Density fluctuations measured by ISEE 1–2 in the Earth’s magnetosheath and the resultant scattering of radio waves

Radio waves undergo angular scattering when they propagate through a plasma with fluctuating density. We show how the angular scattering coefficient can be calculated as a function of the frequency spectrum of the local density fluctuations. In the Earths magnetosheath, the ISEE 1–2 propagation experiment measured the spectral power of the density fluctuations for periods in the range 300 to 1 s, which produce most of the scattering. The resultant local angular scattering coefficient can then be calculated for the first time with realistic density fluctuation spectra, which are neither Gaussian nor power laws. We present results on the variation of the local angular scattering coefficient during two crossings of the dayside magnetosheath, from the quasi-perpendicular bow shock to the magnetopause. For a radio wave at twice the local electron plasma frequency, the scattering coefficient in the major part of the magnetosheath is b(2f_p) 0.5–4 × 10^–9 rad²/m. The scattering coefficient is about ten times stronger in a thin sheet (0.1 to IR_E) just downstream of the shock ramp, and close to the magnetopause.     

A pictorial comparison of interplanetary magnetic field polarity,solar wind speed,and geomagnetic disturbance index during the sunspot cycle

Observations of interplanetary magnetic field polarity, solar wind speed, and geomagnetic disturbance index (C9) during the years 1962–1975 are compared in a 27-day pictorial format that emphasizes their associated variations during the sunspot cycle. This display accentuates graphically several recently reported features of solar wind streams including the fact that the streams were faster, wider, and longer-lived during 1962–1964 and 1973–1975 in the declining phase of the sunspot cycle than during intervening years (Bame et al., 1976; Gosling et al., 1976). The display reveals strikingly that these high-speed streams were associated with the major, recurrent patterns of geomagnetic activity that are characteristic of the declining phase of the sunspot cycle. Finally, the display shows that during 1962–1975 the association between long-lived solar wind streams and recurrent geomagnetic disturbances was modulated by the annual variation (Burch, 1973) of the response of the geomagnetic field to solar wind conditions. The phase of this annual variation depends on the polarity of the interplanetary magnetic field in the sense that negative sectors of the interplanetary field have their greatest geomagnetic effect in northern hemisphere spring, and positive sectors have their greatest effect in the fall. During 1965–1972 when the solar wind streams were relatively slow (500 km s^-1), the annual variation strongly influenced the visibility of the corresponding geomagnetic disturbance patterns.Visiting Scientist, Kitt Peak National Observatory, Tucson, Arizona.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

The photospheric magnetic flux budget

The ensemble of bipolar regions and the magnetic network both contain a substantial and strongly variable part of the photospheric magnetic flux at any phase in the solar cycle. The time-dependent distribution of the magnetic flux over and within these components reflects the action of the dynamo operating in the solar interior. We perform a quantitative comparison of the flux emerging in the ensemble of magnetic bipoles with the observed flux content of the solar photosphere. We discuss the photospheric flux budget in terms of flux appearance and disappearance, and argue that a nonlinear dependence exists between the flux present in the photosphere and the rate of flux appearance and disappearance. In this context, we discuss the problem of making quantitative statements about dynamos in cool stars other than the Sun. This paper evolved out of a more comprehensive version which appeared in Harvey (1993).     

Terrigenous dissolved organic matter along an estuarine gradient and its flux to the coastal ocean

