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See detailL'eau dans le cadre du Diagnostic territorial de la Wallonie préparatoire à l'actualisation du SDER
Everbecq, Etienne ULg; Blockx, Caroline ULg; Grard, Aline ULg et al

Report (2011)

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 ... [more ▼]

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 surface [less ▲]

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See detailLa gestion de l’eau dans les Pays du Sud : Enjeux et échelles spatiales
Deliège, Jean-François ULg; Detienne, Xavier; Blockx, Caroline ULg

Scientific conference (2011, February 22)

L'Aquapôle-Liège est un pôle universitaire d’expertise en sciences de l’eau au service des acteurs de l’eau (institutions publiques et privées), tant au niveau régional qu’international. La Cellule ... [more ▼]

L'Aquapôle-Liège est un pôle universitaire d’expertise en sciences de l’eau au service des acteurs de l’eau (institutions publiques et privées), tant au niveau régional qu’international. La Cellule Latitude Sud de l'Aquapôle traite des problématiques liées à l'eau dans les pays du Sud, elle a développé une expertise dans la gestion de projets dans ces pays. La présentation "La gestion de l'Eau dans les pays du Sud : Enjeux et échelles spatiales" explique comment agir concrètement dans les pays du Sud en faveur du droit à l'eau et d'une gestion intégrée de la ressource. Sont présentés quelques projets concrets, gérés aux échelles : locale, régionale, du bassin versant et internationale en précisant les enjeux qui s'y rapporte. [less ▲]

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See detailPegase : Outil opérationnel de modélisation de la qualité des eaux de surface
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Grard, Aline ULg et al

Poster (2011, January)

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 ... [more ▼]

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. [less ▲]

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See detailAquapôle, Cellule Latitudes Sud : Coopération avec les pays du Sud dans le domaine de l’eau
Deliège, Jean-François ULg; Detienne, Xavier; Grard, Aline ULg et al

Poster (2011, January)

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 ... [more ▼]

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. [less ▲]

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See detailTransnational modeling of the surface water quality in the Maas basin. Dutch part - Final report
Deliège, Jean-François ULg; Grard, Aline ULg; Everbecq, Etienne ULg et al

Report (2010)

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 ... [more ▼]

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 Flemish and Dutch downstream parts of the basin, in order to cover the entire district. In this framework, two contracts between the State of The Netherlands and the Research and Development Unit of Aquapôle have been concluded to extend the surface water quality model PEGASE to the Dutch part of the Meuse basin. This report is related to the PEGASE simulation of the entire Dutch part of the Meuse basin. [less ▲]

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See detailMICROPOLLUTANTS ISSUES: A MODELLING STUDY OF HEAVY METALS WITHIN TWO FRENCH BASINS AND A TEST APPLICATION TO COCAINE IN BELGIUM
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Grard, Aline ULg et al

Poster (2010, April)

European policies (European Framework Directive: Water 2000/60/CE, Directive 76/464/CE) impose to reduce the releases of about a hundred substances in surface water. In the last years, the AQUAPOLE has ... [more ▼]

European policies (European Framework Directive: Water 2000/60/CE, Directive 76/464/CE) impose to reduce the releases of about a hundred substances in surface water. In the last years, the AQUAPOLE has been involved in two studies related to this matter. First, on the request and with the financial support of both the French Ministry of Environment and ONEMA (“Office National de l’Eau et des Milieux Aquatiques”), INERIS (“Institut National de l’Environnement Industriel et des Risques”) drew up the guidelines of a methodology allowing fixing the local Limit Values to Emission so as to abide by the quality standards on the whole watershed. Within this context, INERIS wishes to test the use of pollutant transfer models on pilot sub-basins. The PEGASE model has been used to simulate micropollutants on two concrete use cases (1): (iii) in the Meuse sub-basin, managed by the French Water Agency Rhine-Meuse, for simulations concerning cadmium and zinc; (iv) in the Adour sub-basin, managed by the French Water Agency Adour-Garonne, for simulations applied to cadmium and copper. The choice of each substances and sub-basins was made by mutual agreement between INERIS, the concerned Water Agencies, and the AQUAPOLE. A major selection criterion for the substances and the sub-basins was the availability of data (sources and in situ measurements). For the second study, the PEGASE model has been adapted to describe the cocaine’s behaviour (using a stable metabolite of the cocaine in the environment: the benzoylecgonine (BZE)) in waste water, waste water treatment plants (WWTP) and surface water (2). 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. Simulations of BZE have been done in the Walloon and Flemish regions, where many measurements from the COWAT project (3) were available. The first results are showing good agreement between calculated and measured values. The ability of the model to simulate the fate of studied micropollutants (cadmium, zinc, copper, and the cocaine derivatives) in surface waters should be enhanced and extended to other substances and basins. Moreover, additional data still have to be collected and measured. [less ▲]

