Mawson and Mirnyy Stations: the spatiality of the Australian Antarctic Territory, 1954–61

This article focuses on the spatiality of the Australian Antarctic Territory in the important 1954–61 period. Attending particularly to three key components of polar spatiality—geopolitics, international territorial law, and the built environment—the article analyses the development of the Territory as a unique Australian space. The 1954–61 period is particularly significant: during this period, the International Geophysical Year brought an unprecedented number of people to Antarctica; the continent's first permanent colonies were constructed; and, despite Cold War tensions, the 1961 Antarctic Treaty established the spatial configurations and rules which continue to govern the continent today. The article focuses particularly on two key stations in the Territory constructed during this period: Australia's Mawson Station and the Soviet Mirnyy Station. Mawson is a legal colony, designed to cement Australia's claim to 42 per cent of the Antarctic continent; Mirnyy, in contrast, is an anti-colony, designed to reject Australia's claim. How the individual spatialities of these two stations articulate to the broader politics of Antarctic territoriality—and particularly Australia's claim to the Australian Antarctic Territory—is the focus of this article.     

Mesospheric observations with the EISCAT UHF radar during polar cap absorption events: 3. Comparison with simultaneous EISCAT VHF measurements

Mesospheric observations were obtained by the EISCAT UHF and VHF radars during the solar proton event of March 1990. We present the first comparison of incoherent-scatter spectral measurements from the middle mesosphere using simultaneous, co-located observations by the two radars. VHF spectra observed with a vertical antenna were found to be significantly narrower than model predictions, in agreement with earlier UHF results. For antenna pointing directions that were significantly away from the vertical, the wider VHF radar beam gave rise to broadening of the observed spectra due to vertical shears in the horizontal wind. In this configuration, UHF spectral measurements were found to be more suitable for aeronomical applications. Both radar systems provide consistent and reliable estimates of the neutral wind. Spectral results using both the multipulse and pulse-to-pulse schemes were intercompared and their suitability for application to combined mesosphere - lower thermosphere studies investigated.     

Auroral radio absorption and the westward travelling surge

Measurements from a network of riometers during the passage of an auroral westward travelling surge are presented. These show that the energetic electron precipitation producing the radio absorption expands in an almost identical fashion to the softer precipitation associated with the visible surge, but. it is delayed by about two minutes with respect to the surge. The delay is interpreted as a hardening of the precipitating electron spectrum as the surge goes by. Simultaneous observations of electrons at synchronous orbit are shown to support this conclusion.     

Relationship of Caspian tern foraging ecology to nesting success in the Columbia River estuary, Oregon, USA

The prevalence of juvenile salmonids (Oncorhynchus spp.) and marine forage fishes in the diet of Caspian terns (Hydroprogne caspia) nesting in the Columbia River estuary has been established, but the relationship between diet composition, foraging distribution, and productivity of these birds has received little attention. We used radio-telemetry and on-colony observations to relate changes in off-colony distribution to patterns of colony attendance, diet composition, and productivity of adult terns nesting on East Sand Island during two years of different river and prey conditions. Average distance from the East Sand Island colony (located in the marine zone of the estuary) was 38% (6.6 km) greater in 2000 compared to 2001, associated with lower availability of marine forage fish near East Sand Island and lower prevalence of marine prey in tern diets. Colony attendance was much lower (37.0% vs. 62.5% of daylight hours), average trip duration was 40% longer (38.9 min), and nesting success was much lower (0.57 young fledged pair⁻¹ vs. 1.40 young fledged pair⁻¹) in 2000 compared to 2001. Higher proportions of juvenile salmonids in the diet were associated with relatively high use of the freshwater zone of the estuary by radio-tagged terns, which occurred prior to chick-rearing and when out-migrating salmonid smolts were relatively abundant. Lower availability of marine prey in 2000 apparently limited Caspian tern nesting success by markedly reducing colony attendance and lengthening foraging trips by nesting terns, thereby increasing chick mortality rates from predation, exposure, and starvation.     

