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Context. Accurate detections of frequent small-scale extreme ultraviolet (EUV) brightenings are essential to the investigation of the physical processes heating the corona. Aims. We detected small-scale brightenings, termed campfires, using their morphological and intensity structures as observed in coronal EUV imaging observations for statistical analysis. Methods. We applied a method based on Zernike moments and a support vector machine (SVM) classifier to automatically identify and track campfires observed by Solar Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA). Results. This method detected 8678 campfires (with length scales between 400 km and 4000 km) from a sequence of 50 High Resolution EUV telescope (HRIEUV) 174 Å images. From 21 near co-temporal AIA images covering the same field of view as EUI, we found 1131 campfires, 58% of which were also detected in HRIEUV images. In contrast, about 16% of campfires recognized in HRIEUV were detected by AIA. We obtain a campfire birthrate of 2 × 10−16 m−2 s−1. About 40% of campfires show a duration longer than 5 s, having been observed in at least two HRIEUV images. We find that 27% of campfires were found in coronal bright points and the remaining 73% have occurred out of coronal bright points. We detected 23 EUI campfires with a duration greater than 245 s. We found that about 80% of campfires are formed at supergranular boundaries, and the features with the highest total intensities are generated at network junctions and intense H I Lyman-α emission regions observed by EUI/HRILya. The probability distribution functions for the total intensity, peak intensity, and projected area of campfires follow a power law behavior with absolute indices between 2 and 3. This self-similar behavior is a possible signature of self-organization, or even self-organized criticality, in the campfire formation process.

Coupled atmosphere/fire models are recognized as an efficient and representative way to simulate wildland fire behavior at geographical-to-meteorological scales by representing the two-way interactions between the fire front propagation and the surrounding atmosphere. They rely on a rate-of-spread (ROS) parameterization to represent the fire front propagation speed with respect to environmental factors characterizing biomass fuel properties and moisture content, near-surface wind conditions and terrain slope. In actual wildfire events, these input parameters are only partially known and induce significant uncertainties in the coupled model predictions. To estimate the envelope of plausible wildland fire behavior for a given event, we aim at designing a perturbed-physics ensemble prediction capability based on a coupled atmosphere/fire model. To make the approach feasible, it is essential to identify the relevant subset of parameters to perturb to generate an ensemble of fire front positions and shapes. In the present study, we perform a global sensitivity analysis based on Sobol’ indices to rank the environmental factors by order of influence on the Balbi’s ROS parameterization, and thereby identify the parameters that contribute most to the variability of ROS. Results show the predominance of the near-surface wind speed on the ROS variability, followed by the leaf area index LAI, the ignition temperature T_i, the dead fuel moisture content M_d, the dead fuel particle mass density ho_d, and the fuel layer height e. Results also indicate that the sensitivity of each fuel parameter to the ROS is not constant with respect to the near-surface wind speed, and that the most influential input parameters differ between the head and the back of a fire. This indicates the importance of exploring the spatial and temporal dependencies of coupled model sensitivities in future work.

While near-surface wind is the main influential parameter governing the fire rate of spread (ROS), its characterization remains key to simulate wildland fire behavior. The correct repre- sentation of the intensity and variability of the near-surface wind under complex terrain and vegetation remains an open problem but is essential to make a coupled atmosphere-fire model applicable to actual wildfires. In this work, we study the impact of canopy drag effects on the near-surface flow and the fire behavior simulated by the coupled Meso-NH/BLAZE model in the context of the FireFlux I experimental grass fire for which trees were located upstream and on the flanks. Drag effects can be activated in Meso-NH running in large-eddy simulation mode following work by Aumond et al. (2013). The drag approach formulation consists of adding drag terms to the momentum equation and subgrid turbulent kinetic energy dissipation as a function of the foliage density. This approach is compared to the standard roughness approach and to the homogeneous case considered in Costes et al. (2021) where homogeneous grass was considered over the whole computational domain. Results show the dynamical influence of the surrounding vegetation. Results also indicate that the choice of parameterization, due to the difference in the represented physics, induces differences on the fire front propagation. This encourages us to explore different options to accurately represent the surface boundary layer in presence of complex vegetation for coupled atmosphere-fire modeling in future work.

