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.     

Effect of increased nitrogen fixation on stratospheric ozone

Nitrogen compounds are produced by biological reactions and by industrial processes from the abundant nitrogen gas (N₂) in the atmosphere. The formation of compounds from atmospheric nitrogen is called fixation. In nature, nitrogen compounds undergo many conversions, but under aerobic conditions, characterized by the presence of oxygen, they tend to be converted to the nitrate (NO ₃ ^- ) form. Under anaerobic conditions, characterized by the absence of oxygen, the nitrate is denitrified, and the nitrogen contained therein is converted into nitrogen gas (N₂) and nitrous oxide (N₂O), which escape into the atmosphere. The nitrous oxide diffuses into the stratosphere, where it decomposes to yield nitrogen gas and small amounts of nitric oxide (NO) and nitrogen dioxide (NO₂), which react with ozone (O₃) to convert it to oxygen (O₂). The ozone in the stratosphere is produced by the reaction of light with oxygen and is destroyed primarily by reactions with the nitrogen oxides.As long as the production and destruction are equal, the ozone in the stratosphere is maintained at a constant concentration. Increased nitrogen fixation will lead to increased denitrification, increased amount of nitrous oxide moving into the stratosphere, and a reduction in ozone concentration.Ozone in the stratosphere attenuates the ultraviolet light received from the sun. As the ozone concentration decreases, more ultraviolet light will reach the surface of the earth. The fear is that this additional radiation will have detrimental effects on living organisms and possibly on the climate.Because the global use of fixed nitrogen in fertilizers has increased greatly in recent years and in 1974 amounted to almost 40 million metric tons, the eventual generation of nitrous oxide from the fertilizer nitrogen after application to the soil has been cited as a potential environmental hazard. In response to this concern, this document estimates nitrogen fixation, nitrous oxide production, and ozone reduction based on two methods of calculation and on various increases in nitrogen fixation. Uncertainties and information gaps in the nitrogen cycle are pointed out.This document does not review either the projected biological effects of ozone depletion or the stratospheric chemistry of ozone. These topics are dealt with at length in other studies.World fixation of nitrogen in 1974, expressed in millions of metric tons per year (MT/yr), was estimated to be as follows.Most of the estimates given are based on inadequate data; consequently, actual amounts may be significantly different from those shown. The study of nitrogen fixed in the oceans has not progressed far enough to permit reliable estimates. However, estimates of the amount of nitrogen fixed for fertilizer and other industrial uses in 1974 are considered reliable. The trend of industrial fixation of nitrogen offers some indication of the trend in total amount of nitrogen fixed. It is estimated that 174 MT of nitrogen were fixed by all processes in 1950. Total fixation in 1850 could have been 150 MT of nitrogen.Nitrous oxide-nitrogen production on land is estimated as 5 to 10 MT/yr; published estimates of production in the ocean, however, range from less than 1 to 100 MT/yr. The higher value was based on reported supersaturation of ocean waters with nitrous oxide.Two methods of estimating the decrease in ozone concentration in the stratosphere were used. Method I is based on nitrogen fixation. It involves the assumptions that the relative increase in production of nitrous oxide is proportional to the relative increase in total nitrogen fixation and that sufficient time has elapsed for the rate of denitrification to come to equilibrium with fixation; i.e., the lag time between increased fixation and increased denitrification has passed. This method, using fixation estimated for 1950 as a base, suggests that the reduction in ozone would be 5.8 and 11.5% as a consequence of increased fixation of 50 and 100 MT of nitrogen per year, respectively.Method II is based on nitrous oxide evolution. It involves the assumption that the global rate of production of nitrous oxide is 100 MT/yr (based on supersaturation of this gas in the ocean and on changes in measured concentrations of nitrous oxide in the atmosphere). Method II leads to estimates of ozone reduction much lower than those from Method I. For example, on the assumption that global production of nitrous oxide-nitrogen is 100 MT/yr and that 5% of the nitrogen denitrified is released as nitrous oxide, the estimated ozone reduction is 1% with an increase of 100 MT/yr in nitrogen fixation. This method is forced to assume an unknown source of nitrous oxide in the ocean and an unknown sink for nitrous oxide in the troposphere.There are great uncertainties in many of the estimates that have been made for nitrogen fixation and for nitrous oxide production, and there are many information gaps that need to be filled before the question of the effects of increased nitrogen fixation on the ozone layer can be answered. Perhaps the biggest information needs are in the areas of nitrogen transformations and the quantities of nitrous oxide produced in the ocean. Other needs deal with the complexities of the nitrogen cycle on land. The lag time between fixation by various processes and denitrification must be known as a basis for estimating how soon predicted effects based on equilibrium conditions can be expected. Concentrations of nitrous oxide and their fluctuations in the troposphere (lower atmosphere) need to be monitored to provide an index to variations and increases in production. Improved models are needed to relate the ozone concentration in the stratosphere to nitrogen fixation and nitrous oxide production on earth.In spite of the uncertainties in the predictions of the effects of increased fixation of nitrogen on stratospheric ozone, the potential hazard is sufficiently serious that, in addition to research on the various phases of the global nitrogen cycle that impinge upon the nitrous oxide-ozone question, research on the efficiency of use of all fixed forms of nitrogen should be worthwhile. Editor's Note: Although the data for sources, sinks, reservoirs, and rate processes in this article are undergoing rapid revision presently, it, nonetheless, is one of the clearest statements of the physics, chemistry, and biology of the fertilizer/ozone problem available to date.This report was developed by eleven scientists (see Appendix 1 for names and affiliations) representing the subject matter areas of atmospheric chemistry, chemical engineering, environmental science and chemistry, microbiology, oceanography, plant genetics, soil biochemistry, soil physics, and soil chemistry. This task force of scientists chaired by Parker F. Pratt, met under the auspices of the Council for Agricultural Science and Technology (CAST), whose headquarters office is at the Department of Agronomy, Iowa State University, Ames, Iowa 50011, U.S.A. The task force met in Denver, Colorado from October 23 to 25, 1975, to prepare a first draft of the report. The chairman then prepared a revised version and returned it to members of the task force for review and comment. A second revision was then prepared and returned for further comment. Finally, the report was edited and reproduced for transmittal through the U.S. Congressional Committees concerned with the matter of ozone depletion. It was originally issued as a CAST Report Number 53, January, 1976, but had not been formally published heretofore.     

