Observations of the structure and evolution of solar flares with a soft X-ray telescope

132 soft X-ray flare events have been observed with The Aerospace Corporation/Marshall Space Flight Center S-056 X-ray telescope that was part of the ATM complement of instruments aboard Skylab. Analyses of these data are reported in this paper. The observations are summarized and a detailed discussion of the X-ray flare structures is presented. The data indicated that soft X-rays emitted by a flare come primarily from an intense well-defined core surrounded by a region of fainter, more diffuse emission. Loop structures are found to constitute a fundamental characteristic of flare cores and arcades of loops are found to play a more important role in the flare phenomena than previously thought. Size distributions of these core features are presented and a classification scheme describing the brightest flare X-ray features is proposed. The data show no correlations between the size of core features and: (1) the peak X-ray intensity, as indicated by detectors on the SOLRAD satellite; (2) the rise time of the X-ray flare event, or (3) the presence of a nonthermal X-ray component. An analysis of flare evolution indicates evidence for preliminary heating and energy release prior to the main phase of the flare. Core features are found to be remarkably stable and retain their shape throughout a flare. Most changes in the overall configuration seem to be the result of the appearance, disappearance or change in brightness of individual features, rather than the restructuring or re-orientation of these features. Brief comparisons with several theories are presented.     

Scaling of response spectrum and duration for aftershocks

Aftershocks have the potential to cause collapse of a structure that has been already damaged by the preceding main shock. Seismic safety of a structure should therefore be ascertained through a damage analysis using the anticipated main shock and few larger-aftershock motions. Simulation of aftershock motions needs characterization of the seismic hazard due to aftershocks, and therefore it will be useful to develop a conditional scaling model that can predict the response spectrum of an anticipated aftershock motion consistent with the design spectrum of the main shock motion anticipated at the same station. In this study an attempt is made to develop a conditional scaling model for the pseudo spectral velocity spectrum via linear regression analysis on the aftershock and main shock recordings for the 1999 Chi–Chi earthquake. It is shown that it may be possible to obtain a simpler and approximate version of the conditional model from an unconditional model. Damage-causing potential of a ground motion also depends on its strong motion duration (SMD) and therefore a conditional scaling model is developed for SMD of the aftershock motion in several narrow frequency-bands. The model is developed for the larger-aftershock motions and it is shown that a reasonable replacement of such a model may be obtainable directly from an unconditional model. Finally, a simple weighted averaging scheme is proposed to obtain the composite SMD from the SMDs for different frequency bands by using the pseudo spectral acceleration spectrum of the motion.     

Oceanic versus island arc origin of ophiolites

The silica content of basaltic rocks is an unreliable variable with which to distinguish ultramafic-mafic complexes developed at ocean ridges from those potentially formed beneath volcanic island arcs. Data from Appalachian ophiolites supports the view that silica metasomatism is responsible for the high silica content of supposed calc-alkaline basaltic rocks found in ophiolites such as Troodos, and that the high-silica (70 wt.%) leucocratic rocks associated with ophiolites are of tholeiitic rather than calc-alkaline parentage. The use of titanium as a discriminant of tectonic environment is also suspect because the titanium content of basalts associated with Appalachian ophiolites as well as those recently recovered from the Atlantic ocean floor ranges from values even lower than those typical of island arc tholeiites to values typical of abyssal tholeiites. However, the internal stratigraphy of ophiolites in both the Appalachian and Tethyan systems can only be explained on the basis of the postulate that ophiolites originate at oceanic spreading centres rather than beneath island arcs.     

An assessment of geologic sequestration potential in the panhandle of Florida USA

One alternative to reduce global greenhouse gas emissions is to store the emissions in underground geologic sequestration repositories. The efficacy of this approach has been favorably evaluated by numerous authors over the last 15 years. This paper discusses an assessment of the overall feasibility of storing emissions in three different repositories in the Florida panhandle located in the Southeastern United States. The feasibility assessment evaluates both saline aquifers and oil reservoirs located in the panhandle region. The overall feasibility is driven by the available geologic sequestration capacity, the transportation cost to deliver emissions to a respective repository, and other engineering and regulatory issues. The geologic sequestration capacity is generally controlled by the so-called storage efficiency, a variable dependent on the site-specific geology, reservoir conditions, and the injected fluid characteristics. For this paper, storage efficiency for saline repositories was assessed in more detail using numerical modeling. Based on the work completed, the 3 repositories studied have at least 4.55 gigatonnes of capacity to sequester CO₂.     

Das Problem des Fazieswechsels in der Mitteltrias der Südtiroler Dolomiten

Ohne ZusammenfassungVortrag, gehalten in der Hauptversammlung der Geologischen Vereinigung in Frankfurt a. M., am 7. I. 1928. Ausführlichere Mitteilungen über dieses Thema werden im Rahmen einer größeren Abhandlung über die südalpine Mitteltrias an anderer Stelle veröffentlicht werden.     

