Evolution of double layers in magnetised plasmas contaminated with dust charge fluctuations

Coherent structures entailing the existence of double layers have been studied in magnetised plasma contaminated with dust charging fluctuations. It has been shown that the dust charging in magnetic plasma leads to complexity in the derivation of the Sagdeev wave equation, but under way new procedure enable one to study the nature of double layers showing the effective role of the constituents of the plasma. A parametric analysis is a subject of interest in laboratory and space plasmas, and it has been explained with the input of various typical plasma numerics. The proposed mathematical mechanism has shown the success to yield plasma acoustic modes in a dusty plasma which, in turn, has been solved convincingly for double layers. Observations have been evaluated in an appropriate model with a view to agree with the observations in astrophysical problems dealing with present new findings.     

Kinetics of silica sorption and clay dissolution reactions at 1 and 670 atm

Rates of reactions between clay minerals and silica-spiked seawater and the effect of pressure on the direction, extent and rate of such reactions have been studied. Kinetic behavior of short-term, clay-silica reaction indicates that diffusion is the rate controlling process in both clay dissolution and clay reconstitution reactions. Rate constants of these reactions are of the order of 10^?13 moles/ sec^{$\text{1}\text{2}$}cm². No significant pressure effect on the rate of clay dissolution was observed. Estimates of diffusion coefficient of silicic acid for clay dissolution and silica sorption reactions indicate that the true value lies within the range, 10^?13–10^?17cm²/sec, thus reflecting the semicrystalline or amorphous nature of the reaction product through which diffusion is occurring.     

Late Cretaceous mafic dykes in the Dharwar craton

Palaeomagnetic, geochemical and geochronological studies have been conducted on a set of dolerite dykes intruding the Peninsular gneisses near Huliyurdurga town, Karnataka, as a reconnaissance survey indicated a Cretaceous age for them. The dykes are mainly tholeiitic in composition with their 87Sr/86Sr ratios tightly clustered around 0·7045. Their palaeomagnetic data (D _m =329°,I _m =−55°) and the corresponding palaeopole coordinates (λ _p = 34°S,L _p =108°E) are strikingly close to those of the Deccan Traps to the north. Whole rock K-Ar ages of these dykes ranging between 69 and 84 Ma are also similar to the range of K-Ar ages of the Deccan basalts. The chemical, palaeomagnetic and temporal coherence between the dykes and the Deccan basalts indicate that they may indeed be tectonically related events.     

Observed energy flux anomalies during MONEX-79 over the Bay of Bengal

Summary The dominant surface energy budget parameters, namely the net radiation fluxes, must be precisely known for an understanding of southwest monsoon behaviour and the early stages of formation of a meteorological system, i.e. trough, low pressure, depression, cyclone etc., and break monsoon conditions over the Bay of Bengal region. The data measured during the MONEX-79 period from July 16–31 are used in order to study the fluctuations of energy fluxes and the net radiation in the month of July over the region. During this period the total energy flux is increasing from South to North with a maximum over the head of the Bay. However, the fluctuation of net radiation is not significant. There is an outstanding increase in the energy flux with anomalies of values 240 W/m².

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Zusammenfassung Für das Verständnis des Südwestmonsuns und für die Entwicklung eines meteorologischen Systems, wie Trog-Tiefdruck-Depression-Zyklone etc., sowie für die Bedingungen des Monsunendes über der Bengalischen Bucht, ist das genaue Wissen um die wichtigen Parameter der Energiebilanz an der Oberfläche, insbesondere der Strahlungsbilanz und der anderen Energieflüsse, unverzichtbar. Die Beobachtungsdaten vom 16.–31. Juli während MONEX-79 werden zum Studium der Energieflußfluktuationen und der Strahlungsbilanz für Juli in diesem Gebiet herangezogen. In dieser Periode nahm die Energieflußsumme nach Norden zu, mit einem Maximum über dem nördlichsten Teil der Bucht, während die Fluktuation der Strahlungsbilanz unbedeutend blieb. Trotzdem zeigt sich eine bedeutende Erhöhung des Energieflusses von bis zu 240 W/m².