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See detailPEGASE, an integrated river/basin model dedicated to surface water quality assessment: application to cocaine
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Magermans, Pol ULg et al

in Acta Clinica Belgica (2010), 65(Supplement 1), 42-48

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 ... [more ▼]

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. [less ▲]

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See detailEvaluation de l’impact de la mise en service de la station d’épuration de Signeulx sur la qualité de l’eau de la rivière réceptrice (la Vire)
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Grard, Aline ULg et al

Report (2009)

Le présent rapport reprend l’étude de l’impact de la mise en service de la station d’épuration de Signeulx sur la qualité de l’eau du milieu récepteur (essentiellement la rivière « la Vire »). La Vire est ... [more ▼]

Le présent rapport reprend l’étude de l’impact de la mise en service de la station d’épuration de Signeulx sur la qualité de l’eau du milieu récepteur (essentiellement la rivière « la Vire »). La Vire est un affluent du Ton, situé au sud-est de la Belgique (province du Luxembourg), à l’est de la ville de Virton. Une partie de son bassin versant se trouve en France. PEGASE (PLANIFICATION ET GESTION DE L’ASSAINISSEMENT DES EAUX) est un modèle intégré bassin hydrographique / rivières qui permet de calculer de façon déterministe et non stationnaire la qualité des eaux des rivières en fonction des rejets et apports de pollution. Il permet également de calculer de façon prévisionnelle les améliorations de la qualité de l'eau qui résultent d'actions d'épuration ou de réduction des rejets. PEGASE est ainsi un outil opérationnel pour aider les administrations à remplir leurs obligations liées à la Directive Cadre Eau. L’objectif de l’étude est de réaliser une modélisation de la qualité physico-chimique de la Vire afin d’évaluer l’impact de la mise en service de la station d’épuration de Signeulx sur la qualité de la rivière, en fonction des différentes options possibles. [less ▲]

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See detailRapport sur l’étude de faisabilité d’une méthodologie de modélisation à l’échelle globale du bassin versant de la Medjerda (Tunisie)
Deliège, Jean-François ULg; Bourouag, Mohamed ULg; Blockx, Caroline ULg et al

Report (2009)

Depuis 2007, l’Aquapôle appuie l’Agence Nationale de Protection de l’Environnement (ANPE - Tunisie) dans sa mission de contrôle de la pollution des eaux par la mise en place d’un réseau de contrôle de la ... [more ▼]

