Podcasts about radiative

SpaceTime Series 27 Episode 117*The Biggest Black Hole Jets Ever SeenAstronomers have detected the largest pair of black hole jets ever observed, stretching an astounding 23 million light years. Named Porphyron, this jet megastructure dates back to when the universe was just 6.3 billion years old. The discovery, published in the journal Nature, suggests that these colossal jets had a significant impact on galaxy formation during the universe's early epochs.*NASA's Europa Clipper Mission Ready for LaunchAll systems are go for next month's launch of NASA's Europa Clipper mission, set to study the oceans of Jupiter's ice moon, Europa. The spacecraft will be launched aboard a SpaceX Falcon Heavy rocket and will undertake a series of 49 close flybys to determine if Europa's subsurface ocean could be habitable.*Iran Tests Another Nuclear Capable MissileIn defiance of United Nations resolutions, Iran has tested a new medium-range ballistic missile capable of carrying nuclear warheads. The launch of the Karam 100 missile is part of Tehran's ongoing efforts to develop its nuclear weapons delivery systems.www.spacetimewithstuartgary.comwww.bitesz.com

How do you make some things stay hot and others stay cool? Neil deGrasse Tyson, with the help of comedian Chuck Nice, explains the physics of heat transfer, insulation, and why your Stanley cup can keep your drink cold during a fire. NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/neils-guide-to-heat-transfer-physics/Thanks to our Patrons Kiril Stoilov, aaron tanenbaum, Oswaldo Asprino, cary mannaberg, Taylor Jenkins, BeerandBrat, and J Maz for supporting us this week.

GUEST OVERVIEW: Prof. Valentina Zharkova. PhD is the Director of ZVS Research Enterprise Ltd.​ She is also Emerita Prof. of Mathematics​ at the Department of Mathematics, Physics and Electrical Engineering​ at Northumbria University​ in Newcastle upon Tyne​. Valentina obtained her PhD in Astrophysics ​ with a thesis concerning ‘Radiative transfer of solar prominences' ​conducting research at the Main Astronomical Observatory, Kiev, Ukraine. ​Valentina is currently one of the foremost solar researchers in Great Britain and the world at large and discovered sunquakes induced by flaring processes, publish​ing a paper ​on the topic in Nature, 1998 with wide media coverage. ​She's published more th​an 200 papers​ including ​her study predicting the modern Grand Solar Minimum (2020-2053).​. She has received a SOHO/MDO team award for discovery of sunquake (1999), RHESSI award for outstanding research (2005), NSF US award for advanced studies of solar flares (2002).

On today's show, we delve into Valentina's perspective on the October 13th headline from The Guardian, which advocates for the IMF to allocate $300 billion annually to assist poor countries in combating the climate crisis, according to Joseph Stiglitz. Following that, we shift our focus to the BBC's admission of misleading the public concerning pro-Palestine protests across the UK. In a candid conversation, Lembit and Neil explore the issue of BBC bias, with Neil drawing from his personal experiences. He will shed light on his views regarding the shortcomings of the public broadcaster in delivering the news. GUEST 1 OVERVIEW: Prof. Valentina Zharkova. PhD is the Director of ZVS Research Enterprise Ltd.​ She is also Emerita Prof. of Mathematics​ at the Department of Mathematics, Physics and Electrical Engineering​ at Northumbria University​ in Newcastle upon Tyne​. Valentina obtained her PhD in Astrophysics ​ with a thesis concerning ‘Radiative transfer of solar prominences' ​conducting research at the Main Astronomical Observatory, Kiev, Ukraine. ​Valentina is currently one of the foremost solar researchers in Great Britain and the world at large and discovered sunquakes induced by flaring processes, publishing a paper ​on the topic in Nature, 1998 with wide media coverage. ​ She's published more th​an 200 papers​ including ​her study predicting the modern Grand Solar Minimum (2020-2053).​. She has received a SOHO/MDO team award for discovery of sunquake (1999), RHESSI award for outstanding research (2005), NSF US award for advanced studies of solar flares (2002). GUEST 2 OVERVIEW: Neil Liversidge is an Independent Financial Adviser who has worked in the sector since 1980. He runs his own business, West Riding Personal Financial Solutions Ltd in Castleford, West Yorkshire, which he founded in 2004, managing close-on £100m in assets. Neil was National Chairman of The Motorcycle Action Group, a bikers' lobby group, from 1989 to 2002, and in 1998 founded FEMA, the Federation of European Motorcyclists' Associations. Neil was re-elected MAG National Chairman again in 2021 and founded Transport Reality to campaign against the UK Government's proposed ban on fossil-fuelled private transport. Neil is an extensively published writer and describes himself as “100% a Brexiteer.” In broadcasting, Neil has worked with the BBC for many years, contributing to programs on political, financial and motorcycling issues. Neil's main leisure interests are motorcycling, history, music, movies, and DIY.

Did you know that Saharan ants inspired the development of an electricity-free cooling technology?Tapping on scientific research findings of their supervisor, Dr Edwin Tso Chi-yan from the City University of Hong Kong's School of Energy and Environment (SEE), research assistant Shirley Du and PhD student Martin Zhu, set up “i2Cool” to develop and promote zero-energy, low-cost, highly-efficient passive radiative cooling paint to save energy and reduce carbon emissions in cooling buildings.One of the product's they developed is a radiative paint, that when applied to the exterior wall of a building, can simultaneously reflect sunlight and dissipate the building's heat into space, resulting in a drop in the building's indoor temperature.On this episode of Open for Business, we speak with Dr Martin Zhu, CEO and Co-founder of i2Cool Limited, about how ants inspired the tech behind this paint, why 2 academics jumped into the startup world, and what lies ahead for i2cool. I2Cool Limited is a start-up technology company, incubated by HK TECH 300 in the City University of Hong Kong (CityU) and Hong Kong Science and Technology Park

Show Notes 21 July 2023Story 1: World's Largest Nuclear Fusion Rocket Engine Begins ConstructionSource: ScienceAlert.com Story by David NieldLink: https://www.sciencealert.com/worlds-largest-nuclear-fusion-rocket-engine-begins-constructionSee video here: https://www.youtube.com/watch?v=EIp60JwMLhIStory 2: This ‘thermal cloak' keeps spaces from getting either too hot or cold - The prototype fabric could one day help reduce heating and cooling energy costSource: ScienceNews.org Story by Skyler WareLink: https://www.sciencenews.org/article/thermal-cloak-material-temperatureStory 3: This High-Tech Paint Could Cool the WorldSource: Popular Mechanics Story by Jackie Appel [July 14, 2023]Link: https://www.msn.com/en-us/weather/topstories/this-high-tech-paint-could-cool-the-world/ar-AA1dSeJMLink: https://www.purdue.edu/newsroom/releases/2021/Q2/the-whitest-paint-is-here-and-its-the-coolest.-literally..htmlStory 4: Unraveling connections between the brain and gut - MIT engineers' new technology can probe the neural circuits that influence hunger, mood, and a variety of diseases.Source: MIT News Story by Anne TraftonLink: https://news.mit.edu/2023/unraveling-connections-between-brain-gut-0622For more articles, show notes, news, reviews, and more, check out: ComputerAmerica.com

Shattering and growth of cold clouds in galaxy clusters: the role of radiative cooling, magnetic fields and thermal conduction by Fred Jennings et al. on Wednesday 30 November In galaxy clusters, the hot intracluster medium (ICM) can develop a striking multi-phase structure around the brightest cluster galaxy. Much work has been done on understanding the origin of this central nebula, but less work has studied its eventual fate after the originally filamentary structure is broken into individual cold clumps. In this paper we perform a suite of 30 (magneto-)hydrodynamical simulations of kpc-scale cold clouds with typical parameters as found by galaxy cluster simulations, to understand whether clouds are mixed back into the hot ICM or can persist. We investigate the effects of radiative cooling, small-scale heating, magnetic fields, and (anisotropic) thermal conduction on the long-term evolution of clouds. We find that filament fragments cool on timescales shorter than the crushing timescale, fall out of pressure equilibrium with the hot medium, and shatter, forming smaller clumplets. These act as nucleation sites for further condensation, and mixing via Kelvin-Helmholtz instability, causing cold gas mass to double within 75 Myr. Cloud growth depends on density, as well as on local heating processes, which determine whether clouds undergo ablation- or shattering-driven evolution. Magnetic fields slow down but don't prevent cloud growth, with the evolution of both cold and warm phase sensitive to the field topology. Counter-intuitively, anisotropic thermal conduction increases the cold gas growth rate compared to non-conductive clouds, leading to larger amounts of warm phase as well. We conclude that dense clumps on scales of $500$ pc or more cannot be ignored when studying the long-term cooling flow evolution of galaxy clusters. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.09183v2

Shattering and growth of cold clouds in galaxy clusters: the role of radiative cooling, magnetic fields and thermal conduction by Fred Jennings et al. on Wednesday 30 November In galaxy clusters, the hot intracluster medium (ICM) can develop a striking multi-phase structure around the brightest cluster galaxy. Much work has been done on understanding the origin of this central nebula, but less work has studied its eventual fate after the originally filamentary structure is broken into individual cold clumps. In this paper we perform a suite of 30 (magneto-)hydrodynamical simulations of kpc-scale cold clouds with typical parameters as found by galaxy cluster simulations, to understand whether clouds are mixed back into the hot ICM or can persist. We investigate the effects of radiative cooling, small-scale heating, magnetic fields, and (anisotropic) thermal conduction on the long-term evolution of clouds. We find that filament fragments cool on timescales shorter than the crushing timescale, fall out of pressure equilibrium with the hot medium, and shatter, forming smaller clumplets. These act as nucleation sites for further condensation, and mixing via Kelvin-Helmholtz instability, causing cold gas mass to double within 75 Myr. Cloud growth depends on density, as well as on local heating processes, which determine whether clouds undergo ablation- or shattering-driven evolution. Magnetic fields slow down but don't prevent cloud growth, with the evolution of both cold and warm phase sensitive to the field topology. Counter-intuitively, anisotropic thermal conduction increases the cold gas growth rate compared to non-conductive clouds, leading to larger amounts of warm phase as well. We conclude that dense clumps on scales of $500$ pc or more cannot be ignored when studying the long-term cooling flow evolution of galaxy clusters. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.09183v2

