Solar flares are common and strong demonstrations of solar activity. They are observable throughout the whole electromagnetic spectrum. If they show a broadband emission in the visible continuum, then we speak of white-light flares. The origin of white-light flares is not fully understood. We detected 24 white-light flares in SDO/HMI data and analyzed them using SDO/AIA wavelength bands at 1 700 ̊A and 304 ̊A and GONG Hα observations. According to our work, the emission in the 1 700 ̊A band is similar to the white-light emission but usually starts sooner. The positions of intensity enhancements in the 1 700 ̊A band are similar to the positions of the white-light flares and are connected by ribbons visible in the 304 ̊A band and in the Hα line. Then we studied the decay time of white-light flares and found that for most of the white-light flare points the typical decay time ranges in 2 - 3 min. 1

Solar flare is a process which releases magnetic energy stored in the solar corona due to the effect of magnetic reconnection. Similar activity has been observed on other stellar types, namely type K and M stars, which usually have vast and strong magnetic field. Often during flares on M stars we observe asymmetry of profiles of some spectral lines with enhanced red wing. The cause of these asymmetries is not well understood. The aim of this thesis is to analyse spectra of AD Leo, which is frequently flaring dMe star, and to model radiation of the Hα line coming from flare loops analogically to flare loops on the Sun. The light curves of selected spectral lines rise sharply during initial phases of flares and gradually fall back to preflare state. The light curves of continua surrounding these selected spectral lines rise sharply in the blue part of the spectrum during flares. The continua in the red part exhibit only small rise. Simulations of Hα radiation coming from flare loops yield asymmetric profiles with highly enhanced red wings. 1

Reconstruction of volcanic processes in the Komárov Complex: case from the Zaječov volcanic centre Summary Sheet lava flows with pillow breccias and hyaloclastites are interbedded agglomerate and volcaniclastics. This is the basic interpretation of rocks exposed in quarry near the town Zaječov. Rocks are part of geological area called Barrandien. Resediment volcaniclastic particles were transfer by sediment gravity flows. Agglomerates were deposited from volcaniclastic debris flow and fine grain volcanoclastics sediments from turbidity currents or hyperconcentrated flows. These types of flows named as eruption-fed aqueous density current are directly initiated by subaqueous volcanic eruption. One volcaniclastics strata set on the south wall of quarry was formed from subaquatic eruption plume, called steam copula. Steam copula created under the eruptive vent is water exclusion zone. Accretion lapilli can be formed in this zone if the copula is stable for a longer time. Accretion lapilli were generally considered to be able to form only in subaerial conditions, during the phreatomagmatic eruption till lately. Rocks exposed in quarry were probably formed during the Surtseyan eruption in shallow subaqueous setting. According to thin section lava flows are containing pseudomorphosis phenocrysts of olivine and...

We present a unique design of a post-focal instrument suitable to detect fast changes of flux in waveband 350 - 440 nm. As it is not possible to measure the Sun as a star because of a strong background radiation in this waveband and using a thin slit makes it impossible to measure the whole flaring area we made a set of circular diaphragms of different sizes able to collect light only from a limited part of the Sun's atmosphere. For our data we also evolved new software technique based on statistical methods that even more increases a sensitivity on any changes in spectra. First results of observations of three X-class solar flares obtained in June 2014 proved significant increase of flux in Balmer continuum. One of these flares was measured from 20 minutes before a peak in SXR (GOES) so we were able to compare a whole impulsive phase with a state with no signs of a flare before it. Data suggest a radiation at Balmer limit (364,5 nm) of up to 5,5 stronger from flaring kernels compared to the quiet Sun. Powered by TCPDF (www.tcpdf.org)

Solar flares and eruptions are manifestations of violent releases of magnetic energy from the solar atmosphere. They are powered by magnetic reconnection, a mechanism in which magnetic field lines change their connectivities to reach a lower-energetic state. Theoretical predictions regarding the generalised three-dimensional magnetic reconnection are imposed by the standard flare model in 3D. In this work we present the results of five peer-reviewed publications in which we focused on different predicted aspects of magnetic reconnection in 3D. We analyse evolution and morphology of seven eruptive flares, primarily using observations of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. In the first publication, (Lörinčík et al., 2019a), we interpreted variations of velocities of slipping flare kernels using the mapping norm of field line connectivity simulated via the model. In Lörinčík et al. (2019b) we showed that the observed conversion of filament strands to flare loops is a signature of the 'ar-rf' reconnection geometry between erupting flux rope and overlying coronal arcades. In another observation (Dudík, Lörinčík et al. (2019)), all constituents of this geometry were successfully identified together with the constituents of the 'rr-rf' geometry between two...

This thesis examines Late Minoan Settlements in Crete that were destroyed or abandoned due to the consequences of the Santorini volcano eruption. A summary of geological history of Crete, Thera and the surrounding area is given in the first part. The next chapter sums up the research in the fields of relative and mainly absolute chronology, of which scientists have not yet been able to provide a convincing calendar date for the eruption of the volcano nor a possible fixed absolute chronology of the general Later Bronze Age not only in the Aegean. The development of the Santorini Volcano eruption in the Late Minoan IA period (LM IA) is described. According to the research, this eruption must have caused earthquakes and tsunamis. The possible impact on the near island of Crete, its inhabitants and settlements, mainly in the coastal area of north-northeast part of the island, is also discussed.

This master's thesis deals with the issue of volcanic ash as a complex and its impact on aviation, including the volcanic activity itself (conditions for its existence, for existence of eruptions and their basic products). In addition, the thesis also deals with effect of volcanic ash on aircraft and airports, possibilities of its detection or monitoring as well as mechanism of its spreading in airspace. The emphasis is laid mainly on air incidents related to volcanic ash and on danger it poses to the airspace of the Czech Republic.