The satellites of Jupiter as a source of very energetic magnetospheric particles

The Jovian satellites and ring are continuously bombarded by high-energy galacic cosmic rays and magnetospheric ions. Nuclear interactions will create very energetic neutrons and pions. The decay of some of these unstable particles within the Jovian magnetosphere wil result in trapped protons and ultrarelativistic electrons and positrons. Although this source is weak compared to those that yield lower-energy magnetospheric particles, it is expected to generate the most energetic Jovian particles. These processes are briefly described.     

Effect of drift-resonance broadening on radial diffusion in the magnetosphere

In the quasilinear theory of magnetospheric radial diffusion caused by fluctuating electrostatic (E) or magnetic (B) fields, the diffusion coefficientD _LLis proportional to the spectral density of E or B at the particle drift frequency ₃/2. Since ₃ varies withL at fixedM andJ (adiabatic invariants), the drift resonance =₃ can be maintained only transiently, and therefore is not perfectly sharp. Its bandwidth ^* is approximately (16D _LL /L ²₃)^1/3₃. In magnetospheric radial diffusion caused mainly by electrostatic fluctuations, the value of ^*₃ typically exceeds 0.4 for particle energiesE40 keV. However, the numerical value ofD _LLis correctly given (within 1% in all cases) by quasilinear theory because the spectrum of E is rather flat at resonance frequencies for which the bandwidth is an appreciable fraction of ₃. (Numerical conclusions are based on a quasilinear model forD _LLused successfully by Cornwall in 1972.)     

Mobility of heavy metals in harbour sediments: an environmental aspect for the reuse of contaminated dredged sediments

Different methods to determine the source strength of two harbour sediment fractions were applied and are discussed with a focus on As, Cd, Cr, Co, Cu, Mo, Ni, Pb, and Zn. Four different batch experiments were performed with both the sandy and the silty fractions of harbour sediments sampled at the disposal site for dredged material in Bremen Seehausen, north Germany. In addition to the batch experiments a modified centrifugation tube was used in order to obtain pore water from the unsaturated silty fraction. Column experiments were run with the sandy fraction of the material under saturated and unsaturated conditions, irrigated with artificial acid rain water. The results show that the legal threshold value applying to Mo and Pb is not exceeded in any of the methods applied to the sandy or the silty fractions. As for the sandy fraction, Cr and Co were also below this limit. Cd, Ni, Cu and Zn exceeded the threshold values in some of the batch experiments applied to both fractions, depending on the pH value and the elution agent used in the experiment. All results obtained from saturated column leaching were below the respective threshold values; however, it should be noted that the pH was between 7 and 8 throughout the entire experiment. This pH also applied to the unsaturated column, with the exception of the first flush. This first sample had a pH value of 3.8, which was due to sulphide oxidation at the beginning of the experiment and led to strong leaching of all the elements under study. As a consequence, arsenic, Cu and Ni values exceeded their respective threshold values.     

Stationarity of Turbulence in Light Winds during the Maritime Continent Thunderstorm Experiment

Non-stationary turbulence can invalidate eddy flux calculations. Two-hour longrecords of wind velocity, temperature and humidity are classified as stationaryor non-stationary based on the behaviour of the flux as a function of Reynoldsaveraging period; a number of indicators of stationarity are investigated. Thetwo-hour Maritime Continent Thunderstorm Experiment wind datasets are notcompletely stationary, as indicated by the lack of a spectral gap, but can beclassified as approximately stationary, when the mean wind speed is greaterthan 3.8 m s^-1, or the standard deviation of true wind direction is 10°, or the ratio of horizontal wind variance to wind speed is <0.25. In the stationary case the calculated friction velocity exhibits a 7% decrease on average when the Reynolds averaging period is doubled, while data classified as non-stationaryexhibit an increase of 32%. There is little non-stationary behaviour in the kinematicheat fluxes, and is independent of the non-stationarity of the friction velocity. Thekinematic heat fluxes show small decreases (around 3%) when the Reynolds averagingperiod is doubled.     

Interplanetary sector structure and the helliomagnetic equator

The magnetohydrodynamics of solar-wind flow lead logically to the formation of one warped annular neutral surface that apparently extends from ≈ 2r _⊙ (solar radii) to the boundary of the heliosphere. The most likely asymptotic configuration for this neutral sheet intersects the heliomagnetic equatorial plane along four corotating arcs. The observer sees a reversal of magnetic polarity on each crossing of the neutral surface, and so interprets each reversal as the crossing of a sector boundary.     

Das Bleiglanzvorkommen von Puchenstuben in Niederösterreich

Zusammenfassung Das Bleierzvorkommen von Puchenstuben (nö. vom Ötscher) in Niederösterreich wurde vom Aufschluß bis zum Schiliff untersucht. Die monomineralische Bleiglanzvererzung tritt innerhalb eines ladinischen Kalk-Dolomit-Gesteins der Annaberger Decke auf. Beweise für primäre, submarin-externe Erzanlagerung konnten nicht gefunden werden. Erzmineral und Nebengestein sind mehrfach umkristallisiert.Auf Grund teilweise schichtparalleler Lagerung der nicht abbauwürdigen Erze und ihrer nachkristallinen Deformation, wird hypothetisch syngenetische Erzausscheidung im Ladin mit nachfolgender Umkristallisation angenommen; nicht zuletzt auch deshalb, weil die geologische Position, nämlich inverse Lagerung des vererzten Schichtkomplexes, eine hydrothermale Stoffzufuhr im Tertiär sehr fraglich erscheinen läßt.

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Summary The galena deposit of Puchenstuben (north-east of Ötscher) in Lower Austria was examined in the exposure and under the microscope. The monomineral formation of galena is found within a ladinian limestone-dolomite rock of the Annaberg nappe. No proofs could be obtained of the primary submarine external ore deposition. Ore mineral and country rock were recrystallized several times. Owing to partly conformal bedding of the not workable ores and of their post-crystalline deformations syngenetic ore formation followed by crystallization is assumed to have occurred in the Ladinian. This assumption is further substantiated by the fact that a hydrothermal supply of material in the Tertiary appears doubtful because of the geological position, namely a recumbent fold of the mineralized strata.

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Mit 7 Textabbildungen

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Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.     

The potential formation of acid mine drainage in pyrite-bearing hard-coal tailings under water-saturated conditions: an experimental approach

 Annually, an amount of approximately 13 million cubic meters of hard-coal tailings must be disposed of in the German Ruhr Valley. Besides the waste of land in a densily populated region, the disposal of the pyrite-bearing material under atmospheric conditions may lead to the formation of acid mine drainage (AMD). Therefore, alternative disposal opportunities are of increasing importance, one of which being the use of tailings under water-saturated conditions, such as in backfilling of abandoned gravel pits or in the construction of waterways. In this case, the oxidation of pyrite, and hence the formation of AMD, is controlled by the amount of oxygen dissolved in the pore water of tailings deposited under water. In case the advective percolation of water is suppressed by sufficient compaction of the tailings, oxygen transport can be reduced to diffusive processes, which are limited by the diffusive flux of dissolved oxygen in equilibrium with the atmospheric pO₂. Calculations of the duration of pyrite oxidation based on laboratory experiments have shown that the reduction of oxygen is mainly controlled by the content of organic substance rather than the pyrite content, a fact that is supported by results from oxidation experiments with nitrate. A "worst case" study has lead to the result that the complete oxidation of a 1.5-m layer of hard-coal tailings deposited under water-saturated conditions would take as much as several hundred thousand years. Received: 6 May 1996 · Accepted: 2 August 1996