Theoretical and Experimental Studies of the Rigidity Spectrum of the 27-Day Variation of the Galactic Cosmic Ray Intensity in Different Epochs of Solar Activity

Recently Pop (Solar Phys. 276, 351, 2012) identified a Laplace (or double exponential) distribution in the number of days with a given absolute value in the change over a day, in sunspot number, for days on which the sunspot number does change. We show this phenomenological rule has a physical origin attributable to sunspot formation, evolution, and decay, rather than being due to the changes in sunspot number caused by groups rotating onto and off the visible disc. We also demonstrate a simple method to simulate daily sunspot numbers over a solar cycle using the Pop (Solar Phys. 276, 351, 2012) result, together with a model for the cycle variation in the mean sunspot number. The procedure is applied to three recent solar cycles. We check that the simulated sunspot numbers reproduce the observed distribution of daily changes over those cycles.     

Native iron in Quaternary deposits of the Darhad Basin (northern Mongolia)

Quaternary sediments from the borehole DBC-1 drilled in the Darhad Basin, northern Mongolia, have been studied by thermomagnetic analysis (248 samples) and probe microanalysis (9 samples) to determine the origin (cosmic or terrestrial) of native iron. Most of the samples showed extremely low contents of native iron. Only 26 samples have iron in contents sufficient for its reliable identification (10^–5–10^–3%). The negligible content of native iron in the Darhad Basin sediments distinguishes them from the earlier studied sediments of different geologic associations of Eurasia and the Atlantic, which we explain by the high sedimentation rate in this basin. However, the bimodal distribution of native-iron contents in the samples with a distinct “zero” mode, similar to that in the objects of Eurasia and the Atlantic, testifies to the predominantly cosmic origin of the native iron.     

Identification of arid phases during the last 50 cal. ka BP from the Fuentillejo maar‐lacustrine record (Campo de Calatrava Volcanic Field,Spain)

Geochemical (element analysis, molecular analysis of organic compounds), physical, palynological, mineralogical and sedimentary facies analysis were performed to characterise the sedimentary record in Fuentillejo maar‐lake in the Central Spanish Volcanic Field of Campo de Calatrava, in order to reconstruct the palaeoenvironmental and palaeoclimatic processes which controlled vegetation patterns and deposition of different sedimentary facies. The upper 20 m of core FUENT‐1 show variations in clastic input, water chemistry, vegetation and organic fraction sources in the lake throughout the Late Pleistocene and Holocene. The temporal framework provided by ¹⁴C accelerator mass spectrometry dating allows assigning the sequence to the last 50 cal. ka BP. Arid phases identified in the FUENT‐1 sequence are correlated to Heinrich events (HE) and to stadials of the Dansgaard/Oeschger (D/O) cycles. Siliciclastic facies with high magnetic susceptibility values, high Juniperus pollen content, a low Paq index (aquatic macrophysics proxy index), a decrease in the relative percentage of the n‐C₂₇ and an increase in the n‐C₃₁ alkanes are indicative of arid and colder climatic events related to HE 2, HE 1 and the Younger Dryas (YD). Similar short cold and arid phases during the Holocene were identified at 9.2–8.6, 7.5–7 and 5.5–5 cal. ka BP. In dolomite–mud facies, the pollen data show an increase in the herbs component, mainly – Chenopodiaceae, Artemisia and Ephedra – steppe taxa; a low Paq index, a decrease in the relative percentage of the n‐C₂₇ alkane and an increase in the n‐C₃₁ alkane are also observed. This facies was probably the result of lower lake levels and more saline–alkaline conditions, which can be interpreted as linked to arid–warm periods. These warm and arid phases were more frequent during Marine Isotope Stage (MIS) 3 and the interstadials of MIS 2. HE 4, HE 2, HE 1 and the YD in core FUENT‐1 were immediately followed by increases of warm steppe pollen assemblages that document rapid warming similar to the D/O cycles but do not imply increasing humidity in the area. Fuentillejo hydrology is controlled by changes in the atmospheric and oceanic systems that operated on the North Atlantic region at millennial scale during the last 50 cal. ka BP. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal X-ray emission from hot polar cap in drifting subpulse pulsars

Within the framework of the partially screened inner acceleration region the relationship between the X-ray luminosity and the circulational periodicity of drifting subpulses is derived. This relationship is quite well satisfied in pulsars for which an appropriate radio and X-ray measurements exist. A special case of PSR B0943+10 is presented and discussed. The problem of formation of a partially screened inner acceleration region for all pulsars with drifting subpulses is also considered. It is argued that an efficient inner acceleration region just above the polar cap can be formed in a very strong and curved non-dipolar surface magnetic field. We acknowledge the support of the Polish State Committee for scientific research under Grant P03D 029 26. G.M. was partially supported by Georgian NSF grant ST06/4-096.     

Las Cargas: Characterization and Prehistoric Use of a Southern Andean Obsidian Source

The importance of obsidian from the northern Patagonian source at Las Cargas is reflected in its early use (∼8000 years B.P.) and extensive geographic diffusion but is nonetheless surprising in light of the source's high altitude (located in the Andes Cordillera), which makes it both difficult to access under ideal conditions and inaccessible for much of the year. Prehistoric use of the Las Cargas source can inform us about mobility, subsistence choices, economics of stone consumption, trade, and territoriality. Here we present the results of various lines of evidence (surface survey, X‐ray fluorescence and instrumental neutron activation analyses, artifact morphometry, and obsidian hydration dating) used to characterize obsidian from Las Cargas and its prehistoric use during the Holocene. Results indicate that Las Cargas obsidian occurs at the source as blocks and nodules, which are chemically homogeneous and of variable quality. Use of the source was nearly continuous through time, and the primary knapping activities performed there were the production of blanks and preparation of cores.     

