Radial variation of differential rotation in the solar electron corona

Long-lived brightness structures in the solar electron corona persist over many solar rotation periods and permit an observational determination of coronal magnetic tracer rotation as a function of latitude and height in the solar atmosphere. For observations over 1964–1976 spanning solar cycle 20, we compare the latitude dependence of rotation at two heights in the corona. Comparison of rotation rates from East and West limbs and from independent computational procedures is used to estimate uncertainty. Time-averaged rotation rates based on three methods of analysis demonstrate that, on average, coronal differential rotation decreases with height from 1.125 to 1.5 R _S. The observed radial variation of differential rotation implies a scale height of approximately 0.7 R _S for coronal differential rotation.Model calculations for a simple MHD loop show that magnetic connections between high and low latitudes may produce the observed radial variations of magnetic tracer rotation. If the observed tracer rotation represents the rotation of open magnetic field lines as well as that of closed loops, the small scale height for differential rotation suggests that the rotation of solar magnetic fields at the base of the solar wind may be only weakly latitude dependent. If, instead, closed loops account completely for the radial gradients of rotation, outward extrapolation of electron coronal rotation may not describe magnetic field rotation at the solar wind source. Inward extrapolations of observed rotation rates suggest that magnetic field and plasma are coupled a few hundredths of a solar radius beneath the photosphere.     

Application of the hypersonic analog to the standing shock of Mars

A magnetospheric boundary and its associated standing-shock wave for the earth are scaled down in size to apply to Mars. A suggestion by the Mariner-IV experimenters that their magnetometer may have detected a Martian shock at 0123 UT (earth) on July 15, 1965, is accepted. The scaling procedure used previously in the case of the Mariner-II flyby of Venus on December 14, 1962, as well as in the present case of Mars is repeated but with a different model. We propose a magnetospheric boundary for the earth, which is based on a maximum radius of 22 R _E suggested by Imp-1 magnetometer data. We further suggest a low value (1.2) of the adiabatic exponent, . In addition we propose the use of the interplanetary magnetoacoustic Mach number, M_*, which is a combination of both Alfvén and ordinary gasdynamic Mach numbers. Our choice of values for these parameters is not unique since many such combinations exist which will show good agreement with observation. For example, the ratio of the Martian dipole moment to that for the earth is found to be 2.1 × 10^–4 by our application of the hypersonic analog. This value compares very closely with 3 × 10^–4 deduced as an upper bound by the Mariner-IV investigators. The present synthesis is presented as an independent calculation based on the above theoretical considerations, together with the experimenters' probable observation of a Martian shock wave.Since this paper was submitted for publication, theoretical calculations of the steady-state average magnetic induction in the transition region for an interplanetary field oriented at several angles to the velocity vector have been published by A. Y. Alksne, Planetary Space Science 15 (1967), 239–245. As anticipated in the text above, the magnitudes are slightly changed, but the polarities are significantly different.Formerly the Central Radio Propagation Laboratory of the National Bureau of Standards.     

On the mean particle size and water content of polar mesospheric clouds

The ultraviolet spectrometer on board the Solar Mesosphere Explorer (SME) satellite has been measuring the scattering of ultraviolet sunlight from optically thin cloud layers in the upper boundary of the mesosphere (85 km) since the launch of the spacecraft in October 1981. These layers are present only at high latitudes during the summer season. During Summer 1983 an observing sequence was undertaken to measure the cloud radiance at two different scattering angles—one in the forward hemisphere at 50°, the other in the backward hemisphere at 130°. The data show a pronounced tendency for the brighter clouds to exhibit greater forward-scattering behavior, indicating that particle size may be the most important factor in determining the cloud brightness. We conclude that if the particles are monodisperse water ice aggregates, their radii do not exceed 70 nm. Estimates are provided for the water content and column particle number of the clouds, depending upon the unknown shape of the particle size distribution. Characterizing the distribution by two parameters, the spherical equivalent particle radius and the width of the distribution, the bulk cloud properties are shown to be dependent upon the limb radiance and the width parameter. For narrow widths the water ice content is less than that expected for the water vapor content at mesopause heights of a few parts per million. This confirms our earlier analysis using a smaller data set and assuming the cloud particles are monodisperse. However if the size dispersion is broad, the implied water ice exceeds the static atmospheric water supply. The calculated column number for the brightest clouds exceeds our estimates for the total supply of condensation nuclei. The alternative is that the brighter clouds are limited to a fairly narrow range of particle sizes from 40 to 60 nm. This conclusion is supported by theoretical time dependent calculations by Turco et al. (1982).     

