A5000115308- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Dark Matter and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Solar Radiation and Photovoltaics
- Adaptive optics and wavefront sensing
- Astrophysics and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Astronomy and Astrophysical Research
- Particle Detector Development and Performance
- Geomagnetism and Paleomagnetism Studies
- Fluid Dynamics and Turbulent Flows
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Quantum Chromodynamics and Particle Interactions
- Neutrino Physics Research
- Computational Fluid Dynamics and Aerodynamics
- Ionosphere and magnetosphere dynamics
- Nuclear physics research studies
- Planetary Science and Exploration
- Radiation Therapy and Dosimetry
- Atomic and Molecular Physics
Institut für Sonnenphysik
2014-2023
Universität Hamburg
2014-2023
Federal Institute For Materials Research and Testing
2023
Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut
2023
Max Planck Institute for Solar System Research
1998-2017
University of Göttingen
2009-2017
Max Planck Society
1998-2013
Max Planck Institute for Astrophysics
1972-2013
University of Würzburg
2005-2010
Max Planck Institute for Mathematics
2009
We study two limiting cases of turbulence forcing in numerical experiments: solenoidal (divergence-free) forcing, and compressive (curl-free) compare our results to observations reported the literature. solve equations hydrodynamics on grids with up 1024^3 cells for purely forcing. Eleven lower-resolution models mixtures both forcings are also analysed. find velocity dispersion--size relations consistent independent simulations, irrespective type However, yields stronger turbulent...
The probability density function (PDF) of the gas in turbulent supersonic flows is investigated with high-resolution numerical simulations. In a systematic study, we compare statistics compressible turbulence driven by usually adopted solenoidal forcing (divergence-free) and compressive (curl-free). Our results are agreement studies using forcing. However, yields significantly broader distribution standard deviation ~3 times larger at same rms Mach number. deviation-Mach number relation used...
The Sunrise balloon-borne solar observatory consists of a 1m aperture Gregory telescope, UV filter imager, an imaging vector polarimeter, image stabilization system and further infrastructure. first science flight yielded high-quality data that reveal the structure, dynamics evolution convection, oscillations magnetic fields at resolution around 100 km in quiet Sun. After brief description instruments data, qualitative results are presented. In contrast to earlier observations, we clearly...
This paper describes the Polarimetric and Helioseismic Imager on Solar Orbiter mission (SO/PHI), first magnetograph helioseismology instrument to observe Sun from outside Sun-Earth line. It is key meant address top-level science question: How does solar dynamo work drive connections between heliosphere? SO/PHI will also play an important role in answering other questions of Orbiter, as well hosting potential a rich return further science. measures Zeeman effect Doppler shift FeI 617.3nm...
Context. Supersonic turbulence is ubiquitous in the interstellar medium and plays an important role contemporary star formation.
Supermassive black holes with up to a 109 M⊙ dwell in the centres of present-day galaxies, and their presence has been confirmed at z ≥ 6. Their formation such early epochs is still an enigma. Different pathways have suggested assemble supermassive first billion years after big bang. Direct collapse emerged as highly plausible scenario form it provides seed masses 105–106 M⊙. Gravitational atomic cooling haloes virial temperatures Tvir 104 K may lead massive intense background ultraviolet...
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by four institutions in Spain that flew on board the Sunrise balloon-borne telesocope June 2009 for almost six days over Arctic Circle. As polarimeter IMaX uses fast polarization modulation (based use of two liquid crystal retarders), real-time image accumulation, and dual beam polarimetry to reach sensitivities 0.1%. spectrograph, instrument LiNbO3 etalon double pass narrow band pre-filter achieve spectral resolution...
In a systematic study, we compare the density statistics in high resolution numerical experiments of supersonic isothermal turbulence, driven by usually adopted solenoidal (divergence-free) forcing and compressive (curl-free) forcing. We find that for same rms Mach number, produces much stronger enhancements larger voids compared to Consequently, Fourier spectra fluctuations are significantly steeper. This result is confirmed using Delta-variance analysis, which yields power-law exponents...