Radiative Transfer as a Bayesian Linear Regression problem by Frederik De Ceuster et al. on Thursday 24 November Electromagnetic radiation plays a crucial role in various physical and chemical processes. Hence, almost all astrophysical simulations require some form of radiative transfer model. Despite many innovations in radiative transfer algorithms and their implementation, realistic radiative transfer models remain very computationally expensive, such that one often has to resort to approximate descriptions. The complexity of these models makes it difficult to assess the validity of any approximation and to quantify uncertainties on the model results. This impedes scientific rigour, in particular, when comparing models to observations, or when using their results as input for other models. We present a probabilistic numerical approach to address these issues by treating radiative transfer as a Bayesian linear regression problem. This allows us to model uncertainties on the input and output of the model with the variances of the associated probability distributions. Furthermore, this approach naturally allows us to create reduced-order radiative transfer models with a quantifiable accuracy. These are approximate solutions to exact radiative transfer models, in contrast to the exact solutions to approximate models that are often used. As a first demonstration, we derive a probabilistic version of the method of characteristics, a commonly-used technique to solve radiative transfer problems. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12547v1

Radiative Transfer as a Bayesian Linear Regression problem by Frederik De Ceuster et al. on Wednesday 23 November Electromagnetic radiation plays a crucial role in various physical and chemical processes. Hence, almost all astrophysical simulations require some form of radiative transfer model. Despite many innovations in radiative transfer algorithms and their implementation, realistic radiative transfer models remain very computationally expensive, such that one often has to resort to approximate descriptions. The complexity of these models makes it difficult to assess the validity of any approximation and to quantify uncertainties on the model results. This impedes scientific rigour, in particular, when comparing models to observations, or when using their results as input for other models. We present a probabilistic numerical approach to address these issues by treating radiative transfer as a Bayesian linear regression problem. This allows us to model uncertainties on the input and output of the model with the variances of the associated probability distributions. Furthermore, this approach naturally allows us to create reduced-order radiative transfer models with a quantifiable accuracy. These are approximate solutions to exact radiative transfer models, in contrast to the exact solutions to approximate models that are often used. As a first demonstration, we derive a probabilistic version of the method of characteristics, a commonly-used technique to solve radiative transfer problems. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12547v1

Photochemistry and Heating Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations by Jeong-Gyu Kim et al. on Monday 17 October We present an efficient heating/cooling method coupled with chemistry and ultraviolet (UV) radiative transfer, which can be applied to numerical simulations of the interstellar medium (ISM). We follow the time-dependent evolution of hydrogen species (H$_2$, H, H$^+$), assume carbon/oxygen species (C, C$^+$, CO, O, and O$^+$) are in formation-destruction balance given the non-steady hydrogen abundances, and include essential heating/cooling processes needed to capture thermodynamics of all ISM phases. UV radiation from discrete point sources and the diffuse background is followed through adaptive ray tracing and a six-ray approximation, respectively, allowing for H$_2$ self-shielding; cosmic ray (CR) heating and ionization are also included. To validate our methods and demonstrate their application for a range of density, metallicity, and radiation field, we conduct a series of tests, including the equilibrium curves of thermal pressure vs. density, the chemical and thermal structure in photo-dissociation regions, H I-to-H$_2$ transitions, and the expansion of H II regions and radiative supernova remnants. Careful treatment of photochemistry and CR ionization is essential for many aspects of ISM physics, including identifying the thermal pressure at which cold and warm neutral phases co-exist. We caution that many current heating and cooling treatments used in galaxy formation simulations do not reproduce the correct thermal pressure and ionization fraction in the neutral ISM. Our new model is implemented in the MHD code Athena and incorporated in the TIGRESS simulation framework, for use in studying the star-forming ISM in a wide range of environments. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.08024v1

A Note on the "Various Atmospheres over Water Oceans on Terrestrial Planets with a One-Dimensional Radiative-Convective Equilibrium Model by Tetsuya Hara et al. on Sunday 16 October It has been investigated the possibility of the various atmospheres over water oceans. We have considered the H$_2$ atmosphere and He atmosphere concerning to N$_2$ atmosphere over oceans. One of the main subjects in astrobiology is to estimate the habitable zone. If there is an ocean on the planet with an atmosphere, there is an upper limit to the outgoing infrared radiation called the Komabayashi-Ingersoll limit (KI-limit). This limit depends on the components of the atmospheres. We have investigated this dependence under the simple model, using the one-dimensional gray radiative-convective equilibrium model adopted by Nakajima et al. (1992). The outgoing infrared radiation ($F_{IRout}$) with the surface temperature ($T_s$) has shown some peculiar behavior. The examples for H$_2$, He, and N$_2$ background gas for H$_2$O vapour are investigated. There is another limit called the Simpson-Nakajima limit (SN-limit) mainly composed of vapour. This steam limit does not depend on the background atmosphere components. Under super-Earth case ($g=2times$9.8 m/s$^2$), several cases are also calculated. The KI-limit dependence on the initial pressure is presented. The various emission rates by Koll & Cronin (2019) are investigated. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.05963v2

A Note on the "Various Atmospheres over Water Oceans on Terrestrial Planets with a One-Dimensional Radiative-Convective Equilibrium Model by Tetsuya Hara et al. on Sunday 16 October It has been investigated the possibility of the various atmospheres over water oceans. We have considered the H$_2$ atmosphere and He atmosphere concerning to N$_2$ atmosphere over oceans. One of the main subjects in astrobiology is to estimate the habitable zone. If there is an ocean on the planet with an atmosphere, there is an upper limit to the outgoing infrared radiation called the Komabayashi-Ingersoll limit (KI-limit). This limit depends on the components of the atmospheres. We have investigated this dependence under the simple model, using the one-dimensional gray radiative-convective equilibrium model adopted by Nakajima et al. (1992). The outgoing infrared radiation ($F_{IRout}$) with the surface temperature ($T_s$) has shown some peculiar behavior. The examples for H$_2$, He, and N$_2$ background gas for H$_2$O vapour are investigated. There is another limit called the Simpson-Nakajima limit (SN-limit) mainly composed of vapour. This steam limit does not depend on the background atmosphere components. Under super-Earth case ($g=2times$9.8 m/s$^2$), several cases are also calculated. The KI-limit dependence on the initial pressure is presented. The various emission rates by Koll & Cronin (2019) are investigated. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.05963v2

A Note on the "Various Atmospheres over Water Oceans on Terrestrial Planets with a One-Dimensional Radiative-Convective Equilibrium Model by Tetsuya Hara et al. on Wednesday 12 October It has been investigated the possibility of the various atmospheres over water oceans. We have considered the H$_2$ atmosphere and He atmosphere concerning to N$_2$ atmosphere over oceans. One of the main subjects in astrobiology is to estimate the habitable zone. If there is an ocean on the planet with an atmosphere, there is an upper limit to the outgoing infrared radiation called the Komabayashi-Ingersoll limit (KI-limit). This limit depends on the components of the atmospheres. We have investigated this dependence under the simple model, using the one-dimensional gray radiative-convective equilibrium model adopted by Nakajima et al. (1992). The outgoing infrared radiation ($F_{IRout}$) with the surface temperature ($T_s$) has shown some peculiar behavior. The examples for H$_2$, He, and N$_2$ background gas for H$_2$O vapour are investigated. There is another limit called the Simpson-Nakajima limit (SN-limit) mainly composed of vapour. This steam limit does not depend on the background atmosphere components. Under super-Earth case ($g=2times$9.8 m/s$^2$), several cases are also calculated. The KI-limit dependence on the initial pressure is presented. The various emission rates by Koll & Cronin (2019) are investigated. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.05963v1

A Note on the "Various Atmospheres over Water Oceans on Terrestrial Planets with a One-Dimensional Radiative-Convective Equilibrium Model by Tetsuya Hara et al. on Wednesday 12 October It has been investigated the possibility of the various atmospheres over water oceans. We have considered the H$_2$ atmosphere and He atmosphere concerning to N$_2$ atmosphere over oceans. One of the main subjects in astrobiology is to estimate the habitable zone. If there is an ocean on the planet with an atmosphere, there is an upper limit to the outgoing infrared radiation called the Komabayashi-Ingersoll limit (KI-limit). This limit depends on the components of the atmospheres. We have investigated this dependence under the simple model, using the one-dimensional gray radiative-convective equilibrium model adopted by Nakajima et al. (1992). The outgoing infrared radiation ($F_{IRout}$) with the surface temperature ($T_s$) has shown some peculiar behavior. The examples for H$_2$, He, and N$_2$ background gas for H$_2$O vapour are investigated. There is another limit called the Simpson-Nakajima limit (SN-limit) mainly composed of vapour. This steam limit does not depend on the background atmosphere components. Under super-Earth case ($g=2times$9.8 m/s$^2$), several cases are also calculated. The KI-limit dependence on the initial pressure is presented. The various emission rates by Koll & Cronin (2019) are investigated. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.05963v1

Evaluation of different recipes for chromospheric radiative losses in solar flares by J. Tian et al. on Monday 10 October Context. Radiative losses are an indispensable part in the numerical simulation of flares. Detailed calculations could be computationally expensive, especially in the chromosphere. There have been some approximate recipes for chromospheric radiative losses in flares, yet their feasibility in flare simulations needs further evaluation. Aims. We aim to evaluate the performance of different recipes for chromospheric radiative losses in flare simulations. Methods. We compare the atmospheric structure and line profiles in beam-heated flares calculated with detailed radiative losses and the approximate recipes. Results. Both GF90 and HCD22 recipes provide acceptable total radiative losses compared with detailed one, but there are discrepancies in the different atmospheric layers during the different evolutionary phases, which leads to misestimations of temperature and line intensity. The recipe of GF90 overestimates the coolings in the upper chromosphere greatly when temperature exceeds 10^5 K, which also affects the flare evolution and line asymmetries. Radiative heating in the middle chromosphere only functions in the initial stage and could be safely neglected. However, radiative heating from Lyman continuum could dominate near the transition region. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.04461v1

