30 research outputs found

    Statistical properties of flux closure induced by solar wind dynamic pressure fronts

    Full text link
    peer reviewedWe present a statistical study of flux closure intervals induced by solar wind dynamic pressure fronts. We consider that a dynamic pressure front reaches the Earth when a dayside subauroral proton flash is observed in the SI2 channel of the IMAGE-FUV experiment. This pragmatic criterion selects both weak and strong pressure fronts. It is found that the preconditioning of the magnetosphere prior to the pressure pulse arrival mainly governs the magnetospheric response to a weak solar wind dynamic pressure front. This preconditioning includes the amount of open magnetic flux available in the magnetosphere prior to the pressure front arrival and the size of the magnetospheric cavity. However, in the case of a strong pressure pulse, the magnetospheric response is more sensitive to the solar wind properties characterizing the dynamic pressure front. The pressure jump is not the only one important, but also the variation of the solar wind velocity and IMF magnitude. In overall terms, we find that a strong dynamic pressure front is typically characterized by a dynamic pressure increase larger than Ë 2.8 nPa that takes place on timescales of the order of a few minutes

    PEGASE: UN MODÈLE INTÉGRÉ BASSIN HYDROGRAPHIQUE/ RIVIÈRES: PREMIÈRE APPLICATION TEST À LA COCAÏNE.

    Full text link
    Le modèle PEGASE (Planification Et Gestion de l’ASsainissement des Eaux), développé à l’Aquapôle de l’Université de Liège a été utilisé pour réaliser une première simulation test de la cocaïne dans le réseau hydrographique belge. La principale conclusion de cette simulation test est qu’il est possible de simuler le devenir des dérivés de la cocaïne dans les eaux de surface ; cela démontre également la cohérence des mesures réalisées dans le cadre de l’étude COWAT. Des améliorations mineures au modèle PEGASE et aux données d’entrée seraient cependant souhaitables pour améliorer cette modélisation (possibilité de faire varier l’équivalent-habitant par zones).PEGASE: UN MODÈLE INTÉGRÉ BASSIN HYDROGRAPHIQUE / RIVIÈRES: PREMIÈRE APPLICATION TEST À LA COCAÏNE

    A comparison between FUV remote sensing of magnetotail stretching and the T01 model during quiet conditions and growth phases

    Get PDF
    In a previous study, Blockx et al. (2005) showed that the SI12 camera on board the IMAGE spacecraft is an excellent tool to remotely determine the position of the isotropy boundary (IB) in the ionosphere, and thus is able to provide a reasonable estimate of the amount of stretching of the magnetic field lines in the magetotail. By combining an empirical model of the magnetospheric configuration with Sergeev's criterion for non-adiabatic motion, it is also possible to obtain a theoretical position of IB in the ionosphere, for known conditions in the solar wind. Earlier studies have demonstrated the inadequacy of the Tsyganenko-1989 (T89) model to quantitatively reproduce the field line stretching, particularly during growth phases. In this study, we reexamine this question using the T01 model which considers the time history of the solar wind parameters. We compare the latitude of IB derived from SI12 global images near local midnight with that calculated from the T01 model and the Sergeev's criterion. Observational and theoretical results are found to frequently disagree. We use in situ measurements of the magnetic field with the GOES-8 satellite to discriminate which of the two components in the calculation of the theoretical position of the IB (the T01 model or Sergeev's criterion) induces the discrepancy. For very quiet magnetic conditions, we find that statistically the T01 model approximately predicts the correct location of the maximum proton precipitation. However, large discrepancies are observed in individual cases, as demonstrated by the large scatter of predicted latitudes. For larger values of the AE index, the model fails to predict the observed latitude of the maximum proton intensity, as a consequence of the lack of consideration of the cross-tail current component which produces a more elongated field configuration at the location of the proton injection along the field lines. We show that it is possible to match the observed location of the maximum proton precipitation by decreasing the current sheet half-thickness D parameter. We thus conclude that underestimation of the field line stretching leads to inadequately prediction of the boundary latitude of the non-adiabatic proton precipitation region

    PEGASE, an integrated river/basin model dedicated to surface water quality assessment: application to cocaine

