Holes in the Hα Eruptive Prominence Structure

The eruptive prominence observed on 27 May 1999 in H at Ondejov Observatory is analyzed using image-processing techniques. To understand the physical processes behind the prominence eruption, heated structures inside the cold H prominence material are sought. Two local minima of intensity (holes), the first above and the second below the erupting H prominence, have been found in the processed H images. A comparison of H images with the SOHO/EIT and Yohkoh/SXT images showed: (a) the cold H prominence is visible as a dark feature in the EIT images, (b) the upper local minimum of intensity in the H image corresponds to a hot structure seen in EIT, (c) the lower minimum corresponds to a hot loop observed by SXT. The physical significance of the H intensity minima and their relation to the hot structures observed by EIT and SXT is discussed. The time sequence of observed processes is in favor of the prominence eruption model with the destabilization of the loop spanning the prominence. For comparison with other events the velocities of selected parts of the eruptive prominence are determined.     

On the Integrability of Limited-Area Numerical Weather Prediction Model ALADIN over Extended Time Periods

This note summarizes results of the first integration of regional numerical weather prediction model ALADIN in a climate mode. The ALADIN model, developed in an international cooperation led by Météo France, is operationally used for weather prediction. The grid step of the model is 12 km; the integration domain covers a major part of Europe. A one-month-long run has been performed with this model on observed boundary conditions (represented by assimilations by the global model ARPEGE). It is demonstrated that no excessive error is generated and accumulated in the model during the integration; hence the model is integrable for extended time periods and may serve a basis for a development towards a regional climate model.     

Winter severity and snowiness and their multiannual variability in the Karkonosze Mountains and Jizera Mountains

This paper analyses winter severity and snow conditions in the Karkonosze Mountains and Jizera Mountains and examines their long-term trends. The analysis used modified comprehensive winter snowiness (WSW) and winter severity (WOW) indices as defined by Paczos (1982). An attempt was also made to determine the relationship between the WSW and WOW indices. Measurement data were obtained from eight stations operated by the Institute of Meteorology and Water Management – National Research Institute (IMGW–PIB), from eight stations operated by the Czech Hydrological and Meteorological Institute (CHMI) and also from the Meteorological Observatory of the University of Wroc?aw (UWr) on Mount Szrenica. Essentially, the study covered the period from 1961 to 2015. In some cases, however, the period analysed was shorter due to the limited availability of data, which was conditioned, inter alia, by the period of operation of the station in question, and its type.Viewed on a macroscale, snow conditions in the Karkonosze Mountains and Jizera Mountains (in similar altitude zones) are clearly more favourable on southern slopes than on northern ones. In the study area, negative trends have been observed with respect to both the WSW and WOW indices—winters have become less snowy and warmer. The correlation between the WOW and WSW indices is positive. At stations with northern macroexposure, WOW and WSW show greater correlation than at ones with southern macroexposure. This relationship is the weakest for stations that are situated in the upper ranges (Mount ?nie?ka and Mount Szrenica).     

Evolution of borate minerals from contact metamorphic to hydrothermal stages: Ludwigite-group minerals and szaibélyite from the Vysoká – Zlatno skarn,Slovakia

Mineralogy and Petrology - Borate minerals of the ludwigite group (LGM) and szaibélyite in association with hydroxylclinohumite, clinochlore, a serpentine mineral, magnesian magnetite, spinel,...     

Automated Meteor Detection by All-Sky Digital Camera Systems

We have developed a set of methods to detect meteor light traces captured by all-sky CCD cameras. Operating at small automatic observatories (stations), these cameras create a network spread over a large territory. Image data coming from these stations are merged in one central node. Since a vast amount of data is collected by the stations in a single night, robotic storage and analysis are essential to processing. The proposed methodology is adapted to data from a network of automatic stations equipped with digital fish-eye cameras and includes data capturing, preparation, pre-processing, analysis, and finally recognition of objects in time sequences. In our experiments we utilized real observed data from two stations.     

Multichannel Blind Deconvolution As A Tool For Solar Image Restoration

A principle of restoration methods based on multichannel blind deconvolution (MBD) is introduced. The methods assume that for every un-degraded unobservable image several degraded observed images are available. It is better conditioned than classical single channel approach. The first algorithm represents a generalization of iterative deconvolution scheme introduced for single images. The second MBD algorithm is based on so-called subspace technique. The subspace method is not iterative and this possibly implies an implementation that can be computationally more efficient. Both methods are presented in applications to artificial image data (computer-generated multichannel degraded data) with known ideal image to get a comparison with restored one. Performance in a real situation on solar photosphere images is shown.     

Vilnius Photometry of Red Giant Stars in the Open Cluster NGC 7789

Photoelectric Vilnius seven-color photometry is presented and analyzed for a sample of 24 red giant branch and clump stars in the open cluster NGC 7789. For each star we have determined photometric spectral type, absolute magnitude, interstellar reddening, effective temperature, metallicity, and surface gravity. From averages over the stars in the sample we find the mean reddening to the cluster E _Y−V = 0.21± 0.02 (s.d.), or E _B−V = 0.25, and the apparent distance modulus (m−M) _V = 12.21± 0.10 (s.d.), which yield a distance of 1840 pc. The mean overall metallicity is found to be [Fe/H] = −0.18± 0.09 (s.d.). The clump stars, on average, appear to be slightly more metal-rich than the other red giants, which is most probably caused by evolutionary changes of carbon and nitrogen molecular bands falling in the photometric passbands. A difference in mass between the two groups of stars has also been detected, which suggests that the clump stars might have undergone extra mass loss before reaching their core He-burning phase of evolution.     

An analysis of Skylab X-ray pictures of a giant coronal arch

The limb event of 13/14 August, 1973, imaged by Skylab in soft X-rays, proved to be a giant arch, quite similar to those observed in 1980–1986 on SMM. High spatial resolution (by a factor of 4–5 better than in SMM data) made it possible to see the internal structure of the arch. Its brightest part consisted of loops very similar to, but higher than, post-flare loops, surrounded by a rich system of weak loop structures extending up to altitudes of 260 000 km. While the main brightest structure of the arch was newly formed, the weak very large loops had existed above the active region before and were only enhanced during the event.Skylab data support the model proposed by Kopp and Poletto that the giant arch is formed by reconnections high in the corona, different from the reconnection process in the underlying flare. However, contrary to Kopp and Poletto's suggestion, the data strongly indicate that the field lines that reconnect in the arch did not open before, as in the Kopp and Pneuman model: more likely, we encounter here an interaction of large-scale loops high in the corona. (The interaction of two of them is clearly seen.) Thus, while post-flare loops are formed by the Kopp and Pneuman mechanism, giant arches above eruptive flares may originate through interactive reconnections of large-scale magnetic field lines which form loops high in the corona. These loops are brought close to each other in consequence of changes in the coronal structure caused by the eruptive flare phenomenon. The arch-associated enhancement of the pre-existing large-scale active-region loops may be caused by electrons accelerated during the reconnection process and diffusing across field lines, as suggested by Achterberg and Kuipers (1984).