AXIOM: advanced X-ray imaging of the magnetosphere

Planetary plasma and magnetic field environments can be studied in two complementary ways—by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth’s magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth’s magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth’s magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose ‘AXIOM: Advanced X-ray Imaging of the Magnetosphere’, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth–Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterise the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission.     

Timing of deformation and exhumation across the Karari Shear Zone,north-western Gawler Craton,South Australia

In the north-western Gawler Craton of South Australia, the Karari Shear Zone defines a boundary between late-Archean to earliest Paleoproterozoic rocks, which have remained largely undisturbed since the earliest Paleoproterozoic, and younger Paleoproterozoic rocks that have been reworked through multiple late Paleoproterozoic and Mesoproterozoic metamorphic and deformation events. The history of movement across the Karari Shear Zone has been investigated via new U–Pb and ⁴⁰Ar/³⁹Ar geochronology, in combination with pre-existing geochronological and metamorphic constraints, as well as the structural geometry revealed by a recently acquired reflection seismic transect. The available data suggest a complex history of shear-zone movement in at least four stages, with contrasting sense of motion at different times. The first period of movement across the Karari Shear Zone is inferred to have been a period of extension at ca 1750–1720 Ma. This was likely closely followed by reactivation during the Kimban Orogeny between ca 1720 and 1680 Ma, although the sense of movement during this period is unclear. Further reactivation, in a thrust sense, occurred between ca 1580 and 1560 Ma, resulting in significant exhumation of marginal domains of the Gawler Craton to the north of the Karari Shear Zone. A final episode of largely strike-slip shear-zone movement occurred at ca 1450 Ma.     

Ground motion characteristics and shaking damage of the 11th March 2011 M w9.0 Great East Japan earthquake

A catastrophic M _w9.0 earthquake and subsequent giant tsunami struck the Tōhoku and Kanto regions of Japan on 11th March 2011, causing tremendous casualties, massive damage to structures and infrastructure, and huge economic loss. This event has revealed weakness and vulnerability of urban cities and modern society in Japan, which were thought to be one of the most earthquake-prepared nations in the world. Nevertheless, recorded ground motion data from this event offer invaluable information and opportunity; their unique features include very strong short-period spectral content, long duration, and effects due to local asperities as well as direction of rupture/wave propagation. Aiming at gaining useful experience from this tragic event, Earthquake Engineering Field Investigation Team (EEFIT) organised and dispatched a team to the Tōhoku region of Japan. During the EEFIT mission, ground shaking damage surveys were conducted in Sendai, Shirakawa, and Sukagawa, where the Japan Meteorological Agency intensity of 6+ was observed and instrumentally recorded ground motion data were available. The damage survey results identify the key factors for severe shaking damage, such as insufficient lateral reinforcement and detailing in structural columns from structural capacity viewpoint and rich spectral content of ground shaking in the intermediate vibration period range from seismic demand viewpoint. Importantly, inclusion of several ground motion parameters, such as nonlinear structural response, in shaking damage surveys, can improve the correlation of observed ground motion with shaking damage and therefore enhance existing indicators of potential damage.     

A comparison of geographic datasets and field measurements to model soil carbon using random forests and stepwise regressions (British Columbia,Canada)

We used geographic datasets and field measurements to examine the mechanisms that affect soil carbon (SC) storage for 65 grazed and non-grazed pastures in southern interior grasslands of British Columbia, Canada. Stepwise linear regression (SR) modeling was compared with random forest (RF) modeling. Models produced with SR performed better than those produced using RF models (r² = 0.56–0.77 AIC = 0.16–0.30 for SR models; r² = 0.38–0.53 and AIC = 0.18–0.30 for RF models). The factors most significant when predicting SC were elevation, precipitation, and the normalized difference vegetation index (NDVI). NDVI was evaluated at two scales using: (1) the MOD 13Q1 (250 m/16-day resolution) NDVI data product from the moderate resolution imaging spectro-radiometer (MODIS) (NDVI_MODIS), and (2) a handheld multispectral radiometer (MSR, 1 m resolution) (NDVI_MSR) in order to understand the potential for increasing model accuracy by increasing the spatial resolution of the gridded geographic datasets. When NDVI_MSR data were used to predict SC, the percentage of the variance explained by the model was greater than for models that relied on NDVI_MODIS data (r² = 0.68 for SC for non-grazed systems, modeled with SR based on NDVI_MODIS data; r² = 0.77 for SC for non-grazed systems, modeled with SR based on NDVI_MSR data). The outcomes of this study provide the groundwork for effective monitoring of SC using geographic datasets to enable a carbon offset program for the ranching industry.     

