Multi-wavelength study of a high-latitude EUV filament

A large filament was observed during a multi-wavelength coordinated campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE) and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman series with the SOHO/SUMER spectrometer. Because of its high-latitude location, it is possible to disentangle the physical properties of the Hα filament and the filament channel seen in EUV lines. TRACE images point out a dark region fitting the Hα fine-structure threads and a dark corridor (filament channel), well extended south of the magnetic inversion line. A similar pattern is observed in the CDS EUV-line images. The opacity of the hydrogen and helium resonance continua at 171 Å is almost two orders of magnitude lower than that at the Hi head (912 Å) and thus similar to the opacity of the Hα line. Since we do not see the filament channel in Hα, this would imply that it should also be invisible in TRACE lines. Thus, the diffuse dark corridor is interpreted as due to the coronal ‘volume blocking’ by a cool plasma which extends to large altitudes. Such extensions were also confirmed by computing the heights from the projection geometry and by simulations of the CDS and TRACE line intensities using the spectroscopic model of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally, our NLTE analysis of selected hydrogen Lyman lines observed by SUMER also leads to a conclusion that the dark filament channel is due to a presence of relatively cool plasma having low densities and being distributed at altitudes reaching the Hα filament.     

Prediction of deuterium abundance in comets

Using a chemical scheme based on ion-molecule reactions in cool interstellar clouds, the possibility of a deuterium enrichment of volatile material in comets is discussed. It is assumed that the hydrogen-containing molecules are deuterated before accretion and condensation on the coremantle dust particles from which the cometesimals are formed. The D/H ratio in comets may be enhanced in respect to the average value by a factor of 10². Therefore comets are not promising objects for testing the primordial deuterium abundance.     

Eclipsing Binaries with Possible Light-Time Effect

The period changes of six eclipsing binaries have been studied with focus on the light-time effect. With the least squares method we also calculated parameters of such an effect and properties of the unresolved body in these systems. With these results we discussed the probability of presence of such bodies in the systems with respect to possible confirmation by another method. In two systems we also suggested the hypothesis of fourth body or magnetic activity for explanation of the "second-order variability" after subtraction of the light-time effect of the third body.     

Study of the filamentary infrared dark cloud G192.76+00.10 in the S254–S258 OB complex

We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide(CO), ammonia(NH3) and carbon monosulfide(CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, and its fragmentation and physical parameters. The gas temperature is derived from the NH3(J, K) =(1,1),(2, 2) and ~(12)CO(2-1) lines, and the ~(13)CO(1-0), ~(13)CO(2-1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2-1)data. Values of the gas temperature lie in the range 10-35 K, and column density N(H2) reaches the value 5.1 x 10~(22) cm~(-2). The width of the filament is of order 1 pc. The masses of the dense clumps range from ～ 30 M_☉ to ～ 160 M_☉. They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse.     

Beta-carotene—A possible biomarker in the Martian evaporitic environment: Raman micro-spectroscopic study

Due to the discovery of the evaporitic environment on the Martian surface, there is a reasonable possibility that evaporites served (or still serve) as habitats for microbial life if ever present on Mars. At the very least, if no signatures of extant life exist within these rocks, it may sustain molecular remnants as evidence for living organisms in the past. β-Carotene, among other carotenoids, could be such a suitable biomarker. In this study, Raman micro-spectroscopy was tested as a nondestructive method of determining the presence of β-carotene in experimentally prepared evaporitic matrices. Samples prepared by mixing β-carotene with powdered gypsum (CaSO₄·2H₂O), halite (NaCl) and epsomite (MgSO₄·7H₂O) were analyzed using a 785 nm excitation source. Various concentrations of β-carotene in the matrices were investigated to determine the lowest β-carotene content detectable by Raman micro-spectroscopy. Mixtures were also measured with a laser beam permeating the crystals of gypsum and epsomite in order to evaluate the possibility of identifying β-carotene inside the mineral matrix.We were able to obtain a clear β-carotene signal at the 10 mg kg⁻¹ concentration level—the number of registered β-carotene Raman bands differed depending on the particular mineral matrix. Spectral signatures of β-carotene were detected even when analyzing samples containing 1 mg kg⁻¹ of this molecule. The 10-100 mg kg⁻¹ of β-carotene in mineral matrices (halite, epsomite) was detected when analyzed through the monocrystal of gypsum and epsomite, respectively. These results will aid both in-situ analyses on Mars and sample analyses on Earth.     

The year-long unprecedented European heat and drought of 1540 – a worst case

The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring–summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km², we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models.     

Ice cover variability in the Caspian and Aral seas from active and passive microwave satellite data

The paper discusses time and space variations of ice extent in the Caspian and Aral seas during the last decade (1992-2002). It uses synergy of data from active (radar altimeter) and passive (radiometer) microwave nadir-looking instruments onboard the TOPEX/Poseidon satellite. The proposed approach is substantiated and validated using both in situ and satellite imagery data for the Caspian Sea. The results indicate significant spatial and temporal variability of ice conditions, with a significant decrease of both the duration of ice season and ice extent during the last four winters (1998-2002). The TOPEX/Poseidon-derived time series of sea ice extent are very valuable in view of the fragmentary and mostly unpublished data on ice conditions on the Caspian and Aral seas since the mid-1980s.