Hydromagnetic “whistles” at the dayside cusps: IPRP events

The current status of the morphological properties of the variation of the earth's magnetic field known as Intervals of Pulsations with Rising Periods (IPRP) observed at the polar cusp stations Casey, Mirny and Heiss throughout 1978 is presented. They have the characteristic of a “whistle” with steadily falling tone. Comprehensive observational and dynamical morphological accounts of the IPRP phenomenon are presented including new analyses of polarisation, power spectra and digital sonograms. Simultaneously occurring IPRP at the two widely spaced stations Casey and Mirny are examined. In an accompanying paper (Cole et al., 1982) a theory which accounts for the properties of the phenomenon is presented.     

The ratio between magnetotail height and neutral point height

The ratio between the magnetotail height and the neutral point height is exactly 2 in the classical calculation of the shape of the magnetopause following Chapman and Ferraro. This ratio is useful in assessing the results of calculations. There exist possibilities for improvement of magnetopause shape calculations, especially in the tail region or in the neutral point region for “tilted” cases.     

The quantity and condition of Martian underground water

It is widely accepted that Mars holds a quantity of water in its surface crustal region but the amount is unknown. The present arguments quantify this suspicion, offering an estimate of the quantity on the basis of certain consequences of the comparison between the present observed compositions of the atmospheres of the planets Earth, Venus, and Mars, and the inferred compositions of the mantles of the icy satellites. The results are consistent with alternative estimates such as they are but offer possibilities of regarding the problems of the crustal region of Mars in a different way.     

Detritus fuels ecosystem metabolism but not metazoan food webs in San Francisco estuary's freshwater delta

Detritus from terrestrial ecosystems is the major source of organic matter in many streams, rivers, and estuaries, yet the role of detritus in supporting pelagic food webs is debated. We examined the importance of detritus to secondary productivity in the Sacramento and San Joaquin River Delta (California, United States), a large complex of tidal freshwater habitats. The Delta ecosystem has low primary productivity but large detrital inputs, so we hypothesized that de tritus is the primary energy source fueling production in pelagic food webs. We assessed the sources, quantity, composition, and bioavailability of organic matter among a diversity of habitats (e.g., marsh sloughs, floodplains, tidal lakes, and deep river channels) over two years to test this hypothesis. Our results support the emerging principle that detritus dominates riverine and estuarine organic matter supply and supports the majority of ecosystem metabolism. Yet in contrast to prevailing ideas, we found that detritus was weakly coupled to the Delta's pelagic food web. Results from independent approaches showed that phytoplankton production was the dominant source of organic matter for the Delta's pelagic food web, even though primary production accounts for a small fraction of the Delta's organic matter supply. If these results are general, they suggest that the value of organic matter to higher trophic levels, including species targeted by programs of ecosystem restoration, is a function of phytoplankton production.     

Corrosion of metal roof materials related to volcanic ash interactions

Metal roofing material is commonly used for residential and industrial roofs in volcanically active areas. Increased corrosion of metal roofing from chemically reactive volcanic ash following ash deposition post-eruption is a major concern due to decreasing the function and stability of roofs. Currently, assessment of ash-induced corrosion is anecdotal, and quantitative data are lacking. Here, we systematically evaluate the corrosive effects of volcanic ash, specifically ash leachates, on a variety of metal roofing materials (i.e. weathered steel, zinc, galvanized steel, and Colorsteel©) utilizing weathering chamber experiments and direct acid treatments. Weathering chamber tests were carried out for up to 30 days, and visual, chemical, and surface analyses did not definitively identify significant corrosion in any of the test roofing metal samples. Direct concentrated acid treatments with hydrochloric (HCl), sulphuric (H₂SO₄), and hydrofluoric (HF) acids demonstrate that roofing materials are chemically resilient. Our experimental results suggest that ash-leachate-related corrosion is a longer-term process (>1 month), potentially related to a multitude of factors including increased ash leachate concentrations, the dissolution of the glass matrix of the ash, moisture retention at the ash-surface boundary, and potential reactions involving photo-oxidation. Overall, corrosion is not a simple process related to the short-term release of acid and/or salt leachates from the ash surface, but a product of dynamic interactions involving ash and water at the surface of metal roofing material for extended periods.     

The Subtropical Convergence east of New Zealand

Hydrographic data from the region of the Subtropical Convergence east of New Zealand between 177°E and 179°E show that in spring the convergence occurs near the Chatham Rise. North of the Chatham Rise the structure is fairly regular with isolines of temperature and salinity sloping upwards towards the south. To the south of the Chatham Rise the structure is more complex with an apparent intrusion of Subtropical Water into the Sub‐antarctic Water below depths of about 150 m.     

Simultaneous horizontal and vertical acoustic sounding of the atmospheric boundary layer

Some preliminary results from a series of experiments of simultaneous horizontal and vertical acoustic sounding of the atmosphere are described and discussed. The novel horizontal configuration offers some potential for investigating thermal plume motion and characteristics within the boundary layer. It could also be of use in assessing the importance of excess attenuation in quantitative acoustic sounding.