Discourse on pivotal current issues through and in education is the best approach to promote civic engagement and meaningful political participation among the youth. In this paper, the benefits of civic education empowerment from among Grade 12 students of Sablan National High School was explored. The essence of civic education empowerment has three main goals: political knowledge and understanding, democratic attitudes, and a readiness for democratic political action. Schools play an important role in catalyzing increased civic engagement; they can do this by enabling the youth to develop and practice the knowledge, beliefs, and behaviours needed to participate in civic life. The ripple effect of civic education empowerment is manifested in the relevant learning experiences obtained by the participants in terms of their civic knowledge and civic skills. As to how these civic knowledge and civic skills enhance their civic dispositions and participation, it is evident that participant-respondents assimilated the necessary civic knowledge for an informed choice which reflects their civic dispositions in the formulation of their standards for suffrage. Civic knowledge, civic skills, and civic dispositions and participation constitute the core elements of an informed and active citizenship.

The goal of this paper is to study the smallest brightening events observed in the EUV quiet Sun. We use commissioning data taken by the EUI instrument onboard the recently launched Solar Orbiter mission. On 2020 May 30, EUI was situated at 0.556AU from the Sun. Its HRIEUV telescope 17.4nm passband reached an exceptionally high two-pixel spatial resolution of 400km. The size and duration of small-scale structures is determined in the HRIEUV data, while their height is estimated from triangulation with the simultaneous SDO/AIA data. This is the first stereoscopy of small scale brightenings at high resolution. We observed small localised brightenings ("campfires") in a quiet Sun region with lengthscales between 400km and 4000km and durations between 10 and 200s. The smallest and weakest of these HRIEUV brightenings have not been observed before. Simultaneous HRILYA observations do not show localised brightening events, but the locations of the HRIEUV events correspond clearly to the chromospheric network. Comparison with simultaneous AIA images shows that most events can also be identified in the 17.1nm, 19.3nm, 21.1nm, and 30.4nm passbands of AIA, although they appear weaker and blurred. DEM analysis indicates coronal temperatures peaking at log(T)~6.1-6.15. We determined the height of a few campfires, which is between 1000 and 5000km above the photosphere. We conclude that "campfires" are mostly coronal in nature and are rooted in the magnetic flux concentrations of the chromospheric network. We interpret these events as a new extension to the flare/microflare/nanoflare family. Given their low height, the EUI "campfires" could be a new element of the fine structure of the transition region/low corona: apexes of small-scale loops that are internally heated to coronal temperatures., Comment: 12 pages, 14 figures

This paper presents a novel method for solving partial differential equations on three-dimensional CAD geometries by means of immersed isogeometric discretizations that do not require quadrature schemes. It relies on a new developed technique for the evaluation of polynomial integrals over spline boundary representations that is exclusively based on analytical computations. First, through a consistent polynomial approximation step, the finite element operators of the Galerkin method are transformed into integrals involving only polynomial integrands. Then, by successive applications of the divergence theorem, those integrals over B-Reps are transformed into first surface and then line integrals with polynomials integrands. Eventually these line integrals are evaluated analytically with machine precision accuracy. The performance of the proposed method is demonstrated by means of numerical experiments in the context of 2D and 3D elliptic problems, retrieving optimal error convergence order in all cases. Finally, the methodology is illustrated for 3D CAD models with an industrial level of complexity., Comment: 24 pages, 15 figures, 1 table

Context. The three-dimensional fine structure of the solar atmosphere is still not fully understood as most of the available observations are taken from a single vantage point. Aims. The goal of the paper is to study the three-dimensional distribution of the small-scale brightening events (“campfires”) discovered in the extreme-UV quiet Sun by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter. Methods. We used a first commissioning data set acquired by the EUI’s High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and we combined it with simultaneous data taken by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171 Å passband. The two-pixel spatial resolution of the two telescopes is 400 km and 880 km, respectively, which is sufficient to identify the campfires in both data sets. The two spacecraft had an angular separation of around 31.5° (essentially in heliographic longitude), which allowed for the three-dimensional reconstruction of the campfire position. These observations represent the first time that stereoscopy was achieved for brightenings at such a small scale. Manual and automatic triangulation methods were used to characterize the campfire data. Results. The height of the campfires is located between 1000 km and 5000 km above the photosphere and we find a good agreement between the manual and automatic methods. The internal structure of campfires is mostly unresolved by AIA; however, for a particularly large campfire, we were able to triangulate a few pixels, which are all in a narrow range between 2500 and 4500 km. Conclusions. We conclude that the low height of EUI campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops heated internally to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become feasible.

