The polarization of X-ray emission of some solar flares in July 1974

Preliminary results of polarization measurements at three solar flares of July 5 and 6, 1974, are given. The measurements were performed at h 15 keV with Thomson-scattering polarimeter on the Intercosmos 11 satellite.At the decay phase of the flare on July 5 we obtained P = 3.4–5.0%, which did not exclude some contribution from non-thermal processes. At the flares of July 6 we found P =1.0–1.9% and P = 0.1–2.0%, respectively: neither value exceeds the level of statistical fluctuations.Presented at XVIII COSPAR Meeting (VARNA, May–June 1975), contribution III.B.2.9.     

Bias of ostracod stable isotope data caused by drying of sieve residues from water

Stable isotope analysis of ostracod shells is used routinely for palaeoenvironmental studies of ostracod-bearing records. Sample treatment usually involves the disaggregation of sediments and sieving; before the sieving residues were washed with water onto petri dishes and oven-dried. In our study, we compared δ¹⁸O and δ¹³C values of shells that were oven-dried from water and from ethanol alternatively. Large isotopic differences of up to 3‰ were determined for δ¹⁸O values, whereas differences in δ¹³C values were less pronounced with differences of up to 1.6‰. Stable isotope values of shells dried from water were lower for both oxygen and carbon as a result of calcite crystals precipitated on the shell surfaces during the drying process. Therefore, ostracod shells for stable isotope analysis should not be prepared by drying from water. Instead, shells should be dried from ethanol to obtain reliable stable isotope data; likewise freeze-drying is expected to provide trustworthy results.     

青藏高原东缘晚新生代成都盆地物源分析与水系演化

成都盆地位于青藏高原东缘,夹于龙门山与龙泉山之间,盆地中充填了3.6Ma以来的大邑砾岩、雅安砾石层和晚更新世—全新世砾石层,其物源均来源于盆地西侧的龙门山,具横向水系和单向充填的特征。本次以物源区分析作为切入点,以岷江和青衣江水系为重点,采用砾岩成分分析、砂岩岩屑成分分析、重矿物分析和砾石的地球化学分析等基本方法,开展青藏高原东缘晚新生代以来的古水系重建工作,研究结果表明,成都盆地主要有两个物源区,其中成都盆地北部的都江堰街子场、崇州白塔山、大邑白岩沟、大邑氮肥厂、彭州丁家湾、彭州葛仙山等剖面中的砾石层在碎屑成分、重矿物和花岗岩砾石的地球化学成分等方面相似,应为古岷江的产物,而其与现代岷江在砾岩成分和重矿物特征等方面的差异性则表明古岷江可能存在改道的现象;成都盆地南部的庙坡剖面和熊坡东剖面中的砾石层在碎屑成分、重矿物和花岗岩砾石的地球化学成分等方面相似,应为古青衣江的产物,但其流向却与现代青衣江的流向不同,表明熊坡背斜是在大邑砾岩沉积之后隆起的,它的隆起迫使古青衣江改道。     

The Intensity–Velocity Phase Spectra of Evanescent Oscillations and Acoustic Sources

There are three major issues in modeling solar evanescent oscillations: the variation of the intensity [I]–velocity [V] phase difference of p-modes close to the base of photosphere; the existence of a plateau of negative I–V phase differences below and between the ridges of the low-frequency p-modes; the explanation of the I–V cross-spectra of the evanescent oscillations. We present new interpretations for the first two issues, based on modeling intensity fluctuations taking steep temperature gradients, opacity, and non-adiabatic cooling into account. We also discuss consequences of our model for the explanation of power spectra and cross-power spectra of p-modes. In particular, we present evidence that the acoustic sources that generate evanescent waves produce a coherent background that explains the plateau–interridge regime of negative I–V phase difference.     

3‐D hydrodynamic simulations of the solar chromosphere

We present first results of three‐dimensional numerical simulations of the non‐magnetic solar chromosphere, computed with the radiation hydrodynamics code CO⁵BOLD. Acoustic waves which are excited at the top of the convection zone propagate upwards into the chromosphere where the waves steepen into shocks. The interaction of the waves leads to the formation of complex structures which evolve on short time scales. Consequently, the model chromosphere is highly dynamical, inhomogeneous, and thermally bifurcated.     

Clam community composition and prey shell size impacts moon snail (Gastropod: Naticidae) drilling frequencies in South Carolina,USA

Moon snail predation on clams is a common model system of predator–prey interactions. In this system, the predator bores through the shell of its prey, leaving a distinct and identifiable hole. Some paleoecological and behavioral research on moon snails suggests a trend in predation preference directed toward clams with small shells. Rarely, however, have studies tested relative drilling frequencies across species and size ranges in natural assemblages of clam communities. We examined the clam community composition at two beaches in South Carolina, USA, and we then tested moon snail predator preferences for (a) clam prey species and (b) whether their selection is related to prey shell size. We collected a total of 1,879 clam shells, identified each shell to species and recorded their anteroposterior length. The species composition of clams differed significantly between the two beaches; Anadara ovalis was dominant at both sites, but three of ten total species were only collected at one beach. Folly Beach had nearly a 60% higher the overall drilling frequency (34.6%) versus Edisto Beach (21.8%), and this may be linked to the differences in clam community compositions at the sites. For A. ovalis and Mulinia lateralis, shells with larger lengths have lower probabilities of being bored by a moon snail. Anadara brasiliana, which generally is a thinner‐shelled clam species, had the highest total drilling frequency (77.2%), and Noetia ponderosa, a thicker‐shelled clam, had a considerably lower drilling frequency (12.0%). We conclude that both community level factors (species composition) and population characteristics (shell size distributions) may influence the local drilling frequency by moon snails.     

