Contents to Volume 8

Volume Contents

Contents to Volume 8     

NOAA AR 8210: EVOLUTION AND FLARES FROM MULTIBAND DIAGNOSTICS

NOAA 8210 has been a region showing a remarkable level of activity well before solar maximum. Dominated by a large, rapidly rotating spot, it produced several intense flares during its disk passage at the end of April–beginning of May 1998. We examine the development of AR 8210 in H and white light (WL) and study the evolution of its complex magnetic topology. While the other principal flares are briefly reviewed, the great X1.1/3B flare of 2 May, which was observed at Kanzelhöhe Solar Observatory during a SOHO/UVCS ground support campaign, is studied in detail. This event has been documented in full-disk H and Na-D intensitygrams, Dopplergrams, and magnetograms, with a time cadence of one minute each. The flare was associated with a CME and produced significant geomagnetic effects. Furthermore, we point out the perspectives for our planned Flare Monitoring and Alerting System, since the two new instruments (Magneto-Optical Filter and Digital H camera), which made their first operational run with the campaign, are crucial components for this program.     

Structure of a Large low-Latitude Coronal Hole

Coronal holes on the Sun are the source of high-speed solar wind streams that produce magnetic disturbances at the Earth. A series of multi-wavelength, multi-instrument observations obtained during the 1996 Whole Sun Month campaign examined a large coronal hole in greater detail than ever before. It appeared on the Sun in August, and extended from the north pole to a large active region in the southern hemisphere. Its physical and magnetic structure and subsequent evolution are described.     

Seismic Moment Tensor Resolution on a Local Scale: Simulated Rockburst and Mine-induced Seismic Events in the Kopanang Gold Mine, South Africa

Seismic records contain information about the effect of the source as well as the effect of wave propagation through the rock mass. The effect of wave propagation is usually not well known as only simplified models of geological structures are available. Therefore, the information about the source retrieved by inverting seismograms may include errors due to incomplete knowledge of the rock mass along the propagation path, which in turn cause a distortion in the calculated moment tensor (MT). The distortion of the MT on a local scale was observed by inverting records of a simulated rockburst conducted at the Kopanang gold mine in South Africa. A dominant isotropic component of the explosive characteristics was found from the inversion. The deviatoric components retrieved from the blast are spurious. A test of their stability indicated that they are not significant, assuming an uncertainty above 5% for velocities and 10% for attenuation within the homogeneous model available for the mine. Thus, the retrieval of the MT from records of local networks in mines using a homogeneous model of the rock mass seems to be feasible. However, the homogeneous model of the rock mass can only be applied to close stations, within a few kilometers of the source. The seismic records from distant stations were too complex to be modelled by a homogeneous rock mass. Records of six mine-induced seismic events recorded at the Kopanang gold mine were also inverted. A vertical linear dipole along the pressure (P) axis was found for three of the events, suggesting a pillar burst. The mechanism of two events contains an isotropic implosion together with a nearly vertical dip-slip, and seems to indicate a combination of a cavity collapse with a down dip-slip along a nearly vertical fault. One event corresponds to a dipole along the tensional (T) axis. However, it is vertical, thus its association with tensile faulting of the hangingwall is uncertain.     

R&D Subsidies and Climate Policy: Is There a “Free Lunch”?

Because of the long-term nature of the climate problem, technological advances are often seen as an important component of any solution. However, when considering the potential for technology to help solve the climate problem, two market failures exist which lead to underinvestment in climate-friendly R&D: environmental externalities and the public goods nature of new knowledge. As a result, government subsidies to climate-friendly R&D projects are often proposed as part of a policy solution. Using the ENTICE model, I analyze the effectiveness of such subsidies, both with and without other climate policies, such as a carbon tax. While R&D subsidies do lead to significant increases in climate-friendly R&D, this R&D has little impact on the climate itself. Subsidies address the problem of knowledge as a public good, but they do not address the environmental externality, and thus offer no additional incentive to adopt new technologies. Moreover, high opportunity costs to R&D limit the potential role that subsidies can play. While R&D subsidies can improve efficiency, policies that directly affect the environmental externality have a much larger impact on both atmospheric temperature and economic welfare.     

