The North—South Asymmetry of Soft X-Ray Flare Index During Solar Cycles 21, 22 and 23

In this paper the N—S asymmetry of the soft X-ray flare index (FI _SXR) during solar cycles 21, 22 and 23 has been analyzed. The results show the existence of a real N—S asymmetry which is strengthened during solar minimum. The slope of regression lines fitted to the daily values of asymmetry time series is negative in all three cycles. The yearly asymmetry curve can be fitted by a sinusoidal function with a period of eleven years. The power spectral analysis of daily asymmetry time series reveals significant periods of around 28.26 days, 550.73 days and 3.72 years.     

Trace analysis of hydrocarbons in coral cores from Saudi Arabia

As part of a long-term environmental assessment of the impact of the 1991 Gulf War on coral reefs, the Australian Institute of Marine Science (AIMS) conducted growth and chemistry studies on coral cores from the Arabian Gulf. Twenty-eight cores were collected from four coral reefs located offshore from Saudi Arabia.Annual coral growth bands surrounding the 1991 oil spill were analysed in selected cores. Additionally, in cores that extended to the early 1980s, annual layers from 1980 to 1986 were analysed for possible residues from the 1983–4 oil spill caused by the Nowruz oil field blowout during the Iraq–Iran war. Both major spill events were targeted to provide additional confidence in relating oil concentrations to specific pollution events. We detected petroleum biomarkers in several coral annual bands related to the major pollution events. However, the oil remaining in these cores has been altered over time and the biomarker ratios found in these oil residues differed from Gulf crude oils.The concentrations of hydrocarbons were compared with the growth parameters of the coral cores. Only one sample may have recorded an “impact” of oil exposure. There was no other correspondence between slight changes in growth parameters between years and the trace chemistry. Therefore, chemical analysis enabled detection of the exposure incident, but provided no insight into the amount of oil to which the coral had been exposed. The chemical data can only infer biological impact if growth was significantly decreased.The average coral growth characteristics of Porites from the four sites in the Arabian Gulf were normal, as predicted from the average water temperatures of the region. There was an indication of an overall decline in growth over time, which should be monitored in the future.     

The role of SST on the South American atmospheric circulation during January, February and March 2001

Precipitation deficits were observed over southeastern, northeastern and Central Brazil during the 2001 Austral Summer. They contributed to the worsening of the energy crisis that was occurring in the country. A low-level anomalous anticyclonic circulation observed over eastern Brazil enhanced the deviation of moisture transport that usually occurs from the Amazon Basin to southeastern Brazil and inhibited the occurrence of South Atlantic Convergence Zone events in that period. However, an anomalous low-level northerly moisture flux was observed over the La Plata Basin, and positive precipitation anomalies occurred over Bolivia, Paraguay, northeastern Argentina and southern Brazil. Using the ensemble technique, a numerical study was carried out to investigate the role of different sea surface temperature (SST) forcings observed over this anomalous South American atmospheric circulation. Reynolds SST monthly means were used as boundary conditions to study the influence of South Atlantic, South Indian, South Pacific and Equatorial Pacific oceans. The simulations were run from September 2000 to April 2001 using the Community Climate Model version 3.6 General Circulation Model. Ten integrations using different initial conditions were done to each experiment. Numerical experiments suggested that the combined influence of South Pacific and Equatorial Pacific oceans could be responsible for the drought observed over Central Brazil. These experiments simulated the low-level anticyclonic anomaly observed over eastern Brazil. However, both experiments have poorly reproduced the intensity of the anomalous low-level northerly moisture flux observed over the La Plata Basin. Therefore, the intensity of the simulated precipitation anomalies over the subtropical regions was much weaker than observed.     

