Editorial

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Spontaneous current-layer fragmentation and cascading reconnection in solar flares: II. Relation to observations

In the paper by B\'arta et al. (arXive:astro-ph:/1011.4035, 2010) the authors addressed some open questions of the CSHKP scenario of solar flares by means of high-resolution MHD simulations. They focused, in particular, on the problem of energy transfer from large to small scales in decaying flare current sheet (CS). Their calculations suggest, that magnetic flux-ropes (plasmoids) are formed in full range of scales by a cascade of tearing and coalescence processes. Consequently, the initially thick current layer becomes highly fragmented. Thus, the tearing and coalescence cascade can cause an effective energy transfer across the scales. In the current paper we investigate whether this mechanism actually applies in solar flares. We extend the MHD simulation by deriving model-specific features that can be looked for in observations. The results of the underlying MHD model showed that the plasmoid cascade creates a specific hierarchical distribution of non-ideal/acceleration regions embedded in the CS. We therefore focus on the features associated with the fluxes of energetic particles, in particular on the structure and dynamics of emission regions in flare ribbons. We assume that the structure and dynamics of diffusion regions embedded in the CS imprint themselves into structure and dynamics of flare-ribbon kernels by means of magnetic-field mapping. Using the results of the underlying MHD simulation we derive the expected structure of ribbon emission and we extract selected statistical properties of the modelled bright kernels. Comparing the predicted emission and its properties with the observed ones we obtain a good agreement of the two.Comment: 7 pages, 5 figure

Influence of atmospheric turbulences on the optical beam

Tato práce popisuje optický bezkabelový spoj a jeho využití v komunikačních technologiích. Vymezuje možné rušivé vlivy na přenášený optický signál, mezi něž patří šum signálu, útlum atmosféry a atmosférické turbulence. Práce se podrobně zaměřuje na vliv atmosférických turbulencí na optický svazek. Ke zjištění tohoto vlivu bylo provedeno měření fluktuací optické intenzity a fluktuací teploty v optickém svazku. Z naměřených hodnot byl vypočten strukturní parametr indexu lomu a pomocí něho zjištěna míra turbulence.The aim of this thesis is to study a free space optics and its application in communication technologies. It describes possible interrupting impacts on the beamed optical signal, which are signal noise, attenuation of the atmosphere and atmospheric turbulence. The basis of the thesis is to describe the impact of the atmospheric turbulences on the optical beam. Fluctuation of optical intensity in the optical beam has been measured and index of refraction structure parameter calculated. With its assistance, turbulence rate has been determined.

Teorie a interpretace slunečních decimetrových radiových vzplanutí

Teorie a interpretace slunečních decimetrových radiových vzplanutí (doktorská disertace) Miroslav Bárta 2002 Abstrakt Radiové záření Slunce představuje významný zdroj přímých informací o mnoha fyzikálních procesech spojených s urychlováním částic ve sluneční atmosféře. Zejména radiová vzplanutí - intenzivní a velmi proměnlivá složka slunečního radiového záření - v sobě nese otisk fyzikálních vlastností zdroje a procesů spjatých s prvotním uvolněním energie ve slunečních erupcích. Decimetrová (dm) radiová vzplanutí a jejich studium pak nepochybně poskytují nejvíce bezprostřední pozorovatelský vhled do oblasti magnetické rekonexe a oblastí urychlování částic. Na druhou stranu, vyzařovací mechanismy slunečních dm vzplanutí jsou typicky netermální a zahrnují mnoho mikroskopických (kinetických) plazmových nestabilit a transformací plazmových vlnových modů. Nelinearita procesů plazmové radiové emise pak přináší zvýšené nároky na správnou interpretaci pozorovaných vzplanutí a na nalezení vztahů mezi pozorovanými veličinami (např. radiový tok, frekvenční emisní profil a jeho časový vývoj) a fyzikálními vlastnostmi a procesy ve zdroji. Tato disertace cílí na dva specifické okruhy ve výzkumu slunečních radiových vzplanutí a jejich aplikace na diagnostiku erupčního plazmatu: (1) Fyzikální interpretaci dvou...Theory and Interpretation of Solar Decimetric Radio Bursts (doctoral thesis) Miroslav Bárta 2002 Abstract Solar radio emission represents an important source of direct information about many physical processes related to particle acceleration in the solar atmosphere. Namely, the radio bursts - intense and highly variable component of solar radio radiation - bear many signatures of underlying physics related to primary energy release in solar flares and eruptions. Indeed, decimetric (dm) radio bursts and their careful analysis provide the closest observational insight into the region of magnetic reconnection and the particle acceleration sites. On the other hand, emission mechanisms of solar dm radio bursts are typically non-thermal, involving various plasma micro-instabilities and wave-mode transformations. High non-linearity of the radio emission process thus put strong demands on correct physical interpretation of the observed bursts and on finding the relations between observed features (e.g., intensity, frequency profile and its dynamics) and underlying physics. This doctoral thesis addresses two particular areas of research in the solar radio bursts and their utilization in the flare plasma diagnostics: (1) Physical interpretation of two particular classes of radio bursts related to solar flares, and,...Faculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Optimization design of back injection molds, for stability of the process and elimination optical defects of parts