Rice research for food security and sustainable agricultural development in Asia: Achievements and future challenges

Rice is the major staple food of Asia, and an important source of employment and income in rural areas, particularly in low-income countries. Research has contributed significantly in achieving food security by increasing the yield potential of rice in irrigated systems, reducing the crop maturity period and achieving yield stability by developing resistance against major insects and diseases in the modern high-yielding varieties. Poverty is, however, still extensive in fragile rainfed rice ecosystems where rice yield has remained low, as scientists have yet to develop high-yielding varieties resistant to abiotic stresses and problem soils. Rice production needs to be increased by another 70% over the next 30 years to meet growing food needs. This has to be achieved with less land, less water, and less labor to accommodate the demand for these inputs from the expanding nonagricultural sectors. The challenge to the rice research community is to make further shifts in yield potential of rice for the irrigated systems, to close the yield gaps in the rainfed systems through developing resistance of high yielding varieties to abiotic stresses, and greater understanding of the interactions between genotypes and environment, developing durable resistance against pests and diseases to reduce farmers' dependence on harmful agrochemicals, and to increase efficiency in the use of water, labor and fertilizers. As further intensification of rice cultivation is inevitable, scientists must understand the negative environmental side-effects of increasing rice productivity, to develop appropriate mitigation options.     

Contributions from oceanic and ionospheric dynamos to the lunar daily variation at Alibag

Summary. The contributions from the oceanic and ionospheric dynamos, L_o and L_I respectively, to the geomagnetic lunar daily variation, L , at Alibag, a coastal station in the Indian equatorial region, are calculated from the L harmonics derived from a 41–yr long series of observations. The analysis in the calendar months shows a steady and significant ocean dynamo contribution in the vertical component, Z, in all the months except April. Examination, by an analysis of the data year by year, of the association of L_o and L_I with varying solar and magnetic activities reveals, surprisingly, a stable correlation between the magnetic activity index A _P and the oceanic part in the horizontal and vertical components but not in declination, which probably indicates the influence of induced currents, along the latitudes, on L _o.     

Human-induced Changes in the Groundwater Chemical Composition within an Oil Field Area

The effect of highly saline oil-field water on soils and potable groundwater is considered. Three phases of the hydrochemical evolution of groundwater quality affected by transborder pollution and field development that has deteriorated potable groundwater in the two topmost aquifers are identified.     

From Celsius to Chaos to Cyclones: Using Temperature-Conversion Equations to Introduce Advanced Mathematical Concepts in Earth Science Courses

The Fahrenheit-to-Celsius temperature-conversion equation is a basic component of many introductory earth science courses. Despite its simplicity, it presents a challenge to students and instructors alike because residents of the United States are unfamiliar with the Celsius scale. By solving for the point at which these two temperature scales are equal, it is possible to use the equations for temperature conversion as a springboard to more advanced topics. It is demonstrated that temperature-conversion equations and chaotic equations can be solved using identical numerical and graphical techniques. As a result, the fundamental concepts of chaos theory and numerical methods can be introduced to students in the context of the simplest equations in the earth sciences. These solution methods are applied to the quantitative theory of the extratropical cyclone as an example of the utility and broad scope of this educational approach.     

The contribution of sulphur dioxide from ablating micrometeorites to the atmospheres of Earth and Mars

Atmospheric composition is a key control on climate and the habitability of planetary surfaces. Ablation of infalling micrometeorites has been recognised as one way in which atmospheric chemistry can be changed, especially at times in solar system history when the infall rates of exogenous material were high. Despite its potential to influence climate and habitability, extraterrestrial sulphur dioxide is currently an unquantified contribution to the atmospheres of the terrestrial planets. We have used flash pyrolysis to simulate the atmospheric entry of micrometeorites and Fourier-transform infrared spectroscopy to identify and quantify the sulphur dioxide produced from the carbonaceous meteorites Orgueil (CI1), ALH 88045 (CM1), Cold Bokkeveld (CM2), Murchison (CM2) and Mokoia (CV3). We have used this approach to understand the introduction of sulphur dioxide to the atmospheres of Earth and Mars from infalling micrometeorites. Sulphates, present in carbonaceous chondrites at a few wt.%, are resistant to thermal decomposition, limiting the yields of sulphur dioxide from unmelted micrometeorites. Infalling micrometeorites are a minor source of present-day sulphur dioxide on Earth and Mars, calculated to be up to around 2400 tonnes and about 350 tonnes, respectively. During the Late Heavy Bombardment (LHB), the much greater infall rates of micrometeoritic dust are calculated to be associated with average production rates of sulphur dioxide of around 20 Mt yr⁻¹ for the early Earth and 0.5 Mt yr⁻¹ for early Mars, for a LHB of 100 Myr. These rates of delivery of sulphur dioxide at high altitudes would have reduced the solar energy reaching the surfaces of these planets, via scattering of sunlight by stratospheric sulphate aerosols, and may have had detrimental effects on developing biospheres by promoting cooler climates and reducing the probability of liquid water on planetary surfaces.