The influence of the anomalous cosmic-ray component on the dynamics of the solar wind

It is well known that both the galactic and anomalous cosmic rays show positive intensity gradients in the outer heliosphere which are connected with corresponding pressure gradients. Due to an efficient dynamical coupling between the solar wind plasma and these highly energetic media by means of convected MHD turbulences, there exists a mutual interaction between these media. As one consequence of this scenario the enforced pressure gradients influence the distant solar wind expansion. Here we concentrate in our theoretical study on the interaction of the solar wind only with the anomalous cosmic-ray component. We use the standard two-fluid model in which the cosmic-ray fluid modifies the solar wind flow via the cosmic-ray pressure gradient. Then we derive numerical solutions in the following steps: first we calculate an aspherical pressure distribution for the anomalous cosmic rays, describing their diffusion in an unperturbed radial solar wind. Second, we then consider the perturbation of the solar wind flow due to these induced anomalous cosmic-ray pressure gradients. Within this context we especially take account of the action of a non-spherical geometry of the heliospheric shock which may lead to pronounced upwinddownwind asymmetries in the pressures and thereby in the resulting solar wind flows. As we can show in our model, which fits the available observational data, radial decelerations of the distant solar wind by between 5 to 11% are to be expected, however, the deviations of the bulk solar wind flow from the radialdirections are only slightly pronounced.     

Choice chamber experiments to test the attraction of postflexion Rhabdosargus holubi larvae to water of estuarine and riverine origin

Although the recruitment of larvae and juveniles of marine fishes into estuaries has been well documented, little is known about the factors governing the immigration of estuary-associated marine fishes into estuaries. Fishes have a well-developed sense of smell and it has been suggested by several workers that olfactory cues of freshwater or estuarine origin serve as stimuli, attracting larvae and juveniles of estuary-associated species into estuaries. Attraction of postflexion Rhabdosargus holubi larvae to estuary and river water from the Kowie estuarine system, South Africa, was measured using a rectangular choice chamber. In experiments, conducted during peak recruitment periods, larvae selected estuary and river water with a significantly higher frequency than sea water. This study, the first to assess the possible role of olfaction in the recruitment process of an estuary-associated marine fish species, demonstrates that larvae are able to recognise water from different origins, probably based on odour.     

The development and structure of nocturnal slope winds in a simple valley

The results of an observational and modeling study of the nocturnal slope winds in a simple valley are presented. The valley was approximately 225 m deep in the region of the measurements, and featured a uniform slope angle of approximately 23 ° on one of its sidewalls. The wind and temperature structure of the katabatic flows on the valley sidewalls were measured with tower-mounted instruments, and a Doppler sodar and instruments on a tethered balloon and a 61-m tower were used to determine the atmospheric conditions near the center of the valley. The temperature structure of the slope flows was summarized by characteristic scale parameters h and T for the inversion depth and strength, respectively. On the sidewalls 50 m above the valley floor, the inversion depths were generally smaller and the inversion strengths were weaker than they were on the sidewalls 100 m higher. These results differ significantly from those obtained over a simple slope of an isolated mountain or ridge. The down-valley winds are shown to be important in limiting the strength of the sidewall inversions. The formation of an inversion in the valley also has a pronounced effect on the structure of the slope flows. Numerical simulations suggest that the presence of adiabatic layers in the valley atmosphere is associated with decreases in the slope-flow inversion depth with increasing downslope distance. The simulations also indicate that the length scales that characterize the momentum and inversion depths behave similarly in flows down simple slopes but not in flows down the sidewalls of a valley.Work supported by the U.S. Army Research Office under Contract DA-AG29-K-0231 and the U.S. Department of Energy under Contract DE-AC06-76RLO 1830.     

Bergfußflächen und das System der Flächenbildung in den ariden Subtropen und Tropen

Zusammenfassung In den Trockengebieten sind in der Fußregion von Bergen und Gebirgen ausgedehnte Fußflächen entstanden. Sie sind Ausgleichsflächen zwischen den in Abtragung befindlichen höheren Reliefteilen und den tiefer liegenden Vorlandebenen. Zerschnitten oder unzerschnitten haben sie entscheidenden Anteil am gesamten Flächenrelief. Die Tendenz zur Erhaltung älterer Flächenteile prägt das Gesamtbild des Flächenreliefs der ariden Zone. Bereiche der Zerschneidung und solche der Flächenerhaltung schließen sich klimazonal nicht aus. Die Morphogenese aller Fußflächen beginnt mit der ersten syn- bzw. posttektonischen Anlage einer Initialfläche.Fußflächen mit mehreren Niveaus und Terrassen bilden auf morphologisch weichen (wechselharten) Sedimentgesteinen ein Glacis-System, während besonders auf Kristallingestein ausgedehnte Pedimentflächen entstanden sind. Mit zunehmend ariderem Klima sind alle Fußflächen wenig oder nicht mehr zerschnitten. Morphogenetisch sind Glacis und Pedimente gleichartige Bildungen desselben klimatisch-geomorphologischen Systems der ariden Zone, morphographisch zeigen sie Unterschiede.Die ariden Subtropen und Tropen bilden klimatisch-morphologisch ein eigenes morphodynamisches und genetisches System der Flächenbildung auf der Erde.