StaNdaRT: A repository of standardized test models and outputs for supernova radiative transfer by Stéphane Blondin et al. on Monday 26 September We present the first results of a comprehensive supernova (SN) radiative-transfer (RT) code-comparison initiative (StaNdaRT), where the emission from the same set of standardized test models is simulated by currently-used RT codes. A total of ten codes have been run on a set of four benchmark ejecta models of Type Ia supernovae. We consider two sub-Chandrasekhar-mass ($M_mathrm{tot} = 1.0$ M$_odot$) toy models with analytic density and composition profiles and two Chandrasekhar-mass delayed-detonation models that are outcomes of hydrodynamical simulations. We adopt spherical symmetry for all four models. The results of the different codes, including the light curves, spectra, and the evolution of several physical properties as a function of radius and time, are provided in electronic form in a standard format via a public repository. We also include the detailed test model profiles and several python scripts for accessing and presenting the input and output files. We also provide the code used to generate the toy models studied here. In this paper, we describe in detail the test models, radiative-transfer codes and output formats and provide access to the repository. We present example results of several key diagnostic features. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.11671v1

StaNdaRT: A repository of standardized test models and outputs for supernova radiative transfer by Stéphane Blondin et al. on Monday 26 September We present the first results of a comprehensive supernova (SN) radiative-transfer (RT) code-comparison initiative (StaNdaRT), where the emission from the same set of standardized test models is simulated by currently-used RT codes. A total of ten codes have been run on a set of four benchmark ejecta models of Type Ia supernovae. We consider two sub-Chandrasekhar-mass ($M_mathrm{tot} = 1.0$ M$_odot$) toy models with analytic density and composition profiles and two Chandrasekhar-mass delayed-detonation models that are outcomes of hydrodynamical simulations. We adopt spherical symmetry for all four models. The results of the different codes, including the light curves, spectra, and the evolution of several physical properties as a function of radius and time, are provided in electronic form in a standard format via a public repository. We also include the detailed test model profiles and several python scripts for accessing and presenting the input and output files. We also provide the code used to generate the toy models studied here. In this paper, we describe in detail the test models, radiative-transfer codes and output formats and provide access to the repository. We present example results of several key diagnostic features. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.11671v1

The Synchrotron Low-Energy Spectrum Arising from the Cooling of Electrons in Gamma-Ray Bursts by A. D. Panaitescu et al. on Wednesday 21 September This work is a continuation of a previous effort (Panaitescu 2019) to study the cooling of relativistic electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses, with application to the spectra and light-curves of the synchrotron Gamma-Ray Burst produced by such cooling electrons. Here, we derive the low-energy slope b_LE of GRB pulse-integrated spectrum and quantify the implications of the measured distribution of b_LE. If the magnetic field lives longer than it takes the cooling GRB electrons to radiate below 1-10 keV, then radiative cooling processes of power P(gamma) ~ gamma^n with n geq 2, i.e. synchrotron and inverse-Compton (iC) through Thomson scatterings, lead to a soft low-energy spectral slope b_LE leq -1/2 of the GRB pulse-integrated spectrum F_eps ~ eps^{b_LE} below the peak-energy E_p, irrespective of the duration of electron injection t_i. IC-cooling dominated by scatterings at the Thomson--Klein-Nishina transition of synchrotron photons below E_p has an index n = 2/3 -> 1 and yield harder integrated spectra with b_LE in [0,1/6], while adiabatic electron-cooling leads to a soft slope b_LE = -3/4. Radiative processes that produce soft integrated spectra can accommodate the harder slopes measured by CGRO/BATSE and Fermi/GBM only if the magnetic field life-time t_B is shorter than the time during which the typical GRB electrons cool to radiate below 1-10 keV, which is less than (at most) ten radiative cooling timescales t_rad of the typical GRB electron. In this case, there is a one-to-one correspondence between t_B and b_LE. To account for low-energy slopes b_LE > -3/4, adiabatic electron-cooling requires a similar restriction on t_B. In this case, the diversity of slopes arises mostly from how the electron-injection rate varies with time and not from the magnetic field timescale. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.10014v1

Radiative transfer in stars by feebly interacting bosons by Andrea Caputo et al. on Monday 19 September Starting from first principles, we study radiative transfer by new feebly-interacting bosons (FIBs) such as axions, axion-like particles (ALPs), dark photons, and others. Our key simplification is to include only boson emission or absorption (including decay), but not scattering between different modes of the radiation field. Based on a given distribution of temperature and FIB absorption rate in a star, we derive explicit volume-integral expressions for the boson luminosity, reaching from the free-streaming to the strong-trapping limit. The latter is seen explicitly to correspond to quasi-thermal emission from a "FIB sphere" according to the Stefan-Boltzmann law. Our results supersede expressions and approximations found in the recent literature on FIB emission from a supernova core and, for radiatively unstable FIBs, provide explicit expressions for the nonlocal ("ballistic") transfer of energy recently discussed in horizontal-branch stars. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2204.11862v2

On large-scale dynamos with stable stratification and the application to stellar radiative zones by Valentin Skoutnev et al. on Sunday 18 September Our understanding of large-scale magnetic fields in stellar radiative zones remains fragmented and incomplete. Such magnetic fields, which must be produced by some form of dynamo mechanism, are thought to dominate angular-momentum transport, making them crucial to stellar evolution. A major difficulty is the effect of stable stratification, which generally suppresses dynamo action. We explore the effects of stable stratification on mean-field dynamo theory with a particular focus on a non-helical large-scale dynamo (LSD) mechanism known as the magnetic shear-current effect. We find that the mechanism is robust to increasing stable stratification as long as the original requirements for its operation are met: a source of shear and non-helical magnetic fluctuations (e.g. from a small-scale dynamo). Both are plausibly sourced in the presence of differential rotation. Our idealized direct numerical simulations, supported by mean-field theory, demonstrate the generation of near equipartition large-scale toroidal fields. Additionally, a scan over magnetic Reynolds number shows no change in the growth or saturation of the LSD, providing good numerical evidence of a dynamo mechanism resilient to catastrophic quenching, which has been an issue for helical dynamos. These properties -- the absence of catastrophic quenching and robustness to stable stratification -- make the mechanism a plausible candidate for generating in-situ large-scale magnetic fields in stellar radiative zones. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2203.01943v2

On Quantum and Classical Treatments of Radiative Recombination by Barabanov A. L. et al. on Thursday 15 September The quantum-mechanical solution to the problem of radiative recombination of an electron in a Coulomb field, obtained in the approximation of the smallness of the electron coupling with the radiation field, has been known for a long time. However, in astrophysics, the classical approach, which does not explicitly use this smallness, is sometimes used to describe similar processes in systems of magnetic monopoles or self-interacting dark matter particles. The importance of such problems is determined by the fact that recombination processes play a crucial role in the evolution of the large-scale structure of the Universe. Therefore, of particular interest is the fact that the classical and quantum expressions for the recombination cross section differ significantly in magnitude. It is shown that the applicability of quantum and classical approaches to radiative recombination is closely related to the radiated angular momentum and its quantization. For situations where the classical approach is not suitable, a semi-classical approach based on the angular momentum quantization is proposed, in some respects an alternative to the well-known semi-classical Kramers' approach. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2204.10860v2

The importance of radiative pumping on the emission of the H 2O submillimeter lines in galaxies by Eduardo González-Alfonso et al. on Wednesday 14 September H_2O submillimeter emission is a powerful diagnostic of the molecular interstellar medium in a variety of sources, including low- and high-mass star forming regions of the Milky Way, and from local to high redshift galaxies. However, the excitation mechanism of these lines in galaxies has been debated, preventing a basic consensus on the physical information that H_2O provides. Both radiative pumping due to H_2O absorption of far-infrared photons emitted by dust and collisional excitation in dense shocked gas have been proposed to explain the H_2O emission. Here we propose two basic diagnostics to distinguish between the two mechanisms: 1) in shock excited regions, the ortho-H_2O 3_{21}-2_{12} 75um and the para-H_2O 2_{20}-1_{11} 101um rotational lines are expected to be in emission while, if radiative pumping dominates, both far-infrared lines are expected to be in absorption; 2) based on statistical equilibrium of H_2O level populations, the radiative pumping scenario predicts that the apparent isotropic net rate of far-infrared absorption in the 3_{21}-2_{12} (75um) and 2_{20}-1_{11} (101um) lines should be higher than or equal to the apparent isotropic net rate of submillimeter emission in the 3_{21}-3_{12} (1163 GHz) and 2_20-2_{11} (1229 GHz) lines, respectively. Applying both criteria to all 16 galaxies and several galactic high-mass star-forming regions where the H_2O 75um and submillimeter lines have been observed with Herschel/PACS and SPIRE, we show that in most (extra)galactic sources the H_2O submillimeter line excitation is dominated by far-infrared pumping, with collisional excitation of the low-excitation levels in some of them. Based on this finding, we revisit the interpretation of the correlation between the luminosity of the H_2O 988 GHz line and the source luminosity in the combined galactic and extragalactic sample. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.06444v1