    Full text link
    The Aquapôle of the University of Liège has been involved in environmental modeling for more than 20 years. Among other, its current R&D unit focuses on the compartment of surface water, and – for modeling processes – is specialized on the water quality. One of its environmental models, called Pegase (Planification Et Gestion de l’ASsainissement des Eaux), French acronym for “Planning and management of water purification” is devoted to the modeling of the environmental state of surface water, at different scales from small watersheds (10 km²) and basins up to entire transnational Districts (more than 100.000 km²). The software is used operationally by several administrations (Agencies and Ministries) mainly through Europe (France and Benelux, Germany ...), and several calculations have also been performed at international District levels for international commissions (Scheldt, Meuse, Moselle ...) Recently, the Pegase model has been adapted to describe the cocaine’s behavior (using a stable metabolite of the cocaine in the environment: the benzoylecgonine) in waste water, waste water treatment plants (WWTP) and surface water. The cocaine is newly described in the model as an additional micropollutant (Pegase already treats numerous heavy metals), thanks to the implementation of new state variable equations and their specific parameterizations. At a first stage, only the urban sources (releases associated to the consumption by inhabitants) were considered as the industrial releases and the soil loads are assumed to be negligible. Simulations of benzoylecgonine have been done in the Walloon and Flemish regions, where many measurements from the COWAT project were available. These first results are showing a good agreement between calculated and measured values. This ability of the model to simulate the fate of the cocaine derivatives in surface waters should be continued and extended to other metabolites

    L'eau dans le cadre du Diagnostic territorial de la Wallonie préparatoire à l'actualisation du SDER

    Full text link
    Dans le cadre des travaux d'actualisation du Schéma de Développement de l'Espace Régional (SDER), la Conférence Permanente de Développement Territorial (CPDT) a mené, d’octobre 2010 à octobre 2011, à la demande du Gouvernement Wallon, les travaux concernant le diagnostic. Ces travaux ont mené à la construction, pour chacune des 15 thématiques abordées, d'indicateurs permettant d'évaluer la situation passée, existante et future. Cette note de recherche présente les réflexions menées sur le choix, la conception et le calcul des 3 indicateurs "eau" développés : (i) un indicateur sur la consommation d'eau, (ii) un indicateur sur l'épuration des eaux usées et (iii) un indicateur sur la qualité des eaux de surfaceConférence Permanente du Développement Territorial - CPDTActualisation du SDER - Diagnostic territoria

    Pegase : Outil opérationnel de modélisation de la qualité des eaux de surface

    Full text link
    Pegase (Planification Et Gestion de l’ASsainissement des Eaux) est un modèle intégré bassins hydrographiques/rivières qui permet de calculer de façon déterministe et prévisionnelle la qualité des eaux des rivières en fonction des rejets et apports de pollution (relation pression-impact), pour des situations hydrologiques constantes ou non-stationnaires. Pegase est un outil opérationnel doté d’une interface conviviale, s’interfaçant avec des outils propriétaires de type ArcGIS et permettant d’orienter les choix des opérateurs publics et privés en matière de gestion des eaux de surface à l’échelle des bassins versants.PEGAS

    Aquapôle, Cellule Latitudes Sud : Coopération avec les pays du Sud dans le domaine de l’eau

    Full text link
    L’objectif de la Cellule Latitudes Sud au sein de l'Aquapôle de l'Université de Liège est de favoriser le développement de projets liés à l’eau dans les pays du Sud, et en particulier dans les pays en développement. La Cellule Latitudes Sud intervient au niveau de la promotion, la réalisation et/ou la collaboration à différents projets avec une approche pluridisciplinaire et plurisectorielle. Elle s’appuie sur les compétences de l’Aquapôle (ULg) et également sur le réseau de compétences que constituent ses services membres

    Création d'une ferme-école pour la production de spiruline en Haïti, un documentaire de Daniel Bay

    Full text link
    Depuis 2010, l'Aquapôle travaille activement à la mise en place d'une ferme-école pour la production de spiruline à Port-au-Prince en Haïti. Ce projet devrait contribuer activement à la lutte contre la mal-nutrition dans un pays considéré comme un des plus pauvres au monde.Appui à la création d’une ferme-école pour la formation à la production de la spiruline en Haïti et au développement de micro-activités basées sur la production et l’exploitation de spirulin

    Extension of the surface water quality modeling Pegase to the Northern part of the Maas basin (German part of the basin)

    Full text link
    PEGASE (Planification Et Gestion de l’ASsainissement des Eaux) is an integrated model “basin/river” which makes possible to calculate in a deterministic way the water quality of rivers according to pollutant contributions and releases, for various stationary hydrological situations (see http://hdl.handle.net/2268/35224 for more information). In the scope of the Water Framework Directive international coordination, the transnational surface water quality model PEGASE is already in use (since 2005) for the Southern part of the Meuse basin (France, Luxemburg, Wallonia and a small part of Flanders). It was thus of great interest to extend this surface water quality application to the Northern part of the Meuse basin, i.e. the German, Flemish and Dutch downstream parts of the basin, in order to cover the entire district. This document describes the tasks which were devoted to the Research & Development Unit of the Aquapôle of the University of Liège (Aquapôle-ULg) in order to realize the extension of the Pegase database to the German Maas basin and to run the model on the German watershed.PEGAS
    corecore