X-ray observations of a major eruptive flare behind the limb

We analyze X-ray images and spectra of a coronal structure which extended to altitudes over 130 000 km above an eruptive flare located 20° behind the western solar limb. The images were obtained by the Flat Crystal Spectrometer (FCS) and the spectra were obtained by the Bent Crystal Spectrometer (BCS) aboard the SMM spacecraft. Images in Oviii and Mgxi lines cover the period from before the flare onset (which occurred at 22:31 UT on 16 February, 1986) through 17 UT on 17 February and were used for determination of temperature and emission measure within the structure. BCS obtained Caxix spectra of the coronal event, benefiting from the occultation of the active region behind the solar limb.The BCS data show, and FCS data confirm, that the temperature, after an initial rise and decline, stayed almost constant for many hours after 04:30 UT on 17 February. This may indicate that initially we observed the rise and decay of post-flare loops, but later the X-ray emission came predominantly from a post-flare giant arch that formed above them. This has been observed in many previous cases. However, a comparison with other events characterized by very high post-flare loops, such as those that occurred on 29 July, 1973 (Skylab data) and on 14 February, 1986 (from this same region), suggests that we may be observing the same system of slowly growing groups all the time. Therefore, we suggest a third possibility, i.e., that such anomalously high loop systems first behave like post-flare loops but gradually take over some characteristics of a post-flare giant arch. The Soft X-ray Telescope aboardYohkoh, with spatial resolution improved by nearly an order of magnitude, might be able to check up on the development of such large-scale coronal structures if proper observational modes are applied after the occurrence of major eruptive flares.Deceased 1 June, 1993.     

Rotational distortion on the surfaces of Jupiter and Saturn

Having formulated the Clairaut second-order differential equations up to the fourth order in superficial distortion due to Hensen's coefficients in the previous article (El-Sharawyet al., 1989 III, hereafter denotes by SM3), we are now in a position to solve them. In this paper we shall discuss the methods of solving the Clairaut theory, to give an explicit form about the distortion of the surfaces of Jupiter and Saturn, numerically up to the fourth-order.     

HEATING DEGREE DAY RESEARCH IN ALBERTA: RESIDENTS CONSERVE NATURAL GAS

A high correlation exists between monthly population-weighted heating degree days (below 18C) and the use of natural gas per household for residential heating in Alberta for the period 1962–80. The use of natural gas for residential heating per household declines since 1973 following a sharp increase in gas prices.     

The spatio-temporal development of Copenhagen’s bicycle infrastructure 1912–2013

Cycling plays an important role in low-carbon transitions. Around the globe, cities are constructing bicycle infrastructure. The city of Copenhagen has a bicycle-friendly infrastructure celebrated for its fine-meshed network. This study documents the spatio-temporal development of Copenhagen’s bicycle infrastructure and explores how the development corresponds to other processes of urban transformation. The study builds on historical maps of bicycle infrastructure that are digitised into geographical information, which allows for a comprehensive analysis of the formation of the network. In search for identifying drivers, the study analyses the city’s spatial growth pattern, migration pattern, development of road network and changes in the transport culture. Analyses reveal that the bicycle infrastructure expanded at a relatively constant pace during distinct periods of urban transformation, including periods when the city suffered from spatial, economic and demographic decline, and dominance of car traffic. By discussing reasons and demands for constructing bicycle infrastructure, the study identifies four distinct periods in which bicycle infrastructure was constructed to enhance comfort and safety (first cycling city); the flow for cars (car city); urban liveability for soft transport (liveable city); and, finally, to improve the flow for cyclists as part a strategic re-design of urban space (liveable cycling city).     