Assessing multifaceted vulnerability and resilience in order to design risk-mitigation strategies

Vulnerability studies have evolved significantly in recent decades. Although not overly theoretical compared with some other fields of science, some important conceptual progress has been made. At the practical level, vulnerability indicators have been used either at a generic level or for particular hazard contexts. However, these indicators are often predictably too narrow in their coverage of aspects of vulnerability. An important need remains to produce more conceptually informed vulnerability indicators or parameters and more satisfactory operational tools to assess weaknesses and resilience in coping with natural risks. In this paper, we present the methodology developed in the context of a recently concluded EU funded project, ENSURE (Enhancing resilience of communities and territories facing natural and na-tech hazards). The resulting vulnerability and resilience assessment framework tool adopts a systemic approach embedding and integrating as much as possible the multifaceted and articulated nature of concepts such as vulnerability and resilience. The tool guides evaluators towards a comprehensive and context-related understanding of strengths and fragilities of a given territory and community with respect to natural extremes. In this paper, both the framework tool and its application to Sondrio in Italy, which is exposed to flash floods, are presented and discussed. The merits and demerits of the new tool are discussed, and the results of the application to Sondrio indicate where data are currently missing, suggesting the kind of data, which will need to be gathered in future to achieve more complete assessments. The results also suggest vulnerability reduction policies and actions and further ways of revising the existing framework tool in the future.     

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures

We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky  (| b | > 10°)  . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with  ( K , H , J , r _F, b _J) ≤ (12.65, 12.95, 13.75, 15.60, 16.75)  . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with   z ≤ 0.1  , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS .     

Modelled and measured concentrations of peroxy radicals and nitrate radical in the U.S. Gulf Coast region during TexAQS 2006

Measurements of total peroxy radicals (HO₂?+?RO₂) and nitrate radical (NO₃) were made on the NOAA research vessel R/V?Brown along the U.S. Gulf Coast during the TexAQS 2006 field campaign. The measurements were modelled using a constrained box-model based upon the Master Chemical Mechanism (MCM). The agreement between modelled and measured HO₂?+?RO₂ was typically within ??40% and, in the unpolluted regions, within 30%. The analysis of the model results suggests that the MCM might underestimate the concentrations of some acyl peroxy radicals and other small peroxy radicals. The model underestimated the measurements of NO₃ by 60?C70%, possibly because of rapid heterogeneous uptake of N₂O₅. The MCM model results were used to estimate the composition of the peroxy radical pool and to quantify the role of DMS, isoprene and alkenes in the formation of RO₂ in the different regions. The measurements of HO₂?+?RO₂ and NO₃ were also used to calculate the gas-phase budget of NO₃ and quantify the importance of organic peroxy radicals as NO₃ sinks. RO₂ accounted, on average, for 12?C28% of the total gas-phase NO₃ losses in the unpolluted regions and for 1?C2% of the total gas-phase NO₃ losses in the polluted regions.     

Distribution and assessment of sediment toxicity in Tamaki Estuary,Auckland, New Zealand

Heavy metal levels in surface sediments from Tamaki Estuary demonstrate significant up estuary increases in Cu, Pb, Zn, Cd and mud concentrations. Increased metal levels towards the head of the estuary are linked to local catchment sources reflecting the historical development, industrialisation and urbanisation of catchment areas surrounding the upper estuary. The relatively narrow constriction in the middle estuary (Panmure area), makes it susceptible to accumulation of upper estuary pollutants, since the constriction reduces circulation and extends the time required for fine waterborne sediments in the upper estuary to exchange with fresh coastal water. As a result fine fraction sediments trapped in the upper estuary facilitate capture and retention of pollutants at the head of the estuary. The increase in sandy mud poor sediments towards the mouth of the estuary is associated with generally low metal concentrations. The estuary’s geomorphic shape with a mid estuary constriction, sediment texture and mineralogy and catchment history are significant factors in understanding the overall spatial distribution of contaminants in the estuary. Bulk concentration values for Cu, Pb, Zn, and Cd in all the studied surface samples occur below ANZECC ISQG-H toxicity values. Cd and Cu concentrations are also below the ISQG-L toxicity levels for these elements. However, Pb and Zn concentrations do exceed the ISQG-L values in some of the surface bulk samples in the upper estuary proximal to long established sources of catchment pollution.     

AVIAN NESTING HABITS AND VEGETATION STRUCTURE

Discriminant analysis is used to identify relationships between vegetation structure and nesting behavior in 78 breeding bird communities in North America. Results indicated that bird communities associated with structurally similar vegetation exhibited similar arrays of nesting habits despite their geographical separation. Tree-cavity, intermediate-cup, and high-cup nesters dominated forests and woodlands; ground-cup and ground-scrape nesters dominated grasslands; and low-cup nesters dominated desert, scrub, and some woodland sites. These functional relationships are distinct from previously reported continental scale relationships between avian feeding habits and gross vegetation structure. Links between nesting behavior and vegetation structure provide us, as geographers, with a means for placing birds into a physical landscape perspective.