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Polarized Radiative Transfer in Solar Atmosphere
Štěpán, Jiří ; Heinzel, Petr (advisor) ; Degĺ Innocenti, Egidio Landi (referee) ; Bueno, Javier Trujillo (referee)
The adequate theoretical models of the NLTE radiative transfer are needed for interpretation of the complicated spectra emerging from the magnetized solar atmosphere. In the first part of the thesis, the quantum theory of polarization is reviewed along with the problem of NLTE radiative transfer of the 2nd kind. A general notation for a numerical treatment of the atomic density matrix is introduced. A lambda-operator splitting technique is presented and used for development of a novel preconditioning method analogous to the Jacobi iteration algorithm. Number of processes is taken into account: atomic polarization, level-crossings, Paschen-Back effect, Hanle and Zeeman effects, optical pumping, collisional (de)polarization. A nonlinear multigrid technique is developed in the framework of polarized radiative transfer theory and the eficiency of the method is discussed. The potential of this new solver is demonstrated on an example of transfer of the optically thick line of a multiterm atom in the Paschen-Back effect regime. In the second part of the thesis, the particular problem of impact polarization of the hydrogen H-alpha line in solar flares is considered. The semi-empirical models of the flaring chromosphere are used to find the differential effects of the proton beam on the line intensity and linear...
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Spectral analysis of flares on AD Leo
Wollmann, Jiří ; Heinzel, Petr (advisor) ; Korčáková, Daniela (referee)
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
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Study of white-light flares
Mravcová, Lucia ; Švanda, Michal (advisor) ; Heinzel, Petr (referee)
Solar flares are a relatively common and strong demonstration of the solar ac- tivity and are observable throughout the whole electromagnetic spectrum. Some- times, solar flares are also accompanied with an emission in white-light contin- uum, then we speak of white-light flares. The origin of white-light flares is not entirely understood up to this day. The detection of white-light flares can be difficult, therefore we developed a program for automatic detection of white-light flares in SDO/HMI observations. After that, we studied properties of the detected white-light flares. Our work implies that there are two types of white-light flares depending on an X-ray flux of a solar flare. The difference between these two groups can be caused by a different behaviour of the magnetic field in the neigh- bourhood of the detected white-light flares. Our discovery could help in a better understanding of the origin of white-light flares. 1
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Polarized Radiative Transfer in Solar Atmosphere
Štěpán, Jiří ; Heinzel, Petr (advisor) ; Degĺ Innocenti, Egidio Landi (referee) ; Bueno, Javier Trujillo (referee)
The adequate theoretical models of the NLTE radiative transfer are needed for interpretation of the complicated spectra emerging from the magnetized solar atmosphere. In the first part of the thesis, the quantum theory of polarization is reviewed along with the problem of NLTE radiative transfer of the 2nd kind. A general notation for a numerical treatment of the atomic density matrix is introduced. A lambda-operator splitting technique is presented and used for development of a novel preconditioning method analogous to the Jacobi iteration algorithm. Number of processes is taken into account: atomic polarization, level-crossings, Paschen-Back effect, Hanle and Zeeman effects, optical pumping, collisional (de)polarization. A nonlinear multigrid technique is developed in the framework of polarized radiative transfer theory and the eficiency of the method is discussed. The potential of this new solver is demonstrated on an example of transfer of the optically thick line of a multiterm atom in the Paschen-Back effect regime. In the second part of the thesis, the particular problem of impact polarization of the hydrogen H-alpha line in solar flares is considered. The semi-empirical models of the flaring chromosphere are used to find the differential effects of the proton beam on the line intensity and linear...
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