Origin of magnetic minerals and natural remanent magnetization of basaltic rocks from Lower Silesia,Poland

Summary Two groups of basaltic rocks with normal and reversed NRM were examined. It was found that in both groups the primary NRM, synchronous with the period of rock formation, is preserved. Relations of the primary NRM to the origin and the degree of oxidation of magnetic minerals were considered in detail.     

Some observations of bipolar flashes during summer thunderstorms near Warsaw

Lightning discharges monitored by the SAFIR network system in Poland have been additionally identified over the 100×100 km area near Warsaw by single-point independent recordings of electric field and Maxwell current rapid changes. The data collected in summer thunderstorm days of 2002 showed some untypical properties of the lightning discharges which are rarely observed. Especially remarkable was a number of ground multi-stroke flashes with the return strokes (RS) which transported to the earth charges of opposite signs. Bipolar flashes (BF) of this kind were mostly involved in the events in which the nearby intracloud (ic) and cloud-to-ground (c-g) discharges were very closely associated in time. Events of such a close collocation of two different types of lightning discharges, previously called the complex lightning discharge events (CLDE), were quite often observed during summer thunderstorms in Poland. The events of this kind, i.e. 8 flashes, identified by the SAFIR detection system as BF’s present the multiple stroke flashes of the mean horizontal separation distance between striking points of particular RS equal to (2.8 ± 2.1) km and of the mean time interval between strokes of (46.8 ± 74.4) ms. The time separation between the observed BF and the adjacent ic flashes was from 0.1 to 335 ms, and horizontal separation distance between them ranged from 1.8 to 14.5 km. The multiplicity of the recorded BF’s ranged from 2 to 4 strokes. Four of these BF’s followed the ic discharge, but the other three preceded the ic and one was alone with no close ic.     

Compositions,sources and depositional environments of organic matter from the Middle Jurassic clays of Poland

The comprehensive biomarker characteristics from previously undescribed Middle Jurassic clays of Poland are presented. The molecular composition of the organic matter (OM) derived from clays of Aalenian to Callovian age has not changed significantly through time. High relative concentrations of many biomarkers typical for terrestrial material suggest a distinct dominance of OM derived from land plants. Increasing concentrations of C₂₉-diaster-13(17)-enes towards the northern part of the basin indicate an increase in terrestrial input. This terrestrial material would have originated from the enhanced transport of organic matter from land situated at the northern bank of the basin, i.e., the Fennoscandian Shield. The organic matter was deposited in an oxic to suboxic environment, as indicated by relatively low concentrations of C₃₃–C₃₅ homohopanes, moderate to high Pr/Ph ratio values, an absence of compounds characteristic for anoxia and water column stratification, such as isorenieratane, aryl isoprenoids and gammacerane, as well as common benthic fauna and burrows. δ¹⁸O measurements from calcitic rostra of belemnites suggest that the mean value of the Middle Jurassic sea-water temperature of the Polish Basin was 13.1 °C. It is suggested that this mirrored the temperature of the lower water column because belemnites are considered here to be necto-benthic. The organic matter from the Middle Jurassic basin of Poland is immature. This is clearly indicated by a large concentration of biomarkers with the biogenic configurations, such as ββ-hopanes, hop-13(18)-enes, hop-17(21)-enes, diasterenes and sterenes. The identification of preserved, unaltered biomolecules like ferruginol, 6,7-dehydroferruginol and sugiol in Protopodocarpoxylon wood samples from these sediments present particularly strong evidence for the presence of immature OM in the Middle Jurassic sediments. Moreover, the occurrence of these polar diterpenoids is important due to the fact that they are definitely the oldest known natural products detected in geological samples.     

Diurnal atmospheric forcing and temporal variations of the nutation amplitudes

A 29-year time-series of four-times-daily atmospheric effective angular momentum (EAM) estimates is used to study the atmospheric influence on nutation. The most important atmospheric contributions are found for the prograde annual (77 μas), retrograde annual (53 as), prograde semiannual (45 as), and for the constant offset of the pole (δψsinɛ₀=−86 as, δɛ=77 as). Among them only the prograde semiannual component is driven mostly by the wind term of the EAM function, while in all other cases the pressure term is dominant. These are nonnegligible quantities which should be taken into account in the new theory of nutation. Comparison with the VLBI corrections to the IAU 1980 nutation model taking into account the ocean tide contribution yields good agreement for the prograde annual and semiannual nutations. We also investigated time variability of the atmospheric contribution to the nutation amplitudes by performing the sliding-window least-squares analysis of both the atmospheric excitation and VLBI nutation data. Almost all detected variations of atmospheric origin can be attributed to the pressure term, the biggest being the in-phase annual prograde component (about 30 as) and the retrograde one (as much as 100200 as). These variations, if physical, limit the precision of classical modeling of nutation to the level of 0.1 mas. Comparison with the VLBI data shows significant correlation for the retrograde annual nutation after 1989, while for the prograde annual term there is a high correlation in shape but the size of the atmospherically driven variations is about three times less than deduced from the VLBI data. This discrepancy in size can be attributed either to inaccuracy of the theoretical transfer function or the frequency-dependent ocean response to the pressure variations. Our comparison also yields a considerably better agreement with the VLBI nutation data when using the EAM function without the IB correction for ocean response, which indicates that this correction is not adequate for nearly diurnal variations. Received: 10 September 1997 / Accepted: 5 March 1998     

