Simultaneous measurements of No and No2 in the stratosphere

Simultaneous measurements of NO and NO₂ in the stratosphere leading to an NO_x determination have been performed by means of i.r. absorption spectrometry using the Sun as a source in the 5·2 μm band of NO and in the 6·2 μm band of NO₂. The observed abundance of NO_P peaks at 26 km where it is equal to (4·2 ± 1) × 10⁹ cm^?3. The volume mixing ratio of NO_p was observed to vary from 1·3 × 10^?9 at 20 km to 1·3 × 10^?8 at 34 km.     

Perturbation of the granular pattern by the presence of magnetic flux tubes

The presence of flux tubes, visible as Network Bright Points (NBP) at the surface of the Sun outside active regions, disturbs the granular pattern in a similar way as it can be observed in laboratory convection experiments. Around an NBP, granules are smaller, more numerous than around a normal intergranular space without NBP; they are elongated and pointing towards it. Such a perturbation is visible several minutes before the appearance of the NBP, indicating that the magnetic flux, although not yet visible as a bright point, is already interacting with the convection pattern. The perturbation reaches its maximum within one minute after the NBP appearance; and the granular pattern returns to normal just after the NBP disappearance.     

Lunar surface mass distribution from dynamical point-mass solution

Combined efforts of the Jet Propulsion Laboratory and Aerospace Corporation have provided a front side lunar gravity field using the Doppler tracking data from the United States Lunar Orbiters IV and V. Data reduction was accomplished with a model which included all dynamical motion due to gravitational perturbations, as well as all tracking geometries. The field is represented as a grid of 580 surface mass points which are contoured and show correlations with various lunar surface features.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.     

Guest Editorial Latest developments in GIS/LIS

Abstract

Significant achievements have taken place in Geographical/Land Information Systems (GIS/LIS). An attempt is made to give an overview of the state of the art as well as a vision of progress still to be accomplished. Key issues are discussed in various GIS/LIS activities. A generic analysis shows that most of the applications are environment-oriented. The various GIS/LIS topical issues are discussed in the order of an ascending graph, including data capture, data structure and modelling, data quality and standards, institutions, ethics, education, visualization and interface, spatial decision support systems, and applications. Finally a brief assessment of the role and nature of GIS is made. It is noted, in particular, that there are great discrepancies in the spread and success of GIS/LIS at the international level. This is true between developed and developing countries, but the case can also be made between western industrialized countries. It is also observed that there is an increasing number of professions involved in GIS/LIS activities and an increasing collaboration between those professions. Finally, it is observed that GIS/LIS are used predominantly as a tool to manage and keep records, although there are signs that GIS/LIS are also leading the way towards a new spatial science. This is only a 1993 ‘snap shot’, and is expected that many of the statements have only a limited life, considering the rapid changes in both theory and technology.     

SAVONOSKI CRATER,ALASKA: A POSSIBLE METEORITE IMPACT STRUCTURE

Savonoski Crater, a small basin about 1700 feet in diameter, is located on a ridge of gently-dipping Jurassic sandstone in Katmai National Monument, southwestern Alaska. Reconnaisance geological, geophysical, and petrographic studies suggest that it was formed either by volcanic processes or meteorite impact prior to the end of the latest glaciation in the region. Surface ejecta, if originally present, apparently have been removed by glaciation. No distinctive shock-metamorphic effects were observed in the few rock specimens collected. Final determination of the crater's origin will require more extensive field studies or drilling in the center of the crater.     

Non-Varying Granulation and Photospheric Network During the Extended 2007?�C?2009 Solar Minimum

We have analysed the wide band images taken by Hinode/SOT, in a blue continuum window and in the G-band, more or less on a daily basis in the frame of the synoptic program, to investigate the variation of the solar granulation and of the photospheric network with the activity cycle. A particular attention has been given to disentangle solar effects from instrumental ones. It appears that a substantial fraction of the images are more or less blurred and/or defocussed. During the analysed period November 2006??C?July 2010, the granulation contrast of the sharpest selected images decreased steadily, the granulation scale increased and the number of MBPs decreased (they are the Bright Points of Magnetic origin which form the photospheric network in G-band images). These trends are likely of instrumental origin. Consequently, the granulation and the photospheric network have most probably not changed during the extended solar minimum 2007??C?2009.     