Impact of offsite sediment transport and toxicity on remediation of a contaminated estuarine bay

Sediment of Ostrich Bay, an arm of Dyes Inlet on Puget Sound, was historically contaminated with ordnance compounds from an onshore US Navy facility. An initial recommendation for a sediment cover to mitigate benthic risks was followed by studies of sediment transport and deposition to determine whether contaminated sediment from Dyes Inlet or other offsite sources in Puget Sound may contribute to Ostrich Bay impacts. A Sediment Trend Analysis (STA) identified net sediment transport pathways throughout the bay and inlet by examining changes in grain size distributions in multiple adjacent samples. Results indicated that fine-grained sedimentary material transports into and deposits throughout the Dyes Inlet system, with no erosion or transport out of Ostrich Bay. Echinoderm larvae mortality bioassay results were elevated in fine-grained sediments of both Ostrich Bay and Dyes Inlet. Ordnance compounds were undetected, and although sediment mercury concentrations were elevated at 0.48-1.4 mg/kg in both waterbodies, the relationship with toxicity was weak. Results of the studies and sedimentation modeling indicate that impacted sedimentary material deposits throughout the Dyes Inlet/Ostrich Bay system from unknown sources and will prevent natural recovery of Ostrich Bay as well as negate long-term effectiveness of active remedial measures. Stakeholders have recognized that remediation of the bay can be achieved only after the toxicity of depositing sediment decreases.     

Application of biomarkers for assessing the biological impact of dredged materials in the Mediterranean: the relationship between antioxidant responses and susceptibility to oxidative stress in the red mullet (Mullus barbatus)

In the period 1997-2000, approximately 1,800,000 m3 of material dredged from the Port of Leghorn was discharged into a sea dumping site located 14 miles from the coast. The red mullet (Mullus barbatus) was used as a bioindicator species for monitoring the biological impact of these discharges on a geographical and temporal scale. Organisms were sampled over three years (1998-2000) at different stations and several biomarkers, both of exposure and effect, were analyzed. Bioavailability of specific classes of pollutants was evaluated by analyzing levels of metallothioneins, the activity of cytochrome P450 1A (CYPIA) and of glutathione S-transferases. Among biomarkers of effect, special attention was paid to the balance between prooxidant challenge and antioxidant defenses, and to the appearance of damage caused by oxidative stress. The analyses of the main components of the antioxidant system included superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glyoxalase I and II, and total glutathione. These data were integrated with the measurement of total oxyradical scavenging capacity (TOSC) as an indication of the overall biological resistance to toxicity of different forms of oxyradicals (peroxyl radicals, hydroxyl radicals and peroxynitrite). Results indicated a biological impact in organisms sampled near the disposal site; the impact was particularly evident during 1999 and mainly related to organic chemicals such as PAH. Exposure to these pollutants also caused variations in the levels and activity of several antioxidants. The analysis of TOSC, however, revealed that the overall capacity of specific tissues of organisms to absorb various oxidants was not seriously compromised when challenged with increased prooxidant pressures. Variations of single antioxidants were useful in revealing early warning "biological responses", while integration with TOSC analyses indicated if such changes also reflect a more integrated and functional "biological effect" with possible consequences at the organisms level. The red mullet appears to be a useful sentinel species for a biomarker approach to monitoring impact caused by dredged materials.     

Basic properties of magnetic flux tubes and restrictions on theories of solar activity

It is shown that the mean longitudinal field in a magnetic flux tube is reduced, rather than enhanced, by twisting the tube to form a rope. It is shown that there is no magnetohydrostatic equilibrium when one twisted rope is wound around another. Instead there is rapid line cutting (neutral point annihilation). It is shown that the twisting increases, and the field strength decreases, along a flux tube extending upward through a stratified atmosphere.These facts are at variance with Piddington's recent suggestion that solar activity is to be understood as the result of flux tubes which are enormously concentrated by twisting, which consist of several twisted ropes wound around each other, and which came untwisted where they emerge through the photosphere.This work was supported in part by the National Aeronautics and Space Administration under Grant NGL 14-001-001.     

Upward and downward continuation as inverse problems

Summary . The formalism of Backus & Gilbert is applied to the problems of upward and downward continuation of harmonic functions. We first treat downward continuation of a two-dimensional field to a level surface everywhere below the observation locations; the calculation of resolving widths and solution estimates is a straightforward application of Backus—Gilbert theory. The extension to the downward continuation of a three-dimensional field uses a delta criterion giving resolving areas rather than widths. A feature not encountered in conventional Backus—Gilbert problems is the requirement of an additional constraint to guarantee the existence of the resolution integrals. Finally, we consider upward continuation of a two-dimensional field to a level above all observations. We find that solution estimates must be weighted averages of the field not only on this level, but also on a line passing between the observations and sources. Weighting on the lower line may be traded off against resolution on the upper level.