is found in the framework of relativistic hydrodynamics with pressure, applying momentum conservation. These new formulas are calibrated against a decade of observations of \snr. The existing knowledge of the diffusive processes of ultrarelativistic electrons is reviewed in order to explain the behavior of the `U' shaped profile of intensity versus distance from the center of SN 1993J.Comment: 20 pages 19 figures, Accepted for pubblication in Astrophysics and Space Science 201

Dust in Supernovae and Supernova Remnants I : Formation Scenarios

Supernovae are considered as prime sources of dust in space. Observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. The reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. Considering the top heavy IMF in the early galaxies, supernovae are assumed to be the major contributor to these large amounts of dust. However, the composition and morphology of dust grains formed in a supernova ejecta is yet to be understood with clarity. Moreover, the dust masses inferred from observations in mid-infrared and submillimeter wavelength regimes differ by two orders of magnitude or more. Therefore, the mechanism responsible for the synthesis of molecules and dust in such environments plays a crucial role in studying the evolution of cosmic dust in galaxies. This review summarises our current knowledge of dust formation in supernova ejecta and tries to quantify the role of supernovae as dust producers in a galaxy.Peer reviewe

Climate-change impacts on water resources and hydropower potential in the Upper Colorado River Basin

Study region: The Upper Colorado River Basin (UCRB), comprised of the Colorado and Gunnison River basins, is the prime water source for much of the western United States. Study focus: Future climate change models were used to drive a hydrologic model of the UCRB to evaluate future water resources and hydropower potential of the basin, using three different climate projections. The Intergovernmental Panel on Climate Change (IPCC) emission scenarios, the A2-business as usual, and the B1-reduced emissions scenarios were evaluated. More than 4500 water diversions and 17 reservoirs were incorporated into the hydrologic model. New hydrological insights for the region: Precipitation projections from climate models vary up to 16%; flow projections revealed greater differences, up to 50%. The climate models projected increase in temperature at low elevations with extreme seasonality at high elevations, although summer temperatures increased at all elevations. The models projected a 60% decline in precipitation at lower elevations and a 74% increase at high elevations, although precipitation declined during the summer months at all elevations. Using the A2 scenario an overall decrease in annual flow was predicted, attributed to a reduction in precipitation and increasing temperature trends; however, this was not consistent during the winter months, which showed an increase in precipitation at high elevations and a modest temperature increase during the winter and resulted in an increase in stream flow. The responses to climate change on reservoir levels varied basin-wide due to variability in precipitation, evapotranspiration, and stream flow. Simulations indicated that water levels in Blue Mesa Reservoir (the largest reservoir in the UCRB) would decline by more than 70% with increasing annual temperatures. Reservoirs with smaller surface areas to the volume ratio were not significantly impacted by evapotranspiration. Our results indicate that hydropower management strategies in the UCRB must adapt to potential climate change, but the required adaptations are dependent on several factors including reservoir size and location. Keywords: Hydropower, Climate change, Hydrology, GI

Evaluating Emerging Organic Contaminant Removal in an Engineered Hyporheic Zone Using High Resolution Mass Spectrometry

The hyporheic zone (HZ), located at the interface of surface and groundwater, is a natural bioreactor for attenuation of chemical contaminants. Engineered HZs can be incorporated into stream restoration projects to enhance hyporheic exchange, with flowpaths optimized to promote biological habitat, water quantity, and water quality improvements. Designing HZs for in-stream treatment of stormwater, a significant source of flow and contaminant loads to urban creeks, requires assessment of both the hydrology and biogeochemical capacity for water quality improvement. Here, we applied tracer tests and high resolution mass spectrometry (HRMS) to characterize an engineered hyporheic zone unit process, called a hyporheic design element (HDE), in the Thornton Creek Watershed in Seattle, WA. Dye, NaCl, and bromide were used to hydrologically link downwelling and upwelling zones and estimate the hydraulic retention time (HRT) of hyporheic flowpaths. We then compared water quality improvements across hydrologically-linked surface and hyporheic flowpaths (3–5 m length; ∼30 min to \u3e3 h) during baseflow and stormflow conditions. We evaluated fate outcomes for 83 identified contaminants during stormflow, including those correlated with an urban runoff mortality syndrome in coho salmon. Non-target HRMS analysis was used to assess holistic water quality improvements and evaluate attenuation mechanisms. The data indicated substantial water quality improvement in hyporheic flowpaths relative to surface flow and improved contaminant removal with longer hyporheic HRT (for ∼1900 non-target compounds detected during stormflow, \u3c17% were attenuated \u3e50% via surface flow vs. 59% and 78% via short and long hyporheic residence times, respectively), and strong contributions of hydrophobic sorption towards observed contaminant attenuation. © 2018 Elsevier Lt

The Large-Scale Effect of Forest Cover on Long-Term Streamflow Variations in Mediterranean Catchments of Central Chile

Forest ecosystems play an important role in surface and subsurface runoff, as well as the availability of water. Therefore, it is important to have a greater understanding of the interactions between forests and the production of water in watersheds. In this sense, this study evaluates the long-term effect of native forests and forest plantations on streamflow variations in central Chile, an unusual climatic area characterized by a well-marked annual cycle with dry summers and wet winters. Thus, the temporal pattern of monthly streamflow was evaluated for mean flow (Qmean), maximum flow (Qmax), and minimum flow (Qmin) in 42 large watersheds. Each series of monthly streamflow data was QA/QC, and then evaluated using the Mann–Kendall’s non-parametric statistical test to detect temporal variations between 1994 and 2015. In addition to the previous analysis, the monthly series were grouped into wet seasons (April–September) and dry seasons (October–April), to determine if there were any significant differences within the annual hydrological cycle. The areas covered with native and forest plantations and their relative changes were evaluated for each catchment through the relationship between streamflow variations and forest cover indicators. Results suggest that streamflow variations are positive and significant when more forest cover exists. The intra-catchment relationships observed during dry seasons for both species revealed the significant role of native forests and mixed masses as key ecosystems for the conservation of long-term streamflow variations in Mediterranean catchments of central Chile. These findings encourage an urgent need to create highland afforestation programs on degraded areas of central Chile, to maximize water storage in a region that is quickly drying out due to unsustainable water and land use management practices and the effects of global warming. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]