GOCE Data Processing: The Spherical Cap Regularization Approach

Due to the sun-synchronous orbit of the satellite gravity gradiometry mission GOCE, the measurements will not be globally available. As a consequence, using a set of base functions with global support such as spherical harmonics, the matrix of normal equations tends to be ill-conditioned, leading to weakly determined low-order spherical harmonic coefficients. The corresponding geopotential strongly oscillates at the poles. Considering the special configuration of the GOCE mission, in order to stabilize the normal equations matrix, the Spherical Cap Regularization Approach (SCRA) has been developed. In this approach the geopotential function at the poles is predescribed by an analytical continuous function, which is defined solely in the spatially restricted polar regions. This function could either be based on an existing gravity field model or, alternatively, a low-degree gravity field solution which is adjusted from GOCE observations. Consequently the inversion process is stabilized. The feasibility of the SCRA is evaluated based on a numerical closed-loop simulation, using a realistic GOCE mission scenario. Compared with standard methods such as Kaula and Tikhonov regularization, the SCRA shows a considerably improved performance.     

A McDonald Observatory Study of Comet 19P/Borrelly: Placing the Deep Space 1 Observations into a Broader Context

We present imaging and spectroscopic data on Comet 19P/Borrelly that were obtained around the time of the Deep Space 1 encounter and in subsequent months. In the four months after perihelion, the comet showed a strong primary (sunward) jet that is aligned with the nucleus' spin axis. A weaker secondary jet on the opposite hemisphere appeared to become active around the end of 2001, when the primary jet was shutting down. We investigated the gas and dust distributions in the coma, which exhibited strong asymmetries in the sunward/antisunward direction. A comparison of the CN and C₂ distributions from 2001 and 1994 (during times when the viewing geometry was almost identical) shows that each species is remarkably similar, indicating that the comet's activity is essentially repeatable from one apparition to the next. We also measured the dust reflectivities as a function of wavelength and position in the coma, and though the dust was very red overall, we again found variations with respect to the solar direction. We used the primary jet's appearance on several dates to determine the orientation of the rotation pole to be α=214°, δ=−5°. We compared this result to published images from 1994 to conclude that the nucleus is near a state of simple rotation. However, data from the 1911, 1918, and 1925 apparitions indicate that the pole might have shifted by 5-10° since the comet was discovered. Using our pole position and the published nongravitational acceleration terms, we computed a mass of the nucleus of 3.3×10¹⁶ g and a bulk density of 0.49 g cm⁻³ (with a range of 0.29<ρ<0.83 g cm⁻³). This result is the least model-dependent comet density known to date.     

Tomographic radiotracer studies of the spatial distribution of heterogeneous geochemical transport processes

Within the scope of the further development of geochemical transport models the consideration of the influence of the heterogeneous structures of the geological layers plays an important role. For the verification and parameter estimation of such models it is necessary to measure the heterogeneous transport and sorption processes inside the samples. Tomographic radiotracer methods (positron emission tomography (PET)) enable nondestructive spatially resolved observations of the transport processes in these layers. A special quantitative evaluation system for geoscientific PET studies was developed. Investigations of the water flow distribution in a drill core of a lignite mining dump and of the migration of Cu ions in a horizontal soil column illustrate the potential of this method. Spatial distribution functions of the flow velocity, the specific mass flow and the longitudinal dispersivity were determined on the basis of PET investigations.     

Geochemical signatures of Variscan eclogites from the Saxonian Erzgebirge, central Europe

