Seminář o aktuálních problémech v oblasti geodynamického výzkumu zemského nitra.

Letní semestr / Summer term 2019/20

26. 2. Kateřina Sládková
Slapové procházky na Europě
4. 3. Strouhalovská přednáška
11. 3. Jakub Velímský, Magnus D. Hammer and Christopher C. Finlay
The magnetic signatures of oceanic tides in satellite data: A virtual-observatory approach
The magnetic signatures of the M2, and more recently also the N2, and O1 oceanic tides have been successfully extracted from satellite observations (Grayver & Olsen, 2019). The traditional method uses the spatial representation of the tidal signals by spherical harmonics. Here we present an alternative approach based on the concept of virtual observatories, motivated by similar development in the analysis of the core field (Mandea & Olsen 2006). All quiet-time, night-side vector magnetic field values observed by the satellite(s) in the proximity of a selected virtual observatory are parameterized by a scalar magnetic potential represented by a cubic harmonic polynomial in a local Cartesian coordin ate system. The time-dependence of the polynomial coefficients is constrained by selected tidal frequency, taking into account also the phase and amplitude corrections. The local approach offers several advantages over the use of the global spherical-harmonic base. The disturbances from external field in the polar areas have no impact on the inversion at lower latitudes, and local error estimates can be also provided. In this initial report, we will explore the possibilities of the new technique in terms of resolution, the combination of datasets from multiple satellites and the use of NS and EW field differences from the Swarm A-C pair.
18. 3. Marie Běhounková
25. 3. Tomáš Roubíček
Fully convective models of some processes in the Earth
First, a model of poro-elastodynamics with inelastic strains and with convection/diffusion of water will be formulated fully in the Eulerian setting. There, concepts of gradient of the total strain rate as well as the additive splitting of the total strain rate are used, eliminating the displacement from the formulation. It relies on that the elastic strain is small while the inelastic and the total strains can be large. Also damage/aging can be added to make it capable for earthquakes modelling. One can derive the energetics behind this model, which can further allow for rigorous mathematical analysis as far as for numerically stable and convergent approximation schemes. In some aspects, it improves a mo del of V. Lyakhovsky at al. to make it thermodynamically consistent and amenable for analysis. Coupling with the fluidic parts of the Earth is also possible while using the concept of elastic (so-called semi-compressible) fluids. Also magnetic phenomena will be discussed both in the solid and the fluidic parts, i.e. paleomagnetism and Earth dynamo, respectively. Anisothermal thermodynamically consistent enhancement allows also for solid/liquid phase transformations, possibly relevant for modelling of icy planets or moons. The talk reflects a collaboration with Giuseppe Tomassetti (Univ. Roma Tre).
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Semináře se konají v přednáškové místnosti katedry v Troji o středách od 13:10.