Depuis 2007, l’Aquapôle appuie l’Agence Nationale de Protection de l’Environnement (ANPE - Tunisie) dans sa mission de contrôle de la pollution des eaux par la mise en place d’un réseau de contrôle de la pollution des eaux (projet LIFE Pays Tiers COPEAU 2007- 10). Les données ainsi collectées pourraient être utilement exploitées au travers de l’utilisation de modèles de gestion des ressources en eau. Le modèle PEGASE développé par l’Aquapôle, permet d’établir la relation pression / impact entre les différentes charges de pollution et la qualité de l’eau dans tout le réseau des rivières modélisées associées au bassin versant concerné, et constitue ainsi un puissant outil de gestion des cours d’eau et de leurs bassins versants. Il permet notamment de simuler le transport des polluants et différents scénarios de gestion (planification de l’épuration et de l’assainissement, réduction des pressions, mise aux normes des rejets,…) et d’en déterminer les impacts (gain de qualité) sur l’écosystème. Ce modèle est déjà largement utilisé dans plusieurs pays européens (Belgique, France, Pays-Bas, Allemagne, Luxembourg). La présente étude intitulée « étude de faisabilité d’une méthodologie de modélisation à l’échelle globale du bassin versant de la Medjerda (Tunisie) » a été réalisée entre juin 2008 et décembre 2009 au travers du partenariat entre l’Aquapôle et l’ANPE et ce, avec l’appui de Wallonie Bruxelles International (commission mixte 2008). L’étude dresse un bilan des données disponibles et analyse leur pertinence eu égard de ce qui est requis pour permettre la bonne application du modèle PEGASE à l’ensemble du bassin versant tunisien de la Medjerda. Il s’agit de données géographiques (MNT, réseau hydrographique, limites administratives, occupation des sols etc.), météorologiques (insolation, température, débits), de rejets (domestiques, industriels, STEP, cheptel) et de mesure de qualité. L’étude dresse également un bilan des problématiques spécifiques dont il faudra nécessairement tenir compte dans l’adaptation du modèle au contexte local. Celles-ci concernent principalement la présence de 9 grands barrages implantés le long de la Mejerda et de ses affluents, la forte anthropisation du débit liée notamment aux lâchés de barrages, le caractère intermittent de certains affluents en fonction des périodes de l’année, la présence de prélèvements très importants notamment pour l’irrigation et enfin, des problèmes de crues et d’érosion. En conclusion, l’analyse des échantillons de données transmises par l’ANPE et des problématiques spécifiques aux régions du Nord de la Tunisie montre que le modèle PEGASE est tout à fait applicable au bassin de la Medjerda, moyennant certaines adaptions spécifiques. Cet outil de gestion a toute sa raison d’être dans ce pays où la préservation des ressources en eau constitue un enjeu vital pour les générations actuelles et futures. [less ▲]

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See detailPEGASE: UN MODÈLE INTÉGRÉ BASSIN HYDROGRAPHIQUE/ RIVIÈRES: PREMIÈRE APPLICATION TEST À LA COCAÏNE.
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Magermans, Pol ULg et al

Conference (2009, October 15)

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 ... [more ▼]

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). [less ▲]

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See detailStatistical properties of flux closure induced by solar wind dynamic pressure fronts
Hubert, Benoît ULg; Blockx, Caroline ULg; Milan, S. E. et al

in Journal of Geophysical Research. Space Physics (2009), 114

We 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 ... [more ▼]

We 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. [less ▲]

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See detailContribution du modèle PEGASE à la mise en application de la Directive cadre sur l’eau : Mise au point et application d’une méthodologie de détermination à l’échelle de la masse d’eau des combinaisons de mesures complémentaires les plus efficientes et mise en évidence de motifs de dérogations
Everbecq, Etienne ULg; Grard, Aline ULg; Blockx, Caroline ULg et al

Report (2009)

PEGASE (Planification Et Gestion de l’ASsainissement des Eaux) est un modèle intégré bassins hydrographiques/rivières développé à l’Aquapôle qui permet de calculer de façon déterministe et prévisionnelle ... [more ▼]

PEGASE (Planification Et Gestion de l’ASsainissement des Eaux) est un modèle intégré bassins hydrographiques/rivières développé à l’Aquapôle qui permet de calculer de façon déterministe et prévisionnelle la qualité des eaux des rivières en fonction des rejets et apports de pollution (voir http://hdl.handle.net/2268/35224 pour plus de renseignements). Dans le cadre de cette étude, le modèle a été utilisé afin d'apporter des éléments et des informations techniques nécessaires à la Région Wallonne (S.P.W.) pour la mise en application de la Directive Cadre Eau et, en particulier, les plans de gestion et les programmes de mesures qui y sont associés [less ▲]

