Plane grating as polar heliostat in eclipse observations of the chromosphere and prominences with special application to studies of Doppler-widened Thomson-scattered Fraunhofer lines

Attention is drawn to a very simple instrumental arrangement for eclipse observations of the spectra of the chromosphere and prominences using a plane grating as polar heliostat and a short focus camera. A discussion is made of an infrared chromospheric spectrum showing traces of Thomson-scattered Ca ii absorption lines in the continuous spectrum. If the effect is real, it indicates a temperature of the order of 5000 K. A simple vector formula is presented describing various types of Doppler effects appearing in radiation scattered by moving particles.     

An Hα filament observed against the chromosphere at the limb

Observations are reported of an H filament clearly visible in the image of the chromosphere at the limb as well as in the H spectrum of the same part of the chromosphere. Observations of this kind may give valuable information about the absorption mechanism at work in filaments.     

Stratigraphy of Upper Cretaceous–Palaeogene sequences in the southern and eastern Menderes Massif (western Turkey)

The stratigraphy of the uppermost levels of the Menderes Massif is controversial and within its details lie vital constraints to the tectonic evolution of south-western Turkey. Our primary study was carried out in four reference areas along the southern and eastern Menderes Massif. These areas lie in the upper part of the Menderes metamorphic cover and have a clear stratigraphic relationship and contain datable fossils. The first one, in the Akbük-Milas area, is located south-east of Bafa Lake where the Milas, then KLzLla<aç and KazLklL formations are well exposed. There, the Milas formation grades upwards into the KLzLla<aç formation. The contact between the KLzLla<aç and the overlying KazLklL formation is not clearly seen but is interpreted as an unconformity. The Milas and KLzLla<aç formations are also found north of Mu<la, in the region of Yata<an and KavaklLdere. In these areas, the Milas formation consists of schists and conformably overlying platform-type, emery and rudist-bearing marbles. Rudists form the main palaeontological data from which a Santonian-Campanian age is indicated. The KLzLla<aç formation is characterized by reddish-greyish pelagic marbles with marly-pelitic interlayers and coarsening up debris flow deposits. Pelagic marbles within the formation contain planktonic foraminifera and nanoplankton of late Campanian to late Maastrichtian age. The KazLklL formation is of flysch type and includes carbonate blocks. Planktonic foraminifera of Middle Palaeocene age are present in carbonate lenses within the formation. In the Serinhisar-Tavas area, Mesozoic platform-type marbles (YLlanlL formation) belonging to the cover series of the Menderes Massif exhibit an imbricated internal structure. Two rudist levels can be distinguished in the uppermost part of the formation: the first indicates a middle-late Cenomanian age and the upper one is Santonian to Campanian in age. These marbles are unconformably covered by the Palaeocene-Early Eocene Zeybekölentepe formation with polygenetic breccias. In the Çal-Denizli area, the Menderes massif succession consists of cherty marbles and clastic rocks with metavolcanic lenses. The Lower-Middle Eocene zalvan formation lies unconformably on this sequence and is interpreted as equivalent to the marble horizons at Serinhisar but with pelagic facies. The zalvan formation consists of shale, mafic volcanic rock, lenses of limestone and blocks of recrystallized limestone. The zalvan formation is dated here for the first time by Early-Middle Eocene foraminifera and nanoplankton from the matrix of the formation. An angular unconformity exists between the Upper Cretaceous and Lower Tertiary sequences, suggesting that a phase of deformation affected the southern and eastern part of the Menderes Massif at this time. This deformation may be caused by initial obduction of the Lycian ophiolite onto the passive margin to the north of the Menderes carbonate platform during the latest Cretaceous. Drowning of the platform led to termination of carbonate deposition and deposition of deep water flysch-like clastic sediments.     

Residual Separation of Magnetic Fields Using a Cellular Neural Network Approach

—?In this paper, a Cellular Neural Network (CNN) has been applied to a magnetic regional/residual anomaly separation problem. CNN is an analog parallel computing paradigm defined in space and characterized by the locality of connections between processing neurons. The behavior of the CNN is defined by the template matrices A, B and the template vector I. We have optimized weight coefficients of these templates using Recurrent Perceptron Learning Algorithm (RPLA). The advantages of CNN as a real-time stochastic method are that it introduces little distortion to the shape of the original image and that it is not effected significantly by factors such as the overlap of power spectra of residual fields. The proposed method is tested using synthetic examples and the average depth of the buried objects has been estimated by power spectrum analysis. Next the CNN approach is applied to magnetic data over the Golalan chromite mine in Elazig which lies East of Turkey. This area is among the largest and richest chromite masses of the world. We compared the performance of CNN to classical derivative approaches.     