Effects of Radiative Diffusion on the Dynamical Corotation Torque in Three-Dimensional Protoplanetary Disks by Han-Gyeol Yun et al. on Tuesday 13 September The dynamical corotation torque arising from the deformation of the horseshoe orbits, along with the vortensity gradient in the background disk, is important for determining orbital migration rate and direction of low-mass planets. Previous two-dimensional studies predicted that the dynamical corotation torque is positive, decelerating the inward planet migration. In contrast, recent three-dimensional studies have shown that buoyancy resonance makes the dynamical corotation torque negative, accelerating the inward migration. In this paper, we study the dependence of the dynamical corotation torque on the thermal transport using three-dimensional simulations. We first show that our results are consistent with previous three-dimensional studies when the disk is fully adiabatic. In more realistic radiative disks, however, radiative diffusion suppresses the buoyancy resonance significantly, especially at high-altitude regions, and yields a positive dynamical corotation torque. This alleviates the issue of a rapid migration caused by the negative dynamical corotation torque in the adiabatic disks. Our results suggest that radiative diffusion together with stellar irradiation and accretion heating is needed to accurately describe the migration of low-mass planets. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.05417v1

Effects of Radiative Diffusion on the Dynamical Corotation Torque in Three-Dimensional Protoplanetary Disks by Han-Gyeol Yun et al. on Tuesday 13 September The dynamical corotation torque arising from the deformation of the horseshoe orbits, along with the vortensity gradient in the background disk, is important for determining orbital migration rate and direction of low-mass planets. Previous two-dimensional studies predicted that the dynamical corotation torque is positive, decelerating the inward planet migration. In contrast, recent three-dimensional studies have shown that buoyancy resonance makes the dynamical corotation torque negative, accelerating the inward migration. In this paper, we study the dependence of the dynamical corotation torque on the thermal transport using three-dimensional simulations. We first show that our results are consistent with previous three-dimensional studies when the disk is fully adiabatic. In more realistic radiative disks, however, radiative diffusion suppresses the buoyancy resonance significantly, especially at high-altitude regions, and yields a positive dynamical corotation torque. This alleviates the issue of a rapid migration caused by the negative dynamical corotation torque in the adiabatic disks. Our results suggest that radiative diffusion together with stellar irradiation and accretion heating is needed to accurately describe the migration of low-mass planets. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.05417v1

3D radiative transfer kilonova modelling for binary neutron star merger simulations by Christine E. Collins et al. on Monday 12 September The detection of GW170817 and the accompanying electromagnetic counterpart, AT2017gfo, have provided an important set of observational constraints for theoretical models of neutron star mergers, nucleosynthesis, and radiative transfer for kilonovae. We apply the 3D Monte Carlo radiative transfer code ARTIS to produce synthetic light curves of the dynamical ejecta from a neutron star merger, which has been modelled with 3D smooth-particle hydrodynamics (SPH) and included neutrino interactions. Nucleosynthesis calculations provide the energy released from radioactive decays of r-process nuclei, and radiation transport is performed using grey opacities given as functions of the electron fraction. We present line-of-sight dependent bolometric light curves, and find the emission along polar lines of sight to be up to a factor of ~2 brighter than along equatorial lines of sight. Instead of a distinct emission peak, our bolometric light curve exhibits a monotonic decline, characterised by a shoulder at the time when the bulk ejecta becomes optically thin. We show approximate band light curves based on radiation temperatures and compare these to the observations of AT2017gfo. We find that the rapidly declining temperatures lead to a blue to red colour evolution similar to that shown by AT2017gfo. We also investigate the impact of an additional, spherically symmetric secular ejecta component, and we find that the early light curve remains nearly unaffected, while after about 1 day the emission is strongly enhanced and dominated by the secular ejecta, leading to the shift of the shoulder from 1-2 to 6-10 days. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.05246v1

Resilience of small PAHs in interstellar clouds: Efficient stabilization of cyanonaphthalene by fast radiative cooling by Mark H. Stockett et al. on Monday 12 September After decades of speculation and searching, astronomers have recently identified specific Polycyclic Aromatic Hydrocarbons (PAHs) in space. Remarkably, the observed abundance of cyanonaphthalene (CNN, C10H7CN) in the Taurus Molecular Cloud (TMC-1) is six orders of magnitude higher than expected from astrophysical modeling. Here, we report absolute unimolecular dissociation and radiative cooling rate coefficients of the 1-CNN isomer in its cationic form. These results are based on measurements of the time-dependent neutral product emission rate and Kinetic Energy Release distributions produced from an ensemble of internally excited 1-CNN + studied in an environment similar to that in interstellar clouds. We find that Recurrent Fluorescence - radiative relaxation via thermally populated electronic excited states - efficiently stabilizes 1-CNN+ , owing to a large enhancement of the electronic transition probability by vibronic coupling. Our results help explain the anomalous abundance of CNN in TMC-1 and challenge the widely accepted picture of rapid destruction of small PAHs in space. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.05229v1

Do the solar flares' locations illustrate the boundaries of the solar inner layers? by Ramy Mawad. on Monday 12 September The angular distance of the solar flares from their position to the projection point of the center of the Sun on the solar disk has been studied during the periods 1975${-}$2021 for GOES events and 2002${-}$2021 for RHESSI events. This distribution by the number of events of flare importance gives a specific curvature shape, that remains the same without significant changes, with the different GOES classifications, and with different observational satellites. during each solar cycle. The curvature of the distance distribution has four peaks, which are denoted by the four central rings around the center of the solar disk that look like the solar inner layers in the background. 1) The core circle [0 ${-}$ 15$^{circ}$]: it is a projection of the solar core onto the solar disk. 2) Radiative ring [15$^{circ}$ ${-}$ 45$^{circ}$]. 3) The convection ring [45$^{circ}$ ${-}$ 55$^{circ}$ ]. The limb ring [80$^{circ}$ ${-}$ 90$^{circ}$]. A large number of solar flares occurred in the radiative and convection rings. While we have a few events in the core and limb rings. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.04755v1

Flare Kernels May be Smaller than You Think: Modelling the Radiative Response of Chromospheric Plasma Adjacent to a Solar Flare by Christopher M. J. Osborne et al. on Thursday 08 September Numerical models of solar flares typically focus on the behaviour of directly-heated flare models, adopting magnetic field- aligned, plane-parallel methodologies. With high spatial- and spectral-resolution ground-based optical observations of flares, it is essential also to understand the response of the plasma surrounding these strongly heated volumes. We investigate the effects of the extreme radiation field produced by a heated column of flare plasma on an adjacent slab of chromospheric plasma, using a two-dimensional radiative transfer model and considering the time-dependent solution to the atomic level populations and electron density throughout this model. The outgoing spectra of H$alpha$ and Ca II 854.2 nm synthesised from our slab show significant spatial-, time-, and wavelength-dependent variations (both enhancements and reductions) in the line cores, extending on order 1 Mm into the non-flaring slab due to the incident transverse radiation field from the flaring boundary. This may lead to significant overestimates of the sizes of directly-heated flare kernels, if line-core observations are used. However, the radiation field alone is insufficient to drive any significant changes in continuum intensity, due to the typical photospheric depths at which they forms, so continuum sources will not have an apparent increase in size. We show that the line formation regions near the flaring boundary can be driven upwards in altitude by over 1 Mm despite the primary thermodynamic parameters (other than electron density) being held horizontally uniform. This work shows that in simple models these effects are significant and should be considered further in future flare modelling and interpretation. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.03238v1

Flare Kernels May be Smaller than You Think: Modelling the Radiative Response of Chromospheric Plasma Adjacent to a Solar Flare by Christopher M. J. Osborne et al. on Thursday 08 September Numerical models of solar flares typically focus on the behaviour of directly-heated flare models, adopting magnetic field- aligned, plane-parallel methodologies. With high spatial- and spectral-resolution ground-based optical observations of flares, it is essential also to understand the response of the plasma surrounding these strongly heated volumes. We investigate the effects of the extreme radiation field produced by a heated column of flare plasma on an adjacent slab of chromospheric plasma, using a two-dimensional radiative transfer model and considering the time-dependent solution to the atomic level populations and electron density throughout this model. The outgoing spectra of H$alpha$ and Ca II 854.2 nm synthesised from our slab show significant spatial-, time-, and wavelength-dependent variations (both enhancements and reductions) in the line cores, extending on order 1 Mm into the non-flaring slab due to the incident transverse radiation field from the flaring boundary. This may lead to significant overestimates of the sizes of directly-heated flare kernels, if line-core observations are used. However, the radiation field alone is insufficient to drive any significant changes in continuum intensity, due to the typical photospheric depths at which they forms, so continuum sources will not have an apparent increase in size. We show that the line formation regions near the flaring boundary can be driven upwards in altitude by over 1 Mm despite the primary thermodynamic parameters (other than electron density) being held horizontally uniform. This work shows that in simple models these effects are significant and should be considered further in future flare modelling and interpretation. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.03238v1

Radiative processes as diagnostics of cometary atmospheres by D. Bodewits et al. on Wednesday 07 September In this chapter, we provide a review of radiative processes in cometary atmospheres spanning a broad range of wavelengths, from radio to X-rays. We focus on spectral modeling, observational opportunities, and anticipated challenges in the interpretation of new observations, based on our current understanding of the atomic and molecular processes occurring in the atmospheres of small, icy bodies. Close to the surface, comets possess a thermalized atmosphere that traces the irregular shape of the nucleus. Gravity is too low to retain the gas, which flows out to form a large, collisionless exosphere (coma) that interacts with the heliospheric radiation environment. As such, cometary comae represent conditions that are familiar in the context of planetary atmosphere studies. However, the outer comae are tenuous, with densities lower than those found in vacuum chambers on Earth. Comets, therefore, provide us with unique natural laboratories that can be understood using state-of-the-art theoretical treatments of the relevant microphysical processes. Radiative processes offer direct diagnostics of the local physical conditions, as well as the macroscopic coma properties.These can be used to improve our understanding of comets and other astrophysical environments such as icy moons and the interstellar medium. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02616v1

The radio spectra of SN 2020oi: Effects of radiative cooling on the deduced source properties by C. -I. Bjornsson. on Wednesday 07 September Observations of radiative cooling in a synchrotron source offer a possibility to further constrain its properties. Inverse Compton cooling is indicated in the radio spectra during the early phases of SN,2020oi. It is shown that contrary to previous claims, observations are consistent with equipartition between relativistic electrons and magnetic field as well as a constant mass-loss rate of the progenitor star prior to the supernova explosion. The reason for this difference is the need to include cooling directly in the fitting procedure rather than estimating its effects afterward. It is emphasized that the inferred properties of the supernova ejecta are sensitive to the time evolution of the synchrotron self-absorption frequency; hence, great care should be taken when modeling spectra for which cooling and/or inhomogeneities are indicated. Furthermore, it is noted that the energies of the relativistic electrons in the radio emission regions in supernovae are likely too low for first-order Fermi acceleration to be effective. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.03057v1

