Pravidelné semináře pořádáme jednou měsíčně (říjen–červen, zpravidla první pondělí v měsíci) od 13 hod v seminární místnosti pracoviště Ondřejov. (archiv seminářů)
05. 12. 2011
Validated helioseismic inversions for 3-D vector flows: Applications to SDO data
Abstract: Helioseismic tomography is currently the only one method, which
allows as to "see" beneath the solar photosphere. Various methods utilising
the analysis of the surface waves carrying the information about the
subphotospheric plasma were developed in the last few decades. We improved and
validated travel-time inversions for 3-D vector flows. The main improvement
comes from the explicit minimization of the cross-talk between the three flow
components. The validation was performed using synthetic travel-time maps
obtained by convolving a known flow field from a realistic numerical simulation
of solar convection with travel-time sensitivity kernels computed in the Born
approximation. Realistic noise is added to the travel times. The inversion of
synthetic travel-times returns unbiased answers for horizontal flow velocities
in layers shallower than 4 Mm. We also show that the vertical component of
velocity near the surface can only be inferred under the explicit condition
that the cross-talk between the flow components is minimized. A preliminary
application to SDO/HMI quiet-Sun data is presented.
Dále pořádáme menší semináře jednotlivých oddělení:
Semináře slunečního oddělení
Každé úterý v 12:45 (září–červen, s výjimkou úterků po celoústavním semináři) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
06/12/2011, 13:00IAAMagnetic Bright Points: characteristics over longitude, latitude and timeAbstract: The solar activity cycle is strongly related and rooted to photospheric magnetic fields. Up to the present it was mostly or even solely studied by extended fields such as sunspots, sunspot groups or active regions. Interestingly the domain of magnetic fields on the Sun is not only limited to extended and strong magnetic fields but reaches down to small elements like single flux tubes. These flux elements can be identified in G-band filtergrams as so called magnetic bright points (MBPs). In this talk we want to address such small scale fields and investigate their behaviour with longitude and latitude on the solar disc as well as the temporal evolution of such fields and their characteristic parameters. Especially we are interested in changes over longer time periods (years). Such changes may be related to the solar activity cycle and hence help us to better understand and constrain the solar dynamo in the future.
Zářivě-(magneto)hydrodynamické semináře
Zpravidla 1x za 14 dní ve čtvrtek od 11 hod (říjen–červen) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
01/12/2011, 11:00Konkoly Observatory, Budapest, HungaryThe extreme outburst of the young eruptive star EX Lupi in 2008Abstract: EX Lupi is the prototype of EXors, a spectacular group of low-mass pre-main sequence stars characterized by repetitive optical outbursts of 1-5 mag lasting for a few months-to-few years. The outburst is attributed to enhanced accretion from the inner circumstellar disk (within ^X0.1AU) to the stellar surface, probably triggered by an instability in the disk. The historically largest outburst of EX Lupi in 2008 Jan-Sep offered a unique opportunity to understand deeper the physics of the EXor eruptions. In my talk I will summarize the main results of our coordinated observing campaign, in which we used a large set of telescopes to observe and characterize the path of accretion from the disk onto the stellar surface, with the aim of comparing the different models of outburst physics. Our measurements also demonstrated that the brief episodes of highly increased accretion, apart from contributing to the build-up of the final stellar mass, have substantial effect on the structure and composition of the circumstellar material: We discovered episodic crystallization of silicate grains in the disk surface due to the increased luminosity during the 2008 outburst, resulting in material that forms the building blocks of comets and planets.
Semináře oddělení GPS
Zpravidla v knihovně pracoviště Praha–Spořilov v různé dny.
V nejbližší době nejsou plánovány žádné semináře.