Spectroscopic anatomy of a meteor trail cross section with the European Southern Observatory Very Large Telescope

Abstract— A meteor spectrum was recorded serendipitously at the European Southern Obrervatory (ESO) Very Large Telescope (VLT) during a long exposure in long‐slit spectroscopic mode with FORS1. The ?8 magnitude fireball crossed the narrow 1Î × 7î slit during the observation of a high z supernova in normal service mode operation on May 12, 2002. The spectrum covered the range of 637–1050 nm, where the meteor's air plasma emissions from N₂, N, and O dominate. Carbon atom emission was not detected in the relatively unexplored wavelength range above 900 nm, but the observed upper limit was only 3 sigma less than expected from the dissociation of atmospheric CO₂. The meteor trail was resolved along the slit, and the emission had a Gaussian distribution with a dimension of FWHM = 7.0 (±0.4) * sin(α) * H (km)/90 m, where α is the unknown angle between the orientation of the meteor path and slit and H the assumed altitude of the meteor in km. To our knowledge, this is the first observation of a spatially resolved spectrum across a meteor trail. Unlike model predictions, the plasma excitation temperature varied only from about 4,300 to 4,365 K across the trail, based on the ratio of atomic and molecular nitrogen emissions. Unfortunately, we conclude that this was because the meteor at 100 km altitude was out of focus.     

Orion: A 1–5 Micron Focal Plane for the 21st Century

The Orion program is a project to develop a 2K × 2K infrared focal plane using InSb p-on-n diodes for detectors. It is the natural follow-up to the successful Aladdin 1K × 1K program started in the early 90's. The work is being done at the Raytheon Infrared Operations Division (RIO, previously known as the Santa Barbara Research Center) by many of the same people who created the Aladdin focal plane. The design is very similar to the successful Aladdin design with the addition of reference pixels, whole array readout (no quadrants), two-adjacent-side buttability, and a packaging design that includes going directly to the ultimate focal plane size of 4K × 4K. So far we have successfully made a limited number of hybrid modules with InSb detectors. In this paper we will describe the design features and test data taken from some of these devices. This revised version was published online in July 2006 with corrections to the Cover Date.     

Performance of flexible retaining walls supporting dry cohesionless soils under cyclic loads

A finite element model is proposed for studying the seismic response of a flexible retaining wall/soil system. The model accounts for nonlinear hysteretic soil behaviour, and also for the increase in lateral stresses and settlement related to grain slip caused by cyclic loads. The response computed by the proposed method was compared with responses recorded at the Cambridge centrifuge facility, and found to be in reasonable agreement. The model was then used to identify the importance of factors such as flexibility of the wall and relative density of the backfill. The study reveals that the maximum bending moments given by current design procedures are nonconservative for stiffer walls. Deflections of flexible walls are of major concern. Flexible walls supporting a sand of medium density yield the greatest deflection.     

Periodic orbits in a two-dimensional galactic potential

We use the analytical method of Lindstedt to make an inventory of the families of periodic orbits in a two-dimensional galactic potential first introduced by Contopoulos (1960). We examine the general case of orbital resonance and its neighborhood; two special cases, the 1∶1 and 2∶1 resonances are dealt with separately. The present paper provides a synthesis and an extension of earlier works on this potential in the neighborhood of the integrable case (ε?1).     

Geochemical prospecting for baryte and celestite using a portable radioisotope fluorescence analyser

A method is described for determining the Ba and Sr content of soils in the field laboratory using a portable, isotope source, X-ray fluorescence analyser. The application of these techniques to the exploration for vein-type barytes and stratiform celestite deposits in the west of England is described. Satisfactory accuracy is achieved in comparison with other methods, along with considerable economies in time and effort. Detection limits (2 × standard deviation) are 200–300 ppm for Ba and about 500 ppm for Sr.     

