Interaction of infalling solid bodies with primordial atmospheres of disk-embedded planets

Planets that form early enough to be embedded in the circumstellar gas disk accumulate thick atmospheres of nebular gas. Models of these atmospheres need to specify the surface luminosity (i.e. energy loss rate) of the planet. This luminosity is usually associated with a continuous inflow of solid bodies, where the gravitational energy released from these bodies is the source of energy. However, if these bodies release energy in the atmosphere instead of at the surface, this assumption might not be justified. Our aim is to explore the interactions of infalling planetesimals with primordial atmospheres at an embedded phase of evolution. We investigate effects of atmospheric interaction on the planetesimals (mass loss) and the atmosphere (heating/cooling). We used atmospheric parameters from a snapshot of time-dependent evolution simulations for embedded atmospheres and simulated purely radial, infall events of siliceous planetesimals in a 1D, explicit code. We implemented energy transfer between friction, radiation transfer by the atmosphere and the body and thermal ablation; this gives us the possibility to examine the effects on the planetesimals and the atmosphere. We find that a significant amount of gravitational energy is indeed dissipated into the atmosphere, especially for larger planetary cores, which consequently cannot contribute to the atmospheric planetary luminosity. Furthermore, we examine that planetesimal infall events for cores, $M_\mathrm{C} > 2$M$_{\oplus}$, which actually result in a local cooling of the atmosphere; this is totally in contradiction with the classical model