The contribution of terrigenous organic matter (TOM) to high molecular weight dissolved and particulate organic matter (POM) was examined along the salinity gradient of the Delaware Estuary. Dissolved organic matter (DOM) was fractionated by ultrafiltration into 1–30 kDa (HDOM) and 30 kDa–0.2 μm (VHDOM) nominal molecular weight fractions. Thermochemolysis with tetramethylammonium hydroxide (TMAH) was used to release and quantify lipids and lignin phenols. Stable carbon isotopes, fatty acids and lignin content indicated shifts in sources with terrigenous material in the river and turbid region and a predominantly algal/planktonic signal in the lower estuary and coastal ocean. Thermochemolysis with TMAH released significant amounts of short chain fatty acids (C₉–C₁₃), not seen by traditional alkaline hydrolysis, which appear to be associated with the macromolecular matrix. Lignin phenol distributions in HDOM, VHDOM and particles followed predicted sources with higher concentrations in the river and turbid region of the estuary and lower concentrations in the coastal ocean. TOM comprised 12% of HDOM within the coastal ocean and up to 73% of HDOM within the turbid region of the estuary. In the coastal ocean, TOM from high molecular weight DOM comprised 4% of total DOC. The annual flux of TOM from the Delaware Estuary to the coastal ocean was estimated at 2.0×10¹⁰ g OC year⁻¹ and suggests that temperate estuaries such as Delaware Bay can be significant sources of TOM on a regional scale.     

ISO Far-IR spectroscopy of IR-bright galaxies and ULIRGs

Based on far-infrared spectroscopy of a small sample of nearbyinfrared-bright and ultraluminous infrared galaxies (ULIRGs) with theISO Long Wavelength Spectrometer we find adramatic progression in ionic/atomic fine-structure emission line andmolecular/atomic absorption line characteristics in these galaxiesextending from strong [O III]52,88 m and [N III]57 m lineemission to detection of only faint [C II]158 m line emissionfrom gas in photodissociation regions in the ULIRGs. The molecularabsorption spectra show varying excitation as well, extending fromgalaxies in which the molecular population mainly occupies the groundstate to galaxies in which there is significant population in higherlevels. In the case of the prototypical ULIRG, the merger galaxy Arp220, the spectrum is dominated by absorption lines of OH, H₂O, CH,and [O I]. Low [O III]88 m line flux relative to the integratedfar-infrared flux correlates with low excitation and does not appear tobe due to far-infrared extinction or to density effects. A progressiontoward soft radiation fields or very dusty H II regions may explainthese effects.     

Experimental field assessment of suspended sediment pathways for characterizing hydraulic habitat

The distribution of particulate matter within river channels, including sediments, nutrients and pollutants, is fundamental to the survival of aquatic organisms. However, the interactions between flow and sediment transport at the patch scale of river systems represents an under‐researched component of physical habitat studies, particularly those concerning the characterization of ‘physical biotopes’ (riffles, runs, pools, glides). This paper describes a field methodology for exploring the transfer of particulate matter at small scales within river channels, which may be used to aid hydraulic habitat characterization. The field protocol combines field measurement of high frequency flow properties, to characterize hydraulic habitat units, and deployment of spatial arrays of turbidity probes, to detect the passage of artificially‐induced sediment plumes through different biotope units. Sediment plumes recorded by the probes are analysed quantitatively in the manner of the flood hydrograph, and qualitative inferences are made on the dominant mixing processes operating within different parts of the channel. Relationships between the nature of spatio‐temporal hydraulic variations within glide, riffle and pool biotopes, and the character and mixing behaviour of sediment plumes within these habitat units are identified. Results from these preliminary experiments suggest that investigating and characterizing the transfer and storage of sediments, nutrients and pollutants within and between different biotopes is a viable avenue for further research, with potential to contribute to improved physical habitat characterization for river management and habitat restoration. The experiments are also an illustration of the value of neglected synergies between process geomorphology, ecology and river hydraulics. Copyright © 2010 John Wiley & Sons, Ltd.     

The fate of terrestrial organic matter in two Scottish sea lochs

Sea lochs are zones of rapid organic matter (OM) turnover. Most of this OM is of allochthonous origin, being introduced into the lochs via freshwater input. In this study the behaviour of terrestrially derived OM was elucidated using a combination of parameters which indicate OM diagenesis in the near surface sediments from two Scottish sea lochs, Loch Creran and Loch Etive. Alkaline CuO oxidation was used to determine lignin phenols which serve as biomarkers for terrestrial OM in sediments. Stable carbon isotope, total carbon and nitrogen and total OM (including the labile and refractory fractions) compositions were also determined.     

