| dc.contributor.advisor | Gizon, Laurent Prof. Dr. | |
| dc.contributor.author | Albekioni, Mariam | |
| dc.date.accessioned | 2024-07-17T08:39:59Z | |
| dc.date.available | 2024-07-24T00:50:07Z | |
| dc.date.issued | 2024-07-17 | |
| dc.identifier.uri | http://resolver.sub.uni-goettingen.de/purl?ediss-11858/15372 | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-10574 | |
| dc.format.extent | 93 | de |
| dc.language.iso | eng | de |
| dc.rights.uri | http://creativecommons.org/licenses/by/4.0/ | |
| dc.subject.ddc | 530 | de |
| dc.title | Global-Scale Rossby Waves on Stars | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Tilgner, Andreas Prof. Dr. | |
| dc.date.examination | 2024-05-21 | de |
| dc.subject.gok | Physik (PPN621336750) | de |
| dc.description.abstracteng | 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. Recent discovery of the waves on the Sun and other stars revived the interest towards theoretical investigation of the wave properties in different astrophysical situations. This thesis aims to study the dynamics of the Rossby waves in solar/stellar interiors.
The influence of the latitudinal differential rotation and viscosity on the Rossby waves was studied using 2-dimensional beta-plane approximation on the Sun. Our results showed that the velocity eigenfunctions have a singularity at the critical latitude where the phase speed of the Rossby wave equals with the latitudinal differential rotation. Without viscosity, the eigenvalues are real and continuous, while they become discrete and complex in the presence of viscosity. For Reynolds number of $\sim$ 300, the attenuation and the real part of eigenfunctions are in qualitative agreement with the solar observations. Each longitudinal wavenumber is associated with a latitudinally symmetric Rossby mode trapped at low latitudes by solar differential rotation. In the viscous model, Rossby modes transport significant angular momentum from the dissipation layers toward the equator.
We also studied the Rossby waves in the interiors of uniformly rotating stars with radiative envelopes in the presence of the vertical stratification of the temperature. The initial 3-dimensional linear hydrodynamic equations were separated into vertical and horizontal parts using traditional approximation with a separation constant, which actually is the equivalent depth of the Rossby waves. The vertical structure of the Rossby waves was found to be governed by the Bessel functions and strongly dependent on the vertical temperature gradient. Surface boundary conditions allowed us to obtain the discrete values of the equivalent depth, which correspond to the discrete vertical modes. It is found that the vertical modes are concentrated in the near-surface layer with a thickness of several tens of surface density scale height. Then the obtained equivalent depth was used to solve the horizontal structure equations and the corresponding dispersion relations for Rossby, Rossby-gravity, and inertia-gravity waves were obtained. The solutions were found to be confined around the equator leading to the equatorially trapped waves. It was shown that the wave frequency depends on the vertical temperature gradient as well as on the stellar rotation. Therefore, observations of wave frequency in light curves of stars with known parameters (radius, surface gravity, rotation period) could be used to estimate the temperature gradient in stellar outer layers. Consequently, the Rossby mode may be considered as an additional tool in asteroseismology apart from acoustic and gravity modes. | de |
| dc.contributor.coReferee | Hanslmeier, Arnold Prof. Dr. | |
| dc.subject.eng | Astrophysics - Solar and Stellar Astrophysics | de |
| dc.subject.eng | stars: interiors | de |
| dc.subject.eng | stars: oscillations | de |
| dc.subject.eng | stars: rotation | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-ediss-15372-8 | |
| dc.affiliation.institute | Fakultät für Physik | de |
| dc.description.embargoed | 2024-07-24 | de |
| dc.identifier.ppn | 1895791286 | |
| dc.notes.confirmationsent | Confirmation sent 2024-07-17T08:45:01 | de |