The 2008 August 1 Eclipse Solar-Minimum Corona Unraveled

We discuss results stemming from observations of the white-light and [Fe XIV] emission corona during the total eclipse of the Sun of 2008 August 1, in Mongolia (Altaj region) and in Russia (Akademgorodok, Novosibirsk, Siberia). Corresponding to the current extreme solar minimum, the white-light corona, visible up to 20 solar radii, was of a transient type with well-pronounced helmet streamers situated above a chain of prominences at position angles 48, 130, 241 and 322 degrees. A variety of coronal holes, filled with a number of thin polar plumes, were seen around the poles. Furthering an original method of image processing, stars up to 12 magnitude, a Kreutz-group comet (C/2008 O1), and a coronal mass ejection (CME) were also detected, with the smallest resolvable structures being of, and at some places even less than, 1 arcsec. Differences, presumably motions, in the corona and prominences are seen even with the 19-min time difference between our sites. In addition to the high-resolution coronal images, which show the continuum corona (K-corona) that results from electron scattering of photospheric light, images of the overlapping green-emission-line (530.3 nm, [Fe XIV]) corona were obtained with the help of two narrow-passband filters (centered on the line itself and for the continuum in the vicinity of 529.1 nm, respectively), each with FWHM of 0.15 nm. Through solar observations, on whose scheduling and details we consulted, with the Solar and Heliospheric Observatory, Hinode's XRT and SOT, TRACE, and STEREO, as well as Wilcox Solar Observatory and SOHO/MDI magnetograms, we set our eclipse observations in the context of the current unusually low and prolonged solar minimum.Comment: Accepted in The Astrophysical Journal, 6 July 200

Exploration of the altar painting “Sacra Conversazione” by Bernardino Licinio from the church of St. Francis in Krk

Slika Sacra Conversazione Bernardina Licinija iz crkve Sv. Franje Asiškog u Krku izrađena je tehnikom masne tempere na dasci. Velike dimenzije slike u kombinaciji sa smještajem na visini uz teška oštećenja nosioca i slikanih slojeva, zahtijevala su izvođenje konzervatorsko-restauratorskih istraživanja in situ. Tom je prilikom prvi put u Hrvatskoj izvan radionice, na terenu, primijenjena vizualizacija oltarne pale velikog formata računalnom radiografjom. Omogućila je uvid u stanje nosioca i slikanih slojeva, smanjila rizik demontaže i transporta te usmjerila daljnje konzervatorsko-restauratorske radove.The altar pala Sacra Conversazione, by Bernardino Licinio (Venice, 1485/1489–c. 1550), is located on the main altar of the Church of St. Francis in the town of Krk. It was painted in 1531 in tempera grassa on board. In contrast to the later Venetian Sacra Conversazione by the same artist, painted in 1535, the Krk pala is almost completely unknown in professional literature; it is mentioned only in some older literature, with a short iconographic description. Due to the painting’s large dimensions (280x195 cm) and weight, its location high on the main altar, and the significant damage to the painted layers, its wooden base and the support system, the conservation-restoration explorations were carried out in situ, at the church altar. This significantly reduced the possibility of additional damage being incurred during dismantling and transport. The artefact was filmed in the visible, UV and IR parts of the spectrum, and under slanted light. Samples of pigment and binding material were analysed in a laboratory, and the order of layers was established. A particularly interesting phase of the conservation-restoration exploration was the visualization of the artefact by computer radiography. This method, created and developed for medical purposes, is being applied ever more often in restoration for exploring and documenting artefacts. Prior to this occasion, it had not been used in Croatia for in situ explorations. The visualization of the Krk pala by computer radiography made it possible to assess the condition of the original painted layer, wooden base and support system, which is normally hidden by the large wall at the back of the altar. The computer radiography uncovered grave and extensive damage to the painting base and the painted layers, but which can be remedied and reconstructed. Exploratory attempts to remove the “secondary” coats from the surface of the original painted layer suggested that several interventions had already been made on the artefact, two of them rather substantial, and they included reduction of the altar painting’s format. The explorations carried out thus far have provided the basic information on this artefact, which will be supplemented by further restoration procedures, and archival and art-historical research