Fluid–rock interactions associated with regional tectonics and basin evolution

An integrated approach consisting of fracture analysis, petrography, carbon, oxygen and strontium‐isotope analyses, as well as fluid‐inclusion micro‐thermometry, led to a better understanding of the evolution of fluid–rock interactions and diagenesis of the Upper Permian to Upper Triassic carbonates of the United Arab Emirates. The deposited carbonates were first marked by extensive early dolomitization. During progressive burial, the carbonates were affected by dolomite recrystallization as well as precipitation of vug and fracture‐filling dolomite, quartz and calcite cements. After considerable burial during the Middle Cretaceous, sub‐vertical north–south oriented fractures (F1) were cemented by dolomite derived from mesosaline to hypersaline fluids. Upon the Late Cretaceous maximum burial and ophiolite obduction, sub‐vertical east–west fractures (F2) were cemented by dolomite (Dc2) and saddle dolomite (Ds) derived from hot, highly saline fluids. Then, minor quartz cement has precipitated in fractures from hydrothermal brines. Fluid‐inclusion analyses of the various diagenetic phases imply the involvement of increasingly hot (200°C) saline brines (20 to 23% NaCl eq.). Through one‐dimensional burial history numerical modelling, the maximum temperatures reached by the studied rocks are estimated to be in the range of 160 to 200°C. Tectonically‐driven flux of hot fluids and associated diagenetic products are interpreted to have initiated during the Late Cretaceous maximum burial and lasted until the Oligocene–Miocene compressional tectonics and related uplift. The circulation of such hydrothermal brines led to partial dissolution of dolomites (Dc2 and Ds) and to precipitation of hydrothermal calcite C1 in new (mainly oriented north–south; F3) and pre‐existing, reactivated fractures. The integration of the obtained data confirms that the diagenetic evolution was controlled primarily by the interplay of the burial thermal evolution of the basin and the regional tectonic history. Hence, this contribution highlights the impacts of regional tectonics and basin history on diagenetic processes, which may subsequently affect reservoir properties.     

Rising powers: the evolving role of BASIC countries

The exponential growth in global populations, economic activity and resource utilization means it is becoming increasingly difficult to satisfy global demand for a number of fundamental resources, while some key ecosystems services are under stress. The likelihood of future resource scarcities have begun to influence the positions taken within international climate change negotiations by fast-growing developing countries. When Brazil, South Africa, India, and China formed the BASIC group it took many by surprise. The coordination needed to align this heterogeneous group of countries cannot simply be understood in terms of a set of shared interests around climate policy. How the BASIC group emerged and the nature of its cooperation on climate change are examined within the broader context in which these increasingly powerful countries came to join forces. Although traditionally aligned with the G77 group of developing countries, recent strategising as a group of emerging economies reflects their realization that there are insufficient global resources available to follow the same development pathway as industrialized countries. Hence, they must seek alternative growth pathways, which requires establishing common ground while also keeping track of each others' positions on important global issues like climate change.     

Estimates of recharge in two arid basin aquifers: a model of spatially variable net infiltration and its implications (Red Light Draw and Eagle Flats, Texas, USA)

Methods of estimating recharge in arid basin aquifers (such as the 1 % rule, Maxey-Eakin method, storm-runoff infiltration and others) overlook the potential contribution of direct recharge on the basin floors. In the Trans-Pecos region of west Texas, USA, this has resulted in potential recharge and solute flux to basin aquifers being ignored. Observed trends in groundwater nitrate (NO₃ ^?) concentrations and the presence of young (<70 years old) water in the basins indicate that recharge is occurring through the basin floors. A spatially variable net infiltration model (INFIL 3.0.1) was used to estimate the volume and spatial distribution of potential recharge to two basins: Red Light Draw and Eagle Flats. The INFIL model provides insight into the mechanisms by which recharge and solute flux occurs in arid basin systems. This method demonstrated that recharge is widespread; it is not limited to the mountainous areas and mountain-front recharge mechanisms, and up to 15 % of total potential recharge in these basins occurs across widespread areas of the basin floors. Models such as this should improve scientific understanding and sustainable management of arid basin aquifers in Texas and elsewhere.     

WAVERYS: a CMEMS global wave reanalysis during the altimetry period

Ocean Dynamics - As part of the Copernicus Marine Service, WAVERYS is the multi-year wave reanalysis that provides global wave data with a fine grid resolution of 1/5°. This wave reanalysis...