The dynamical parameters conventionally used to specify the orbit of a test particle in Kerr spacetime are energy E, axial component angular momentum, Lz, and Carter's constant Q. These obtained by solving Hamilton–Jacobi equation for problem geodesic motion. Employing action-angle variable formalism, on other hand, yields different set constants motion, namely, fundamental frequencies ωr, ωθ ωϕ associated with radial, polar azimuthal components orbital respectively. frequencies, naturally,...
Abstract The 1.5 m telescope GREGOR opens a new window to the understanding of solar small‐scale magnetism. first light instrumentation includes Gregor Fabry Pérot Interferometer (GFPI), filter spectro‐polarimeter for visible wavelength range, GRating Infrared Spectro‐polarimeter (GRIS) and Broad‐Band Imager (BBI). excellent performance two instruments has already been demonstrated at Vacuum Tower Telescope. is Europe’s largest number 3 in world. Its all‐reflective Gregory design provides...
A simulation of the thermonuclear explosion a Chandrasekhar-mass C+O white dwarf, most popular scenario type Ia supernova (SN Ia), is presented. The underlying modeling pursued in self-consistent way, treating combustion wave as turbulent deflagration using well tested methods developed for laboratory and based on concept `large eddy simulations' (LES). Such consistency requires to capture onset cascade resolved scales. This achieved by computing dynamical evolution 1024$^3$ moving grid,...
Black holes of a billion solar masses are observed in the infant Universe few hundred million years after big bang. The direct collapse protogalactic gas clouds primordial haloes with Tvir ≥ 104 K provides most promising way to assemble massive black holes. In this study, we aim determine characteristic mass scale seed and time evolution accretion rates resulting from model. We explore formation supermassive via cosmological large eddy simulations (LES) by employing sink particles following...
Abstract This paper describes the main characteristics of GRIS (GREGOR Infrared Spectrograph), grating spectrograph installed in recently inaugurated (May 2012) 1.5‐meter GREGOR telescope located at Observatorio del Teide Tenerife. The has a standard Czerny‐Turner configuration with parabolic collimator and camera mirrors that belong to same conic surface. Although nothing prevents its use visible wavelengths, will be initially used combination infrared detector Tenerife Polarimeter (TIP‐II)...
Abstract The 4‐m aperture Daniel K. Inouye Solar Telescope (DKIST) formerly known as the Advanced Technology (ATST) is currently under construction on Haleakalā (Maui, Hawai'i) projected to start operations in 2019. At time of completion, DKIST will be largest ground‐based solar telescope providing unprecedented resolution and photon collecting power. equipped with a set first‐light facility‐class instruments offering unique imaging, spectroscopic spectropolarimetric observing opportunities...
published or not.The documents may come from teaching and research institutions in France abroad, public private centers.L'archive ouverte pluridisciplinaire
Helium single ionization by 3.6 me V/u ${\mathrm{Ni}}^{24+}$ impact was explored in a kinematically complete experiment combining high-resolution recoil-ion momentum spectrometer with novel $4\ensuremath{\pi}$ low-energy electron analyzer. More than 90% of the "soft electrons" (${E}_{e}\ensuremath{\lesssim}50$ eV) are ejected forward direction agreement classical-trajectory Monte Carlo predictions. The longitudinal is not balanced change projectile but mainly backwards recoiling...
Until today, the small size of magnetic elements in quiet Sun areas has required application indirect methods, such as line-ratio technique or multi-component inversions, to infer their physical properties. A consistent match observed Stokes profiles could only be obtained by introducing a filling factor that specifies fraction pixel filled with field. Here, we investigate properties patch IMaX magnetograph on board balloon-borne telescope Sunrise unprecedented spatial resolution and low...
We characterize the observational properties of convectively driven vortex flows recently discovered on quiet Sun, using magnetograms, Dopplergrams, and images obtained with 1 m balloon-borne Sunrise telescope. By visual inspection time series, we find some 3.1 × 10−3 vortices Mm−2 minute−1, which is a factor ∼1.7 larger than previous estimates. The mean duration individual events turns out to be 7.9 minutes, standard deviation 3.2 minutes. In addition, several appearing at same locations...
Aims. We investigate the interplay between ionization radiation from massive stars and turbulence inside surrounding molecular gas using three-dimensional (3D) numerical simulations.