Present rate of uplift in Fennoscandia from GRACE and absolute gravimetry

Fennoscandia is a key region for studying effects of glacial isostatic adjustment. The associated mass variations can be detected by the Gravity Recovery and Climate Experiment (GRACE) satellite mission, which observes the Earth's gravity field since April 2002, as well as by absolute gravimetry field campaigns. Since 2003, annual absolute gravity (AG) measurements have been performed in Fennoscandia by the Institut für Erdmessung (IfE, Institute of Geodesy) of the Leibniz Universität Hannover, Germany, within a multi-national cooperation. This offers a unique opportunity for validation and evaluation of the GRACE results. In this preliminary study, the GRACE results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the FG5-220 gravimeter of the IfE.The results from GRACE monthly solutions provided by different analysis centres show temporal gravity variations in Fennoscandia. The included secular variations are in good agreement with former studies. The uplift centre is located west of the Bothnian Bay, the whole uplift area comprises Northern Europe. Nevertheless, the differences between the GRACE solutions are larger than expected and the different centre-specific processing techniques have a very strong effect on possible interpretations of GRACE results. The comparison of GRACE to the AG measurements reveals that the determined trends fit well with results from GRACE at selected stations, especially for the solution provided by the GFZ. Variations of land hydrology clearly influence results from GRACE and the AG measurements.     

Spatial and temporal changes in dry-snow line altitude on the Antarctic Peninsula

Drastic changes were detected in glacial systems of the Antarctic Peninsula in the last decades. The observed phenomena comprise the disintegration of ice shelves, acceleration and thinning of glaciers, and retreat of glacier fronts. However, due to the lack of consistent systematic observations in particular of the higher parts of the glacial systems, it is difficult to predict further responses of the Antarctic Peninsula glaciers to climatic change. The present paper analyses spatial and temporal variations of changes in the dry-snow line altitude on the Antarctic Peninsula as extracted from a time series (1992–2005) of ERS-1/2 SAR and Envisat ASAR data. Upward changes in dry-snow line altitude were observed in general, and are attributed to extreme high-temperature events impacting the central plateaus of the Antarctic Peninsula and the increasing duration of warming periods. A mean decrease in dry-snow line altitude was detected on the west side of the peninsula and is identified as a response to recorded increase in precipitation and accumulation. These results validate the capability of SAR data for deriving superficial parameters of glaciers to be used as indicators of climatic changes in high-latitude regions where operational restrictions limit conventional meteorological observations.     

Why delaying emission reductions is a gamble

In the debate on the timing of greenhouse gas emissions reductions the aspect of political feasibility has often been missing. We introduce this aspect and show that, if we decide to delay emissions reductions, and the environmental effectiveness of global mitigation efforts is to remain the same in terms of temperature change, we must be willing and able to undertake much more substantial emission reductions than with early action. Even under conservative assumptions on initial political feasibility (maximum 0.25% year-on-year reductions), a 20-year delay means that we must reduce emissions at an annual rate that is 5 to 11 times greater than with early climate action. Our capacity for technological progress, political change and the inertia of the socio-economic system gives us reason to be concerned about our ability to achieve such higher rates of emission reductions. If we are not able to achieve such higher rates, delaying action will inevitably result in higher temperatures in 2100. Unless we are willing to accept higher temperatures, choosing to delay climate action is a gamble that political feasibility will increase over time as a result of the delay itself.     

Walking through volcanic mud: the 2,100-year-old Acahualinca footprints (Nicaragua)

We present the stratigraphy, lithology, volcanology, and age of the Acahualinca section in Managua, including a famous footprint layer exposed in two museum pits. The ca. 4-m-high walls of the main northern pit (Pit I) expose excellent cross sections of Late Holocene volcaniclastic deposits in northern Managua. We have subdivided the section into six lithostratigraphic units, some of which we correlate to Late Holocene eruptions. Unit I (1.2 m thick), chiefly of hydroclastic origin, begins with the footprint layer. The bulk is dominated by mostly massive basaltic-andesitic tephra layers, interpreted to represent separate pulses of a basically phreatomagmatic eruptive episode. We correlate these deposits based on compositional and stratigraphic evidence to the Masaya Triple Layer erupted at Masaya volcano ca. 2,120 ± 120 a B.P.. The eruption occurred during the dry season. A major erosional channel unconformity up to 1 m deep in the western half of Pit I separates Units II and I. Unit II begins with basal dacitic pumice lapilli up to 10 cm thick overlain by a massive to bedded fine-grained dacitic tuff including a layer of accretionary lapilli and pockets of well-rounded pumice lapilli. Angular nonvesicular glass shards are interpreted to represent hydroclastic fragmentation. The dacitic tephra is correlated unequivocally with the ca. 1.9-ka-Plinian dacitic Chiltepe eruption. Unit III, a lithified basaltic-andesitic deposit up to 50 cm thick and extremely rich in branch molds and excellent leaf impressions, is correlated with the Masaya Tuff erupted ca. 1.8 ka ago. Unit IV, a reworked massive basaltic-andesitic deposit, rich in brown tuff clasts and well bedded and cross bedded in the northwestern corner of Pit I, cuts erosionally down as far as Unit I. A poorly defined, pale brown mass flow deposit up to 1 m thick (Unit V) is overlain by 1–1.5 m of dominantly reworked, chiefly basaltic tephra topped by soil (Unit VI). A major erosional channel carved chiefly between deposition of Units II and I may have existed as a shallow drainage channel even prior to deposition of the footprint layer. The swath of the footprints is oriented NNW, roughly parallel to, and just east of, the axis of the channel. The interpretation of the footprint layer as the initial product of a powerful eruption at Masaya volcano followed without erosional breaks by additional layers of the same eruptive phase is strong evidence that the group of 15 or 16 people tried to escape from an eruption.