Numerical Modelling of Stellar Pulsations in 2D and 3D
Gábor Kovács (ELTE and Konkoly Observatory, Hungary)
Since the first electronic computers became available, astronomers have applied them to model the structure and dynamics of stars. The first attempts neglected convection and turbulence, considering only radiative energy transport. However, it turned out soon that we could not adequately describe pulsation without convection. Moreover, the different improved forms of static mixing length theory were also inadequate. Hence massive research was started to create a time-dependent theory that can describe convection correctly in a one-dimensional approximation. These efforts unfolded some hidden features of phenomena but could not answer all of the questions raised. Since convection and non-radial pulsation are genuinely multi-dimensional phenomena, multi-D models seem inevitable, but this approach requires high computational performance, which was not available decades ago. In addition, the multi-dimensional treatment of the problems allows us to directly study the interaction between convection and pulsation. Besides this advantage, we can also test and calibrate our 1D approaches and understand the connected physical transport processes more deeply and precisely. In the seminar, we will compare two extensively used 1D pulsation models and a multi-dimensional one in detail in case of classical pulsating variable stars. We show two approaches to calibrate our 1D models. Firstly, we calibrate the models to the observational constraints to have our best possible parameter set. Secondly, we can test these 1D systems by the multi-dimensional models, finding out whether the usual conventions of time dependent mixing length theory are valid or not. These calibrations and tests will help us to understand better the multidimensional nature of complex physical phenomena, and also to fully exploit the large amount of photometric and spectroscopic data coming from ongoing and planned large sky surveys.