Teilchenbeschleunigung in galaktischen Winden

Da kosmische Strahlung (CR) im interstellaren Medium (ISM) einen wesentlichen Heizprozess darstellt, sollte eine Berücksichtigung der Wechselwirkung von hochenergetischen, geladenen Teilchen mit dem ISM in sämtlichen Wind-Simulationen erfolgen. Besonders das Gebiet der Simulation von galaktischen Winden sollte sehr stark von der Implementation von CR-Erhaltungsgleichungen profitieren. Diese Arbeit bietet einen Überblick über die verschiedenen Arten der Beschleunigung von geladenen Teilchen, wobei das Hauptaugenmerk auf der Beschleunigung durch einen Fermiprozess 1. Ordnung liegt. Es wird gezeigt, dass es, mit Hilfe von Stoßbeschleunigung durchaus möglich ist, Teilchen auf die höchsten, beobachteten Energien zu beschleunigen, wobei auch das Argument der Steigungsänderung im Bereich von "Knie" und "Knöchel" des CR-Teilchenspektrums diskutiert wird. Weiters wird ein Modell eines galaktischen Windes, unter Berücksichtigung der Physik der CR-Teilchen (Fokker-Planck-Gleichung) und ausgehend von einem Modell zur Simulation von galaktischen Winden (GAWI), erstellt. Dieses Modell beruht auf einem impliziten Code, mit dessen Hilfe es möglich ist, die Ausbreitung eines galaktischen Windes, unter Berücksichtigung der sogenannten Flussröhrengeometrie mit relativ großen Zeitschritten, zu bestimmen. Wesentlich ist, dass im Vergleich zu früheren Modellen der CR-Druck sowie die CR-Energie explizit aus der CR-Erhaltungsgleichung bestimmt werden können, wodurch auch eine direkte Berechnung des CR-Adiabatenkoeffizienten möglich ist. Die aus den Modellrechnungen resultierenden Ergebnisse erweisen sich als außerordentlich gut im Bezug auf den Vergleich mit Testrechnungen. Um die Numerik des Modells zu überprüfen, werden Testrechnungen durchgeführt, wobei davon ausgegangen wird, dass die CRs nicht mit dem hydrodynamischen Stoß koppeln. Die daraus erhaltenen Ergebnisse machen dann einen Vergleich mit einer analytischen Lösung möglich. Weiters wird auch mit verschiedenen Anfangsmdodellen für die CR-Strahlung experimentiert, wobei sich zeigt, dass die Wahl des Anfangsmodells die Genauigkeit des Ergebnisses beeinflusst. Im zweiten Teil der Modellrechnungen werden Simulationen im Realfall (Kopplung Hydrodynamik mit CR-Erhaltung) durchgeführt, welche sich sehr gut mit Ergebnissen aus früheren Simulationen decken. Da bei älteren Modellen die CR-Größen nur sehr stark approximiert eingehen, stellen diese Ergebnisse auch einen Test der numerischen Methodik dar. Abschließend wird noch ein Ausblick auf die Möglichkeiten gegeben, welche durch Implementation der Fokker-Planck-Gleichung nun offenstehen. Die Berücksichtigung der sphärischen Geometrie ermöglicht es beispielsweise stellare Winde und Supernova-Überreste zu untersuchen und die Einbeziehung von Synchrotronverlusten in die Fokker-Planck-Gleichung macht eine Anwendung für Elektronen möglich.Because cosmic rays (CRs) represent a main heating process in the interstellar medium (ISM), interactions of high-energetic, charged particles with the ISM should be considered in all wind simulations. Especially the topic of galactic wind simulations will benefit from an implementation of CR particle conservation equations (Fokker-Planck-equation). This theses gives an overview about the different types of acceleration processes of charged particles, with a main focus on first order Fermi-Acceleration. It will be shown that it is possible to accelerate particles to the highest energies discovered, with the use of shock acceleration only. In doing so, the argument of the different slopes in the range of the "knee" and the "ankle" of the CR particle spectrum will also be discussed. Furthermore, a galactic wind model, which considers the physics of CR particles (Fokker-Planck-equation), on the conception of a model for galactic wind simulations (GAWI) based on older simulations, will be created. This model is based on an implicit code, which makes it possible to explain the expansion of galactic winds in consideration of the so called flux-tube geometry, with the use of relatively large timesteps. In comparison to older models it is important, that CR-pressure and CR-energy have not been computed explicitly from the CR-conservation equation. Therefore it has not been possible to obtain the CR-adiabatic index directly from CR-equations. Remarkable results have been generated, especially in relation to test calculations. These test calculations, with the assumption of CRs behaving as test particles (no coupling of hydrodynamics with CR-equations), have been conducted to prove the reliability of the numerical method, because the obtained results can then be compared with the analytic solution. Moreover, it will be tested using different initial models, which have a strong dependence on the accuracy of simulations. The second part of simulations will be held in a "physically correct" (coupling between hydrodynamics and CR-conservation) state, which correspond thoroughly with results from earlier simulations. As the CR-values in these models are only given as an approximation, the results from the actual model also represent a test of the numerical method. In conclusion, a prospect on further possibilities, due to the use of the Fokker-Planck-equation, will be shown. For example, with introducing spherical geometry, it would be possible to develop more detailed information about the evolution of stellar winds and supernova remnants (SNR). Furthermore, with introducing synchrotron losses in the Fokker-Planck equation, it will be possible to investigate the behavior of electrons (and especially synchrotron-radiation) within that model as well

Time-dependent galactic winds

Cosmic rays (CRs) are transported out of the galaxy by diffusion and advection due to streaming along magnetic field lines and resonant scattering off self-excited Magneto-Hydro-Dynamic (MHD) waves. Thus momentum is transferred to the plasma via the frozen-in waves as a mediator assisting the thermal pressure in driving a galactic wind. Galactic CRs (GCRs) are accelerated by shock waves generated in supernova remnants (SNRs), and they propagate from the disc into the halo. Therefore CR acceleration in the halo strongly depends on the inner disc boundary conditions. We performed hydrodynamical simulations of galactic winds in flux tube geometry appropriate for disc galaxies, describing the CR diffusive-advective transport in a hydrodynamical fashion (by taking appropriate moments of the Fokker-Planck equation) along with the energy exchange with self-generated MHD waves. Our time-dependent CR hydrodynamic simulations confirm that the evolution of galactic winds with feedback depends on the structure of the galactic halo. In case of a wind-structured halo, the wind breaks down after the last super nova (SN) has exploded. The mechanism described here offers a natural and elegant solution to explain the power-law distribution of CRs between the `knee' and the `ankle'. The transition will be naturally smooth, because the Galactic CRs accelerated at SN shocks will be `post-accelerated' by shocks generated at the inner boundary and travelling through the halo.Comment: Galaxies: evolution -- ISM: jets and outflows -- Galaxies: starburst -- supernova remnants -- cosmic ray

