Long-term variations in total solar irradiance

For more than a decade total solar irradiance has been monitored simultaneously from space by different satellites. The detection of total solar irradiance variations by satellite-based experiments during the past decade and a half has stimulated modeling efforts to help identify their causes and to provide estimates of irradiance data, using proxy indicators of solar activity, for time intervals when no satellite observations exist. In this paper total solar irradiance observed by the Nimbus-7/ERB, SMM/ACRIM I, and UARS/ACRIM II radiometers is modeled with the Photometric Sunspot Index and the Mg II core-to-wing ratio. Since the formation of the Mg II line is very similar to that of the Ca II K line, the Mg core-to-wing ratio, derived from the irradiance observations of the Nimbus-7 and NOAA9 satellites, is used as a proxy for the bright magnetic elements. It is shown that the observed changes in total solar irradiance are underestimated by the proxy models at the time of maximum and during the beginning of the declining portion of solar cycle 22 similar to behavior just before the maximum of solar cycle 21. This disagreement between total irradiance observations and their model estimates is indicative of the fact that the underlying physical mechanism of the changes observed in the solar radiative output is not well-understood. Furthermore, the uncertainties in the proxy data used for irradiance modeling and the resulting limitation of the models should be taken into account, especially when the irradiance models are used for climatic studies.     

Magnetic susceptibility as a possible correlation tool in Quaternary alluvial stratigraphy

Correlation of the fluvial magnetic susceptibility (MS) record of borehole Devavanya‐1 in the Körös Basin (eastern Hungary) with Chinese aeolian MS records (Jingbian, Lingtai) and the marine δ¹⁸O record from the Equatorial Pacific (V28‐239) is established here based on cross‐correlations and singular spectral analysis. A basin‐scale well‐to‐well correlation based on magnetic susceptibility records was also performed involving unpublished cores. To refine the age model, a Monte Carlo simulation was conducted using the Chinese Jingbian section as a tuning target. Spectral analysis of the tuned record revealed c. 400, c. 100 and c. 41 ka cycles over the 2.5 million years of the Quaternary fluvial succession. To ensure a complementary palaeoclimate proxy, the full width at half maximum of smectites was measured as a facies‐independent indicator of weathering intensity. This investigation was carried out on a subset of samples involved in MS measurements representing a c. 400 ka time interval across the top of the Olduvai subchron. A phase‐shift between MS and weathering intensity recorded in the clay mineralogy indicates different response times of the considered proxies. The fluvial MS record is determined by the climatic control on delivery and preservation of magnetic minerals, mainly of magnetite. Under cold‐and‐dry climate these minerals were released owing to frost shattering in the adjacent hinterlands and were transported to alluvial plains in the early postglacial periods thanks to the increasing discharge of rivers. With further warming the weathering‐sensitive magnetic minerals soon disappeared from the soils of the catchment area and thus from the fluvial load. As a result, in fluvial successions early postglacial warmings are expressed by the occurrences of MS maxima (magnetic episodes), while the palaeotemperature maximum and the subsequent cooling remain concealed within the tract of low MS values. The early postglacial magnetic episodes may serve as ideal stratigraphical markers in regional and global correlations.     

Evidences for a Noachian-Hesperian orogeny in Mars

A number of tectonic structures have been located at the Thaumasia Plateau, Daedalia Planum and Aonia Terra, Mars. They include isolated folds with axial traces up to 200 km long, trains of tightly folded structures tens of km long, and thrusts. Their size and geometry are similar to those on Earth, and the direction of compression seems to have varied amply with time, suggesting a complex tectonic evolution. Crater counts on the deformed terrain point to Noachian to Early Hesperian ages. On the basis of the geometry and geological relations of these structures, we propose that they form part of an old martian orogen, the Thaumasia-Aonia Orogen, which embraced not only the Thaumasia Plateau, but areas of Daedalia Planum, Aonia Terra and Nereidum Montes as well. A regional coherent layering is previous to the deformation and could represent the trace of even older stresses on the martian lithosphere.     

More than `Anglo-American', it is `Western': hegemony in geography from a Hungarian perspective

The paper assesses the inequalities of the production of geographical knowledge mainly against the backdrop of the East-West relations, which still dominate Hungarian practice. However, it also offers examples of Anglo-American hegemony making itself felt more acutely; or of Hungarian geographers, at the receiving end of these dimensions of hegemony, producing hegemony in a different system of relations. Investigating the political economic power relations underlying this hegemony and the social agents involved in `hegemony-producing' helps establish potential strategies of putting an end to the inequalities of academic knowledge production. Some possibilities of these strategies are outlined.     

Soft-sediment deformation structures in Late Miocene–Pleistocene sediments on the pediment of the Mátra Hills (Visonta, Atkár, Verseg): Cryoturbation, load structures or seismites?

The studied area, built up by silty clayey and partly sandy sediments and paleosols, lies on the tectonically active Northern margins of the Pannonian Basin. Wavy, sagging load casts can be observed in the upper part of the Late Miocene alluvial complex and larger scale sagging load casts, flame structures, drops and pillows detected in its Quaternary cover were studied in detail, in order to understand the origins of soft sediment deformation which characterized this young sedimentary suite. Sedimentological, paleopedological and mineralogical observations suggest that:

1. One of the reasons for the soft-sediment deformation might have been the relatively low cohesive strength of the predominantly smectitic sediment covering a gentle slope similar to the actual landscape.

2. On such a surface, the down-slope gravitational component of the mud-blanket might easily have been sufficient to overcome its cohesive strength.