Reported observations in H-alpha, Ca II H and K or or other chromospheric lines of coronal rain trace back to the days of the Skylab mission. Offering a high contrast in intensity with respect to the background (either bright in emission if observed at the limb, or dark in absorption if observed on disk) these cool blobs are often observed falling down from high coronal heights above active regions. A physical explanation for this spectacular phenomenon has been put forward thanks to numerical simulations of loops with footpoint concentrated heating, a heating scenario in which cool condensations naturally form in the corona. This effect has been termed 'catastrophic cooling' and is the predominant explanation for coronal rain. In this work we further investigate the link between this phenomenon and the heating mechanisms acting in the corona. We start by analyzing observations of coronal rain at the limb in the Ca II H line performed by the SOT instrument on board of the Hinode satellite. We then compare the observations with 1.5-dimensional MHD simulations of loops being heated by small-scale discrete events concentrated towards the footpoints (that could come, for instance, from magnetic reconnection events), and by Alfven waves generated at the photosphere. It is found that if a loop is heated predominantly from Alfven waves coronal rain is inhibited due to the characteristic uniform heating they produce. Hence coronal rain may not only point to the spatial distribution of the heating in coronal loops but also to the agent of the heating itself. We thus propose coronal rain as a marker for coronal heating mechanisms., 29 pages, 8 figures, submitted to ApJ

Embedded systems are specialized computers used in larger systems or machines to control equipments such as automobiles, home appliances, communication, control and office machines. Such pervasivity is particularly evident in immersive realities, i.e., scenarios in which invisible embedded systems need to continuously interact with human users, in order to provide continuous sensed information and to react to service requests from the users themselves. The SM4All project investigates an innovative middleware platform for inter-working of smart embedded services in immersive and person-centric environments, through the use of composability and semantic techniques for dynamic service reconfiguration. This is applied to the challenging scenario of private houses and home-care assistance in presence of users with different abilities and needs (e.g., young, able-bodied, aged and disabled). This paper presentes a brief overview of the SM4All system architecture.

This paper presents theoretical and methodological issues applied to the design and analysis of didactical situations for training to manage open dynamic environment. The study deals with the case of fire-fighter officers training, who are responsible for operations against natural disasters as well as industrial or transportation accidents. Operational training aims at developing collective competencies in decision making at a tactical level in unforeseen situations. At this level, actors have to develop analytical reasoning without having direct information about the "perceived and acted" objects of action. A brief survey of the evolution of training officers at the upper level is presented. Trainees' evolution through a series of situations of simulation is then analysed through the main results of a series of questionnaires. Instructor's activity in managing situation of simulation is then analysed on the basis of the verbal interactions with trainees. Finally, the issue of designing computer-based systems as tools for instructors in managing training situations is discussed.

Context. Observations of reconnection jets in the solar corona are emerging as a possible diagnostic for studying highly elusive coronal heating. Such jets, and in particular those termed nanojets, can be observed in coronal loops and have been linked to nanoflares. However, while models successfully describe the bilateral post-reconnection magnetic slingshot effect that leads to the jets, observations reveal that nanojets are unidirectional or highly asymmetric, with only the jet travelling inward with respect to the coronal loop’s curvature being clearly observed. Aims. The aim of this work is to address the role of the curvature of the coronal loop in the generation and evolution of asymmetric reconnection jets. Methods. We first use a simplified analytical model in which we estimate the post-reconnection tension forces based on the local intersection angle between the pre-reconnection magnetic field lines and their post-reconnection retracting length towards new equilibria. Second, we use a simplified numerical magnetohydrodynamic (MHD) model to study how two opposite propagating jets evolve in curved magnetic field lines. Results. Through our analytical model, we demonstrate that in the post-reconnection reorganised magnetic field, the inward directed magnetic tension is inherently stronger (by up to three orders of magnitude) than the outward directed one and that, with a large enough retracting length, a regime exists where the outward directed tension disappears, leading to no outward jet at large, observable scales. Our MHD numerical model provides support for these results, proving also that in the subsequent time evolution the inward jets are consistently more energetic. The degree of asymmetry is also found to increase for small-angle reconnection and for more localised reconnection regions. Conclusions. This work shows that the curvature of the coronal loops can play a major role in the asymmetry of the reconnection jets and that inward directed jets are more likely to occur and are more energetic than the corresponding outward directed ones.