Statistické ověření modifikovaného Smithova modelu

Pedloená práce se zabývá mechanismem spojité dvojité aukce a modely knihy objednávek. Po struném popisu vybraných model následuje obsáhlejí obezná- mení s obecným modelem spojité dvojité aukce z názvu práce. Následn je uvedena struktura dat z britského trhu a postup jejich zpracování. Na tchto datech je ovována validita Smithova Farmerova modelu a Contova Stoikova modelu v kontextu obecného modelu prostednictvím lineární regrese. v závrené ásti je na základ pedelých výsledk navren vlastní model knihy objednávek a testov ána jeho validita.The present work discuss the continuous double auction mechanisms and the order book models. After a brief introduction to selected models, a general model of the the continuous double auction from the thesis title is described. Further, a structure of british market data is given as well as an approach to them. Based on these data the validity of Smith Farmer's model and Cont Stoikov's model is tested in the context of general model by linear regression. Finally, based on the previous results, the own order book model is suggested and its validity tested.Department of Probability and Mathematical StatisticsKatedra pravděpodobnosti a matematické statistikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Paradoxy v teorii pravděpodobnosti

Táto bakalárska práca sa zaoberá prehl'adom a popisom vybraných pa- radoxov z teórie pravdepodobnosti. Menovite uvedieme paradox Montyho Halla, Bertrandov paradox a Petrohradský paradox. Čitatel' je v každej kapitole najprv oboznámený so zadaním paradoxu a s jeho podstatou. Potom je k uvedenému paradoxu predvedených niekol'ko prístupov k jeho riešeniu. V pôvodnom zadaní Monty Hallovho paradoxu existuje len jedno riešenie, ku ktorému nás privedú dva rôzne postupy. Tento paradox doplníme tiež jednoduchými modifikáciami. Zada- nie Bertrandovho paradoxu je vo svojej podstate nejednoznačné, čo ukážeme na štyroch vybraných prístupoch. Podobná situácia sa vyskytne aj v Petrohradskom paradoxe, ktorý vyriešime tromi vybranými prístupmi. 1The Bachelor's thesis present an overview and description of selected probability theory paradoxes, namely the paradox of Monty Hall, the Bertrand's paradox and the St. Peterburg paradox. In every chapter the reader is at first apprised of the formulation and the essence of the paradox. Then we show some possible solutions of this paradox. In original formulation of Monty Hall paradox there exists just one solution which can be reached by using two different ways. We add also some simple modifications to this particular paradox. The formula- tion of Bertrand's paradox is ambiguous which we show by using four selected approaches. And very similar situation arises in St. Peterburg paradox which we resolve by using three different approaches. 1Department of Probability and Mathematical StatisticsKatedra pravděpodobnosti a matematické statistikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Coronal Fe XIV Emission During the Whole Heliosphere Interval Campaign

Solar Cycle 24 is having a historically long and weak start. Observations of the Fe XIV corona from the Sacramento Peak site of the National Solar Observatory show an abnormal pattern of emission compared to observations of Cycles 21, 22, and 23 from the same instrument. The previous three cycles have shown a strong, rapid "Rush to the Poles" (previously observed in polar crown prominences and earlier coronal observations) in the parameter N(t,l,dt) (average number of Fe XIV emission features per day over dt days at time t and latitude l). Cycle 24 displays a weak, intermittent, and slow "Rush" that is apparent only in the northern hemisphere. If the northern Rush persists at its current rate, evidence from the Rushes in previous cycles indicates that solar maximum will occur in early 2013 or late 2012, at least in the northern hemisphere. At lower latitudes, solar maximum previously occurred when the time maximum of N(t,l,365) reached approximately 20{\deg} latitude. Currently, this parameter is at or below 30{\deg}and decreasing in latitude. Unfortunately, it is difficult at this time to calculate the rate of decrease in N(t,l,365). However, the southern hemisphere could reach 20{\deg} in 2011. Nonetheless, considering the levels of activity so far, there is a possibility that the maximum could be indiscernibleComment: 8 pages, 4 figures; Solar Physics Online First, 2011 http://www.springerlink.com/content/b5kl4040k0626647