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See detailPEGASE : UN MODÈLE INTÉGRÉ BASSIN HYDROGRAPHIQUE / RIVIÈRES POUR LA DIRECTIVE CADRE EUROPÉENNE
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Grard, Aline ULg et al

Conference (2009, April 09)

Presentation of the PEGASE model (Planification Et Gestion de l’ASsainissement des Eaux), developed by the Aquapole Aquapole. New operational way to assess the evolution of the river quality in terms of ... [more ▼]

Presentation of the PEGASE model (Planification Et Gestion de l’ASsainissement des Eaux), developed by the Aquapole Aquapole. New operational way to assess the evolution of the river quality in terms of presures on them, as well as a tool to help competent authorities to optimise the cost/efficiency ratio of the measures foreseen to reduce the impact of these pressures. [less ▲]

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See detailAdaptation du modèle PEGASE à deux substances sur deux sous-bassins situés dans les bassins hydrographiques des Agences Adour-Garonne et Rhin-Meuse
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Grard, Aline ULg et al

Conference (2009, March 16)

L’INERIS (Institut National de l’Environnement Industriel et des Risques) France a élaboré pour le compte du Ministère français de l’Environnement les grandes lignes d’une méthodologie permettant de fixer ... [more ▼]

L’INERIS (Institut National de l’Environnement Industriel et des Risques) France a élaboré pour le compte du Ministère français de l’Environnement les grandes lignes d’une méthodologie permettant de fixer les Valeurs Limites à l’Emission (VLE) locales de manière à respecter les normes de qualité sur l’ensemble d’un bassin versant. Dans ce cadre, l’INERIS désire tester l’utilisation de modèles de transfert de polluants sur des bassins versant pilotes. L’objectif de cette étude est donc d’adapter le modèle PEGASE pour simuler deux micropolluants (à définir) sur deux bassins versants situé dans les bassins hydrographiques gérés par les agences de l’eau française Rhin-Meuse et Adour-Garonne. [less ▲]

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See detailPegase, A software dedicated to Surface Water Quality Assessment and to European database reporting
Deliège, Jean-François ULg; Everbecq, Etienne ULg; Magermans, Pol ULg et al

in Hrebiceck, Jiri (Ed.) Proceedings of the European conference TOWARDS eENVIRONMENT, Opportunities of SEIS and SIZE: Integrating Environmental Knowledge in Europe (2009, March)

The Aquapôle of the University of Liège has been involved in environment modelling for more than 20 years. Its R&D unit focused on the domain of surface water, targeted to water quality. One of its ... [more ▼]

The Aquapôle of the University of Liège has been involved in environment modelling for more than 20 years. Its R&D unit focused on the domain of surface water, targeted to 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 characterization of the environmental state of surface water, at the scale of a whole watershed, basin and district. The software has been used operationally in several countries like France and Benelux, but several calculations have also been performed at international level for the international commissions in charge of the Scheldt and the Meuse. PEGASE model requires as input, at least data like digital terrain models, water flow, water level and other hydrodynamic measurements in some geo-localized points, diffuse loads properties, ecological model data (to characterize bacteria, phytoplankton, zooplankton, macrophytes, shells, etc…), chemical discharges (from industry and cities) and treatment plant effect. The output of the software consists in tables, graphs and maps, showing the state of various calculated parameters of quality (DO, BOD, COD, N, P, Chla,… + indices) either at a specified time, along the river, or the temporal evolution at a given point. It provides printed maps or animations of the evolution of the results on the basin. The software is able to simulate non stationary scenarios from a local scale, up to a global scale i.e. a few km² to hundreds of thousands km² and handles the entire river tree (hundreds to thousands of water bodies). Some results of the model are already used to populate the SoE-Wise databases. On another hand, the model is a tool to validate and check consistency of SoE-Wise data at district (and thus international) level. The flexibility of the model enables to choose the time (daily to yearly periods) and spatial (watershed, water body, district, region, country …) scales of the expected results. PEGASE is also a full-scale operational tool for WFD implementation and WISE databases. This means that our partners handle a software (also known as the model) directly usable – and of direct help – in the implementation of the WFD and other water related directives. The model allows the member states to compare efficiently the collected international WISE data and populate database with relevant model results. We propose not only to read the data directly from the database to avoid manipulation mistakes, but also we propose to generate output data in a format directly exploitable by WISE databases administration. [less ▲]

