ELFT HÍRADÓ

[uhlar AT konkoly.hu (Karola_Uhlar)]

                                Meghívó
        az  MTA Konkoly Thege Miklós Csillagászati Kutatóintézete 
                             szemináriumára

Elõadók: Petrovay Kristóf, Tian Chunlin (Eötvös University, Department of 
Astronomy, Budapest)

Cím: The morphology of convection and magnetoconvection in solar and 
stellar envelopes

Kivonat: 
The talk presents the current status of our understanding of the 
geometrical structure of compressible convection in the Sun and stars. In 
the simplest case of nonmagnetic convection in a chemically homogeneous 
layer this problem was basically solved 20 years ago and recent work only 
focused on a better understanding of intermittency and fine structures. In 
the understanding of semiconvection a breakthrough has recently been made 
by H.C. Spruit et al. in Garching. The study of magnetoconvection is the 
subject of ongoing research, realistic simulations being developed in the 
MPI Lindau while idealized experimental setups have been studied by Weiss 
et al. in Cambridge and recently by our group in Budapest. A common 
feature of semiconvection and magnetoconvection is the importance of 
subcritical onset of convective transport, making considerations based on 
linear stability theory irrelevant for the nonlinear problem. Our most 
recent simulations, however, indicate that in the strong field case this 
subcritical mode has a structure corresponding more closely to the 
so-called "convectons" of nonlinear analytic theory than to the structure 
previously found by Weiss et al. The relation of small scale structure 
observed in sunspots, such as umbral dots and light bridges, to the 
structures seen in the simulations is discussed.

Az elõadás idõpontja: 2011.  május 25., szerda  14 óra 

Helye: MTA KTM CSKI elõadóterme 
Budapest, XII., Konkoly Thege M. út 15-17.