A Contribution to the History of European Winters: Some Climatological Proxy Data from Early-Sixteenth Century Swedish Documentary Sources

In this paper, the potential is explored for climatological information on winter weather in a hitherto largely neglected category of historical documentary sources (correspondence letters) covering two decades of the less studied intermediate stages between the proposed warm High Middle Ages and what has been termed `the Little Ice Age'. A discussion concerning some problems of interpretation is presented from a historical methodological point of view. Content analysis, with special attention paid to contemporary terms and expressions linked to transport and travel, shows that winters in Sweden during the first decades of the sixteenth century, in comparison with the average of the late twentieth century, were on the whole somewhat shorter in duration. Two of the winters studied can be said to display some extreme characteristics; one exceptionally mild, and one with an unusually early onset. On the whole, the result diverges slightly from previously published winter severity indices and confirms regional disparities in the middle phase between a possible warm High Middle Ages and the so-called `Little Ice Age'.     

ISOTOPE RECORDS FROM MONGOLIAN AND ALPINE ICE CORES AS CLIMATE INDICATORS

The link between long term changes in the isotopic composition of precipitation and surface air temperature at a given location is of exceptional importance for paleoclimatic studies, as ahs been demonstrated by many recent publications based on the isotope records from polar ice cores. By means of direct comparison with instrumental data, this paper evaluates the potential of the deuterium and oxygen-18 records from two continental glaciers for monitoring climatic trends. The isotopic data presented characterize climatically contrasted enviroments. The records from the Swiss glacier show distinct seasonal variations. Oxygen-18 is fairly well correlated with the instrumental record of atmospheric temperature; the seasonal differences in deuterium excess reflect nearness to the oceanic moisture source. By contrast, the isotope data from the Mongolian site show poor correlation with atmospheric temperature. The seasonal variations in deuterium excess, with higher values during summer time, indicate that precipitation largely originates from re-evaporated continental moisture sources. In both cases however, the correlation with temperature is significantly improved by the elimination of values derived from years where major changes in seasonal distribution and/or snow loss obviously have occurred, thereby distoring the isotopic ratios for that particular year. Depending on the site selected for study, the stable isotope composition of ice cores should therefore be viewed not only as a proxy for atmospheric temperature, but also as an additional hydrometeorological parameter and source indicator for atmospheric moisture.     

The Ionospheric foF2 Data over Istanbul and their Response to Solar Activity for the Years 1964–1969 and 1993

A Polish-made vertical ionosonde (VI) has been operated at the Kandilli Observatory in Istanbul, for almost one year (May 1993 - April 1994) as part of the COST 238, PRIME Project, The critical frequencies were obtained for every half-hour interval. The data obtained during this campaign, on the descending branch of solar cycle 22, and the data measured earlier in Istanbul for cycle 20 were analysed and the characteristic behaviour of the F2 region ionosphere over Istanbul has been determined. This is a unique data set for this area. Several markers of the solar cycle activities in terms of the daily relative sunspot numbers, F10.7 cm solar radio flux and solar flare index, and the magnetic daily index of Ap were then used to seek the possible influence of the solar and ionospheric activities on the critical frequencies observed in Istanbul. It was found that the solar flare index, as a solar activity index, was more reliable in determining quiet ionospheric days. It is shown that the minimum and maximum time values of the solar activity are more convenient for ionospheric prediction and modelling.     

Crustal Seismicity In and Around Turkey

Vertical and horizontal variations of the frequency of crustal earthquakes (h ≤ 35 km) that have occurred in and around Turkey are analyzed, using data from the Global Hypocenter Data Base and the IRIS data for the period 1964–1998. Fits of various magnitude scales to the observations have been used to construct a homogeneous catalogue. Depth distribution of the parameters derived from the Gutenberg–Richter relationship reveals that there is a depth dependence in the a- and b-values of the frequency distribution. It is observed that unknown focal depths (0, 10, 33 km) are dominant in the total seismicity reported, and give rise to substantial changes to the vertical distribution of these parameters. It is also observed that the parameters of either a or b alone may not be used as a measure of regional seismicity of the study area in which high and low seismic activity observed over short distances. In contrast, distribution of modal (a/b) values provides detailed images of the local areas presented by high and low seismic zones. This study presents evidence that low b-values are associated with major strike-slip faults, particularly exhibiting high apparent stresses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Das Tauernproblem in den Ostalpen

Ohne Zusammenfassung     

Horizontal and vertical variations in sedimentation and resuspension rates in a stratifying lake – effects of internal seiches

The temporal and spatial variations in the rate of sedimentation and sediment resuspension in Lake Rehtijärvi (southern Finland) were studied by sediment traps deployed in the stratifying and non‐stratifying regions of the lake. Both the gross sedimentation rate and the resuspension rate recorded by near‐bottom traps were significantly higher in the stratifying region (>20 m depth) than in the shallow part of the lake (2 m depth). These rate changes were caused by temporarily elevated hypolimnetic resuspension rates exceeding 40 g dry weight m^?2 day^?1 in July 2005, whereas in the shallow station no such peak was observed and the resuspension rate remained below 30 g dry weight m^?2 day^?1 throughout the study. The elevated resuspension rate in the hypolimnion could not be attributed to surface wave action or sediment disturbance by fish, but was due to the occurrence of internal seiches. The seiche amplitude was on average the highest in July, although the wind velocities were low; this was because winds temporarily were blowing along the longitudinal axis of the lake. Due to the steep slopes, the sediments of Lake Rehtijärvi are prone to redistribution and sediment focusing towards the accumulation areas also affected trap catches in the deep stations.