52 s. :obr., tab., grafy +CD ROMBakalářská práce se zabývá analýzou problematických forem zadního vstřikování a dekorů. Navrhuje možnosti řešení dané problematiky, pro eliminaci optických vad, aplikuje vybrané řešení do forem, vyhodnocuje přínosy

Preferential acceleration of heavy ions in magnetic reconnection: Hybrid-kinetic simulations with electron inertia

Solar energetic particles (SEPs) in the energy range 10s KeV/nucleon - 100s MeV/nucleon originate from Sun. Their high flux near Earth may damage the space borne electronics and generate secondary radiations harmful for the life on Earth and thus understanding their energization on Sun is important for space weather prediction. Impulsive (or ${}^{3}$He-rich) SEP events are associated with the acceleration of charge particles in solar flares by magnetic reconnection and related processes. The preferential acceleration of heavy ions and the extra-ordinary abundance enhancement of ${}^3$He in the impulsive SEP events are not understood yet. In this paper, we study ion acceleration in magnetic reconnection by two dimensional hybrid-kinetic plasma simulations (kinetic ions and inertial electron fluid). All the ions species are treated self-consistently in our simulations. We find that heavy ions are preferentially accelerated to energies many times larger than their initial thermal energies by a variety of acceleration mechanisms operating in reconnection. Most efficient acceleration takes place in the flux pileup regions of magnetic reconnection. Heavy ions with sufficiently small values of charge to mass ratio ($Q/M$) can be accelerated by pickup mechanism in outflow regions even before any magnetic flux is piled up. The energy spectra of heavy ions develop a shoulder like region, a non-thermal feature, as a result of the acceleration. The spectral index of the power law fit to the shoulder region of the spectra varies approximately as $(Q/M)^{-0.64}$. Abundance enhancement factor, defined as number of particles above a threshold energy normalized to total number of particles, scales as $(Q/M)^{-\alpha}$ where $\alpha$ increases with the energy threshold. We discuss our simulation results in the light of the SEP observations.Comment: Submitte

New geodetic control network at Czech concession at Abusir

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Tomb at Abusir South from a time of change belonging to Ankhires, inspector of hairdressers of the Great House (AS 98)

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ALMA as a prominence thermometer: First observations

We present first prominence observations obtained with ALMA in Band 3 at the wavelength of 3 mm. High-resolution observations have been coaligned with the MSDP H$\alpha$ data from Wroclaw-Bialk\'{o}w large coronagraph at similar spatial resolution. We analyze one particular co-temporal snapshot, first calibrating both ALMA and MSDP data and then demonstrating a reasonable correlation between both. In particular we can see quite similar fine-structure patterns in both ALMA brightness temperature maps and MSDP maps of H$\alpha$ intensities. Using ALMA we intend to derive the prominence kinetic temperatures. However, having current observations only in one band, we use an independent diagnostic constraint which is the H$\alpha$ line integrated intensity. We develop an inversion code and show that it can provide realistic temperatures for brighter parts of the prominence where one gets a unique solution, while within faint structures such inversion is ill conditioned. In brighter parts ALMA serves as a prominence thermometer, provided that the optical thickness in Band 3 is large enough. In order to find a relation between brightness and kinetic temperatures for a given observed H$\alpha$ intensity, we constructed an extended grid of non-LTE prominence models covering a broad range of prominence parameters. We also show the effect of the plane-of-sky filling factor on our results.Comment: 9 pages, 3 figures, accepted for publication in the The Astrophysical Journal Letter