Size fractionation and optical properties of colloids in an organic-rich estuary (Thurso, UK)

The optical characteristics of a black water river estuary from the north coast of Scotland were examined in the filtered (0.4 µm), ultrafiltered (5 kDa) and colloid-enriched fractions of estuarine samples. The samples were collected over the full salinity range during a period when the pH was relatively constant (8.2–8.5) throughout the estuary, allowing the influence of salinity on estuarine colloidal processes to be distinguished. The properties examined in the bulk, the low molecular weight (LMW) and the colloidal fraction (HMW) were UV–visible absorption, 3-D fluorescence excitation–emission matrix (EEM) spectrum, inorganic and organic carbon, mean size (by dynamic light scattering), and size distribution by flow field-flow fractionation analysis (FlFFF). The combined results of these analyses support the view that river-borne, humic-rich colloids underwent two types of transformation upon mixing with the seawater end member. The first one resulted in an apparent increase in the abundance of LMW constituents and may be explained by coiling of the individual humic macromolecules. The second one resulted in an increase in the mean size measured in both the lower and higher colloidal size ranges, and may be explained by aggregation of colloids to form entities that were still mostly colloidal i.e., smaller than 0.4 µm. The LMW contribution to the bulk optical properties increased with increasing salinity. Very similar findings were obtained from simulated mixing experiments using a Nordic Reference NOM extract as a source of freshwater colloids. This indicates that changes in the molecular architecture and molar mass of river-borne colloids—not changes in their chemical nature—were responsible for the observed variations in the spectral characteristics of CDOM in this estuary.     

Radiation-induced paramagnetic defects in natural kaolinites: Alpha dosimetry with ion beam irradiation

Three types of paramagnetic radiation-induced defects (RID), namely A, A′ (Si-O^?-centers) and B (Al-O^?-Al center), had been identified in natural kaolinites by means of electron paramagnetic resonance spectroscopy. The A-center, stable at the scale of geological periods, was thought to be of particular relevance to quantify past transits of radionuclides in the geosphere. Alpha radiation being likely the main source of RID in kaolinite, the objective of this paper is to define the role of α-particles on the creation of RID and to test the use of A-centers for an α-dosimetry. Three kaolinites with different crystalline order and containing other clays as impurities were irradiated with He⁺ ion beams. The radiation dose range (0–750 MGy) was consistent with natural radioactivity in environments from the Earth's surface. Irradiation drastically enhanced the original signals due to RID. An important increase of concentration of the unstable B-center, partly due to unrealistic dose rate provided by accelerator ion beam, was observed from the lower doses. The most stable defects remained of the Atype all along experimental irradiations. The contribution of ancillary phyllosilicates to EPR spectra was negligible. The concentration of the three types of RID was related to radiation doses up to 30 MGy. Dosimetry growth curves for the A-centers exhibited variable efficiencies and saturation levels that were related to the structural order and the chemical purity of the kaolinites: the more ordered and purer the kaolinite, the higher the efficiency and the lower the saturation plateau. Moreover, these results are of geochemical significance: dosimetry based on A-centers could be directly used to quantify past migrations of radioelements in the geosphere, by determination of the naturally-cumulated doses (paleodose) of kaolinites.     

Stratospheric methane measurements and predictions

A new determination of stratospheric methane from 22 km to 35 km altitude with implications on the abundance of this constituent at greater heights is presented. Previous measurements, some of which showed large discrepancies with currently admitted values, have been reinterpreted and brought into agreement. The results are in contradiction according to present theories with thein situ determined CH₄ abundances at the upper edge of the stratosphere. Implications on the vertical transport coefficient used in one dimensional models are discussed.