Fatty acids and sterols as source markers of organic matter in sediments of the North Carolina continental slope

To estimate the source and diagenetic state of organic matter reaching bottom sediments, fatty acids and sterols were measured in unconsolidated surface material (flocs) at 12 sites ranging from 600 to 2000 m across the mid-Atlantic continental slope off Cape Hatteras, North Carolina. Total free and esterefied fatty acids were similar in distribution and concentration to other coastal systems, with values ranging from 0.64 to 46.52 μg mg⁻¹ organic carbon (1.10–68.85 μg g⁻¹ dry sediment). Although shallow (600 m) stations contained significantly greater fatty acid concentrations than deep (> 1400m) stations, high variability observed at mid-depth (800 m) collections precluded a consistent relationship between total fatty acid concentration and station depth. At three sites where underlying sediments were also collected, decreases in total fatty acids, reduced amounts of polyenoic acids and significant presence of bacterial fatty acid suggest rapid reworking of labile organic material that reaches the sediment surface. The distribution of sterols was remarkably consistent among all sites even though there were large variations in concentrations (1.8–20.7 μg mg⁻¹ organic carbon). Sterol composition indicated phytoplankton, principally diatoms and dinoflagellates, as the principal source of labile organic matter to sediments, together with a significant input of cholest-5-en-3β-ol typical of zooplankton and their feeding activity. A minor but widespread terrigenous input was also evident based upon significant concentrations of sterols dominant in vascular plants.     

Geochemistry and petrology of selected coal samples from Sumatra, Kalimantan, Sulawesi, and Papua, Indonesia

Indonesia has become the world's largest exporter of thermal coal and is a major supplier to the Asian coal market, particularly as the People's Republic of China is now (2007) and perhaps may remain a net importer of coal. Indonesia has had a long history of coal production, mainly in Sumatra and Kalimantan, but only in the last two decades have government and commercial forces resulted in a remarkable coal boom. A recent assessment of Indonesian coal-bed methane (CBM) potential has motivated active CBM exploration. Most of the coal is Paleogene and Neogene, low to moderate rank and has low ash yield and sulfur (generally < 10 and < 1 wt.%, respectively). Active tectonic and igneous activity has resulted in significant rank increase in some coal basins. Eight coal samples are described that represent the major export and/or resource potential of Sumatra, Kalimantan, Sulawesi, and Papua. Detailed geochemistry, including proximate and ultimate analysis, sulfur forms, and major, minor, and trace element determinations are presented. Organic petrology and vitrinite reflectance data reflect various precursor flora assemblages and rank variations, including sample composites from active igneous and tectonic areas. A comparison of Hazardous Air Pollutants (HAPs) elements abundance with world and US averages show that the Indonesian coals have low combustion pollution potential.     

Characteristic size and diffusion of quiet sun magnetic patterns

We have previously studied large-scale motions using high-resolution magnetograms taken from 1978 to 1990 with the NSO Vacuum Telescope on Kitt Peak. Latitudinal and longitudinal motions were determined by a two-dimensional crosscorrelation analysis of pairs of consecutive daily observations using small magnetic features as tracers. Here we examine the shape and amplitude of the crosscorrelation functions. We find a characteristic length scale as indicated by the FWHM of the crosscorrelation functions of 16.6 ± 0.2 Mm. The length scale is constant within ±45° latitude and decreases by about 5% at 52.5° latitude; i.e., the characteristic size is almost latitude independent. The characteristic scale is within 3% of the average value during most times of the solar cycle, but it increases during cycle maximum at latitudes where active regions are present. For the time period 1978–1981 (solar cycle maximum), the length scale increases up to 1.7 Mm or 10% at 30° latitude. In addition, we derive the average amplitude of the crosscorrelation functions, which reflects the diffusion of magnetic elements and their evolutionary changes (including formation and decay). We find an average value of 0.091 ± 0.003 for the crosscorrelation amplitude at a time lag of one day, which we interpret as being caused by the combined effect of the lifetime of magnetic features and a diffusion process. Assuming a lifetime of one day, we find a value of 120 km² s^–1 for the diffusion constant, while a lifetime of two days leads to 230 km² s^–1.Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.