Radiative processes as diagnostics of cometary atmospheres by D. Bodewits et al. on Wednesday 07 September In this chapter, we provide a review of radiative processes in cometary atmospheres spanning a broad range of wavelengths, from radio to X-rays. We focus on spectral modeling, observational opportunities, and anticipated challenges in the interpretation of new observations, based on our current understanding of the atomic and molecular processes occurring in the atmospheres of small, icy bodies. Close to the surface, comets possess a thermalized atmosphere that traces the irregular shape of the nucleus. Gravity is too low to retain the gas, which flows out to form a large, collisionless exosphere (coma) that interacts with the heliospheric radiation environment. As such, cometary comae represent conditions that are familiar in the context of planetary atmosphere studies. However, the outer comae are tenuous, with densities lower than those found in vacuum chambers on Earth. Comets, therefore, provide us with unique natural laboratories that can be understood using state-of-the-art theoretical treatments of the relevant microphysical processes. Radiative processes offer direct diagnostics of the local physical conditions, as well as the macroscopic coma properties.These can be used to improve our understanding of comets and other astrophysical environments such as icy moons and the interstellar medium. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02616v1

Radiative processes as diagnostics of cometary atmospheres by D. Bodewits et al. on Wednesday 07 September In this chapter, we provide a review of radiative processes in cometary atmospheres spanning a broad range of wavelengths, from radio to X-rays. We focus on spectral modeling, observational opportunities, and anticipated challenges in the interpretation of new observations, based on our current understanding of the atomic and molecular processes occurring in the atmospheres of small, icy bodies. Close to the surface, comets possess a thermalized atmosphere that traces the irregular shape of the nucleus. Gravity is too low to retain the gas, which flows out to form a large, collisionless exosphere (coma) that interacts with the heliospheric radiation environment. As such, cometary comae represent conditions that are familiar in the context of planetary atmosphere studies. However, the outer comae are tenuous, with densities lower than those found in vacuum chambers on Earth. Comets, therefore, provide us with unique natural laboratories that can be understood using state-of-the-art theoretical treatments of the relevant microphysical processes. Radiative processes offer direct diagnostics of the local physical conditions, as well as the macroscopic coma properties.These can be used to improve our understanding of comets and other astrophysical environments such as icy moons and the interstellar medium. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02616v1

Radiative processes as diagnostics of cometary atmospheres by D. Bodewits et al. on Wednesday 07 September In this chapter, we provide a review of radiative processes in cometary atmospheres spanning a broad range of wavelengths, from radio to X-rays. We focus on spectral modeling, observational opportunities, and anticipated challenges in the interpretation of new observations, based on our current understanding of the atomic and molecular processes occurring in the atmospheres of small, icy bodies. Close to the surface, comets possess a thermalized atmosphere that traces the irregular shape of the nucleus. Gravity is too low to retain the gas, which flows out to form a large, collisionless exosphere (coma) that interacts with the heliospheric radiation environment. As such, cometary comae represent conditions that are familiar in the context of planetary atmosphere studies. However, the outer comae are tenuous, with densities lower than those found in vacuum chambers on Earth. Comets, therefore, provide us with unique natural laboratories that can be understood using state-of-the-art theoretical treatments of the relevant microphysical processes. Radiative processes offer direct diagnostics of the local physical conditions, as well as the macroscopic coma properties.These can be used to improve our understanding of comets and other astrophysical environments such as icy moons and the interstellar medium. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02616v1

Radiative reconnection-powered TeV flares from the black hole magnetosphere in M87 by Hayk Hakobyan et al. on Tuesday 06 September Active Galactic Nuclei in general, and the supermassive black hole in M87 in particular, show bright and rapid gamma-ray flares up to energies of 100 GeV and above. For M87, the flares show multiwavelength components, and the variability timescale is comparable to the dynamical time of the event horizon, suggesting that the emission may come from a compact region nearby the nucleus. However, the emission mechanism for these flares is not well understood. Recent high-resolution general relativistic magnetohydrodynamics simulations show the occurrence of episodic magnetic reconnection events that can power flares nearby the black hole event horizon. In this work we analyze the radiative properties of the reconnecting current layer under the extreme plasma conditions applicable to the black hole in M87 from first principles. We show that abundant pair production is expected in the vicinity of the reconnection layer, to the extent that the produced secondary pair-plasma dominates the reconnection dynamics. Using analytic estimates backed by two-dimensional particle-in-cell simulations we demonstrate that even in the presence of strong synchrotron cooling, reconnection can still produce a hard power-law distribution of pair plasma imprinted in the outgoing synchrotron (up to few tens of MeV) and the inverse-Compton signal (up to TeV). We produce synthetic radiation spectra from our simulations, which can be directly compared with the results of future multiwavelength observations of M87* flares. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02105v1

NEWS   Stanford engineers invent a solar panel that generates electricity at night | Interesting Engineer (01:08) Solar panels at night can freely radiate infrared light out into space.Solar panels — like everything warmer than absolute zero — emit infrared radiation.  Cloudless nights being optimal, because no clouds equals less reflection of the infrared light onto the ground.Radiative cooling (surface is cooler than air) phenomenon that only happens when skies are clear.  That flow of energy enables the device Stanford University researchers created — an ordinary solar panel outfitted with a thermoelectric generator — to generate a small amount of electricity from the slight difference in temperature between the ambient air and the surface of a solar panel pointed deep into space.  Lead researcher,  Sid Assawaworrarit, states:“There's actually light going out [from the solar panel], and we use that to generate electricity at night. The photons going out into the night sky actually cool down the solar cell.” Photons leave the sky facing surface of the solar panel, and they carry heat with them. The surface of a solar panel will be a few degrees cooler than the air around it.  A device called a thermoelectric generator can capture some of the heat flowing from the warmer air to the cooler solar panel and convert it into electricity. On a clear night, the device tested on the Stanford rooftop generates roughly fifty milliwatts for every square meter of solar panel (50 mW/m2). They believe the “theoretical limit is probably about one or two watts per square meter” Not a huge number but some SMALL applications could use this powerNight Light Home phone Unlike batteries that degrade substantially after a few thousand charge cycles, the kind of thermoelectric generators used in these solar panels are solid state, so according to Sid, the lifetime is “pretty much forever”. Another possible use for the technology is powering the immense network of environmental sensorsUsed to keep tabs on everything from weather conditions to invasive species in far-flung corners of the globe.   Rocket Lab prepares its chopper to catch a returning booster in midair | New Atlas (07:28) Recycling has quickly become the name of the game in the world of commercial spaceflight.SpaceX & Blue Origin with reusable rockets Rocket Lab has plans on recycling their first stage of its Electron booster, but they plan on getting it back in a different way.The plan will soon achieve a key milestone by collecting the first stage in midair with a customized Sikorsky S-92 helicopter. Their reusability goal has been laid out since 2019, where their initial plans were to have the stage land in the water where a recovery vessel could go retrieve it.Accomplished this back in 2020 In parallel, it has been gathering data and fine-tuning the descent process with a view to recovering the rocket in a more audacious way. In 2020, they succeeded in using a helicopter to catch a replica of its Electron first-stage over the open ocean in New Zealand Now they plan on trying to catch the real thing. Later this month, the Electron rocket will carry out its 26th launch, taking off from New Zealand to deliver 34 small satellites to orbit. Before lift-off, a modified Sikorsky S-92 will move into the "capture zone" around 150 nautical miles (277 km) offshore. It will wait for the first stage to hurtle back toward Earth at up to 8,300 km/h (5,150 mph). At an altitude of 13 km (8.3 miles), Electron will deploy a smaller drogue parachute before deploying a main parachute at around 6 km (3.7 miles).  This will slow the first stage to speeds of just 10 meters a second (22.3 mph), enabling the chopper to hook the parachute line. This first attempt at mid-air recovery will take place in late April, with the 14-day launch window scheduled to open on the 19th.   Looking Through Mojo Vision's Newest AR Contact Lens |  IEEE Spectrum (12:17) This article is the author's (Tekla S. Perry) account of getting to Mojo Vision's AR contact lens. Note: It is still a prototype, and still needs clinical testing and further development ahead before it can apply for FDA approval. She was given a demo. The contact lens wasn't actually placed in her eye because that would require an eye exam but she held a lens very close to one eye and peeked through.That means that the lens would not be able to track eye movements since it is not on the eyeball.  Additionally since it was one lens the images appear 2D but with 2 contacts in it would appear 3D in the final product. Several apps were utilized in the demo:One being a simple app that would tag compass headings as she turned to face different directions.  A teleprompter app that naturally scrolled up and down to move through the text A video stream Possible travel tool apps,High-resolution monochrome image of an incoming Uber driver Biking app that called up heart rate and other training information Image sensors—a feature of earlier demos that showed off edge detection in low light and other vision enhancements—have yet to be built into the current prototype, but they are in the works according to the company. Here is Steve Sinclair, Mojo senior vice president of product and marketing giving more information about the battery on the lens:“The battery is in the outer ring, embedded in the lens. We are partnering with a medical-grade battery company that makes implantable microbatteries for things like pacemakers, to design something safe to wear” The company is looking to help people with low vision issues.Low vision is a vision problem that makes it hard to do everyday activities. It can't be fixed with glasses, contact lenses, or other standard treatments like medicine or surgery.  Steve continues talking about developing tools to help people with low vision issues, “We've been using mainly low-vision capabilities built into smartphones right now to take pictures of things and bring them up to your eye for zooming in and out; we'll add in the imager and test those capabilities out next.” What is next for the company?They want to start testing the complete prototype on-eye, and see how well it works in different situations. According to Steve, the first test subjects will be Drew Perkins, the CEO and probably Mike Wiemer, the CTO.   Simple delivery method enhances a promising cancer treatment | MedicalXPress (20:11)  One cutting-edge cancer treatment exciting researchers today involves collecting and reprogramming a patient's T cells and then putting them back into the body ready to detect and destroy cancerous cells.Works great for widespread blood cancers like leukemia, but not so much for solid tumors. Because they are dense, exist in specific locations and have defenses to hide from and fend off immune cells. Maybe that will change with a new delivery technique developed by Stanford University engineers, which enhances the "attack power" of the modified immune cells.Called chimeric antigen receptor (CAR) T cells The researchers add CAR-T cells and specialized signaling proteins to a hydrogel—a water-filled gel that has characteristics in common with biological tissues—and inject the substance next to a tumor. Protein is called cytokines, which tell the engineered immune cells to rapidly replicate and prepare to destroy a tumor. With the normal IV approach the amount of cytokines needed to activate the T-cells to destroy a solid tumor would be toxic to the body. The gel gives a temporary environment for the immune cells to multiply and activate in preparation to fight cancerous cells.  Additionally, the gell acts like a leaky holding pen that pumps out activated CAR-T cells to continuously attack the tumor over time. Eric Appel, senior author on the paper talks on how this research is focusing on area not thought about:“A lot of the CAR-T cell field is focusing on how to make better cells themselves, but there is much less focus on how to make the cells more effective once in the body …  So what we're doing is totally complementary to all of the efforts to engineer better cells." Now to see if it works on mice models:The researchers found that all experimental animals injected with gel containing both CAR-T cells and cytokines became cancer-free after 12 days. Also tried delivering just CAR-T cells in the gel, but the tumors disappeared more slowly or not at all in some mice. Additionally, the gel did not induce adverse inflammatory reactions in the mice, and it fully degraded within the body in a few weeks. Appel says his lab's next set of experiments will further explore the gel delivery method's ability to treat faraway tumors. This research proposes a simple and effective way to improve a promising cancer treatment.   Israeli bee tech startup Beewise pulls in $80m investment for robotic beehives | Times of Israel (27:19) We have a problem with the honeybee population. In the US alone, beekeepers lost an estimated 45% of their managed honeybee colonies between April 2020 and April 2021, marking the second-highest annual loss on record. This could be a result of a “perfect storm” of multiple issues happening at once. Climate issues, habitat loss, excessive use of agricultural chemicals, parasitic mites, and various pathogens. A new startup that recently received an $80m investment, Beewise, is looking at ways to combat this growing problem globally.  They developed the “Beehome.”A solar-powered, converted container that brings together robotics, artificial intelligence, imaging, a software platform, and a mobile application to monitor and care for honeybees around the clock.  The device can house up to 24 bee colonies  Automatically controls for climate and humidity conditions,  Detects and eliminates pests and parasites,  Identifies when a colony is preparing to swarm, sends alerts when human intervention is needed Even harvests the honey the bees produce. CEO Saar Safra, discusses the benefits of robot bee keeping:“Treating and caring for living biological beings in real-time helps keep them strong and healthy. A robot can do this all day long; it doesn't get tired. Humans can't treat bees in real-time. If there's a problem, you don't know about it until you get to the hives. They [beekeepers] need to drive into the field — if they have 1,000 boxes scattered around, they need to look into them to see what's happening, and often it's too late as the colony has collapsed.” According to the company's initial internal findings, colony collapse with the Beehome is reduced to about 10 percent. A step in the right direction, hopefully they can boost that number higher. In addition to more investments, Beewise also announced a lighter-weight version of the Beehome with a more effective feeding system and stronger solar panels. Beewise is fulfilling thousands of orders in the US and, with the funding, “will be able to meet incredible market demand through increased manufacturing, develop additional product iterations, and further improve pollination,” according to the CEO.    