Climate stability and the development of agricultural societies

Although Modern Man had developed long before the migration from Africa began ～ 55,000 years ago no agricultural societies developed until about ～ 10,000 years ago. In the next 5,000 years agricultures developed independently in at least six regions of the world. It is virtually certain that it was not a chance occurrence that so many new agricultures appeared in the same 5,000 years. What inhibited agriculture world wide for 44,000 years and what changed ～ 10,000 years ago? Here we suggest that a major factor influencing the development of agricultural societies was climate stability. From the experience of four cultures we estimate that the development of agriculture needed ～ 2,000 years of climate free from significant climate variations on time scales of a few centuries. Using the Empirical Mode Decomposition technique specifically designed to exhibit the time history of the amplitude of variations in non-stationary time series such as climate proxy records, we find that between 50,000 years ago and the termination of the Younger Dryas ～ 11,600 years ago there was probably no time span as long as 2,000 years that was free of relatively large century scale variations. Furthermore variations on these time scales appear to have been relatively small since the Younger Dryas (YD) ended, supporting our proposition concerning the importance of climate stability in the history of human culture.     

Waterspouts of the Adriatic, Ionian and Aegean Sea and their meteorological environment

The synoptic and mesoscale conditions associated with waterspout occurrence in the Adriatic, Ionian and Aegean Sea are examined in an attempt to quantitatively assess the meteorological environment favourable to the development of waterspouts. For this study, synoptic circulation patterns have been examined for 28 waterspout events in the central-eastern Mediterranean. The waterspouts were reported within the summer and fall of 2002, from July to November, a period of unusually high whirlwind activity. The Adriatic was most active during July, August and September and the Ionian and Aegean during September, October and November. Of the examined waterspout cases, 13 out of the total of 28 were found to be fair-weather waterspouts, while 15 represent tornadic events. For waterspout days, the frequency and distribution of four basic synoptic types, namely, south-west flow (SW), long-wave trough (LW), closed low (CLOSED) and short-wave trough (SWT), were investigated. The particular synoptic features that contributed to the development of waterspout activity were examined, based on five selected waterspout case studies. The mesoscale environment was explored using thermodynamic indices, moisture and wind parameters as derived by operational soundings from the nearest sites (preferably upwind) and closest in time to the waterspout occurrences. The results present an analysis of waterspout types in conjunction to thermodynamic and wind parameters for the purpose of determining synoptic patterns and mesoscale conditions most relevant to waterspout occurrences in these sea areas of the Mediterranean.     

Properties and depositional environment of the Neogene Elhovo Lignite, Bulgaria

Several Mio-Pliocene aged lignite seams occur as part of a non-marine transgressive sequence in the Elhovo graben in south-eastern Bulgaria. The present study is focused on 45 samples collected from three boreholes in the eastern part of the basin. Petrographic data along with ash and sulphur contents were used in order to determine the lateral and vertical variations of the coal facies and depositional environment of the Elhovo lignite.The lignite seams accumulated in a rheotrophic, low-lying mire with high pH value and are characterized by high ash yields and sulphur contents. Despite of the neutral to weakly alkaline environment the bacterial activity was limited and the tissue preservation and gelification were mainly controlled by the redox conditions.Vegetation rich in decay resistant conifers dominated in the Elhovo basin together with mesophytic angiosperm species. The absence of algal remains and sapropelic coal indicated that open water areas were not present during peat accumulation. The latter processed in an environment, characterized by low subsidence rate, in which prior to the burial the woods were subjected to severe mechanical destruction. According to our interpretation, the enhanced impregnation of the tissues bacteria and fungi played only a secondary role in the process of humification. The lignite from borehole 122 and partly from BH 145 deposited in an environment characterized by relatively low (ground)water table, whereas to the south an area dominated by a flooded forest swamp (BH 104) formed. This is suggested by the better tissue preservation and gelification of the organic matter in BH 104. The vertical variation of the maceral composition in the studied lignite is interpreted as a consequence of vegetational changes, rather than to changes in the depositional environment. The low contents of inertinite macerals indicate that despite of the low water level the environment was relatively wet and the thermal and oxidative destruction of the tissues was limited.Peat accumulation was terminated by a major flooding event and a short term establishment of a lake. In contrast to the West Maritsa basin, no seam formed in the Elhovo basin during the filling stage of the lake.