An Event-Based Verification Scheme for the Real-Time Flare Detection System at Kanzelhöhe Observatory

In the framework of the Space Situational Awareness program of the European Space Agency (ESA/SSA), an automatic flare detection system was developed at Kanzelhöhe Observatory (KSO). The system has been in operation since mid-2013. The event detection algorithm was upgraded in September 2017. All data back to 2014 was reprocessed using the new algorithm. In order to evaluate both algorithms, we apply verification measures that are commonly used for forecast validation. In order to overcome the problem of rare events, which biases the verification measures, we introduce a new event-based method. We divide the timeline of the H\(\upalpha\) observations into positive events (flaring period) and negative events (quiet period), independent of the length of each event. In total, 329 positive and negative events were detected between 2014 and 2016. The hit rate for the new algorithm reached 96% (just five events were missed) and a false-alarm ratio of 17%. This is a significant improvement of the algorithm, as the original system had a hit rate of 85% and a false-alarm ratio of 33%. The true skill score and the Heidke skill score both reach values of 0.8 for the new algorithm; originally, they were at 0.5. The mean flare positions are accurate within \({\pm}\,1\) heliographic degree for both algorithms, and the peak times improve from a mean difference of \(1.7\pm 2.9~\mbox{minutes}\) to \(1.3\pm 2.3~\mbox{minutes}\). The flare start times that had been systematically late by about 3 minutes as determined by the original algorithm, now match the visual inspection within \(-0.47\pm 4.10~\mbox{minutes}\).     

Use of Roche coordinates in the problems of small oscillations of tidally-distorted stellar models

Kopal's method of Roche coordinates used by us in an earlier paper (Mohan and Singh, 1978) to study the problems of small oscillations of tidally-distorted stars has been extended further to take into account the effect of second-order terms in tidal distortion. Our results show that the effect of including terms of second order of smallness in tidal distortion in the metric coefficients of the Roche coordinates of tidally distorted stars is quite significant, especially in case of stars with extended envelopes and (or) larger values of the mass ratio of the companion star producing tidal distortion. Some of the models which were earlier found stable against small perturbations now become dynamically unstable with the inclusion of the terms of second order of smallness in tidal effects.At present on leave of absence with the department of Mathematics, College of Science, Baghdad, Iraq.     

Variability of ozone in the marine boundary layer of the equatorial Pacific Ocean

This study examines the processes controlling the diurnal variability of ozone (O₃) in the marine boundary layer of the Kwajalein Atoll, Republic of the Marshall Islands (latitude 8° 43′ N, longitude 167° 44′ E), during July to September 1999. At the study site, situated in the equatorial Pacific Ocean, O₃ mixing ratios remained low, with an overall average of 9–10 parts per billion on a volume basis (ppbv) and a standard deviation of 2.5 ppbv. In the absence of convective storms, daily O₃ mixing ratios decreased after sunrise and reached minimum during the afternoon in response to photochemical reactions. The peak-to-peak amplitude of O₃ diurnal variation was approximately 1–3 ppbv. During the daytime, O₃ photolysis, hydroperoxyl radicals, hydroxyl radicals, and bromine atoms contributed to the destruction of O₃, which explained the observed minimum O₃ levels observed in the afternoon. The entrainment of O₃-richer air from the free troposphere to the local marine boundary layer provided a recovery mechanism of surface O₃ mixing ratio with a transport rate of 0.04 to 0.2 ppbv per hour during nighttime. In the presence of convection, downward transport of O₃-richer tropospheric air increased surface O₃ mixing ratios by 3–12 ppbv. The magnitude of O₃ increase due to moist convection was lower than that observed over the continent (as high as 20–30 ppbv). Differences were ascribed to the higher O₃ levels in the continental troposphere and weaker convection over the ocean. Present results suggest that moist convection plays a role in surface-level O₃ dynamics in the tropical marine boundary layer.     