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See detailContributions of the driven process and the loading-unloading process during substorms: A study based on the IMAGE-SI12 imager
Blockx, Caroline ULg; Gérard, Jean-Claude ULg; Coumans, Valérie ULg et al

in Journal of Geophysical Research (2009), 114

Substorm energetics has been shown to have two components, the "loading-unloading'' component releasing energy previously stored in the tail and the "directly driven'' component dissipating simultaneously ... [more ▼]

Substorm energetics has been shown to have two components, the "loading-unloading'' component releasing energy previously stored in the tail and the "directly driven'' component dissipating simultaneously fed solar wind energy. Previous studies disagree about the relative importance of each process. The SI12 spectral imager onboard the IMAGE satellite provides images of the Doppler-shifted Lyman alpha auroral emission at 121.8 nm every 2 min. It has been used to determine the auroral intensity during substorms, which may be compared to the solar wind characteristics and interplanetary magnetic field components before and/or after substorm onsets. In this study, we analyze 256 substorms between June 2000 and December 2002, which satisfy criteria relative to the viewing conditions. We compare the mean nightside intensity during the expansion phase with the magnetic open flux, the epsilon parameter, and other coupling functions (used as proxies of transfer of solar wind energy to the magnetosphere) integrated over the growth phase or the expansion phase. The mean auroral intensity during the expansion phase correlates well with coupling functions integrated over the growth phase. We also find that the correlation between the auroral precipitation during the expansion phase and the coupling functions integrated over the expansion phase is lower but still significant. This implies that, even though both mechanisms contribute to the energy precipitated during substorms, the loading-unloading process is statistically dominant. [less ▲]

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See detailGlobal morphology of substorm growth phases observed by the IMAGE-SI12 imager
Coumans, Valérie ULg; Blockx, Caroline ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research (2007), 112(A11),

We present case studies and a statistical summary of optical observations of proton precipitation made during substorm growth phases. Our analysis is based on observations of the Doppler-shifted Lyman ... [more ▼]

We present case studies and a statistical summary of optical observations of proton precipitation made during substorm growth phases. Our analysis is based on observations of the Doppler-shifted Lyman-alpha auroral emission obtained with the SI12 Spectrographic Imager on board the IMAGE satellite. These images are used to determine the morphology and dynamics of the auroral oval and of the polar cap boundary on a global scale, as well as the total open magnetic flux and its time evolution. We also investigate the relationship with the solar wind and the interplanetary magnetic field ( IMF) characteristics measured by the ACE satellite and with the magnetic elevation angle measured by GOES-8. The statistical study shows that the sector of maximum proton precipitation during the growth phase is on average centered around 2200 MLT and rapidly shifts in local time by about 1.2 h toward midnight at the time of the onset. The open magnetic flux increases by 33% on average during the growth phase. The mean value of the open flux immediately before the substorm onset is about 0.66 GWb for substorms triggered by a northward turning of B-z and 0.74 GWb for nontriggered substorms. The averaged open flux at the substorm onset is smallest when the substorm is triggered by a sudden reversal of B-z, suggesting that the accumulation of energy by the magnetosphere is perturbed by changes in B-z. The open magnetic flux continues to increase during the 20 min following the onset, for a large number of events. The rate of equatorward displacement of the auroral oval boundaries during growth phase is typically similar to 3 deg/h. It is statistically correlated (r=0.40) with the magnitude of the Bz component of the IMF measured by the ACE satellite. It is also correlated, with higher coefficient (r=0.54), with functions describing the efficiency of solar wind energy transfer involving the transverse electric field carried by the solar wind. The equatorward motion may be global, restricted to local time sectors or a combination of both. At no nightside local time sector does the motion of the equatorial boundary appear more pronounced than at others, but the maximum displacement of the polar boundary is statistically located around midnight MLT. [less ▲]