Russia Leaves Radiative Chernobyl, Chris Rock Is Still “Processing” The Slap, Is COVID Over? With Jerry Malcolm, Grant Cardone, and Jonathan Bing Our live show gives our listeners the chance to actually hear us perform and even influence the show and gives us the unique opportunity to create a bond with our already captive listeners. The instant feedback – the laughs, the gasps, that sense of connection. They're coming to our show to feel part of a conversation and voice their opinion every time we record a podcast episode. The people that attend our live podcast show have a great time, tell their friends and family and attract some very powerful champions of each spirited DEBATE The NEWS episode. Here at DTN, We DEBATE The News! We Allow You To Present Your Interpretation On Today's Local, National, & World News Topics. Spirited & Informed Discussions Are Encouraged. Engage and Sharpen Your Mind with Intellectual Combat! Live On the Clubhouse APP: https://www.debatethenews.com/jointheclub (Clubhouse Link) M-F 6:00 PM - 9:00 PM EST / 3:00 PM - 6:00 PM PST Meet the Host(s): https://www.debatethenews.com/gat (Get Access Tour | MasterClass)

The Earth has been cooling slowly since its creation ~4.5 billion years ago, but new research on the mantle-derived mineral, bridgmanite, suggests it's actually a bit faster than previously expected. What does this mean for the future of our planet? Source Material: M. Murakami, A.F. Goncharov, N. Miyajima, D. Yamazaki, N. Holtgrewe, Radiative thermal conductivity of single-crystal bridgmanite at the core-mantle boundary with implications for thermal evolution of the Earth, Earth and Planetary Science Letters, Volume 578. Read here for free: https://www.sciencedirect.com/science/article/pii/S0012821X21005859 Download the Callin app for iOS and Android to listen to this podcast live, call in, and more! Also available at callin.com

In this episode, I have talked about Radiative Forcing in climate change and its limitations.Topics covered:Radiative ForcingConceptEffective Radiative ForcingLimitationsGrouping Forcing Compounds by Common PropertiesCalculation of RFContinentalityAdditional Info:The tropopause is the boundary in the Earth's atmosphere between the troposphere and the stratosphere. It is a thermodynamic gradient stratification layer, marking the end of the troposphere. It lies, on average, at 17 kilometres (11 mi) above equatorial regions, and about 9 kilometres (5.6 mi) over the polar regions.Emission metrics such as Global Warming Potential (GWP) and Global Temperature change Potential (GTP) can be used to quantify and communicate the relative and absolute contribu-tions to climate change of emissions of different substances, and of emissions from regions/countries or sources/sectors. The metric that has been used in policies is the GWP, which integrates the RF of a substance over a chosen time horizon, relative to that of CO2. The GTP is the ratio of change in global mean surface temperature at a chosen point in time from the substance of interest relative to that from CO2.Forcing and temperature response can also be attributed to sec-tors. From this perspective and with the GTP metric, a single year's worth of current global emissions from the energy and industrial sec-tors have the largest contributions to global mean warming over the next approximately 50 to 100 years. Twitter:https://twitter.com/realyashnegiWebsite: climatology.inSuggestions are always welcome: yashnegi@climatology.inSupport the show (https://paypal.me/yashnegi27?locale.x=en_GB)

Comenzamos el Trasnoshot, un nuevo podcast de la casa de Shots de Ciencia hablando de cambio climático, Colombia y la COP 25 con dos grandes invitadas. Tatiana Pardo, periodista ambiental, y Ángela Amaya, abogada especializada en derecho ambiental, nos explican y cuentan el cambio climático como una narrativa que supera la ciencia y es transversal a la política, la economía y la gente. Esto es Colombia, cambio climático y la COP -Apóyanos en Patreon: www.patreon.com/shotsdeciencia -O apóyanos con una donación en www.ciencialegible.com/apoyanos Referencias y recursos: How do we know more CO2 is causing warming? https://skepticalscience.com/print.php?r=257 What does past climate change tell us about global warming? https://skepticalscience.com/climate-change-little-ice-age-medieval-warm-period.htm Ocean-Atmosphere CO2 Exchange https://sos.noaa.gov/datasets/ocean-atmosphere-co2-exchange/ Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL071930 Anthropogenic and Natural Radiative Forcing https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter08_FINAL.pdf Climate myths: Human CO2 emissions are too tiny to matter https://www.newscientist.com/article/dn11638-climate-myths-human-co2-emissions-are-too-tiny-to-matter/#ixzz6DJ9f4l9V Climate Change: How Do We Know? (Gráfica de NOAA) https://climate.nasa.gov/evidence/ The Causes of Climate Change https://climate.nasa.gov/causes/ Largest carbon dioxide sink in renewable forests https://www.eurekalert.org/pub_releases/2019-03/kift-lcd031319.php

Learn more about radiative forcing, the environment, and how global temperature changes with atmospheric absorption with this Problem Episode about you walking your (perhaps fictional?) dog around a park. This episode is distributed under a CC BY-SA license. For more information, visit CreativeCommons.org. [Featuring: Sofía Baca, Gabriel Hesch] --- This episode is sponsored by · Anchor: The easiest way to make a podcast. https://anchor.fm/app Support this podcast: https://anchor.fm/breakingmathpodcast/support

Keep up with us at 4iiii, and X3. If you like the show, rate and review us on iTunes and tell your friends!

