Bidimensional spectroscopy of network bright points

We develop an automatic, computer controlled procedure to select and to analyze the Network Bright Points (NBPs) on solar images. These have been obtained at the Sac Peak Vacuum Tower Telescope by means of the Universal Birefringent Filter and Zeiss H filters, tuned, respectively, along the profiles of the H, Mg-b1, Na-D2, and H lines.A structure is identified as an NBP if at the wavelength H- 1.5 A its maximum intensity is greater than I + 3 and its area is greater than 1.5 arc sec² at I + 1.5, where I is the mean value and the standard deviation of the intensity distribution on the image. Each detected NBP is then searched and confirmed in all the remaining 31 images at different wavelengths.For each NBP several parameters are measured (position, area, mean and maximum contrast, Dopplergram velocity, compactness, and so on) and some identification constraints are applied.The statistical analysis of the various parameter distributions, for NBPs present within an active region and its surroundings, shows that two types of NBPs can be identified according to the value of their mean contrast C _min the H- 1.5 Å image (C _m 0.1 type I, C _m> 0.1 type II). The type I NBPs (all occurring on the boundaries of the supergranular network) appear to be much more frequent (180/26) than the type II ones.The size A of type I NBPs is less than 1.0 arc sec for H/H wings but of the order of 1.2 arc sec for Na-D2 and Mg-bl. The mean contrast C _m is around the value of 10% along the Na-D2 and Mg-bl profiles and of 20% along the H/H wings.The C _m - A scatter diagrams show, for the photospheric radiation (h < 100 km), a narrow range of variability for C _min correspondence with a wide range for A. For radiation orginated at higher levels (h > 200 km), the C _m- A scatter diagrams seem to indicate, even if with a large variance, that the highest C _m's tend to correspond to the highest A values.The mean Doppler shift is close to zero for Na-D2 and Mg-bl lines but negative (downward motion) for H and H lines.The type II NBPs tends to be preferentially located in the neighbourhood of small, compact sunspots and their detectability is almost constant through all the 4 studied line profiles. No conclusions can be derived on the mean size, contrast and Doppler shift values because their distributions are too dispersed. The only positive information is that its C _m- A scatter diagram, in H and H wings, indicates a wide range of variability for C _m in correspondence with very narrow range of variability for A.     

Effects of mass transfer on an oscillating free-convection flow in the Stokes's problem past an infinite porous vertical limiting surface with heat sources and variable suction

An analysis of the effects of the mass transfer on the unsteady free-convection flow of a viscous incompressible fluid, past an impulsively started infinite porous vertical limiting surface with heat sources is presented, when the free-stream velocity and the suction velocity, are oscillating in the time about constant mean values. Approximate solutions for the coupled nonlinear equations are derived for the mean velocity, the mean temperature, the mean skin-friction, and the mean rate of heat transfer. All the above quantities are shown graphically followed, by a discussion.     

Problems with the interpretation of the 220 nm interstellar feature

The bump in the ultraviolet part of the interstellar extinction curve provides a great challenge in the modelling of interstellar dust. Its shape can be well approximated by a classical dispersion profile with a total halfwidth of 48 nm centred at 217 nm. Apart from few slightly deviating cases the parameters of the band seem to be surprisingly constant in the solar neighbourhood.The equivalent widthW of the 217 nm band shows a very tight correlation with the colour excessE(B-V). Studies of correlations with the strength of diffuse interstellar bands gave no conclusive results as to the nature of the band.The most common interpretation of the 217 nm feature as originating from small graphite grians meets several difficulties. No final decision on the carrier can be made at present.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.     

