Theory and numerical modeling of electrical self-potential signatures of unsaturated flow in melting snow

We have developed a new theory and numerical model of electrical self-potential (SP) signals associated with unsaturated flow in melting snow. The model is applicable to continuous natural-melt and transient-flow phenomena such as melt-water pulses, and is tested using laboratory column experiments. SP signals fundamentally depend on the temporal evolution of snow porosity and melt-water flux, electrical conductivity (EC) and pH. We infer a reversal of the sign of the zeta potential (a fundamental electrical property of grain surfaces in porous media), consistent with well-known elution sequences of ions that cause progressive increases and decreases in melt-water pH and EC respectively. Injection of fully-melted snow samples, containing the entire natural range of ions, into melting snow columns caused additional temporary reversals of the sign of the zeta potential. Widely-used empirical relationships between effective saturation, melt-water fraction, EC and pH, as well as snow porosity, grain size and permeability are found to be robust for modelling purposes. Thus, non-intrusive SP measurements can serve as proxies for snow melt-water fluxes and the temporal evolution of fundamental snow textural, hydraulic or water-quality parameters. Adaptation of automated multi-sensor SP acquisition technology from other environmental applications thus promises to bridge the widely acknowledged gap in spatial scale between satellite remote sensing and point measurements of snow properties. SP measurements and modelling may therefore contribute to solving a wide range of problems related to the assessment of water resource availability, avalanche or flood risk, or amplification of climatic forcing of ice-shelf, ice-sheet or glacier dynamics

Dynamics of Wetting Fronts in Porous Media

We propose a new phenomenological approach for describing the dynamics of wetting front propagation in porous media. Unlike traditional models, the proposed approach is based on dynamic nature of the relation between capillary pressure and medium saturation. We choose a modified phase-field model of solidification as a particular case of such dynamic relation. We show that in the traveling wave regime the results obtained from our approach reproduce those derived from the standard model of flow in porous media. In more general case, the proposed approach reveals the dependence of front dynamics upon the flow regime.Comment: 4 pages, 2 figures, revte

Surface permeability of particulate porous media

The dispersion process in particulate porous media at low saturation levels takes place over the surface elements of constituent particles and, as we have found previously by comparison with experiments, can be accurately described by super-fast non-linear diffusion partial differential equations. To enhance the predictive power of the mathematical model in practical applications, one requires the knowledge of the effective surface permeability of the particle-in-contact ensemble, which can be directly related with the macroscopic permeability of the particulate media. We have shown previously that permeability of a single particulate element can be accurately determined through the solution of the Laplace-Beltrami Dirichlet boundary-value problem. Here, we demonstrate how that methodology can be applied to study permeability of a randomly packed ensemble of interconnected particles. Using surface finite element techniques we examine numerical solutions to the Laplace-Beltrami problem set in the multiply-connected domains of interconnected particles. We are able to directly estimate tortuosity effects of the surface flows in the particle ensemble setting

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

First observations of separated atmospheric nu_mu and bar{nu-mu} events in the MINOS detector

The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of nuµ and [overline nu ]µ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving Rup/downdata/Rup/downMC=0.62-0.14+0.19(stat.)±0.02(sys.). An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field nuµ and [overline nu ]µ interactions are separated. The ratio of [overline nu ]µ to nuµ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving R[overline nu ][sub mu]/nu[sub mu]data/R[overline nu ][sub mu]/nu[sub mu]MC=0.96-0.27+0.38(stat.)±0.15(sys.), where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for nuµ and [overline nu ]µ