Browsing Naturwissenschaften, Mathematik und Informatik by Referee "Tilgner, Andreas Prof. Dr."
Now showing items 1-20 of 54
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Iterative helioseismic holography
(2024-08-28)The understanding of the solar interior, in particular the subsurface solar flows, is im- portant for understanding the solar activity cycle. Traditional local helioseismology does not use all the seismic information ... -
Global-Scale Rossby Waves on Stars
(2024-07-17)Rossby waves (r-modes) arise due to the conservation of absolute vorticity on rotating spheres. The waves govern the large-scale dynamics of the Earth's atmosphere/oceans and have been intensively studied during decades. ... -
Investigations of the solar dynamo within the framework of the Babcock-Leighton mechanism
(2024-06-13)Sunspots are dark blemishes on the surface of the Sun whose number waxes and wanes over the course of approximately eleven years. This solar cycle is believed to be powered by a hydromagnetic dynamo, whereby the interaction ... -
Understanding heat transport processes in shallow subground resulting from external and internal impacts
(2024-01-18)Heat conduction in the subsurface environment is the result of internal and external impacts and is governed by different forces in the short and long term. Externally, this phenomenon is related to daily temperature ... -
Numerical Modelling of Zonal Winds on Gas Giants
(2023-12-22)The outer regions of both Jupiter and Saturn host strong, alternately eastward and westward zonal winds. These are essentially steady in time and cover all latitudes, albeit diminished in amplitude at the mid-to-high ... -
Experimentelle Untersuchung von thermohalinen Treppen in doppelt-diffusiver Konvektion
(2023-01-12)This study deals with the modeling of a laboratory experiment where steady states as well as transients of double diffusive staircases can be observed by Particle Image Velocimetry (PIV) in a fluid layer. A stabilizing ... -
Proton Beam Writing
(2022-12-16)Proton beam writing (PBW) is a mask-less 3D structuring method that uses a focused, relatively high energy Proton beam, followed by an etching step to create free standing 2D and 3D structures in a large variety of target ... -
Physical modeling of motile and sedimenting plankton: from simple flows to turbulence
(2022-11-22)Planktonic microorganisms play a fundamental role in oceanic ecology and chemical cycles. Different planktonic species are found at various levels of the oceanic trophic chain, ranging from photosynthetic organisms to ... -
Theory of solar oscillations in the inertial frequency range
(2022-11-16)Recent observations have revealed that we lack a fundamental understanding of the large scale (with spherical harmonic degrees $l < 60$) flows in the Sun. Flows at these large scales are strongly influenced by rotation. ... -
Solar surface flows during active region emergence
(2022-06-16)The aim of this thesis is to improve our understanding of the emergence of magnetic flux in the form of active regions (ARs) to the solar surface. Active regions are concentrations of strong magnetic field at the surface ... -
Thermal Convection: Differential heating, travelling thermal waves and turbulent superstructures
(2022-05-30)Turbulent thermal convection is ubiquitous in geophysical, astrophysical, and industrial applications. In the present work, various phenomena in the convective paradigm systems of horizontal convection and Rayleigh-Bénard ... -
Experimental investigation of a sheared thermally unstable boundary layer
(2021-07-02)In many natural and industrial systems, heat is transported by mixed convection, where an externally driven flow causes advection of the temperature field in addition to the fluid motion due to buoyancy of differentially ... -
Modelling the corona of stars more active than the Sun using 3D MHD simulations
(2021-06-10)Cool stars like our Sun are surrounded by coronae with temperatures up to several million Kelvin. After decades of research, there has been no definite explanation as to why the coronae of stars are several orders of ... -
Observations of large-scale solar flows
(2021-04-13)In this dissertation, several components of large-scale solar flows are studied observationally: solar equatorial Rossby waves (waves of radial vorticity), large-scale convection, and surface flows around active regions. ... -
Effective Description of Superstructures in Turbulent Convection
(2021-03-04)This thesis is dedicated to the study of turbulent superstructures in Rayleigh-Bénard convection. Turbulent superstructures are horizontally extended large-scale flow patterns that emerge despite the presence of strong ... -
Superstructures, heat and momentum transport in inclined turbulent thermal convection of low-Prandtl-number fluids
(2020-09-24)Recent experiments by Vasil’ev et al. (2015a) using liquid sodium as working fluid inside an extremely slender Rayleigh-Bénard convection (RBC) cell of the diameter-to-height aspect ratio Γ = 1/20, which was inclined ... -
Probing Light-Matter Interactions in Plasmonic Nanotips
(2020-09-03)The exploration of light-matter interaction has inspired some of the most essential theories and applications in fundamental science and technology. Cutting-edge research, such as ultrafast time-resolved and super-resolution ... -
Analysis of Space Weather Impacts on the Terrestrial Ionosphere and Development and Testing of a Coronagraph for Space Weather Forecasts
(2020-07-22)The ionosphere is a conductive layer of the Earth's atmosphere, characterised by the presence of free electrons. Through interaction with electromagnetic waves, it influences a wide spectrum of radio wave communications, ... -
Global magneto-convection models of stars with varying rotation rate
(2020-06-12)The solar magnetic field is mostly axisymmetric at the largest scale. Latitudinal dynamo waves propagate from mid-latitudes towards the equator, as can be seen, for example, from sunspot observations. Reproducing this ... -
Preferential flow dynamics in the vadose zone of fractured and fractured-porous media: Development of a parallelized multi-scale Smoothed Particle Hydrodynamics model
(2020-03-23)The main objective of this thesis is the development of a smoothed particle hydrodynamics (SPH) model to study preferential flow dynamics in partially saturated porous-fractured media at core- and micro scale. The research ...