From the abundant metre to km-sized eclogite bodies in the Variscan crystalline complex of the Saxonian Erzgebirge we have investigated 19 samples from the ultrahigh pressure area at the Saidenbach reservoir. Twenty-two samples were from the south-western Erzgebirge, and from occurrences located only some km away from the reservoir. These samples were analysed for major and trace elements using X-ray fluorescence (XRF) spectrometry and inductively coupled plasma mass spectrometry (ICP-MS).The non-Saidenbach eclogites (SiO₂=49–53 wt%) can be derived from N-mid-ocean ridge basalts (MORBs) partially transitional to P-MORBs (e.g., (Nb)_N: 3–36; (Sr)_N: 4–17; (La/Sm)_N<1.5 (in most instances <0.7) and (Sm/Yb)_N around 1.2). Eclogites from the Saidenbach reservoir (SiO₂=49–61 wt%) are characterised by (Nb)_N: 20–170; (Sr)_N: 9–43; (La/Sm)_N: 1.2–3.0; (Sm/Yb)_N: 1.4–8.8, and a clear negative Eu anomaly for the Si-rich samples, thus, being significantly different from the other investigated eclogites. These signatures point to protoliths related to within plate igneous rocks. However, we also discuss the possibilities of (1) protoliths related to a magmatic arc along an active continental margin and (2) the formation by melting of crustal material in the deep mantle and final crystallisation in the lowermost continental crust similar to the adjacent diamondiferous quartzofeldspathic rocks.Due to the specific geochemical signatures of eclogites in the Saidenbach area including other facts, this ultrahigh pressure region is believed to represent a section of lowermost crust not outcropping in other portions of the Saxonian Erzgebirge.     

Cosmic-ray Periodicity at 170 Days

Power-spectral analysis of cosmic-ray indices (CRI) data for the years 1989–1991 shows a 170-day periodicity of cosmic rays. The periodicity is related to a strong magnetic field. Power-spectral analysis of the long-term periodicity (11 years) of the CRI data for the years 1953–1997 shows that the period 1989–1991 is a unique one in the sense of the discussed pronounced periodicity. The 170-day periodicity of cosmic rays was interpreted in the base of six solar rotations (1 SR = 28.3-day periodicity of 10.7 cm solar radio flux) and may be connected to the instability of the solar core.     

The sedimentation of copper-bearing shales (Kupferschiefer) in the sudetic foreland

The profile of the copper-bearing shales (Kupferschiefer) displays 3 types of lithological developments of the Sudetic Foreland:

in reduction facies: with the notably diminishing of participation of clay minerals and organic substance from bottom to top.

Many horizons of concentration of copper, lead and zinc are present.

in oxidation facies: where marley shales are forming, the metals decrease to trace contents.

in intermediate zones, from reduction facies to oxidation facies shales, the lithological formation is changing and the greatest variability is encountered in the intensity of metal contents.

The concentrations of copper sulphides occur in lagoonal areas in which an oxigen deficiency was associated with a great amount of organic matter. The beds formed in the oxidation facies represent the coastal zones of an open sea basin where the influence of inflow and outflow were considerable.     

Characterization of the shallow groundwater system in an area with thin soils and sinkholes

Door County, Wisconsin, is a region of karst topography underlain by Silurian dolomite bedrock. Numerous sinkholes intercept much of the surface runoff and act as sites for direct groundwater recharge. The clay-rich and impermeable Upper Ordovician Maquoketa formation separates the dolomite aquifer from the deeper aquifers and appears to be a factor in groundwater circulation and karst formation Thin glacial drift and Quaternary materials overlie the dolomite and are hydrologically connected with it The interactions of surface and groundwater, and the role of solution features in water interchange were studied in a small drainage basin. This basin contains several large sinkholes and a nearby spring complex Mapping identified many additional sinks and swallets in surface drainage routes Water flowing into two sinks was traced and found to have a residence time of several hours. Water flowing into sinkholes and from the spring was sampled to identify the quality and seasonal trends in composition of the shallow groundwater Water quality parameters monitored include magnesium, sodium, potassium, chloride, phosphorous, nitrate and ammonia, nitrogen, alkalinity, pH, turbidity, and specific conductance. Nitrate levels were found to increase 5 to 6 times during periods when there was zero input through sinkhole recharge sites. Nitrate levels approached the 10 mg/l NO₃ ⁻-N limit set by the U.S. Public Health Service for drinking water In this basin sandy soils are most susceptible to sink development, whereas clay-rich soils have a lesser number of sinks. It appears, however, that a network of bedrock solution features exists under all soils The loss of soil into sinkholes has impacted groundwater quality and reduced agricultural productivity through a reduction in tillable acreage and water retention capacity.