Prospects for Solar and Space Weather Research with Polish Part of the LOFAR Telescope

The LOw-Frequency ARray (LOFAR) is a new radio interferometer that consists of an array of stations. Each of them is a phase array of dipole antennas. LOFAR stations are distributed mostly in the Netherlands, but also throughout Europe. In the article we discuss the possibility of using this instrument for solar and space weather studies, as well as ionosphere investigations. We are expecting that in the near future the LOFAR telescope will bring some interesting observations and discoveries in these fields. It will also help to observe solar active events that have a direct influence on the near-Earth space weather.     

Novel aryl polycyclic aromatic hydrocarbons: Phenylphenanthrene and phenylanthracene identification, occurrence and distribution in sedimentary rocks

Numerous reports have recognised the presence of compounds with molecular weight 254 a.m.u. in aromatic fractions. However, their unequivocal identification has not been achieved due to a lack of reference substances. In geological samples, such m/z 254 compounds could potentially be represented by a number of structural isomers of binaphthyl, phenylphenanthrene, phenylanthracene and indenofluorene with each compound type possessing several positional isomers. In this work, all these m/z 254 compounds, with the exception of the tentatively recognised indenofluorenes, have been unequivocally identified in sedimentary rocks for the first time. Comparison of the mass spectra and the gas chromatography (GC) retention times of synthesised standards with the natural compounds in rocks shows that the major components of aromatic fractions are phenylphenanthrene isomers and, to a lesser extent, binaphthyls and 9-phenylanthracene. The elution sequence expressed as standard retention indices of all these m/z 254 isomers were determined by using high resolution capillary GC with three stationary phases: 5%, 35% and 50% (mole fraction) phenyl substituted methylpolysiloxane on HP-5MS, DB-35MS and DB-17MS columns, respectively. A survey of more than 350 sedimentary rock samples of varying origins and maturity (R_r 0.3–1.4%) reveals that relative abundances of the m/z 254 isomers depend on the maturity of the organic matter. The isomers initially appear at the onset of oil generation (R_r > 0.5%) exclusively in diagenetically/catagenetically oxidised samples containing varying proportions of Types II and III kerogen. Interestingly, all five possible positional phenylphenanthrene isomers (including the most sterically hindered isomer 4-phenylphenanthrene) are present from the beginning of the oil generation window. Such a distribution suggests that low-regioselectivity reactions are likely to be involved in the formation. Interaction, during maturation, of phenyl radicals from primary cracking with aromatic moieties of more resistant terrigenic components of kerogen in an oxidising diagenetic realm is postulated to be responsible for the neoformation of phenylated aromatics in geological samples. Up to the final stages of oil generation, the evolution of the phenyl PAH distributions presumably involve 1,2-phenyl shift reactions and cyclisation, if allowed by the molecular geometry. A near thermodynamically-controlled distribution, with only 3- and 2-phenylphenanthrene and minor 2,2′-binaphthyl remaining, is approached when vitrinite reflectance reaches 1.2% (R_r). The three compounds seem to be persistent beyond the oil window as is suggested by their presence in hydrothermal oil formed at T > 300 °C.     

Anthropogenic changes in the sediment composition of Lake Gości& aogon;ż (central Poland), during the last 330 yrs*

According to historical sources, the development of settlement around Lake Goci& aogon; during the last 330 yrs was intense at two time periods: the second half of the 1700's, and from ca. 1880 until 1944. The small farms were then abandoned, following which the lake surroundings were planted with forest trees. The presented study of human influence on the lake ecosystem and surrounding vegetation has been based on analyses of general sediment composition and its chemistry, pollen, Cyanobacteria, Chlorophyceae, Rotatoria, Cladocera, and a preliminary diatom survey. The history of human impact has been divided into four phases: 1. Phase of small local hamlets (before ca. 1770): The human impact was rather moderate then, but the cultivation of Canabis sativa, Secale cereale and later of Fagopyrum is evidenced from that time. 2. Phase of Hollandii settlement (ca. 1770-1863). Its influence is indicated first by the recession of deciduous wood (Corylus, Carpinus) stands, which triggered drastic drop of calcium in sediments. The development of rural economy in the area, including, an extension of agriculture (Secale and other cereals, crucifers, potatoes), and animal breeding based partly on grazing in the forest, is evidenced only after 1820. 3. Phase of German colonization (1863-1944): In the early periods (before 1910) the pollen spectra do not document any essential change in the type of farming, however, a serious disturbance of the lake ecosystem and sediment chemistry is evidenced by the blooms of Araphidinae diatoms and Tetraedron minimum, a maximum frequency of Bosmina longirostris, disturbances of the regular spring blooms of Chrysophyceae, appearance of vivianite, distinct maxima of organic matter, potassium, and iron concentration in sediments and an increase of the sedimentation rate. An intensification of agricultural activities commenced around 1910; woods, including also pinewoods, were then heavily devastated, and farming extended on poor soils, what was symptomatic for the general poverty of population. Coincidently in the lake, Centriceae showed blooms, Araphidinae diatoms and Tetraedron minimum developed, and the content of potassium, iron and phosphorus increased substantially, indicating altogether rising eutrophication. 4. Phase of restoration of the natural landscape (after 1945): The farm degradation from ca. 1944 is very weakly expressed in pollen data, which show a substantial fall of farming indicators from 1953/6 only, when the whole area was used for forest plantation. It was accompanied by a certainly spontaneous development of Betula and Alnus woods, this process progressing till recent time. The gradual extinction of farming activity near Lake Goci was accompanied by abrupt changes in the lake ecosystem, expressed by the restored blooms of Chrysophyceae expansion of planktonic Cladocera, rapid decline of phosphorus and extinction of vivianite from sediments. As documented by the drop of Cu/Zn ratio, lake hypolimnion has been weakly oxidized since 1949, what was probably responsible for the drop of Fe and Mn content in sediments. Increasing strength of overturns affected preservation of laminae in sediments, which almost completely disappeared after 1966.     

Middle and Late Pleistocene fluvial systems in central Poland

This reconstruction of the fluvial palaeogeography of central Poland is based on an exhaustive and critical review of the published and archival data for the Middle and Late Pleistocene sediments of the area. The Warsaw Basin in central Poland was a major confluence area during the Middle and Late Pleistocene. The fluvial watersheds have been only slightly modified since that time. The past river systems resembled the contemporary one, therefore indicating rebuilding during successive interglacials, at least since the Holsteinian when the sea undoubtedly occupied the southern Baltic Basin. The Weichselian fluvial system was strongly influenced by the Scandinavian ice sheet, especially by meltwater runoff in the extraglacial area and ice-damming in the Warsaw Basin where a large proglacial lake developed. The Weichselian fluvial sediments form up to three terraces in the valleys of the Vistula and its tributaries. The most contentious issue is the mutual relation of the ice-dammed lake and ice marginal spillways in the Warsaw Basin, both being important fragments of a widespread drainage network in the Central European Lowland.     

On geophysical explanation of some irregular variations of the mean latitudes of latitude stations

Mean latitude variations computed by Orlovs or other filters have some irregular variations in addition to secular ones. These are of the order of ±0.05 to ±0.1, they can last several years and sometimes show regional similarities. In looking for an explanation of such latitude variations several physical mechanisms have been investigated. The most probable one is the mechanism of stress propagation in the lithosphere and asthenosphere. The consequent gravitational and deformational effects could explain both the magnitude and the time dependance of the irregular latitude variations.