An estimate of the contribution of high nergy cosmic-ray protons to the absorbed dose inventory of a cometary nucleus

We discuss the contribution of cosmic-ray protons at all energies above 1 MeV to the absorbed doses of the surface layers of a comet. Since there exists no calculation which takes into account proton energy losses by means of losses to electrons and nuclear collisions (in a cascade process), and losses due to the low energy end-products of the cascade, we have made a rough estimate of all of these contributions. An analytical formula is proposed that allows a rapid estimate of ranges and the dose absorbed at any depth. We give dose-depth curves for two extreme values of the energy at which nuclear collisions begin to dominate the slowing-down process, and for an intermediate value we display the dose-depth curve down to 20 m from the surface. The relevance of these findings to dosimetry in comets and some alterations of cometary material are considered. The need for improving the analytical expression proposed is stressed.     

An analysis of the spectrum of the zeta geminorum

Four spectrograms of the cepheid Geminorum at different phases have been analysed for the determination of the abundances of various elements. The analysis shows that the atmosphere of Gem has an essentially solar composition.     

Culgoora radio and skylab euv observations of emerging magnetic flux in the lower corona

Detailed comparisons of Culgoora 160 MHz radioheliograms of solar noise storms and Skylab EUV spectroheliograms of coronal loop structures are presented. It is concluded that: (1) there is a close association between changes in large-scale magnetic fields in the corona and the onset or cessation of noise storms; (2) these coronal changes result from the emergence of new magnetic flux at the photospheric level; (3) although new magnetic flux at the photospheric level is often accompanied by an increase in flare activity the latter is not directly responsible for noise storm activity; rather the new magnetic flux diffuses slowly outwards through the corona at rates 1–2 km s^–1 and produces noise storms at 160 MHz 1–2 days later; (4) the coronal density above or in large-scale EUV loop systems is sufficiently dense to account for noise storm emission at the fundamental plasma frequency; (5) the scatter in noise storm positions can be accounted for by the appearance and disappearance of individual loops in a system.     

Polarimetry of comets: A review

Some attempts of polarimetric sounding of Comet Halley will be undertaken from the flyby probes. In order to facilitate the final planning and the future interpretation of these experiments we have done a thorough analysis of practically all available polarimetric observations. An emphasis is made on interpretation attempts and their discussion. The results of the phase dependence of polarization investigations are presented covering a wide range of phase angles . The chief peculiarities of this dependence are: maximum polarization at = 90, diminishing through zero at 20, negative values up to several per cent and a final growth to zero at zero . A division into gaseous and dusty comets on polarimetric basis is revealed. The wavelength dependence of polarization is discussed. The numerous results of detailed polarimetry are compared to the negative results of attempts to detect the elliptical polarization. New observational problems arising from the evidence given by the negative polarization at small phase angles and by the opposition effect recently discovered are discussed.     

Premature mortality in the Republic of Ireland

Regional variations in the incidence of premature deaths between 1971 and 1981 arc examined by mapping standardised mortality ratios for deaths under the age of 65. Premature mortality is also examined with regards to the number of years of normal life lost by those who die prematurely, using a specially defined unfulfilled life index. Unfulfilled life and premature deaths arc found to have a higher incidence in the major urban areas and a lower incidence in western counties, although there are some interesting differences in their spatial distributions. Differences with regard to sex. age at death and cause of death are also examined.     

Population development in Greater Santiago between 1970 and 1982: an analysis of district census results

"An attempt is made in the light of an analysis of population changes occurring in several sub-districts of Greater Santiago in the period between the last population censuses of 1970 and 1982, based on small-area census units (distritos and communas) to draw attention to the effects on the spatial growth of the city resulting from changed conditions in the political and juridical sphere since the change of power in 1973." The effect of changes in government policy concerning the liberalization of the property market and the illegal occupation of land are noted. (summary in ENG)     

Nonlinear wave conversion in electron-positron plasmas

Wave conversion mechanisms causing large-frequency shifts are considered for an electron-positron plasma in a strong magnetic field. In particular, we discuss the effects of the nonlinear erenkov as well as the cyclotron resonances in order to associate pulsar radio-emissions with our present model for nonlinear conversion of high-frequency radiation into the low-frequency region.