Summary of recent volcanic activity

Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network, v. 29, no. 4, April 2004 (on the Internet at ). Edited by scientists at the Smithsonian, this Bulletin includes reports provided by a worldwide network of correspondents. The reports contain the names and contact information for all sources. Please note that these reports are preliminary and subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism, seismic unrest, monitoring data, and field observations.     

The meteorological framework and the cultural memory of three severe winter-storms in early eighteenth-century Europe

Three violent eighteenth-century storms that ravaged the North Sea area (1703), western central Europe (1739) and Portugal (1739) are investigated from the point of view of their meteorological setting, their socio-economic impact, and whether and by what means they secured an enduring place in the cultural memory. The evidence draws on individual narrative sources such as chronicles and poems, and institutional sources such as ship’s logbooks and state-organised ‘windthrow’ inventories of tree loss. Each of the three storms had socio-economic impacts that could be described as ‘war-like’ in the damage caused to buildings and the destruction of forests. The “Great Storm” of December 1703 jeopardized English naval supremacy in the War of the Spanish Succession by sinking a number of Royal Navy ships and taking the life of more than 8000 seamen. In January 1739 two similarly destructive storms swept over mainland Europe. The cultural memory of the three events here considered was however strikingly different. The sequence of storms in January 1739 though being the most protracted of the last centuries, and well-chroniceled, did not persist in the collective memories of those in France, Switzerland and elsewhere who experienced them. Likewise, the “Great Storm” was quickly forgotten on the continent, whereas its memory remained deeply rooted in England through the writings of Defoe (1704). In Portugal the 1739 storm won a lasting place in the country’s cultural memory owing to two poems that it inspired. Furthermore, it was recorded in the Kingdom’s official newspaper, in the astronomical prognoses and in written records of the Old Regime’s cultural elite.     

European floods during the winter 1783/1784: scenarios of an extreme event during the ‘Little Ice Age’

The Lakagígar eruption in Iceland during 1783 was followed by the severe winter of 1783/1784, which was characterised by low temperatures, frozen soils, ice-bound watercourses and high rates of snow accumulation across much of Europe. Sudden warming coupled with rainfall led to rapid snowmelt, resulting in a series of flooding phases across much of Europe. The first phase of flooding occurred in late December 1783–early January 1784 in England, France, the Low Countries and historical Hungary. The second phase at the turn of February–March 1784 was of greater extent, generated by the melting of an unusually large accumulation of snow and river ice, affecting catchments across France and Central Europe (where it is still considered as one of the most disastrous known floods), throughout the Danube catchment and in southeast Central Europe. The third and final phase of flooding occurred mainly in historical Hungary during late March and early April 1784. The different impacts and consequences of the above floods on both local and regional scales were reflected in the economic and societal responses, material damage and human losses. The winter of 1783/1784 can be considered as typical, if severe, for the Little Ice Age period across much of Europe.     

Modeling to evaluate the response of savanna-derived cropland to warming–drying stress and nitrogen fertilizers

Many savannas in West Africa have been converted to croplands and are among the world’s regions most vulnerable to climate change due to deteriorating soil quality. We focused on the savanna-derived cropland in northern Ghana to simulate its sensitivity to projected climate change and nitrogen fertilization scenarios. Here we show that progressive warming–drying stress over the twenty-first century will enhance soil carbon emissions from all kinds of lands of which the natural ecosystems will be more vulnerable to variation in climate variables, particularly in annual precipitation. The carbon emissions from all croplands, however, could be mitigated by applying nitrogen fertilizer at 30–60 kg N ha^???1 year^???1. The uncertainties of soil organic carbon budgets and crop yields depend mainly on the nitrogen fertilization rate during the first 40 years and then are dominated by climate drying stress. The replenishment of soil nutrients, especially of nitrogen through fertilization, could be one of the priority options for policy makers and farm managers as they evaluate mitigation and adaptation strategies of cropping systems and management practices to sustain agriculture and ensure food security under a changing climate.