Constrained Hyperbolic Divergence Cleaning for Smoothed Particle Magnetohydrodynamics

We present a constrained formulation of Dedner et al's hyperbolic/parabolic divergence cleaning scheme for enforcing the \nabla\dot B = 0 constraint in Smoothed Particle Magnetohydrodynamics (SPMHD) simulations. The constraint we impose is that energy removed must either be conserved or dissipated, such that the scheme is guaranteed to decrease the overall magnetic energy. This is shown to require use of conjugate numerical operators for evaluating \nabla\dot B and \nabla{\psi} in the SPMHD cleaning equations. The resulting scheme is shown to be stable at density jumps and free boundaries, in contrast to an earlier implementation by Price & Monaghan (2005). Optimal values of the damping parameter are found to be {\sigma} = 0.2-0.3 in 2D and {\sigma} = 0.8-1.2 in 3D. With these parameters, our constrained Hamiltonian formulation is found to provide an effective means of enforcing the divergence constraint in SPMHD, typically maintaining average values of h |\nabla\dot B| / |B| to 0.1-1%, up to an order of magnitude better than artificial resistivity without the associated dissipation in the physical field. Furthermore, when applied to realistic, 3D simulations we find an improvement of up to two orders of magnitude in momentum conservation with a corresponding improvement in numerical stability at essentially zero additional computational expense.Comment: 28 pages, 25 figures, accepted to J. Comput. Phys. Movies at http://www.youtube.com/playlist?list=PL215D649FD0BDA466 v2: fixed inverted figs 1,4,6, and several color bar

Saint-Hippolyte – Cave particulière Lo Poux

Le site antique de Lo Poux est connu de longue date. Il se développe au niveau d’une intersection de chemins, dans différentes parcelles. La demande de diagnostic concerne l’une de ces parcelles (AM55) et celle limitrophe (AM53). Toutes deux correspondent à des vignes en exploitation. En fait la cave particulière sera construite dans le tiers ouest de la parcelle AM53, soit au plus loin par rapport au site connu. Ce dernier devrait être partiellement traversé par la mise en place d’un réseau ..

Alénya – Le Petit Littoral

Le lotissement dénommé Le Petit Littoral se situe dans la prolongation de la rue des Jardins, dans la partie sud-est d’Alénya, entre l’avenue de la Mer et celle du Littoral. Il s’agit actuellement d’une zone plane et alluviale. Les tranchées et les sondages profonds ouverts montrent la présence d’un recouvrement sédimentaire fort sur toute l’emprise. Il s’agit d’apports de limon et de sable fin, parfois de cailloutis sur plus de 1,30 m par rapport au sol actuel. Un sondage plus profond permet..

Synthetic X-ray and radio maps for two different models of Stephan's Quintet

We present simulations of the compact galaxy group Stephan's Quintet (SQ) including magnetic fields, performed with the N-body/smoothed particle hydrodynamics (SPH) code \textsc{Gadget}. The simulations include radiative cooling, star formation and supernova feedback. Magnetohydrodynamics (MHD) is implemented using the standard smoothed particle magnetohydrodynamics (SPMHD) method. We adapt two different initial models for SQ based on Renaud et al. and Hwang et al., both including four galaxies (NGC 7319, NGC 7320c, NGC 7318a and NGC 7318b). Additionally, the galaxies are embedded in a magnetized, low density intergalactic medium (IGM). The ambient IGM has an initial magnetic field of $10^{-9}$ G and the four progenitor discs have initial magnetic fields of $10^{-9} - 10^{-7}$ G. We investigate the morphology, regions of star formation, temperature, X-ray emission, magnetic field structure and radio emission within the two different SQ models. In general, the enhancement and propagation of the studied gaseous properties (temperature, X-ray emission, magnetic field strength and synchrotron intensity) is more efficient for the SQ model based on Renaud et al., whose galaxies are more massive, whereas the less massive SQ model based on Hwang et al. shows generally similar effects but with smaller efficiency. We show that the large shock found in observations of SQ is most likely the result of a collision of the galaxy NGC 7318b with the IGM. This large group-wide shock is clearly visible in the X-ray emission and synchrotron intensity within the simulations of both SQ models. The order of magnitude of the observed synchrotron emission within the shock front is slightly better reproduced by the SQ model based on Renaud et al., whereas the distribution and structure of the synchrotron emission is better reproduced by the SQ model based on Hwang et al..Comment: 20 pages, 15 figures, accepted to MNRA

Cosmic-ray driven dynamo in galaxies

We present recent developments of global galactic-scale numerical models of the Cosmic Ray (CR) driven dynamo, which was originally proposed by Parker (1992). We conduct a series of direct CR+MHD numerical simulations of the dynamics of the interstellar medium (ISM), composed of gas, magnetic fields and CR components. We take into account CRs accelerated in randomly distributed supernova (SN) remnants, and assume that SNe deposit small-scale, randomly oriented, dipolar magnetic fields into the ISM. The amplification timescale of the large-scale magnetic field resulting from the CR-driven dynamo is comparable to the galactic rotation period. The process efficiently converts small-scale magnetic fields of SN-remnants into galactic-scale magnetic fields. The resulting magnetic field structure resembles the X-shaped magnetic fields observed in edge-on galaxies.Comment: 6 pages, 4 figures, to appear in Proceedings of IAU Symp. 274, Advances in Plasma Astrophysics, ed. A. Bonanno, E. de Gouveia dal Pino and A. Kosoviche

Co ma Bloom do Barańczaka? (Ewa Rajewska, Stanisław Barańczak – poeta i tłumacz)

Co ma Bloom do Barańczaka? (Ewa Rajewska, Stanisław Barańczak – poeta i tłumacz

Słowa czytane, pisane, audiowizualne. Stan edukacji filmowej w szkole ponadgimnazjalnej

This work presents the results of the research conducted by the author in July 2017 in order to determine to what extent and with what kind of words students of the secondary school (preparing for the matura exam) refer to film in their essays. The author relates cognitively to film education. She noticed that despite poor media education at school, young people are able to interpret films by going with them into a personal dialogue, thereby trying to understand film in the conscious interpretation process.W pracy przedstawiono wyniki badania przeprowadzonego przez autorkę w lipcu 2017 roku w celu określenia, w jakim stopniu i jakimi słowami uczniowie szkoły ponadgimnazjalnej, przygotowujący się do egzaminu maturalnego, odwołują się w swoich wypracowaniach do filmów. Autorka odwołuje się do edukacji filmowej w ujęciu kognitywnym. Zauważa, że młodzi ludzie, mimo ubogiej edukacji medialnej w szkole, odczytują obrazy filmowe, wchodząc z nimi w osobisty dialog i tym samym próbując zrozumieć film w świadomym procesie interpretacji