Scintillations and Interstellar Lévy Flights

We present the new model for interstellar scintillations, which assumes that the electron density fluctuations causing the scintillations obey Lévy statistics rather than Gaussian statistics, as was thought previously. Our model explains the observed anomalous scaling of the signal time-width with respect to the pulsar distance, which remained a puzzle for more than 30 years.     

Geochemistry and petrology of howardite Miller Range 11100: A lithologically diverse piece of the Vestan regolith

The howardite‐eucrite‐diogenite (HED) clan of meteorites, which most likely originate from the asteroid Vesta, provide an opportunity to combine in‐depth sample analysis with the comprehensive remote‐sensing data set from NASA's recent Dawn mission. Miller Range (MIL) 11100, an Antarctic howardite, contains diverse rock and mineral fragments from common HED lithologies (diogenites, cumulate eucrites, and basaltic eucrites). It also contains a rare pyroxferroite‐bearing lithology—not recognized in HED until recently—and rare Mg‐rich (Fo_86‐91) olivine crystals that possibly represent material excavated from the Vestan mantle. Clast components underwent different histories of thermal and impact metamorphism before being incorporated into this sample, reflecting the diversity in geological histories experienced by different parts of Vesta. The bulk chemical composition and petrography of MIL 11100 suggest that it is akin to the fragmental howardite meteorites. The strong lithological heterogeneity across this sample suggests that at least some parts of the Vestan regolith show heterogeneity on the mm‐scale. We combine the outcomes of this study with data from NASA's Dawn mission and hypothesize on possible source regions for this meteorite on the surface of Vesta.     

Variability of emission lines in the optical spectra of the Herbig Be binary system HD 200775

In our previous papers we have improved the value of the orbital period of the binary Herbig Be star HD 200775 and showed that the [O I] and Si II 6347 and 6371 ?A emission lines displayed variations which correlate with the orbital period. In this paper we provide evidences that other broad emission lines of metals in the spectra of HD 200775 also exhibit variability, which is probably related to the orbital cycle of the binary. Analysis was performed based on the high-resolution spectral data collected over a time span of 6 years at the Kourovka Astronomical Observatory of the Ural Federal University(Russia) and the Three College Observatory of the University of North Carolina at Greensboro(USA) as well as archival spectral data compiled since 1994. We report new data points in the radial velocity curve of the He I 5876 ?A line near the extremal values of the radial velocity.     

Some pressure test phenomena of worden and CG-2 (sharpe) gravimeters

Summary The results of pressure tests of gravimeters Worden No. 961, CG-2 Nos 174 G, 323 and 374 in a pressure chamber are presented. Apart from deriving the barometric correction, the authors have also studied accompanying phenomena, which occur during pressure tests of gravimeters — the barometric after-effect and hysteresis. The processing of the results in two ways differing in the method of eliminating the drift of the gravimeter, yields nearly identical results. The hysteresis was investigated for atmospheric pressures of 720±150 Torr (1 Torr=0.133322 kPa), a rate of change of 30 Torr/min and a temperature of 22°C. The barometric after-effect was investigated in greater detail for the CG-2 gravimeter No. 174 G at a pressure difference of 225 Torr, rate of change of 30, 15 and 7.5 Torr/min and a gravimeter heating temperature of 35 °C. It was also found that the barometric correction can be determined, using the method given, with sufficient accuracy. As a result of the existence of hysteresis, however, the derived results must be applied carefully in field gravity measurements with some gravimeters.     

A new conglomerate test in palaeomagnetism

The conglomerate test is widely used in palaeomagnetism to date components of natural remanent magnetization with respect to deposition of conglomerates. It has been demonstrated, however, that this test may be positive even if the data are strongly contaminated by a secondary remanence, especially for the commonly used small number of clasts Starkey & Palmer 1970). Here we show with the aid of numerical simulations that different statistical procedures employed in this test have similar low sensitivities to remagnetization. We suggest a new conglomerate test which incorporates additional information on the direction of a secondary palaeomagnetic component which is isolated from either clasts themselves or their host rocks. Numerical simulations show that this new test is about twice as sensitive to remagnetization as the previous procedures and is robust with respect to small errors in the direction of a secondary component.     

Asteroid 2002NY40 as a source of meteorite-dropping bolides

The existence of asteroidal meteoroid streams capable of producing meteorite-dropping bolides has long being invoked, but evidence is scarce. Recent modelling of previously reported associations suggests that the time-scales to keep the orbital coherence of these streams producing meteorites are too short. We present an unequivocal association between near earth object (NEO) 2002NY40 and at least one bright fireball detected over Finland in 2006 August. Another two additional fireballs recorded from Spain and Finland seem to be related, together producing a fireball-producing stream (β Aquarids). On the basis of historical data, the 2006 finding suggests the existence of a meteoroid complex capable of producing meteorites. Taking into account present time-scales for orbital decoherence, if 2002NY40 has large meteoroids associated with it, such behaviour would be the consequence of a relatively recent asteroidal fragmentation. Supporting our claim, the heliocentric orbits of two recently discovered NEOs, 2004NL8 and 2002NY40, were found to exhibit a good similarity to each other and also to the orbits of the three bolides. The fireball spectra of the two Finish bolides showed that the chemical abundances of these objects are consistent with the main elements found in chondrites. This result is consistent with the probable Low iron, Low metal (LL) chondritic mineralogy of asteroid 2002NY40. Consequently, this asteroid may be delivering LL chondrites to the Earth. Additional fireball reports found in the literature suggest that the associated β Aquarid complex may have been delivering meteorites to the Earth during, at least, the last millennium.     

Bivalves as indicators of environmental variation and potential anthropogenic impacts in the southern Barents Sea

Identifying patterns and drivers of natural variability in populations is necessary to gauge potential effects of climatic change and the expected increases in commercial activities in the Arctic on communities and ecosystems. We analyzed growth rates and shell geochemistry of the circumpolar Greenland smooth cockle, Serripes groenlandicus, from the southern Barents Sea over almost 70 years between 1882 and 1968. The datasets were calibrated via annually-deposited growth lines, and growth, stable isotope (δ¹⁸O, δ¹³C), and trace elemental (Mg, Sr, Ba, Mn) patterns were linked to environmental variations on weekly to decadal scales. Standardized growth indices revealed an oscillatory growth pattern with a multi-year periodicity, which was inversely related to the North Atlantic Oscillation Index (NAO), and positively related to local river discharge. Up to 60% of the annual variability in Ba/Ca could be explained by variations in river discharge at the site closest to the rivers, but the relationship disappeared at a more distant location. Patterns of δ¹⁸O, δ¹³C, and Sr/Ca together provide evidence that bivalve growth ceases at elevated temperatures during the fall and recommences at the coldest temperatures in the early spring, with the implication that food, rather than temperature, is the primary driver of bivalve growth. The multi-proxy approach of combining the annually integrated information from the growth results and higher resolution geochemical results yielded a robust interpretation of biophysical coupling in the region over temporal and spatial scales. We thus demonstrate that sclerochronological proxies can be useful retrospective analytical tools for establishing a baseline of ecosystem variability in assessing potential combined impacts of climatic change and increasing commercial activities on Arctic communities.