Two-dimensional,two-phase granular sediment transport model with applications to scouring downstream of an apron

We present a two-dimensional, two-phase model for non-cohesive sediment transport. This model solves concentration-weighted averaged equations of motion for both fluid and sediment phases. The model accounts for the interphase momentum transfer by considering drag forces. A collisional theory is used to compute the sediment stresses, while a two-equation (k–ε) fluid turbulence closure is implemented. A benchmark sediment transport problem concerning the scouring downstream of an apron is carried out as an example and numerical results agree with existing experimental data.     

Method of monitoring atomic oxygen and molecular nitrogen composition in the upper atmosphere on XUV images of the Sun

A method for determining the basic atmosphere O/N₂ based on the solar observations is described. It is shown that, on XUV images of the Sun received by transillumination of the atmosphere, it is possible to observe its state controlling the O/N₂ ratio. The method allows local inhomogeneities of the upper atmosphere to be studied. Its abilities were demonstrated according to the SPIRIT complex on board the Coronas-F satellite.     

A hybrid method for size characterization of coarse subsurface fluvial sediments

This paper introduces and evaluates a novel method for ascertaining the grain‐size distribution of subsurface sediments that involves profoundly less sampling effort than standard methods. It is based on hybrid sampling principles previously applied to the construction of synthetic surface grain‐size distributions. The method is developed from an empirical demonstration of the approximate similarity of surface and subsurface grain‐size distributions when compared over a common range of sizes. Subsurface hybrid models are found to provide good facsimiles of grain‐size distributions de?ned using standard criteria and to yield distribution percentiles with millimetre accuracy. The technique is presented as an expedient alternative to standard methods for large, perennial gravel‐bed rivers. As this is a new technique, prudent application is advised in lieu of further investigation. Copyright © 2004 John Wiley & Sons, Ltd.     

Systematizing local knowledge using GIS: fisheries management in Bang Saphan Bay, Thailand

Although local knowledge is a crucial source of information for fishery development, its generally unsystematic presentation and nebulous content makes use by policy makers or managers difficult. Based on field data obtained using Participatory Rural Appraisal at Bang Saphan Bay, Prachuap Khiri Khan Province, Thailand, we attempt to show here how local knowledge can be effectively systematized, analyzed and displayed visually using a Geographical Information System (GIS) for use in fisheries management. PRA data on location fished, time of fishing, techniques and technology used and species targeted were obtained from local fishers then mapped using Arcview (3.1). In this way local fisheries knowledge can be converted into geo-spatial data form via GIS, and the succinct results used easily to guide fishery management and planning, especially by offering directions for rights-based fisheries and co-management.     

Aqueous alteration of the Bali CV3 chondrite: evidence from mineralogy, mineral chemistry, and oxygen isotopic compositions

A petrographic, geochemical, and oxygen isotopic study of the Bali CV3 carbonaceous chondrite revealed that the meteorite has undergone extensive deformation and aqueous alteration on its parent body. Deformation textures are common and include flattened chondrules, a well-developed foliation, and the presence of distinctive (100) planar defects in olivine. The occurrence of alteration products associated with the planar defects indicates that the deformation features formed prior to the episode of aqueous alteration. The secondary minerals produced during the alteration event include well-crystallized Mg-rich saponite, framboidal magnetite, and Ca-phosphates. The alteration products are not homogeneously distributed throughout the meteorite, but occur in regions adjacent to relatively unaltered material, such as veins of altered material following the foliation. The alteration assemblage formed under oxidizing conditions at relatively low temperatures (<100 degrees C). Altered regions in Bali have higher Na, Ca, and P contents than unaltered regions which suggests that the fluid phase carried significant dissolved solids. Oxygen isotopic compositions for unaltered regions in Bali fall within the field for other CV3 whole-rocks, however, the oxygen isotopic compositions of the heavily altered material lie in the region for the CM and CR chondrites. The heavy-isotope enrichment of the altered regions in Bali suggest alteration conditions similar to those for the petrographic type-2 carbonaceous chondrites.