On the second episode of Not Cool, Ariel delves into some of the basic science behind climate change and the history of its study. She is joined by Dr. Joanna Haigh, an atmospheric physicist whose work has been foundational to our current understanding of how the climate works. Joanna is a fellow of The Royal Society and recently retired as Co-Director of the Grantham Institute on Climate Change and the Environment at Imperial College London. Here, she gives a historical overview of the field of climate science and the major breakthroughs that moved it forward. She also discusses her own work on the stratosphere, radiative forcing, solar variability, and more. Topics discussed include: History of the study of climate change Overview of climate modeling Radiative forcing What’s changed in climate science in the past few decades How to distinguish between natural climate variation and human-induced global warming Solar variability, sun spots, and the effect of the sun on the climate History of climate denial

"Radiative Forcing" Hosts: Vicky Davis and Darren Weeks COMPLETE SHOW NOTES AND CREDITS AT: https://governamerica.com/radio/radio-archives/22067-govern-america-september-16-2017-radiative-forcing Evil agent out at BLM. Still no pardon for peaceful ranchers / property rights activists. FBI/Comey collusion cash for Trump "pee dossier"? Police state booms as St. Louis burns from riots. London tube explosion boosts perpetual martial law. Were the culprits known to authorities? Diplomacy under attack as U.S. raids Russian facilities in the U.S., and American diplomats in Cuba are attacked by apparent direct energy weaponry. More on Trump's amnesty betrayal, and debt ceiling dance. Storm follow-up as media distorter attempts to stir up racism against relief helpers. Red Cross executive admits he doesn't know where donations go. Canada works to prosecute opposing "climate" opinions. Also, we touch upon the 46th session of the Intergovernmental Panel on Climate Change, which is now incorporating geoengineering as one of its mitigation options for global warming. Phone calls.

This weeks episode is an interview with Will Steffen. He an Australian Earth system scientist and he knows a lot about things like the biosphere, glacial cycles, ocean acidification, fossil industry, geo-engineering, complex system, feedbacks, resilience and tipping points. One of the stories Steffen will share with you is the situation when Nobel prize winner Paul Crutzen invented the name and concept of The Anthropocene. Will was one of the scientists in the room as it happened in at a workshop in Mexico 2000. He will also describe the The Great Acceleration, another concept that was born with Will and his colleagues at IGBP. He shares his top three high-level tasks that we need to manage a lot better than we’ve done so far, Radiative balance, Human Equity and our connection to the Biosphere. We also talk about metaphors, energy, tipping points in nature as well as in the social-political system and the post-truth era in society. Conclusions... a lot. For instance tipping points. Both in nature, for exemplet with the Arctic ice melting and it’s albedo feedback… But also the tipping points in renewable energy. We are so locked in to the view that the price of oil sets the price of all energy, consumption, travel, inflation and people worrying about their energy bills etc. But what happens if/when it is cheaper to build solar farms and put up solar panels on your roof-top than to dig up fossil carbon and build big infrastructure like coal fired power plants? That is a shift, not only in how we produce electricity, but in the way the price is set and who is to get the money. It is a shift of power, in many different ways. I also find the discussion about the feedbacks in system very interesting. You have feedbacks in all complex systems. They take different forms, for example the feedbacks from society to climate, the climate negotiations and the UNFCCC, trying to keep the climate system in a stable situation. And the resilience of the fossil industry threatening the resilience of both climate and civilisation as we know it (and hence of course also the fossil industry itself). I slso ask Will about his favourite metaphors, for example to describe complex systems, feedbacks etc. Martin Hedberg

This weeks episode is an interview with Will Steffen. He an Australian Earth system scientist and he knows a lot about things like the biosphere, glacial cycles, ocean acidification, fossil industry, geo-engineering, complex system, feedbacks, resilience and tipping points. One of the stories Steffen will share with you is the situation when Nobel prize winner Paul Crutzen invented the name and concept of The Anthropocene. Will was one of the scientists in the room as it happened in at a workshop in Mexico 2000. He will also describe the The Great Acceleration, another concept that was born with Will and his colleagues at IGBP. He shares his top three high-level tasks that we need to manage a lot better than we've done so far, Radiative balance, Human Equity and our connection to the Biosphere. We also talk about metaphors, energy, tipping points in nature as well as in the social-political system and the post-truth era in society. Conclusions... a lot. For instance tipping points. Both in nature, for exemplet with the Arctic ice melting and it's albedo feedback… But also the tipping points in renewable energy. We are so locked in to the view that the price of oil sets the price of all energy, consumption, travel, inflation and people worrying about their energy bills etc. But what happens if/when it is cheaper to build solar farms and put up solar panels on your roof-top than to dig up fossil carbon and build big infrastructure like coal fired power plants? That is a shift, not only in how we produce electricity, but in the way the price is set and who is to get the money. It is a shift of power, in many different ways. I also find the discussion about the feedbacks in system very interesting. You have feedbacks in all complex systems. They take different forms, for example the feedbacks from society to climate, the climate negotiations and the UNFCCC, trying to keep the climate system in a stable situation. And the resilience of the fossil industry threatening the resilience of both climate and civilisation as we know it (and hence of course also the fossil industry itself). I slso ask Will about his favourite metaphors, for example to describe complex systems, feedbacks etc. Martin Hedberg

Ein theoretisches Modell welches die Fluktuationen innerhalb eines Wolkenensembles beschreibt, stellt die Basis für stochastische Konvektionsparametrisierung dar. Hochaufgelöste, idealisierte Simulationen eines Wolkenensembles über einer homogenen Meeresoberfläche werden benutzt um die Gültigkeit des theoretischen Modells im Strahlungs-Konvektions-Gleichgewicht zu evaluieren. Im ersten Schritt dieser Studie werden Kontrollsimulationen mit einer horizontalen Auflösung von 2 km durchgeführt, wobei fünf verschiedene Abkühlungsraten benutzt werden um das Wolkenensemble anzutreiben. In den Kontrollsimulationen wird die Gültigkeit einer exponentiellen Verteilung des vertikalen Massenflusses und der Wolkengrößen für alle Abkühlungsraten nachgewiesen. Desweiteren, nimmt die Anzahl der Wolken im Modellgebiet mit steigender Abkühlungsrate linear zu, wohingegen nur eine schwache Abhängigkeit der mittleren Wolkengrößen und deren Vertikalgeschwindigkeiten von der Stärke der Abkühlungsrate beobachtet wird. Diese Ergebnisse zeigen eine gute Übereinstimmung mit dem theoretischen Modell. Im zweiten Teil dieser Studie wird die Gitterweite in den numerischen Simulationen sukzessive bis zu einer Auflösung von 125 m verfeinert. Hierbei treten signifikante Änderungen in der Wolkenstatistik und der Struktur der Wolkenfelder auf. Die Größe der Wolken nimmt mit zunehmender Auflösung stark ab, wohingegen die Anzahl der Gitterpunkte innerhalb einer Wolke ansteigt, da diese mit zunehmender Auflösung besser auf dem numerischen Gitter dargestellt werden können. Im Gegensatz zu den zufällig verteilten Wolken in den Kontrollsimulationen, wird in den feinaufgelösten Wolkenfeldern beobachtet, dass sich die einzelnen konvektiven Zellen in bandartigen Strukturen um wolkenfreie Gebiete anordnen. Der Umkreis einer Wolke in dem diese Cluster-Effekte beobachtet werden, scheint indes unabhängig von der horizontalen Auflösung zu sein. Mit feiner werdender Auflösung weicht darüber hinaus die Wahrscheinlichkeitsdichteverteilung der Wolkengrößen und des vertikalen Massenflusses immer stärker von der exponentiellen Verteilung ab. Für größere Werte in den Verteilungen zeigen sich Übereinstimmungen mit einer Power-Law Verteilung. Durch die Partitionierung der Wolken-Cluster in deren zugrundeliegende, einzelne Aufwindbereiche kann die erwartete, exponentielle Verteilung des Massenflusses und der Wolkengrößen wieder hergestellt werden. Das theoretische Modell ist daher in hochaufgelösten Simulationen für die einzelnen Aufwindbereiche gültig, allerdings müssen die Cluster-Effekte im Wolkenensemble hierbei berücksichtigt werden.

Wed, 1 Jan 2014 12:00:00 +0100 https://epub.ub.uni-muenchen.de/24216/1/oa_24216.pdf Dyk, Danny van; Bobeth, Christoph; Beaujean, Frederik

The available data on | Delta B| = | Delta S| = 1 decays are in good agreement with the Standard Model when permitting subleading power corrections of about 15 at large hadronic recoil. Constraining new- physics effects in C7, C9, C10, the data still demand the same size of power corrections as in the StandardModel. In the presence of chirality- flipped operators, all but one of the power corrections reduce substantially. The Bayes factors are in favor of the Standard Model. Using new lattice inputs for B. K* form factors and under our minimal prior assumption for the power corrections, the favor shifts towardmodelswith chirality- flipped operators. We use the data to further constrain the hadronic form factors in B. K and B. K* transitions.

