Orfeo BELSPO Instutional Open Access Repository for Federal Organisation
Not a member yet
14207 research outputs found
Sort by
Geo-Hydrological Hazard Impacts, Vulnerability and Perception in Bujumbura (Burundi): A High-Resolution Field-Based Assessment in a Sprawling City
No full textEffects of the Geomagnetic Superstorms of 10–11 May 2024 and 7–11 October 2024 on the Ionosphere and Plasmasphere
No full textOn 10 May 2024 at 17 h:07 UTC, the simultaneous arrival of several solar coronal mass ejections (CMEs) generated the strongest geomagnetic storm of the last twenty years, with a minimum Dst = −412 nT, usually referred to as the Mother’s Day event. On 10 October 2024, the second strongest event of solar cycle 25 appeared with a Dst = −335 nT, preceded on 8 October by an event with a Dst = −153 nT. In the present work, with measurements of the vertical total electron content and with ionosonde observations from Europe, USA, and South Korea, we show that the ionization of the upper atmosphere shortly increased at the arrival of the CME for these different events, followed by a fast decrease at all latitudes. The ionization remained very low for more than a full day. While the recovery started at the beginning of the second day after the onset for both events in October, the sudden recovery in the middle of the second day on 12 May is much more unusual. The analysis of the observations at different latitudes and longitudes shows that the causes of the ionization variations during the superstorms were mainly due to strong perturbations in the ionospheric F layer, amplified by the plasmasphere’s influence on the vertical total electron content (VTEC). The erosion of the plasmasphere during these two strong events led to a plasmapause located at exceptionally low radial distances smaller than 2 Re (Earth’s radii) in the post-midnight sector and a rotating plume in the afternoon–dusk sector clearly visible in the BSPM plasmasphere model. It took several days after the storms to recover normal ionization rates
Monitoring potential disease hosts and vectors in Belgium: findings from two case projects
No full textIntroduction: Recent disease outbreaks have underscored the urgent need to survey infectious disease hosts and vectors. Air- and seaports often serve as Point of Entries (PoEs) for organisms or biological products potentially carrying disease-causing agents. Furthermore, the ever-growing flow of goods and people has been associated with the introduction and establishment of non‐native vectors. Hence, surveillance programs have been implemented in Belgium to monitor (1) the illegal imports of (wild) meat and potentially associated pathogens at PoEs (INTERCEPT), and (2) the introduction of exotic mosquitoes at PoEs and over medium distances (MEMO(+)). Methods: In both projects, the intercepted material (e.g. pieces of processed meat, mosquito eggs) usually lacks the morphological characteristics needed to identify the species involved. Hence, DNA barcoding was applied. Results: During targeted passenger control actions at Brussels airport, ~350 meat samples have been seized since mid-2023, of which 30% were of wild origin (27 species). Within wild meat seized, Cane rat (Thryonomys swinderianus) and African brush-tailed porcupine (Atherurus africanus) were predominant (~20%). 9 species were CITES-listed (17.8%). Also, since 2017, ~3600 mosquito samples were barcoded, of which ~260 belonged to Aedes albopictus, ~300 to Ae. japonicus and ~150 to Ae. koreicus. Repeated introductions or establishments of these exotics were revealed, with a rapidly increasing number of introduction events over the last decade for Ae. albopictus- believed to now more frequently hitchhiking from established populations in neighboring countries via ground traffic. Conclusions: DNA barcoding is a well-established tool for monitoring purposes, therewith helping to assess the risk of disease outbreaks, and supporting the implementation of prevention and control measures. The two surveillance projects demonstrated that monitoring the import of potential disease hosts and vectors is not a luxury
Mie theory-based light scattering analysis of entrained grains in Io's Tvashtar plume observed during new horizons' 2007 flyby
Get PDFIo, the most volcanically active body in the Solar System, frequently produces large-scale plumes capable of reaching hundreds of kilometers in height. During the 2007 New Horizons (NH) flyby, the Tvashtar Catena region exhibited a ∼ 350 km high “Pele-type” plume whose canopy radiance in scattered sunlight increased unexpectedly by an order of magnitude over 3–4 days. This radiance surge occurred as the solar phase angle between the Sun, Io, and NH rose from ∼40° to 150°, suggesting that observational geometry could play a key role; earlier investigations found that changes in basic volcanic vent parameters, such as stagnation temperature and vent area, did not fully explain this irregular brightness increase (Adeloye et al., 2025). In this study, we utilize Mie theory to characterize light scattering and integrate multiple lines of analysis to identify the primary factors influencing Tvashtar's plume radiance. We employ Direct Simulation Monte Carlo (DSMC) modeling to simulate SO2 gas dynamics and entrained basaltic grains, assuming a log-normal grain size distribution. Additionally, we examine multiple factors that could potentially contribute to the observed phenomena, including variations in the NH observation geometry, the scattering properties of individual and ensembles of grains, and vent parameters such as mass flow rate and grain mass loading. Our results indicate that no single factor can fully account for the irregular brightness surge. Instead, a combination of observational geometry effects, the optical scattering behavior of the grains in the plume, and changes in grain mass loading are required to reproduce the observed radiance profile and its changes. Although our methodology assumes continuous, steady-state ejection over tens of minutes and does not explicitly model condensation, sublimation, or episodic grain injection at the vent, the integrated approach presented here offers a novel perspective on plume dynamics at Io. These findings not only enhance the interpretation of the NH Tvashtar observations but also provide a framework for future investigations of Io's volcanic plumes and potential exploration missions
Campin in Context : peinture et société dans la vallée de l'Escaut à l'époque de Robert Campin (vers 1380-1450)
Get PDFColloque international, Tournai, Maison de la Culture, 30 mars-1er avril 2006Septième Séminaire d'Histoire de l'Art de l'IRPA (30 mars-1er avril 2006