Neo-liberalism, markets and class structures on the Nepali lowlands: The political economy of agrarian change

In recent years, neo-liberalism has manifested itself in peripheral social formations on an ideological basis through strategies of poverty alleviation. This process is epitomized by Nepal’s donor led agrarian strategy, which constructs farmers as ‘rational entrepreneurs’ responsible for their own welfare. In the process it seeks to encourage smallholders to shift from subsistence to market oriented production. However, over 10 years since the current agrarian strategy was released, there is little evidence of commercialisation and the integration of rural populations into global or domestic markets, while subsistence production remains dominant. To understand this failure, one must examine both the contradictions inherent in neo-liberal ideologies and the rural political economy of Nepal. While the emphasis on self-help through market access can be understood to be an ideological process constitutive of the overdetermined nature of capitalist expansion, contradictions are evident in such ideologies when they are mobilised in regions dominated by non-capitalist economic systems. The depoliticizing assumptions inherent in such ideologies can serve the interests of capitalist expansion through glossing over the associated forms of class exploitation. However, a case study from Nepal’s eastern lowlands demonstrates how they also divert attention from complex non-capitalist modes of surplus appropriation in both the relations of production and circulation. Such forms of exploitation have not only obstructed the process of classical agrarian transition long envisaged in Marxian theory, but have also blocked the emergence of the particular form of rural commodity production envisaged in Nepal’s neo-liberal agrarian strategy itself.     

Hybridity emergent: Geo-history, learning, and land restitution in South Africa

Market-Led Agrarian Reform (MLAR), which is advocated by the World Bank and is being implemented in various contexts around the world, is a more neo-liberal approach to land reform than that we have seen implemented in the past. MLAR principles have underpinned South Africa’s land reform programme, being based on the ‘willing-seller, willing-buyer’ principle, which guarantees market-related prices to sellers. Evidence presented in this paper, however, raises serious questions about the extent to which the South African government has held on to MLAR principles. Specifically, the paper argues that South Africa’s peculiar geo-historical context has in some instances led the government to fuse market-led approaches with more authoritarian interventions that dictate to land reform beneficiaries how the land will be used. A case in point is the government’s approach to the restitution of land rights to communities dispossessed from the Levubu area of Limpopo province. As the paper illustrates, the government has imposed on the intended beneficiaries a so-called ‘strategic partnership’ between them and agribusinesses. Although the government touts the approach as a way to protect the commercial viability of the land and to transfer skills from white farmers to the beneficiaries, the terms of the Levubu solution may turn out to be less than favourable for the beneficiaries.     

Some Thoughts on the Emergence of Digital Close Range Photogrammetry

This presentation offers some thoughts on the emergence (that is essentially to say the commercial acceptance and exploitation) of close range digital photogrammetric systems. The discussion is restricted to systems based on standard photogrammetric processes involving digital frame imagery. Systems are classified into three tiers which are distinguished not only by accuracy and cost, but also by the degree to which a technology transfer has taken place from the specialist photogrammetrist to the non-specialist user. This technology transfer, it will be argued, has facilitated dramatic growth in the application of low accuracy, low cost three dimensional modelling systems in areas such as heritage recording, multimedia, process plant documentation and forensic photogrammetry. Along with automation, this technology transfer has also largely accounted for the wider use of high accuracy, high cost, off line and real time vision metrology systems in large scale industrial metrology. Rapid growth in these two system categories is then contrasted against the more modest advances being witnessed in the traditional close range photogrammetric service sector. Prospects for the future are also touched upon.     

The chemistry of star formation

Understanding the chemistry of molecular clouds is now realized to be fundamental to our understanding of the whole star-formation process. A two-day meeting was held within NAM2002 to bring together chemists and astronomers to discuss this complex subject. Derek Ward-Thompson, Helen Fraser and Jonathan Rawlings report.  

     

Activities of trace elements in silicate melts

A theoretical model has been developed which describes the amphoteric character of oxides in silicate melts. This has been used to account for the increased stability of the higher oxidation states of altervalent trace elements in silicate melts with increasing basicity and to derive a general expression for the estimation of trace element activities in silicate melts.     

A design study for an advanced ocean color scanner system

The spaceborne ocean color scanners currently being planned for flights on Nimbus-G satellite or space shuttle craft are, in every aspect, only a modest beginning towards what is to be expected of ocean color scanners in the eighties. Improvements are necessary in the following areas: present systems provide a spatial resolution on the order of 1 km at nadir, which would not satisfy most of the coastal zone study requirements. Also the present design of radiomers is less than optimum for the removal of the atmospheric effects on ocean colorimetry.Along with a colorimetric data analysis scheme, the instrumental parameters which need to be optimized in future systems are outlined. One technique for meeting these requirements entails use of large linear array detector technology.