Soil moisture is one of the key variables controlling the water and energy exchanges between Earth’s surface and the atmosphere. Therefore, remote sensing based soil moisture information has potential applications in many disciplines. Besides numerical weather forecasting and climate research these include agriculture and hydrologic applications like flood and drought forecasting. The first satellite specifically designed to deliver operational soil moisture products, SMOS (Soil Moisture and Ocean Salinity), was launched 2009 by the European Space Agency (ESA). SMOS is a passive microwave radiometer working in the L-band of the microwave domain, corresponding to a frequency of roughly 1.4 GHz and relies on a new concept. The microwave radiation emitted by the Earth’s surface is measured as brightness temperatures in several look angles. A radiative transfer model is used in an inversion algorithm to retrieve soil moisture and vegetation optical depth, a measure for the vegetation attenuation of the soil’s microwave emission. For the application of passive microwave remote sensing products a proper validation and uncertainty assessment is essential. As these sensors have typical spatial resolutions in the order of 40 – 50 km, a validation that relies solely on ground measurements is costly and labour intensive. Here, environmental modelling can make a valuable contribution. Therefore the present thesis concentrates on the question which contribution coupled land surface and radiative transfer models can make to the validation and analysis of passive microwave remote sensing products. The objective is to study whether it is possible to explain known problems in the SMOS soil moisture products and to identify potential approaches to improve the data quality. The land surface model PROMET (PRocesses Of Mass and Energy Transfer) and the radiative transfer model L-MEB (L-band microwave emission of the Biosphere) are coupled to simulate land surface states, e.g. temperatures and soil moisture, and the resulting microwave emission. L-MEB is also used in the SMOS soil moisture processor to retrieve soil moisture and vegetation optical depth simultaneously from the measured microwave emission. The study area of this work is the Upper Danube Catchment, located mostly in Southern Germany. Since model validation is essential if model data are to be used as reference, both models are validated on different spatial scales with measurements. The uncertainties of the models are quantified. The root mean squared error between modelled and measured soil moisture at several measuring stations on the point scale is 0.065 m3/m3. On the SMOS scale it is 0.039 m3/m3. The correlation coefficient on the point scale is 0.84. As it is essential for the soil moisture retrieval from passive microwave data that the radiative transfer modelling works under local conditions, the coupled models are used to assess the radiative transfer modelling with L-MEB on the local and SMOS scales in the Upper Danube Catchment. In doing so, the emission characteristics of rape are described for the first time and the soil moisture retrieval abilities of L-MEB are assessed with a newly developed LMEB parameterization. The results show that the radiative transfer modelling works well under most conditions in the study area. The root mean squared error between modelled and airborne measured brightness temperatures on the SMOS scale is less than 6 – 9 K for the different look angles. The coupled models are used to analyse SMOS brightness temperatures and vegetation optical depth data in the Upper Danube Catchment in Southern Germany. Since the SMOS soil moisture products are degraded in Southern Germany and in different other parts of the world these analyses are used to narrow down possible reasons for this. The thorough analysis of SMOS brightness temperatures for the year 2011 reveals that the quality of the measurements is degraded like in the SMOS soil moisture product. This points towards radio frequency interference problems (RFI), that are known, but have not yet been studied thoroughly. This is consistent with the characteristics of the problems observed in the SMOS soil moisture products. In addition to that it is observed that the brightness temperatures in the lower look angles are less reliable. This finding could be used to improve the brightness temperature filtering before the soil moisture retrieval. An analysis of SMOS optical depth data in 2011 reveals that this parameter does not contain valuable information about vegetation. Instead, an unexpected correlation with SMOS soil moisture is found. This points towards problems with the SMOS soil moisture retrieval, possibly under the influence of RFI. The present thesis demonstrates that coupled land surface and radiative transfer models can make a valuable contribution to the validation and analysis of passive microwave remote sensing products. The unique approach of this work incorporates modelling with a high spatial and temporal resolution on different scales. This makes detailed process studies on the local scale as well as analyses of satellite data on the SMOS scale possible. This could be exploited for the validation of future satellite missions, e.g. SMAP (Soil Moisture Active and Passive) which is currently being prepared by NASA (National Aeronautics and Space Administration). Since RFI seems to have a considerable influence on the SMOS data due to the gained insights and the quality of the SMOS products is very good in other parts of the world, the RFI containment and mitigation efforts carried out since the launch of SMOS should be continued.

Tue, 17 Apr 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/14935/ https://edoc.ub.uni-muenchen.de/14935/1/Graziani_Luca.pdf Graziani, Luca ddc:530, ddc:500, Fakultät für Physik

Lecture 5. More Ecosystem modeling. I guess I'll finish up Lecture 4. HydroLight training. 5 lectures and labs. All sorts of things from an overview of the software, to demonstration runs, to students running H on their own computers

Tue, 8 Nov 2011 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/13627/ https://edoc.ub.uni-muenchen.de/13627/1/Zhuravleva_Irina.pdf Zhuravleva, Irina ddc:530, ddc:500, Fakultät fü

Dr. Oey's research group, Feedback Activity in Nearby Galaxies (FANG), focuses on this massive star feedback to the interstellar and intergalactic medium, on local, global, and cosmic scales. Radiative feedback: HII nebulae and photoionized gas; Chemical feedback: Enrichment processes and galactic chemical evolution; Kinematic feedback: Supernova-driven superbubbles and galactic superwinds; and Massive stars and clusters

Fri, 18 Mar 2011 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/12898/ https://edoc.ub.uni-muenchen.de/12898/1/Petkova_Margarita.pdf Petkova, Margarita ddc:530, ddc:500, Fakultät für Phy

Dr. Zheng is a YCAA fellow at Yale Center for Astronomy and Astrophysics. Heobtained my PhD in Astronomy at the Ohio State University. Before moving to Yale, he was a postdoc at the Institute for Advanced Study. His main research areas are in cosmology, large-scale structure, galaxy formation and evolution, and Lyman-alpha radiative transfer. He also has broad interests in other fields of astrophysics.Feb. 14, 2011.

In the first part of this thesis, we study classes of hybrid and chaotic inflation models in four-dimensional N=1 supergravity. Therein, the eta-problem can be resolved relying on fundamental symmetries in the Kaehler potential. Concretely, we investigate explicit realizations of superpotentials, in which the flatness of the inflaton potential is protected at tree level by a shift symmetry or a Heisenberg symmetry in the Kaehler potential. In the latter case, the associated modulus field can be stabilized during inflation by supergravity effects. In the context of hybrid inflation, a novel class of models, to which we refer as "tribrid inflation," turns out to be particularly compatible with such symmetry solutions to the eta-problem. Radiative corrections due to operators in the superpotential, which break the respective symmetry, generate the required small slope of the inflaton potential. Additional effective operators in the Kaehler potential can reduce the predicted spectral index so that it agrees with latest observational data. Within a model of chaotic inflation in supergravity with a quadratic potential, we apply the Heisenberg symmetry to allow for viable inflation with super-Planckian field values, while the associated modulus is stabilized. We show that radiative corrections are negligible in this context. In the second part, the tribrid inflation models are extended to realize gauge non-singlet inflation. This is applied to the matter sector of supersymmetric Grand Unified Theories based on the Pati-Salam gauge group. For the specific scenario in which the right-handed sneutrino is the inflaton, we study the scalar potential in a D-flat valley. We show that despite potentially dangerous two-loop corrections, the required flatness of the potential can be maintained. The reason for this is the strong suppression of gauge interactions of the inflaton field due to its symmetry breaking vacuum expectation value. In addition, the production of stable magnetic monopoles at the end of the stage of inflation can be avoided. Finally, we sketch how in tribrid inflation models the concepts discussed in the two parts can be combined to realize inflation via Heisenberg symmetry in local supersymmetric SO(10) grand unification.

Hiptmair, R (ETH Zurich, CH) Thursday 16 September 2010, 14:00-14:30

The most direct way to avoid the formation of a relativistic electron beam under the influence of an electric field in a highly conducting plasma, is to increase the electron density to a value, where the retarding collisional force balances the accelerating one. In a disruptive tokamak plasma, rapid cooling induces a high electric field, which could easily violate the force balance and push electrons into the relativistic regime. Such relativistic electrons, the so-called runaways, accumulate many MeV's and can cause substantial damage when they hit the wall. This thesis is based on the principle of rapidly fueling the plasma for holding the force balance even under the influence of high electric fields typical for disruptions. The method of injecting high amounts of noble gas particles into the plasma from a close distance is put into practice in the ASDEX Upgrade fusion test facility. In the framework of this thesis, a multi-channel photometer system based on 144 AXUV detectors in a toroidal stereo measurement setup was built. It kept its promise to provide new insights into the transport mechanisms in a disruptive plasma under the influence of strong radiative interaction dynamics between injected matter and the hot plasma.

Lambert, H (Exeter) Wednesday 18 August 2010, 14:00-15:00

This thesis addresses two major problems in the field of radiative transfer (RT) in the earth’s atmosphere. The first problem is linked with the need for significant computational resources of RT in a three-dimensional (3D) atmospheric model. Although only highly efficient one-dimensional (1D) RT models are employed for each pixel of the model domain separately and independently, it is still not possible to utilize these models on a frequent basis, compared to the rate at which meteorological variables are computed. That means that the calculated radiative properties (RP) are held constant for a longer period of time, while the prognostic meteorological variables are updated at a rapid rate. Even though there is no detailed study about the consequences of this disproportion, an attempt was made to develop an RT model which permits the fast computation of basic radiative transfer properties which could be used in the future to update this information more frequently. The developed model is based on the application of the radiative transfer perturbation theory to realistic cloud fields column by column. It turned out that the application, intended to replace the Independent Pixel Approximation (IPA), see below, is possible and promising within the assumptions and constraints of the utilized methods. It could be demonstrated that, depending on the actual case, errors in the pixel transmission and reflection stay bounded to values of up to 10%−15%. In one case the achieved acceleration could be investigated. It was about a factor of four compared to the direct application of the usual forward variant of the model, although no numerical optimization was carried out. The second problem concerns the realistic treatment of the 3D interactions of clouds and solar radiation. As implied in the above paragraph, 1D RT models are usually employed column by column which suppresses the exchange of radiation between those columns. Thus, fundamental 3D effects are neglected by this so-called Independent Pixel Approximation (IPA). These comprise not only small scale contributions due to diffuse radiative transport, but also large scale patterns like geometric effects of the inclined solar illumination. Examples are blurred radiative structures due to radiative smoothing and the shifted location of shadows and bright areas. To parameterize those effects strong efforts have been undertaken during the last couple of years. However, no method has proven to be completely satisfactory and ready for implementation. To carry this research one step further two approaches have been adopted and extended. The first is the concept of the Tilted Independent Pixel Approximation (TIPA). In contrast to the IPA, which ignores the solar geometry, this method correctly accounts for the slant illumination due to the correct tracking of the direct beam. As a result, the optical parameters in the slant columns are arranged in a more realistic order and the attenuation and the positions of the RP are less erroneous. To further improve this method a transformation has been developed which yields 3D resolution of the RP in the original grid. Since the TIPA still does not include any diffuse radiative exchange as another approach the Nonlocal Independent Pixel Approximation (NIPA) has been explored. This technique uses 1D results and carries out a convolution product to distribute RP across column boundaries. In order to arrive at a fully independent treatment of this method a simplified derivation of the convolution parameters was developed. Finally, TIPA and NIPA are combined to form NTIPA. These approaches have proven to be superior to IPA with respect to several aspects. The improvement ranges from several percent to 50% if maximum errors of the transmitted and reflected light are considered. Criteria like the distribution of the errors or the vertical profiles of the RP are also more preferable than their counterparts derived by IPA.