Strong spherical shock wave propagation in a self-gravitating RMHD rotating interplanetary medium

In the present paper, we have discussed the propagation of spherical shock waves in a radiating magnetohydrodynamic rotating interplanetary medium. The effects of force of self-gravitation have been taken into account with the assumption that at the equilibrium position the effects of rotation on the force of gravitation are negligible. The combined effects of rotation and gravitation on the variation of flow variables have been shown in tables. The particular cases of the problem have been discussed and compared by considering effects of rotation and gravitation separately.     

Similarity solutions for a stellar line explosion

Similarity solutions for line explosion in a non-uniform self-gravitating medium including the effects of magnetic field radiation flux and neglecting the radiation pressure and energy are investigated. Gas is assumed to be grey and opaque and the shock to be transparent and isothermal.     

Seismic velocities and quantification of gas-hydrates from AVA modeling in the western continental margin of India

The most commonly used marker for the investigation of gas-hydrates is the bottom simulating reflector (BSR), which is caused by gas-hydrate laden sediment underlain by either brine or gas-saturated sediment. A BSR has been identified by seismic experiment in the Kerala-Konkan Basin of the western continental margin of India. Here we perform AVA modeling of seismic reflection data from a BSR to investigate the seismic velocities for quantitative assessment of gas-hydrates and to understand the origin of the BSR. The result reveals a P-wave velocity of 2.245 km/s and an S-wave velocity of 0.895 km/s for the sediments above the BSR. This corresponds to a Poisson ratio of 0.406 and hydrates saturation of ∼30% in the study area. The comparison of estimated P-wave velocity (1.77 km/s) above the hydrates-bearing sediment to that (1.78 km/s) below the BSR implies that the origin of the BSR is mainly due to gas-hydrates, as the presence (even in small quantities) of free-gas reduces the P-wave velocity considerably.     

Predictor selection for streamflows using a graphical modeling approach

Streamflows are influenced by various hydroclimatic variables in complex ways. Accurate prediction of monthly streamflows requires a clear understanding of the dependence patterns among these influencing variables and streamflows. A graphical modeling technique, employing conditional independence, is adopted in this study to quantify the interrelationships between streamflows and a suite of available hydroclimatic variables, and to identify a reduced set of relevant variables for parsimonious model development. The nodes in the undirected graph represent relevant variables, and the strengths of the connections among the variables are learnt from the data. The graphical modeling approach is compared to the state-of-the-art method for predictor selection based on partial mutual information. For a synthetic benchmark dataset and a watershed in southern Indiana, USA, the graphical modeling approach shows more discriminating results while being computationally efficient. Along with artificial neural networks and time series models, results of the graphical model are used for formulating a variational relevance vector machine to predict monthly streamflows and perform probabilistic classification of hydrologic droughts in the watershed being studied. The parsimonious models developed for prediction at different lead times performed as well as the non-parsimonious models during both the calibration and testing periods. Drought forecasting for the study watershed at 1-month lead time was performed using the two selected predictors—soil moisture and precipitation anomalies alone, and the model performance was evaluated. The graphical model shows promise as a tool for predictor selection, and for aiding parsimonious model development applications in statistical hydrology.     

Growth and decay of sonic waves in thermally radiative magnetogasdynamics

The propagation of weak discontinuities headed by a wavefront and their formation into shock waves are investigated in a thermally-radiative ideal plasma. It is found that all compressive waves grow without bound only if the magnitude of initial discontinuity associated with the wave exceeds a critical value. In particular, the grow and decay of weak discontinuities in plane, cylindrical, and spherical geometries have been discussed and the shock formation distance and time in all these cases have been derived in presence of magnetic field and radiation, separately.     

Propagation of spherical MHD shock-waves in self-gravitating gas

A theoretical model of shock-wave propagation has been studied in a heat-conducting and a self-gravitating medium. The effects of magnetic field has been taken into consideration. The shock is strong enough to neglect the ambient gas pressure. The variation of flow variables behind the shock have been investigated numerically.     

Geologic and U–Pb geochronologic evidence for early Paleozoic tectonism in the Dadeldhura thrust sheet, far-west Nepal Himalaya

The Dadeldhura thrust sheet inm western Nepal consists of Proterozoic–Lower Paleozoic sedimentary and plutonic rocks, and their metamorphic equivalents, that rest structurally on Proterozoic strata of the Lesser Himalayan sequence. Although regional metamorphism and ductile deformation were widespread during Tertiary thrust emplacement, relicts of early Paleozoic tectonism are preserved locally. New field and geochronologic studies, together with the findings of previous workers, indicate that this early Paleozoic tectonism included: (1) regional metamorphism to at least garnet grade, (2) regional folding of a thick metamorphic sequence into a broad east–west trending syncline, (3) outcrop-scale folding of metasedimentary rocks, (4) emplacement of Cambro–Ordovician granitic bodies during and after the metamorphism and deformation, (5) uplift and erosion of the metamorphic sequence, with garnet-grade rocks locally exposed at the surface, and (6) derivation of Ordovician conglomeratic sandstones from the early Paleozoic orogen. Similar records of metamorphism, deformation, and uplift/erosion have been found in other regions of the Himalaya, indicating that rocks of the Dadeldhura thrust sheet were originally involved in a regionally extensive orogenic system. Future tectonic models of Himalayan orogenesis must accommodate this early Paleozoic event.     

Velocity-porosity and velocity-density relationship for shallow sediments in the Kerala-Konkan basin of western Indian margin

During the expedition 01 of the National Gas Hydrate Program (NGHP), drilling and coring were carried out at one site in the Kerala-Konkan basin on the west cost of India to validate gas hydrate. Drilling/coring results show a homogenous sequence of oozes and explains that the reflector, which was identified as a bottom-simulating reflector (BSR) on seismic section, is mainly due to changes in formation density because of less clay content in carbonate-rich sediment. Downhole logs collected at this site are of good quality and have been used to establish empirical relationship between the P-wave velocity (V _P ), S-wave velocity (V _S ), density (ρ) and porosity (?). The established relations show very good fit with high R² value (>0.73), and can be used for further studies in this region. Well known existing empirical formulas between V _P , V _S , ρ and ? deviate significantly from our established relations.