A localised co-rotating auroral absorption event observed near noon using imaging riometer and EISCAT

An isolated region of energetic electron precipitation observed near local noon in the auroral zone has been investigated using imaging riometer (IRIS) and inco-herent-scatter radar (EISCAT) techniques. IRIS revealed that the absorption event was essentially co-rotating with the Earth for about 2 h. The spatial and temporal variations in D-region electron density seen by EISCAT were able to be interpreted within a proper context when compared with the IRIS data. EISCAT detected significant increases in electron density at altitudes as low as 65 km as the event drifted through the radar beam. The altitude distribution of incremental radio absorption revealed that more than half of the absorption occurred below 75 km, with a maximum of 67 km. The energy spectrum of the precipitating electrons was highly uniform throughout the event, and could be described analytically by the sum of three exponential distributions with characteristic energies of 6, 70 and 250 keV. A profile of effective recombination coefficient that resulted in self-consistent agreement between observed electron desities and those inferred from an inversion procedure has been deduced. The observations suggest a co-rotating magnetospheric source region on closed dayside field lines. However, a mechanism is required that can sustain such hard precipitation for the relatively long duration of the event.     

Optical detection of electrostatic ion cyclotron waves in the auroral plasma

Spectral analysis of recent photometric observations has revealed the existence of narrow frequency band pulsations in the brightness of some auroras. Peaks in the power spectra, between 25 and 32 Hz have been observed. We suggest that these observations are associated with electrostatic ion cyclotron waves, which are excited when the relative drift between ions and electrons due to field aligned (Birkeland) currents, exceeds a certain critical value.     

Algebraic multigrid techniques for discontinuous Galerkin methods with varying polynomial order

We present a parallel algebraic multigrid (AMG) algorithm for the implicit solution of the Darcy problem discretized by the discontinuous Galerkin (DG) method that scales optimally for regular and irregular meshes. The main idea centers on recasting the preconditioning problem so that existing AMG solvers for nodal lower order finite elements can be leveraged. This is accomplished by a transformation operator which maps the solution from a Lagrange basis representation to a Legendre basis representation. While this mapping function must be user supplied, we demonstrate how easily it can be constructed for somepopular finite element representations includingquadrilateral/hexahedral and triangular/tetrahedral DG formulations. Furthermore, we show that the mapping does not depend on the Jacobian transformation between reference and physical space and so it can be constructed with very limited mesh information. Parallel performance studies demonstrate the versatility of this approach.     

Critical legal geographies of possession: Antarctica and the International Geophysical Year 1957–1958

This is an article about the politics of territory in Antarctica. It revolves around what at first seems like a very simple geopolitical question: who owns Antarctica? As this article demonstrates, this seemingly simple question is far from easy to answer: it cannot be answered with a straightforward list of states, nor by conventional geopolitical understandings of territorial possession (Agnew and Corbridge, Mastering space: Hegemony, territory, and international political economy, 1995). Struggles between states for territorial possession has characterised much recent geopolitical history; struggles for Antarctica do not entirely follow this pattern, and revolve instead on the nature and the concept of territorial possession itself. The article focuses in particular on the debates about, and changes to, Antarctic legal and geopolitical territories triggered by the 1957–1958 International Geophysical Year: before the IGY Antarctica was an unstable composite of state claims, unclaimed terra nullius, and terra communis or land unavailable to state claim. By the 1959 Antarctic Treaty, this unstable composite legal and geopolitical geography emerged as a new form of territory, one in which the conventional global mode of territory—state possession—was no longer dominant. Understanding Antarctic legal geographies adds depth to critical geopolitical studies which focus on the ways in which space is actively constructed by specific discourses, understandings, and groups.     

Computing gravity-driven viscous fingering in complex subsurface geometries: A high-order discontinuous Galerkin approach

We present a formulation of the discontinuous Galerkin method aimed for simulations of gravity-driven viscous fingering instabilities occurring in porous media flow. Specifically, we are targeting applications characterized by complex geometrical features. Viscous fingering instabilities play a very important role in carbon sequestration in brine aquifers. The proposed method has the ability to preserve high order of accuracy on completely unstructured meshes, a feature that makes it ideal for high-fidelity computations of the challenging fingering flow patterns and very complex geometries of actual reservoirs and aquifers. An extensive set of numerical computations is also included, to confirm the stability, accuracy, and robustness of the method.