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With 2 Figures     

Perturbation Features Imprinted on Ionosphere by Successive Clusters of Strong Earthquakes: Role of Atmospheric Coupling Dynamics

Geomagnetism and Aeronomy - The paper presents atmospheric coupling physics through identifying a few significant features imprinted on the ionosphere by certain unique seismic environments when a...     

Studies on emergent flow over vegetative channel bed with downward seepage

Experimental observations in a tilting flume having a bed covered with rice plants (Oryza sativa) are used to analyse the flow characteristics of flexible emergent vegetation with downward seepage. The flow velocity for no-seepage and with seepage is reduced by, on average, 52% and 33%, respectively, as the flow reaches the downstream end with vegetation. Higher Reynolds stress occurs at the start of the vegetation zone; hence, bed material transport occurs in this region. The results indicate that the bed is no longer the primary source of turbulence generation in vegetated flow; rather it is dominated by turbulence generated by the vegetation stems. The local effect of the presence of vegetation causes variations in the hydrodynamic characteristics along the vegetated portion of the channel, which leads to erosion and deposition in the vegetation zone. The experiments show that vegetation can provide considerable stability to channels by reducing channel erosion even with downward seepage.     

The behavior of iron,manganese and silicon in the Peconic River estuary,New York

The behavior of dissolved and particulate iron and manganese and dissolved silicon has been studied as a function of chlorinity in the Peconic River estuary, New York. This study sought to identify important geochemical processes in a relatively pristine estuary facing increasing anthropogenic impact.Dissolved iron behaved in the classical non-conservative manner exhibiting removal of nearly 80% at very low chlorinities, while particulate iron increased by a corresponding amount over the same chlorinity range. Dissolved manganese was enriched by up to 200% over its predicted concentration at low and intermediate chlorinities by desorption from suspended particulates and by a probable benthic flux. Dissolved silicon was enriched by up to 100% at low and intermediate chlorinities also from a probable benthic flux. These fluxes were estimated to be 5 μg cm^?2 day^?1 for dissolved manganese and 70 μg cm^?2 day^?1 for dissolved silicon.The quantity of both particulate iron and manganese increased at high chlorinities due to an influx of suspended inorganic particulates. In the intermediate to high chlorinity region, oxidation of sediment-derived manganese is believed to contribute to the observed increase in particulate manganese.Total iron was essentially conservative throughout most of the estuary, while total manganese was non-conservative presumably due to extensive remobilization of dissolved manganese from the sediments.     

Polarimetry and spectroscopy of RX J1141.3−6410: a single‐pole AM Her system

We present polarimetric and spectroscopic observations of the ROSAT source RX J1141.3−6410, recently identified as a polar. The detection of circular polarization variations, with an amplitude of 10 per cent, over a 3.16-h period confirms that the system is a polar (AM Herculis star). Supporting evidence comes from the nature of the emission lines and their radial velocity variability. In addition, we observe continuum slope changes in the far-red spectral region (∼6000–8200 Å), indicative of phase dependent cyclotron emission. Polarimetric modelling at two wavelengths establishes RX J1141.3−6410 as a single-pole system, with i ∼ β ∼70°. The accretion region is extended in magnetic longitude, and is totally self-occulted for ∼25 per cent of the orbit. The radial velocity curves derived from the emission lines show a phasing with maximum blueshift occurring with Δ φ ∼0.05 of maximum intensity and circular polarisation. In addition, the broader component of the lines exhibit a substantial radial velocity phase shift with respect to the narrower component, in the sense that the broad component preceeds the narrow. This can be readily understood if the narrower component is principally a result of orbital motion of the stream material and the broad component mainly a result of streaming motion near the coupling region. The phasing of the Ca  ii near-infrared line radial velocities also supports this general picture.