Sixty-five years of solar radioastronomy: flares, coronal mass ejections and Sun–Earth connection

This paper will review the input of 65 years of radio observations to our understanding of solar and solar–terrestrial physics. It is focussed on the radio observations of phenomena linked to solar activity in the period going from the first discovery of the radio emissions to present days. We shall present first an overview of solar radio physics focussed on the active Sun and on the premices of solar–terrestrial relationships from the discovery to the 1980s. We shall then discuss the input of radioastronomy both at metric/decimetric wavelengths and at centimetric/millimetric and submillimetric wavelengths to our understanding of flares. We shall also review some of the radio, X-ray and white-light signatures bringing new evidence for reconnection and current sheets in eruptive events. The input of radio images (obtained with a high temporal cadence) to the understanding of the initiation and fast development in the low corona of coronal mass ejections (CMEs) as well as the radio observations of shocks in the corona and in the interplanetary medium will be reviewed. The input of radio observations to our knowledge of the interplanetary magnetic structures (ICMEs) will be summarized; we shall show how radio observations linked to the propagation of electron beams allow to identify small scale structures in the heliosphere and to trace the connection between the Sun and interplanetary structures as far as 4AU. We shall also describe how the radio observations bring useful information on the relationship and connections between the energetic electrons in the corona and the electrons measured in-situ. The input of radio observations on the forecasting of the arrival time of shocks at the Earth as well as on Space Weather studies will be described. In the last section, we shall summarize the key results that have contributed to transform our knowledge of solar activity and its link with the interplanetary medium. In conclusion, we shall indicate the instrumental radio developments at Earth and in space, which are from our point of view, necessary for the future of solar and interplanetary physics.     

Classification of mineral water types and comparison with drinking water standards

In a study of 291 mineral waters from 41 different countries, 9–20% exceeded the Dutch drinking water standards for chloride, calcium, magnesium, potassium, sodium, sulphate, and fluorine. The mineral water quality cannot be qualified as bad because the standards for these compounds (with the exception of fluorine) are not based on health issues, but matters regarding undesirable taste and possible adverse effects on the water supply system. For the mineral water data set, the amount of dissolved compounds, hardness, and chloride content appear to be the most distinctive criteria. A mineral water type classification based on these criteria will offer consumers a tool for assessing mineral water on the basis of the chemical composition data on the bottle label. In terms of the criteria mentioned, average Dutch tap water strongly resembles the Belgian and Dutch mineral waters. This similarity does not extend to the price, since Dutch tap water is about 500 times cheaper.     

Patterns of halite (NaCl) crystallisation in building stone conditioned by laboratory heating regimes

The crystallisation of soluble salts within the pores of the stone is widely recognised as a major mechanism causing the deterioration of the stone-built architectural heritage. Temperature, in turn, is one of the main controls on this process, including salt precipitation, the pressure of crystallisation and the thermal expansion of salts. Most laboratory experiments on decay generated by salts are just carried out with convective heating regimes, while in natural environments building stones can undergo radiative and convective heating regimes. The thermal response of stone to these different heating regimes is noticeably different and might influence the crystallisation patterns of a salt within a stone. The aim of this work is to raise awareness on the different patterns of crystallisation of NaCl within a porous stone tested with different heating regimes (convection and radiation) and the implications that this could have on the design of experimental modelling of natural weathering conditions in laboratory simulations. Results show that heating regime affects the sodium chloride distribution within a stone with high percentage of microporosity. In this case, radiation heating facilitates the generation of subefflorescences, while convection heating promotes efflorescences. This has a clear implication both on the stone decay in natural environments and on the methodologies for testing salt decay, as subefflorescences are more destructive than efflorescences. In this sense, the use of convective heating in laboratory experimentation might underestimate the potential damage that sodium chloride may generate. This counsels the use of radiation heating test methods in addition to convection for the laboratory study of salt crystallisation.     

Le système régional d'action éolienne (SRAE) du bassin de l'Aral (Kazakhstan,Ouzbékistan et Turkménistan)The regional Aeolian action system of the Aral Basin

The endorheic basin of the Aral Sea, a tectonic depression resulting from two Tertiary fault bundles, NNE–SSW and east–west ones, represents the termination of a flow by closure of the Aral Basin opposite Central Asia and Siberia. The conditions of Quaternary climate and sediment deposition, especially aridity increased by coldness, a pedogenesis inhibitor, and absence of palaeosoils favour the activity of the Aralian Regional Aeolian Action System (RAAS), 700 km long. Such a system develops in a lowland topography where wind, in a progressive shift, reconstructs by deflation the sandy material resulting from Pleistocene accumulations, gives rise to thin and vulnerable ergs and explains at once the fertility of Khoresm and the dewatering of the Aral Sea, which is one of the most complex and severe ecological catastrophe in the 20th century. To cite this article: M. Mainguet et al., C. R. Geoscience 334 (2002) 475–480.     

Evolution quantitative à long terme des rotifères au cours de l'eutrophisation du Lac Léman

Eutrophication in Lake Geneva (= Lake Léman) appears primarily as changes in chemical characteristics and plankton populations, inducing quantitative changes in the rotifer assemblages and species combinations.In the course of eutrophication, an increase of the rotifer abundance was found, together with settlement of new species and increase of eutrophication tolerant species, and despite the decrease or disappearance of eutrophication sensitive species.The new equilibrium in the trophic state of Lake Geneva related with the decreasing inputs of nutrients, induces a new structure and less abundance of the total pelagic rotatorian community.

     

Meta-igneous origin of Hercynian peraluminous granites in N.W. French Massif Central: implications for crustal history reconstructions

Seventy samples of Hercynian peraluminous granites (Guéret, Millevaches and Saint Sylvestre massifs) and metamorphic units of the Limousin area were analysed for Rb–Sr and Sm–Nd. The source rocks of the peraluminous granites can be found in the metamorphic rocks of Limousin, among them meta-igneous rocks were largely predominent over meta-sedimentary rocks in the source of the three granites. Millevaches and Guéret granites were generated by the partial melting of rocks comprising meta-volcanics and meta-sediments, whereas the Saint Sylvestre granite was produced exclusively by the melting of late Precambrian granites. This leads to confusing T _DM ^Nd values, the confusion being amplified by the segregation of monazite during the petrogenetic evolution of the peraluminous granites, which leads to dramatic fractionation in Sm/Nd ratios. The data of the present study tend to demonstrate that peraluminous granites do not give a good representation of isotopic mean crustal estimates. Late Precambrian time seems, however, to have been a period of extensive crustal generation in Western Europe.     

The influence of trade winds,local air-masses and topographic obstacles on the aeolian movement of sand particles and the origin and distribution of dunes and ergs in the Sahara and Australia

The Saharan ergs consist of a wide range of aeolian land forms, while in Australia, sand-ridges are the main form. The ergs are situated along major sandflows of continental extent along which sand is transported. These are oriented approximately from NE to SW in the Sahara. In Australia they form an anticlockwise pattern open to the west. The spatial and temporal factors that govern the origin of sand-ridges are reviewed.