Tourist farms in Lower Silesia, Poland

In view of the small size of most Polish farms, attempts have been made to encourage diversification into rural tourism. The paper examines the progress made in Lower Silesia which has good resources for domestic and international tourism. Thanks to the promotional work of the Agricultural Consultative Centres over a hundred farms are now providing services. They do not generate a large share of the farm income but business is expanding and some areas are becoming very popular. Thus a base has been established for future expansion. Further development depends on easier access to credit and government support for ecological agriculture. Better promotion is also needed to increase interest in rural tourism in Poland and attract more visitors from abroad. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evolution of peaks in weakly non-linear density field and dark halo profiles

Using the two-point Edgeworth series up to second order in the linear rms density fluctuation we construct the weakly non-linear conditional probability distribution function for the density field around an overdense region. This requires calculating the two-point analogues of the skewness parameter S ₃. We test the dependence of the two-point skewness on distance from the peak for scale-free power spectra and Gaussian smoothing. The statistical features of such a conditional distribution are given as the values obtained within linear theory corrected by the terms that arise as a result of weakly non-linear evolution. The expected density around the peak is found to be always below the linear prediction while its dispersion is always larger than in the linear case. For large enough overdensities the weakly non-linear corrections can be more significant than the peak constraint introduced by Bardeen et al. We apply these results to the spherical model of collapse as developed by Hoffman & Shaham and find that in general the effect of weakly non-linear interactions is to decrease the scale from which a peak gathers mass and therefore also the mass itself. In the case of an open universe this results in steepening of the final profile of the virialized proto-object.     

Improvement of the geoid in local areas by satellite-to-satellite tracking

Summary The concept of satellite-to-satellite tracking measuring the relative velocity of two orbiting satellites spaced some hundreds kilometers on a close orbit, provides now possibilities for the investigation of the Earth’s gravity field. In the paper only medium and short wave length effects affecting the measured relative velocity have been considered. Collocation is used in such an analysis of local geoid improvement, because this method allows to combine heterogeneous data in a consistent way. Covariance functions relevant for the particular case of a circular equatorial orbit are given. Two kinds of observation equations have been formulated. The choice of observation equation with regard to satellites configuration is discussed. It is found that it is sufficient to have a limited number of satellite-to-satellite observations in a 7^o×7^o area around the estimation point with distances between profiles of about 1^o.5 and between the two satellites forming the pair of 200+350 km; the altitude of satellite-to-satellite observations should be as low as possible. The accuracy of the geoid determination strongly depends on the degree and order of the reference field used. An accuracy of about ±1 m can be achieved with an assumed reference field of (40,40). The influence of measuring errors is discussed and it is shown that only satellite-to-satellite observations with accuracy better then 0.1 mm/sec will give an improvement of the geoid. Finally, some results on the combination of low-low satellite-to-satellite tracking and terrestrial gravity data are given. The proposed method seems to be especially interesting for unsurveyed areas. Furthermore, it has the practical advantage that only a local coverage data is needed.     

A Study of Ozone Laminae Using Diabatic Trajectories, Contour Advection and Photochemical Trajectory Model Simulations.

In this paper, we show that the rate of ozone loss in both polar and mid-latitudes, derived from ozonesonde and satellite data, has almost the same vertical distribution (although opposite sense) to that of ozone laminae abundance. Ozone laminae appear in the lower stratosphere soon after the polar vortex is established in autumn, increase in number throughout the winter and reach a maximum abundance in late winter or spring. We indicate a possible coupling between mid-winter, sudden stratospheric warmings (when the vortex is weakened or disrupted) and the abundance of ozone laminae using a 23-year record of ozonesonde data from the World Ozone Data Center in Canada combined with monthly-mean January polar temperatures at 30 hPa.Results are presented from an experiment conducted during the winter of 1994/95, in phase II of the Second European Stratospheric And Mid-latitude Experiment (SESAME), in which 93 ozone-enhanced laminae of polar origin observed by ozonesondes at different time and locations are linked by diabatic trajectories, enabling them to be probed twice or more. It is shown that, in general, ozone concentrations inside laminae fall progressively with time, mixing irreversibly with mid-latitude air on time-scales of a few weeks. A particular set of laminae which advected across Europe during mid February 1995 are examined in detail. These laminae were observed almost simultaneously at seven ozonesonde stations, providing information on their spatial scales. The development of these laminae has been modelled using the Contour Advection algorithm of Norton (1994), adding support to the concept that many laminae are extrusions of vortex air. Finally, a photochemical trajectory model is used to show that, if the air in the laminae is chemically activated, it will impact on mid-latitude ozone concentrations. An estimate is made of the potential number of ozone molecules lost each winter via this mechanism.