Resik: A Bent Crystal X-ray Spectrometer for Studies of Solar Coronal Plasma Composition

We describe the RESIK (REntgenovsky Spektrometr s Izognutymi Kristalami) instrument, consisting of two double-channel X-ray spectrometers, designed to observe solar active region and flare plasmas. RESIK is one of the instruments making up the scientific payload of the Russian CORONAS-F solar mission. The uncollimated spectrometer uses two silicon and two quartz bent crystals observing flare, active region and coronal spectra in four wavelength bands with a resolving power (/ ) of 1000. The wavelength coverage, 3.3–6.1 Å, includes emission lines of Si, S, Cl, Ar, and K and in the third diffraction order, the wavelength range includes He-like Fe lines (1.85 Å) and Ni lines (1.55 Å) with dielectronic satellites, emitted during intense, hot flares. The instrument is believed to be the best calibrated space-borne crystal spectrometer flown to date. The spectrometer dynamically adjusts the data gathering intervals from 1 s to 5 minutes, depending on the level of solar X-ray emission at the time of observation. The principal aims of RESIK are the measurements of relative and absolute element abundances in the emitting plasma and the temperature distribution of plasma (differential emission measure) over the temperature interval 3 and 50 MK. This paper summarizes the scientific objectives of RESIK and describes the design, characteristics, and performance of the instrument.     

Temperature structure of active regions deduced from the helium-like sulphur lines

Solar active-region temperatures have been determined from the full-Sun spectra of helium-like sulphur (Sxv) observed by the Bragg Crystal Spectrometer on board theYohkoh satellite. The average temperature deduced from Sxv is demonstrated to vary with the solar activity level: A temperature of 2.5 × 10⁶ K is derived from the spectra taken during low solar activity, similar to the general corona, while 4 × 10⁶ K is obtained during a higher activity phase. For the latter, the high-temperature tail of the differential emission measure of active regions is found most likely due to the superposition of numerous flare-like events (micro/nano-flares).     

Meiofauna meso-scale variability in two estuarine habitats

Spatial and temporal variations in meiofauna abundances were measured for 13 months within two estuarine habitats, an intertidal mudflat and a small, usually subtidal pond. Three locales within each habitat were sampled monthly (nine replicate cores per habitat) to quantify nematode and copepod species within-habitat, meso-scale (m-km) variation. Significant levels of variation were found between habitats (all taxa tested), among locales within habitats (all taxa except the harpacticoid species Microarthridion littorale) and among months. The magnitude of variation differed greatly within the two habitats. Species with marsh affinities predominated in two of the three mudflat locales, while the third locale was predominated by subtidal species. This within-habitat heterogeneity was related to the proximity to the marsh and/or to the position on an exposure gradient. Although significant meso-scale variability was also found in the pond, species responses were more individualistic suggesting that physical gradients were not as influential. These data indicate that meso-scale variability should be considered when planning long-term or baseline meiofauna investigations to assure that the study is representative of the habitat and that subsequent ecological inferences are valid.     

Spectroscopy of six highly evolved Abell planetary nebulae

We have undertaken visual spectroscopy of the highly evolved planetary nebulae (PNe) A8, A13, A62, A72, A78 and A83 over a wavelength range  4330 < λ < 6830 Å  . This permits us to specify relative line intensities in various sectors of the nebular shells, and to investigate the variation of emission as a function of radius. We determine that the spectrum of the central star of A78 has varied appreciably over a period of 25 yr. There is now evidence for strong P Cygni absorption in the λ4589 and λ5412 transitions of He  ii , implying terminal velocities of the order of   V _∞≅ 3.83 × 10³ km s⁻¹  . We also note that the emission-line profiles of the sources can be used to investigate their intrinsic emission structures. We find that most PNe show appreciable levels of emission throughout their volumes; only one source (A13) possesses a thin-shell structure. Such results are in conformity with evolutionary theory, and probably reflect the consequences of adiabatic cooling in highly evolved outflows.     

Ulysses observations of the planetary depletion layer at Jupiter

The repeated samplings of the Jovian magnetosheath during the Ulysses encounter with Jupiter provided an opportunity to probe the planetary depletion layer. Of the 10 complete crossings of the Jovian magnetopause, only three contained clear signatures of an overlying depletion layer. All of these occurred on the flanks of the magnetosphere near the dusk terminator; crossings on the dayside were ambiguous or clearly lacked a depletion layer signature. In this paper we present a detailed analysis of the observations by the Ulysses solar wind plasma and magnetometer experiments and discuss conditions favorable and unfavorable for depletion layer observation.     

Standards for multilateral and worldwide exchange of geothermal data

Standards for the exchange of machine-readable data are discussed at five levels covering (1) physical characteristics of the medium used in the exchange, (2) overall structure of the data file, (3) format of individual records, (4) types of information contained in a record, and (5) authority files for information definition. The standards are used by the National Geothermal information Resource for compilations of geothermal energy data.This paper was presented at the International Geological Correlation Program (IGCP) Project 98 entitled Standards for Computer Applications in Resource Studies held at Loen, Norway, September 27–October 1, 1976.     

Rock fragment distributions and regolith evolution in the Ouachita Mountains,Arkansas, USA

Rock fragments in the regolith are a persistent property that reflects the combined influences of geologic controls, erosion, deposition, bioturbation, and weathering. The distribution of rock fragments in regoliths of the Ouachita Mountains, Arkansas, shows that sandstone fragments are common in all layers, even if sandstone is absent in parent material. Shale and sandstone fragments are produced at the bedrock weathering front, but the shale weathers rapidly and intact fragments are rare in the solum. Sandstone is weathered from ridgetop outcrops and transported downslope. Some of these fragments are moved downward, by faunalturbation and by transport into pits associated with rotting tree stumps. Upward movement by treethrow is common, resulting in a net concentration of rocks near the surface. However, the highest fragment concentrations are in the lower regolith, indicating active production at the weathering front. The regolith is a dynamic feature, reflecting the influences of vertical and horizontal processes, of active weathering at the bedrock interface, and of surficial sediment movements. The role of trees in redistributing rock fragments suggests that significant regolith mixing occurs over time scales associated with forest vegetation communities, and that forest soils have likely been extensively mixed within Holocene and historic time. Copyright © 2005 John Wiley & Sons, Ltd.