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.     

Raman spectroscopic investigation of two grains from comet 81P/Wild 2: Information that can be obtained beyond the presence of sp2‐bonded carbon

Abstract– Raman analyses were performed of individual micrometer‐sized fragments of material returned to Earth by the NASA Stardust mission to comet 81P/Wild 2. The studied fragments originated from grains (C2054,0,35,91,0 and C2092,6,80,51,0) of two different penetration tracks that occurred in two different silica aerogel collector cells. All fragments of both particles have Raman spectra characteristic of amorphous sp²‐bonded carbon that are in general agreement with the results published in previous Stardust particle studies. The present study, however, does not focus on the discussion of specific details of the D and G band parameters, but rather reports on additional information that can be obtained from returned Stardust samples via Raman spectroscopy. Most notably, the Raman spectra show that all analyzed fragments of the particles were contaminated with the capture medium (i.e., aerogel). The silica aerogel is laced with organic aliphatic and aromatic hydrocarbon impurities that resulted in strong bands in the ～ 2900 Δcm^?1 spectral range (C‐H stretching modes). Aerogel bands are also found in the 1000–1600 Δcm^?1 spectral range, where they overlap with the bands of the amorphous sp²‐bonded carbon. The peaks associated with the aerogel contamination differ between the two grains that originated from two different aerogel cells. In addition to the bands due to aerogel contamination and the always present sp²‐bonded carbon bands, fragments of particle C2092,6,80,51,0 also show Raman peaks for pyrrhotite and Fa₃₀Fo₇₀ olivine. Complete (up to 4000 Δcm^?1) raw and baseline‐corrected Raman spectra of the Stardust particles are shown and discussed in detail.     

Aquatic and terrestrial proxy evidence for Middle Pleistocene palaeolake and lake-shore development at two Lower Palaeolithic sites of Schöningen,Germany

The archaeological sites in the open-cast mine of Schöningen, Germany, represent outstanding archives for understanding Middle Pleistocene interglacial–glacial transitions and human adaption. Aquatic microfossil and pollen assemblages from the ‘Reinsdorf sequence’, likely correlated to Marine Isotope Stage 9, document environmental changes from a thermal maximum to succeeding glacial conditions recorded in two sequences of excavation sites 12 II and 13 II. Multi-proxy analyses enable detailed reconstruction of lake-shore and landscape developments despite variable microfossil preservation in changing carbonate- and organic-rich deposits. Rich aquatic vegetation with abundant charophytes suggests repeated phases with water depths of 0.5–2 m at site 13 II, while even greater temporary depths are deduced for 12 II DB. Mesorheophilic and mesotitanophilic ostracod species indicate stream inflows with medium–low calcium contents of >18 mg Ca L^–1 originating from nearby springs. Diatoms point to meso-eutrophic conditions and an alkaline pH of the lake water. Interglacial conditions with thermophile forests but no aquatic microfossils preserved, suggesting a dry or only temporarily flooded site, mark the beginning of the sequence. Continuous presence of aquatic organisms and overall dominance of small tychoplanktonic diatoms during a subsequent cool steppe phase provide evidence for increased water depths and unstable habitats characterized by erosion and probably prolonged periods of lake ice cover. During the succeeding boreal forest-steppe phase, surface runoff into the productive, shallow lake decreased due to a more extensive vegetation cover. Concurrently, intensified groundwater input in contact with the nearby salt wall caused elevated salinities. Following a lake level drop, stream inflows and lake levels increased again towards the end of the Reinsdorf sequence and promoted development of a diverse fauna and flora at the lake shore; thereby maintaining an attractive living and hunting environment for early humans during a phase of generally cooler temperatures and landscape instability at the transition into a glacial period.     

Revealing the coastal event-history of the Andaman Islands (Bay of Bengal) during the Holocene using radiocarbon and OSL dating

Earthquakes that trigger tsunamis are of great geological, ecological and socio-economic importance. The knowledge of the recurrence interval of these events will give information about the hazard for a region. Coastal sediments on the Andaman Islands located in the eastern Bay of Bengal were investigated to find evidence for palaeotsunamis and palaeoearthquakes. Fieldwork was conducted on Red Skin Island and North Cinque Island, south of South Andaman. Sediment material from event-layers was dated by optically stimulated luminescence and radiocarbon dating method. The results show evidence possibly for one earthquake at about 1,000 or 3,000 years before the present together with deposits from possible tsunamis and storms. The complex pattern of co- and post-seismic uplift and subsidence of the Andaman Islands is reflected in the investigated sections and made it possible to reconstruct an event-history for the last 3,000 years.     

Seismic stratigraphy of the NW Moroccan Atlantic continental shelf and Quaternary deformation at the offshore termination of the southern Rif front

A recent high resolution seismic survey was carried out along the North-West Moroccan Atlantic continental shelf to perform sequence stratigraphy and to better understand the link between the onshore observations across the western termination of the Rif front and the multibeam bathymetric data previously collected across the Gulf of Cadiz. Seismic interpretation clearly shows evidence of deformation affecting the Pleistocene sedimentary cover. This is mainly located between the Lalla Zahra ridge and the Neogene nappes that outcrop at the seabed to the North of Larache, where the identified structures bound the upper part of a gravitationally spreading lobe and are interpreted to be developed by activation of the major tectonic structures located at the southern front of the Rif Cordillera. The offshore extension of the Lalla Zahra Ridge is characterised by an east-west trending major folded and faulted corridor. This structure marks the active front of Prerifan area and corresponds to a major Quaternary kinematic boundary in the western prolongation of the ENE-WSW trending Jebha fault.