Asteroid polarimetric observations using the Torino UBVRI photopolarimeter

A long-term project of polarimetric observations of minor planets has been carried out since 1995 at the 2.15-m telescope of the El Leoncito Observatory (San Juan, Argentina) using the Torino photopolarimeter. We present here an updated summary of the results, including many measurements obtained during the most recent observing runs. The main purpose of the observations has been to obtain albedo estimates and compare them with previous IRAS radiometric determinations, mainly for objects having small (<50 km) IRAS diameters. Another field of investigation is the measurement of the degree of linear polarization at very small phase angles (less than 1°). The latter observations can be a useful input for modern theoretical models of light scattering from asteroid surfaces. In general, we have obtained a wealth of new results, including objects exhibiting a peculiar polarimetric behavior.     

PS-InSAR processing methodologies in the detection of field surface deformation—Study of the Granada basin (Central Betic Cordilleras,southern Spain)

Differential SAR interferometry (DInSAR) is a very effective technique for measuring crustal deformation. However, almost all interferograms include large areas where the signals decorrelate and no measurements are possible. Persistent scatterer interferometry (PS-InSAR) overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms.Two time series of 29 ERS-1/2 and 22 ENVISAT ASAR acquisitions of the Granada basin, located in the central sector of the Betic Cordillera (southern Spain), covering the period from 1992 to 2005, were analyzed. Rough topography of the study area associated to its moderate activity geodynamic setting, including faults and folds in an uplifting relief by the oblique Eurasian–African plate convergence, poses a challenge for the application of interferometric techniques. The expected tectonic deformation rates are in the order of ～1 mm/yr, which are at the feasibility limit of current InSAR techniques.In order to evaluate whether, under these conditions, InSAR techniques can still be used to monitor deformations we have applied and compared two PS-InSAR approaches: DePSI, the PS-InSAR package developed at Delft University of Technology (TU Delft) and StaMPS (Stanford Method for Persistent Scatterers) developed at Stanford University. Ground motion processes have been identified for the first time in the study area, the most significant process being a subsidence bowl located at the village of Otura.The idea behind this comparative study is to analyze which of the two PS-InSAR approaches considered might be more appropriate for the study of specific areas/environments and to attempt to evaluate the potentialities and benefits that could be derived for the integration of those methodologies.     

Integrating statistical information concerning historical floods: ranking and interval return period estimation

The importance of the historical information in flood analysis has previously been underlined. In this context, we present an integral methodology aimed at the establishment of return periods of different flood units on the unique basis of historical data. Specifically, the reconstruction of the flood chronology extended back to 1900, complemented with a new (historical data-based) event intensity index, and the return period estimation will be addressed. Since some of the historical data are collected from interviews and other sources with different degrees of precision and reliability, two kinds of uncertainty will be considered; namely the statistical variability and the imprecision. We propose an innovative methodology involving intervals (ranges), fuzzy sets, and weights to formalize and average the criteria that determine the importance of the different events. On the other hand, to take into account the statistical variability, we propose to estimate the return period in a flexible and efficient way by considering bootstrap confidence intervals. The methodology is particularly useful at ungauged, or partially gauged, flood inundation areas, where the existing flow gauge stations do not give the flood series at the point of interest. A case study developed in Spain is discussed. The results are supported by two recent events, which have been mapped at 1:5000 scale.     

A geographic data model for representing ground water systems

The Arc Hydro ground water data model is a geographic data model for representing spatial and temporal ground water information within a geographic information system (GIS). The data model is a standardized representation of ground water systems within a spatial database that provides a public domain template for GIS users to store, document, and analyze commonly used spatial and temporal ground water data sets. This paper describes the data model framework, a simplified version of the complete ground water data model that includes two-dimensional and three-dimensional (3D) object classes for representing aquifers, wells, and borehole data, and the 3D geospatial context in which these data exist. The framework data model also includes tabular objects for representing temporal information such as water levels and water quality samples that are related with spatial features.     

On the aberration–retardation effects in pulsars

The magnetospheric locations of pulsar radio emission region are not well known. The actual form of the so-called radius-to-frequency mapping should be reflected in the aberration–retardation (A/R) effects that shift and/or delay the photons depending on the emission height in the magnetosphere. Recent studies suggest that in a handful of pulsars the A/R effect can be discerned with respect to the peak of the central core emission region. To verify these effects in an ensemble of pulsars, we launched a project analysing multifrequency total intensity pulsar profiles obtained from the new observations from the Giant Meterwave Radio Telescope (GMRT), Arecibo Observatory (AO) and archival European Pulsar Network (EPN) data. For all these profiles, we measure the shift of the outer cone components with respect to the core component, which is necessary for establishing the A/R effect. Within our sample of 23 pulsars, seven show the A/R effects, 12 of them (doubtful cases) show a tendency towards this effect, while the remaining four are obvious counterexamples. The counterexamples and doubtful cases may arise from uncertainties in the determination of the location of the meridional plane and/or the core emission component. Hence, it appears that the A/R effects are likely to operate in most pulsars from our sample. We conclude that in cases where those effects are present the core emission has to originate below the conal emission region.