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In arid regions wide piedmont plains (Fußflächen) have been formed as the glacis of higher mountains. They are compensation levels (Ausgleichsflächen) between higher parts of relief which are at present eroded, and the lower foreland plains. Whether they are dissected or not, they constitute a large part of all plains. The trend to conserve older parts of the relief is reflected in the whole appearance of the arid zone. Regions of erosions and of plain conservation do not exclude each other in the same climatic zone. The morphogenesis of all piedmont plains begins with a first syntectonic or posttectonic disposition towards an Initial plain (Initialfläche).Piedmont plains with various levels and terraces may develop as a glacissystem on alternatively soft and hard sediments, while on crystalline material extensive rock pediments are formed.In a climate becoming more arid, dissection of all piedmont plains decreases. From a morphogenetic point of view, glacis and rock pediments are similar formations of the same climatic-geomorphological system of the arid zone. Only morphographically they show differences.With regard to climatic morphology, the arid subtropics and tropics have their own morphodynamic and genetic system of plain formation.

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Résumé Dans les zones arides, des glacis étendus se sont formés dans les régions de piémont. Ils représentent des « surfaces d'aplanissement » entre les régions élevées du relief et les plaines de piémont en contre-bas. Les glacis, qu'ils soient entaillés ou non, ont une part importante dans le relief des surfaces d'érosion de la zone aride. La tendance à la conservation d'aplanissements anciens est caractéristique dans cette zone dans laquelle l'érosion linéaire et la conservation des glacis d'érosion sont de la même efficacité. La morphogenèse de tous les glacis dérive d'une « surface initiale » syntectonique ou post-tectonique, qui est la surface de départ.Les glacis sur roches sédimentaires (peu résistantes ou tendres) présentent une morphologie typique comportant plusieurs niveaux de glacis et terrasses (système de glacis). Dans le domaine des roches résistentes et moins hétérogènes, surtout sur roche cristalline, dominent souvent des surfaces pédimentaire étendues et moins inclinées. Les glacis et les pédiments sont de moins en moins entaillés en fonction de l'aridité croissante du climat. Génétiquement, tous les deux sont des unités du relief très voisines du système zonal aride, morphographiquement ils présentent des différences.Le système morphodynamique et génétique de la zone aride (subtropicale et tropicale) constitue, à côté de la zone tropicale humide, l'un des grands ensembles morphoclimatiques du globe.

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Eine zusammenfassende, bisher unveröffentlichte Darstellung der Flächenbildung in ariden Klimagebieten hat der Verfasser erstmalig auf einem Symposium über Fragen der Flächenbildung in den Tropen und Subtropen in Saarbrücken im Oktober 1967 gegeben. Auf der Jahrestagung der Geologischen Vereinigung in Göttingen im Februar 1968 wurde ebenfalls über diesen Fragenkreis der klimageomorphologischen Forschung referíert. Dieser Beitrag gibt den Inhalt der genannten Vorträge wieder.     

Über den Schwermineralgehalt von anstehendem und verwittertem Brockengranit nördlich St. Andreasberg

Zusammenfassung Es wird der Gehalt an durchsichtigen Schwermineralen im anstehenden Granit und seinen Verwitterungsprodukten am Südrand des Brockengranitmassivs nördlich St. Andreasberg quantitativ untersucht.Die Korngrößenverteilung einzelner Schwerminerale im anstehenden und verwitterten Gestein wird angeführt. Dabei werden Rückschlüsse auf ihre mechanische und chemische Stabilität gezogen. und Zirkon hier fast nurmechanisch beeinflußbar sind.Die Verwitterung begünstigt die Bildung von Anatas, Epidot und vielleicht Brookit.Die Ausbildung der beschriebenen Schwermineralfamilie scheint das Ergebnis pneumatolytischer Bildungsbedingungen und hydrothermal-autometamorpher Umwandlung des Granits zu sein und erfährt letztlich eine Wandlung in situ durch die Verwitterung.     

NIZUSE: a deep seismic reflection line in north-eastern Germany

Out of a dense network of seismic reflection lines for hydrocarbon exploration in the North-east German Basin, several lines were recorded to 12 s TWT to obtain information about the structure of the crust and the crust-mantle transition. One of these profiles is presented here. This stretches for 110 km in a NNE direction between Neustrelitz and the island of Usedom. It reaches from the External Variscides in the south across the North German Massif into the Rügen-Pomorze Terrane in the Baltic Sea. Below Cenozoic-Mesozoic-Paleozoic cover with clear reflections down to base Zechstein, the reflectivity varies considerably with depth and also laterally. The Paleozoic and Precambrian sediments and basement are generally void of reflections, but the lower crust and the Moho show strong reflections. To the north the reflectivity decreases, and the Moho depth increases to beyond the bottom of the record section at 12 s. There are no direct indications for deep-reaching faults such as the Trans-European Fault in the north. The North German Massif acted as a ramp towards the Variscan Orogeny, similar to the London-Brabant Massif further west.     

Dust tail streamers of a comet with rotating nucleus

Synthetic images of the dust tail are presented for a comet which has a rotating nucleus with one predominant dust source fixed to it. The images have been generated using a new computer model which, unlike similar models, allows for the study of dust tails caused by a rotating nucleus with an anisotropic distribution of sources.The dust tail is studied in the post-perihelion phase of a parabolic comet with a perihelion distance of 0.5 AU. One finds that in the case of a rotating nucleus with anisotropic emission characteristics streamers caused solely by the dynamics of the dust particles are forming in the dust tail even if there is no dependence between the solar irradiation angle of the source and the amount of dust emitted. If the dust emission depends on the solar irradiation angle of the dust source, then the brightest tail regions do not necessarily coincide with the synchrones for the times of maximum dust emission.As a consequence, a thorough analysis of streamer patterns in a cometary dust tail requires assumptions on the rotational state and the dust source distribution of the nucleus. Otherwise, it seems not possible to discern between streamers which are caused dynamically by nucleus rotation and others which reflect variations in the emission activity.