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See detailEL - a possible indicator to monitor the magnetic field stretching at global scale during substorm expansive phase: Statistical study
Meurant, M.; Gérard, Jean-Claude ULg; Blockx, Caroline ULg et al

in Journal of Geophysical Research. Space Physics (2007), 112

An interesting open question of magnetospheric physics is the understanding of the dynamics of the magnetotail. The question of the field stretching is even more challenging during substorm periods ... [more ▼]

An interesting open question of magnetospheric physics is the understanding of the dynamics of the magnetotail. The question of the field stretching is even more challenging during substorm periods, mainly because of the short time scales involved during such explosive events. In this study, we asses the ability of global scale proton auroral imaging to provide information on the tail stretching during active periods. We base our investigation on more than 250 isolated substorms observed by IMAGE-SI12 between 2000 and 2002. Applying the algorithm proposed by Donovan et al. (2003) for ground based observations to IMAGE-SI12 data, we determine the Equatorial Limit (EL) of the oval and propose to use it as an indicator of the tail stretching. Simultaneous comparison with GOES-8 allows us to estimate how strong is the relationship between the EL position deduced from SI12 and the magnetic field stretching. The EL indicator is shown to be consistent with previous studies (Sergeev and Gvozdevsky (1995) and Blockx et al. (2005)) and is found to be located in average ~1 degree equatorward of the limit deduced from DMSP measurements. The time evolution of the EL magnetic latitude is also presented for different local times relative to the onset position. This evolution of the EL index presents an asymmetric shape following the time of onset, suggesting a more important stretching of the tail duskward of the onset position. This asymmetric stretching is consistent with GOES-8 in situ measurements. [less ▲]

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See detailGlobal morphology of substorm growth phases observed by the IMAGE-SI12 imager
Blockx, Caroline ULg; Gérard, Jean-Claude ULg; Coumans, Valérie ULg et al

Poster (2007)

Growth phases are observed to start from less than 30 minutes to over an hour before the substorm onset. The sector of maximum proton precipitation during the growth phase is generally located around 2200 ... [more ▼]

Growth phases are observed to start from less than 30 minutes to over an hour before the substorm onset. The sector of maximum proton precipitation during the growth phase is generally located around 2200 MLT. It rapidly moves in local time by about 1.2 hour toward midnight at the time of the onset. The open magnetic flux increases by as much as a 33% during the growth phase. The mean value of the open flux at the end of the growth phase, immediately preceding the substorm, onset is about 0.74. GWb for substorms triggered by external (solar wind) factors and 0.67 GWb for non-triggered substorms. The open magnetic flux generally drops following the onset of triggered substorms but continues to increase for non-triggered events. We interpret this behavior as an indication that the rate of opening of closed field lines on the dayside can exceed that of the nightside reconnection after the onset in non-triggered substorms. By contrast, flux closure is more efficient while the flux opening rate drops in the case of externally triggered onset, so that the closure rate exceeds that of field line opening on the dayside. The rate of equatorward displacement is typically ~ 3 deg/hour. It is statistically correlated with the magnitude of the southward Bz component of the IMF measured by the ACE satellite. It is also correlated with transfer functions describing the efficiency of solar wind energy transfer which involve the transverse electric field carried by the solar wind. The equatorward motion may be global, restricted to local time sectors or a combination of both. No nightside local time sector appears favored where the motion of the equatorial boundary would be more pronounced. The maximum displacement of the polar boundary is statistically located around midnight MLT. [less ▲]

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See detailA comparison between FUV remote sensing of magnetotail stretching and the T01 model during quiet conditions and growth phases
Blockx, Caroline ULg; Gérard, Jean-Claude ULg; Coumans, Valérie ULg et al

in Annales Geophysicae [= ANGEO] (2007), 25(1), 161-170

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 ... [more ▼]

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. [less ▲]

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