A note on ‘composite dike’ in basement granite in the vicinity of Srisailam sub-basin near Akkavaram,Telangana

A composite dike has been noticed in basement granite in the vicinity of Srisailam sub-basin near village Akkawaram, Mahabubnagar district, Telangana. It is trending N-S and traced over an extent of 600m in eastern flank of Akkavaram outlier and comprises rocks of mafic and felsic composition characterized by both gradational and abrupt contacts. On the basis of petrographic studies, felsic part of dike is designated as bostonite and mafic as dolerite. Geochemically, they are grouped into (i) trachyte to trachydacite and (ii) basalt categories. Such dissimilar mineralogical and chemical characters in a single dike may be due to coexistence of magma of contrasting composition and provides vital information for understanding the two phase liquid. Interestingly, high uranium values (0.022% U₃O₈) recorded in parts of felsic portion.     

Spatiotemporal variability of meteorological droughts in southeastern USA

Droughts in the southeast USA have been linked to economic losses and intractable water conflicts. The region has witnessed several severe droughts events during the period from 1901 to 2005. In this study, spatiotemporal variability in meteorological drought characteristics in the southeast were analyzed using two different datasets by the means of standard precipitation index and standard precipitation evapotranspiration index for the period 1901–2005 for agricultural and non-agricultural seasons. The study periods were divided into three epochs 1901–1935, 1936–1970, and 1971–2005 and drought characteristics, in terms of severity, frequency, number, and trends were analyzed. Additionally, areal extent, drought severities and return periods associated with three severe drought years 1904, 1954, and 2000 were analyzed. Except for the state of Florida, results indicate decrease in drought severity during the recent epoch of 1970–2005 in the study domain. Trend analysis confirms that the study domain has become wetter over the last 105 years. Wetting trends were more prominent in the agricultural season. Additionally, droughts seem to have migrated from the western part of the study area encompassing the states of Alabama, Tennessee, Louisiana, and Mississippi to the Florida panhandle region during the recent epoch. Droughts exhibited higher spatiotemporal variability during the agricultural season compared to the non-agricultural seasons. Results also showed that early to mid-1950s experienced some of the most severe droughts in the study domain. Some of the drought events, such as the drought of 1954 and 2000, have been equivalent to a 100-year drought event in the southeast. The results from this study form the benchmark for studying the impacts of future climate change projections on meteorological droughts in the southeast.     

Newtonian analogue of force and motion of a free particle in the gravitational field of theC-metric

In the first part of the paper the Newtonian analogue of force for theC-metric has been investigated. To the first-order of approximation in the absence of acceleration of the particle generating theC-metric, one component of the force vector corresponds to the Newtonian analogue of force. In general there are relativistic correction terms due to acceleration term in theC-metric. In the second part of the paper the motion of a freely falling body has been investigated. It is found that plane orbits are not possible. Also the radial fall is not possible and in the equation of the orbit there are terms having no classical analogue. They can be interpreted as the effect of the dragging of the inertial frame produced by the rectilinear acceleration.     

Numerical investigations of converging cylindrical and spherical shock waves

The converging cylindrical and spherical shock waves have been numerically simulated. The flow is created by rupturing the diaphragm. The behaviour of the solution in the focussing stage is closely investigated and compared with the other results. An invariant difference scheme of Rusanov is used to follow the propagation of the shock wave. The study includes not only the moderate initial pressure ratio but also pressure ratios amounting up to thousands. The same scheme has been used from the initial stage of the focussing stage near the axis.     

Nonlinear stability of Halley cometosheath with transverse plasma motion

Weakly nonlinear MHD stability of the Halley cometosheath determined by the balance between the outward ion-neutral drag force and the inward Lorentz force is investigated including the transverse plasma motion as observed in the flanks with the help of the method of multiple scales. The eigenvalues and the eigenfunctions are obtained for the linear problem and the time evolution of the amplitude is obtained using the solvability condition for the solution of the second order problem. The diamagnetic cavity boundary and the adjacent layer of about 100 km thickness is found unstable for the travelling waves of certain wave numbers. Halley ionopause has been observed to have strong ripples with a wavelength of several hundred kilometers. It is found that nonlinear effects have stabilizing effect.     

Alfvénic drift Kelvin-Helmholtz instability in the presence of an equilibrium electric field

Alfvénic drift Kelvin-Helmholtz instability is discussed in the presence of equilibrium electric and magnetic fields which are perpendicular to each other. A dispersion relation is achieved with the help of WKB approximation and the instability criterion is established. A comparison is made with the previous studies and it is shown that the electric field has a stabilizing or destabilizing effect on the system according to the conditions discussed in the text.     

Magneto-radiative shock wave propagation in a conducting plasma

Similarity solutions describing the flow of a perfect gas behind a spherical and cylindrical shock wave in a magnetic field with radiation heat flux have been investigated. The total energy of the expanding wave has been assumed to remain constant. The solutions, however, are only applicable to a gaseous medium where the undisturbed pressure falls as the inverse square of the distance from the line of explosion.     

Period variations of the eclipsing system EE Aquarii

The O–C diagrams of EE Aquarii have been presented for the first time, the period variations present in the system have been analysed, and tentative results have been presented. In all, four period decreases and three period increases are noted in the time interval 1940 to 1985. The strongest period change is noted in the time interval 1957 to 1959. Sufficiently strong period changes have also been noted in the time intervals, 1948 to 1950 and 1970 to 1976. Besides four period decreases and three period increases, eleven period fluctuations are also seen in the O–C diagram (II) of EE Aqr. The total period change in different portions of the O–C diagram (II) ranges from 1.7×10^–7 d to 8.2×10^–6 d. The period increases are stronger than the period decreases. An overall picture of the period variations suggests that weak period variations are present in the system EE Aqr.     

UBV observations of RS canum venaticorum

Photoelectric observations of eclipsing binary RS CVn carried out at Uttar Pradesh State Observatory Nainital, have been reported. The light curve shows wave-like distortion. Colours and magnitudes of RS CVn and comparison stars BD+35°2421 and BD+35°2422 have been given.     

Excitation rate of sodium D line in the nightglow

The processes responsible for the emission of Na-D line in the Earth's atmosphere and laboratory are briefly reviewed. From the laboratory results of Ghoshet al. (1970), the rate coefficient of reactions exciting sodium D line is estimated to be 4.73×10^–25 cm⁶/sec², and its intensity in the nightglow is found to be about 114R in summer and 302R in winter.