3. Frost action traceable in the studied formations might also have contributed to the observed deformation, particularly along the eroded top of the Late Miocene sediments.

Combined evidence from field observations and laboratory analyses support the idea that liquefaction–fluidization was of prime importance in bringing about the observed structures. In conclusion two alternative Quaternary/Holocene scenarios are proposed, which might have resulted in the unusual behaviour of the sediments/paleosols. One is a seismic event, the other is the combined effect of freeze–thaw cycles and of the sloping foothill position, which might have resulted in episodic downslope transport and the associated deformation of the eroded soil material when its water content surpassed a certain threshold. We accept that the anomalous abundance of soft-sediment deformation in this marginal position may be causally related to paleo-earthquakes, but the obvious complexity of the phenomenon requires caution. In case the proposed scenarios would not have been alternatives but acted simultaneously, the analysed phenomena were to be interpreted as the joint results of tectonics and climate change.     

Kyanite eclogite xenolith from the orthogneiss terrane of the Tisza Megaunit, Jánoshalma area, crystalline basement of southern Hungary

New evidence for high-pressure, eclogite facies metamorphism in the crystalline basement of the Tisza Megaunit (southern Hungary) is reported. The retrogressed mafic eclogite forms a small lens in the orthogneiss and it was found in the borehole near Jánoshalma. The carbonated eclogite contains the peak metamorphic assemblage omphacite + garnet + phengite + kyanite + clinozoizite + rutile + K-feldspar + quartz. Omphacite (Xjd_0.40–0.41Xdio_0.52–0.53Xhd_0.05Xaug_1.55–2.85) occurs in the matrix and as inclusions in garnet (Xpy_0.37–0.38Xgrs_0.21–0.22Xalm_0.39–0.40Xsps_0–0.01Xadr_0–0.01) and kyanite. Thermobarometry based on net-transfer reactions between garnet, omphacite, kyanite and phengite yields P–T conditions of 710 ± 10 °C and 2.6 ± 0.75 GPa. Retrogression during decompression is manifested by formation of symplectites; the most typical are diopside + plagioclase after omphacite, corundum + spinel + plagioclase after kyanite and biotite + plagioclase after phengite. Carbonatization along the veins of the retrogressed eclogite was probably coeval with formation of these symplectites. At places where carbonate is absent the rock was completely hydrated and retrogressed down to the greenschist facies with the development of actinolite. Similar eclogites together with abundant orthogneisses occur mainly in the eastern parts of the Tisza Megaunit, suggesting the existence of an ancient (possibly Variscan) subduction/accretionary complex.     

Conceptual model for surface salinization in an overpressured and a superimposed gravity-flow field, Lake Kelemensz��k area, Hungary

The Duna-Tisza Interfluve, Hungary, is characterized by patchy surface salinization. However, in the Duna Valley, salinized wetlands appear in a N?CS trending continuous zone (Lake Kelemenszék area). The source of the salts is reported to be the overpressured NaCl-type water of the Pre-Neogene basement and the NaHCO₃-type water of the Neogene sediments. This ??basement and basin origin of salts?? concept is based on the strong correlation between the regional distribution of surface salinization and the basinal flow pattern. This study, applying integrated methods, presents hydrogeological evidence for this theory and creates a conceptual model for the salinization. The model reflects that the basement water rises near to the surface through conductive faults crosscutting an extensive aquitard and aquifer. These faults ensure ??shortcut??-type water exchange between the basement and the uppermost aquifer. This hydraulic setting generates chemical anomalies in this aquifer up to the surface, producing Na?CHCO₃?CCl-type water. This water causes extensive surface salinization in those discharge areas where the infiltrating freshwater does not superimpose the upwelling saline water. Where a freshwater lens is located above the ascending saline water, this fresh gravity-driven flow controls the surface distribution of salts, which results in saline patches.     

Activity of sunspots and solar constant variations during 1980

A strong inverse correlation is shown between the irradiance dips observed by the SMM/ACRIM radiometer and the projected areas of the active sunspots. This strong correlation and the results of a preliminary time series analysis indicate that the value of the solar constant decreased when quickly developing sunspot groups with complex structure occurred on the solar disk. On the other hand, when the old groups with simple structure were dominant the value of the solar constant increased slightly or these groups could reduce the effects of the active spots. On the basis of our investigations it seems that the formation of the sunspots and the new activity of the older ones as well as the decreases of the solar constant may be the common symptoms of such a physical process which takes place in deeper regions of the Sun through the interaction of magnetic fields with the convection.     

Variation of the solar constant during the solar cycle

Measurements of the Nimbus-7 and Solar Maximum Mission satellites reported temporary large decreases of the solar constant of the order of a few tenths of a percent on a time-scale from days to weeks. Our investigations show that these decreases were caused by active sunspot groups with fast development and complex structure. This connection between the solar constant variation and the appearance of the active groups seems to be more clear in the maximum of the solar activity. At the time of the solar minimum, mainly in the second part of 1984, there were not any active sunspot groups practically on the solar disk, the value of the solar constant only fluctuated around its mean without large variation. The results of time series analyses show that the periodicity of the solar constant values, of young and active spot areas was nearly 23.5 days in 1980, which increases to 28 days towards the minimum of the solar cycle till 1983. During this time interval the main periodicity of the old, passive spot areas was around 28 days. In 1984, at the time of the solar minimum, there were not any obvious periodicities practically in the projected areas of the different types of the sunspot groups.