Mapping the Distribution of Electron Temperature and Fe Charge States in the Corona with Total Solar Eclipse Observations

The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 August 1 eclipse observations of a number of Fe emission lines yield an empirical value for a distance, which we call Rt , where the emission changes from being collisionally to radiatively dominated. Rt ranges from 1.1 to 2.0 R ☉, depending on the charge state and the underlying coronal density structures. Beyond that distance, the intensity of the emission reflects the distribution of the corresponding Fe ion charge states. These observations thus yield the two-dimensional distribution of electron temperature and charge state measurements in the corona for the first time. The presence of the Fe X 637.4 nm and Fe XI 789.2 nm emission in open magnetic field regions below Rt , such as in coronal holes and the boundaries of streamers, and the absence of Fe XIII 1074.7 nm and Fe XIV 530.3 nm emission there indicate that the sources of the solar wind lie in regions where the electron temperature is less than 1.2 × 106 K. Beyond Rt , the extent of the Fe X [Fe9+] and Fe XI emission [Fe10+], in comparison with Fe XIII [Fe12+] and Fe XIV [Fe13+], matches the dominance of the Fe10+ charge states measured by the Solar Wind Ion Composition Spectrometer, SWICS, on Ulysses, at –43° latitude at 4 AU, in March-April 2006, and Fe9+ and Fe10+ charge states measured by SWICS on the Advanced Composition Explorer, ACE, in the ecliptic plane at 1 AU, at the time of both eclipses. The remarkable correspondence between these two measurements establishes the first direct link between the distribution of charge states in the corona and in interplanetary space

Structure and Dynamics of the 2012 November 13/14 Eclipse White-light Corona

Continuing our series of observations of coronal motion and dynamics over the solar-activity cycle, we observed from sites in Queensland, Australia, during the 2012 November 13 (UT)/14 (local time) total solar eclipse. The corona took the low-ellipticity shape typical of solar maximum (flattening index ε = 0.01), a change from the composite coronal images we observed and analyzed in this journal and elsewhere for the 2006 and 2008-2010 eclipses. After crossing the northeast Australian coast, the path of totality was over the ocean, so further totality was seen only by shipborne observers. Our results include velocities of a coronal mass ejection (CME; during the 36 minutes of passage from the Queensland coast to a ship north of New Zealand, we measured 413 km s6(–1)) and we analyze its dynamics. We discuss the shapes and positions of several types of coronal features seen on our higher-resolution composite Queensland coronal images, including many helmet streamers, very faint bright and dark loops at the bases of helmet streamers, voids, and radially oriented thin streamers. We compare our eclipse observations with models of the magnetic field, confirming the validity of the predictions, and relate the eclipse phenomenology seen with the near-simultaneous images from NASA's Solar Dynamics Observatory (SDO/AIA), NASA's Extreme Ultraviolet Imager on Solar Terrestrial Relations Observatory, ESA/Royal Observatory of Belgium's Sun Watcher with Active Pixels and Image Processing (SWAP) on PROBA2, and Naval Research Laboratory's Large Angle and Spectrometric Coronagraph Experiment on ESA's Solar and Heliospheric Observatory. For example, the southeastern CME is related to the solar flare whose origin we trace with a SWAP series of images

3D Coronal Density Reconstruction and Retrieving the Magnetic Field Structure during Solar Minimum

Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. We employed STEREO/COR1 data obtained during a deep minimum of solar activity in February 2008 (Carrington rotation CR 2066) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 Rsun using a tomography method. With this, we qualitatively deduced structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in the 195 A band obtained by tomography for the same CR. A global 3D MHD model of the solar corona was used to relate the reconstructed 3D density and emissivity to open/closed magnetic field structures. We show that the density maximum locations can serve as an indicator of current sheet position, while the locations of the density gradient maximum can be a reliable indicator of coronal hole boundaries. We find that the magnetic field configuration during CR 2066 has a tendency to become radially open at heliocentric distances greater than 2.5 Rsun. We also find that the potential field model with a fixed source surface (PFSS) is inconsistent with the boundaries between the regions with open and closed magnetic field structures. This indicates that the assumption of the potential nature of the coronal global magnetic field is not satisfied even during the deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.Comment: Published in "Solar Physics