Landfill mining: development of a theoretical method for a preliminary estimate of the raw material potential of landfill sites

In recent years, the rising need for raw materials by emerging economies (e.g. China) has led to a change in the availability of certain primary raw materials, such as ores or coal. The accompanying rising demand for secondary raw materials as possible substitutes for primary resources, the soaring prices and the global lack of specific (e.g. metallic) raw materials pique the interest of science and economy to consider landfills as possible secondary sources of raw materials. These sites often contain substantial amounts of materials that can be potentially utilised materially or energetically. To investigate the raw material potential of a landfill, boreholes and excavations, as well as subsequent hand sorting have proven quite successful. These procedures, however, are expensive and time consuming as they frequently require extensive construction measures on the landfill body or waste mass. For this reason, this article introduces a newly developed, affordable, theoretical method for the estimation of landfill contents. The article summarises the individual calculation steps of the method and demonstrates this using the example of a selected Austrian sanitary landfill. To assess the practicality and plausibility, the mathematically determined raw material potential is compared with the actual results from experimental studies of excavated waste from the same landfill (actual raw material potential)

Exploring the Phenomenon of Zero Waste and Future Cities

The evolving phenomenon of zero waste encompasses the theory, practice, and learning of individuals, families, businesses, communities, and government organisations, responding to perceptions of crisis and failure around conventional waste management. The diverse and growing body of international zero waste experience, can be portrayed as both, an entirely new and alternative waste management paradigm, and or, interpreted as overlapping, extending, and synergetic with a general evolution towards more sustainable waste/resource management practices. Combining the terms zero and waste provokes creative, intellectual, and pragmatic tensions, which provide a contemporary axis for necessary debate and innovation in this sphere of resource management. This commentary draws on an interdisciplinary perspective and utilises some elements of the critique of zero waste, as a lens to examine and better understand this heterogeneous global community of practice. In particular, how the concept and implementation of a zero waste goal can increase community engagement and be a catalyst for the design and management of a more circular urban metabolism and hence, more adaptive, resilient, and sustainable future (zero waste) cities

Post-consumer plastic packaging waste in England: Assessing the yield of multiple collection-recycling schemes

The European Commission (EC) recently introduced a ‘Circular Economy Package’, setting ambitious recycling targets and identifying waste plastics as a priority sector where major improvements are necessary. Here, the authors explain how different collection modalities affect the quantity and quality of recycling, using recent empirical data on household (HH) post-consumer plastic packaging waste (PCPP) collected for recycling in the devolved administration of England over the quarterly period July-September 2014. Three main collection schemes, as currently implemented in England, were taken into account: (i) kerbside collection (KS), (ii) household waste recycling centres (HWRCs) (also known as ‘civic amenity sites’), and (iii) bring sites/banks (BSs). The results indicated that: (a) the contribution of KS collection scheme in recovering packaging plastics is higher than HWRCs and BBs, with respective percentages by weight (wt%) 90%, 9% and 1%; (b) alternate weekly collection (AWC) of plastic recyclables in wheeled bins, when collected commingled, demonstrated higher yield in KS collection; (c) only a small percentage (16%) of the total amount of post-consumer plastics collected in the examined period (141 kt) was finally sent to reprocessors (22 kt); (c) nearly a third of Local Authorities (LAs) reported insufficient or poor data; and (d) the most abundant fractions of plastics that finally reached the reprocessors were mixed plastic bottles and mixed plastics