Equilibrium structure for a plasma magnetosphere around compact objects     

A. R. Prasanna  S. C. Tripathy  A. C. Das 《Journal of Astrophysics and Astronomy》1989,10(1):21-34

Starting from a set of general equations governing the dynamics of a magneto-fluid around a compact object on curved space time, a fairly simple analytical solution for a test disc having only azimuthal component of velocity has been obtained. The electromagnetic field associated has a modified dipole configuration which admits a reasonable pressure profile for the case of fully relativistic treatment of Keplerian type of velocity distribution  相似文献   

Nonlinear waves to study the evolution of collapsed soliton and its radiation     

G.C. Das 《Planetary and Space Science》2004,52(7):581-586

It has been shown that the Korteweg-de Vries equation, derived in inhomogeneous plasma, finds difficulty in obtaining the complete soliton solution and its propagation in plasma and thus fails to exhibit the actual nature of plasma acoustic-wave. The key here lies in the use of an approach, known as sine-Gordon method, which describes successfully soliton propagation along with its precursor. The study shows that the soliton, due to the interaction of negative ions, collapses expecting a source of soliton radiation. Moreover, inhomogeneity, along with weak ionization, effects the precursor to grow faster by generating the energy from its main soliton. The results are interesting in the light of having a parallel observation on radiation, and the formation of dip and hump solitons as similar to those observations made by the scientific satellites.  相似文献   

Preliminary report on global seismicity-frequency energy distribution of earthquakes     

R. K. S. Chouhan  U. C. Das 《Pure and Applied Geophysics》1971,89(1):98-108

Summary In this paper frequency magnitude analysis of the world shallow, Intermediate and deepshocks, has been made by univariate least-square method and also by maximum likelihood method using all the earthquakes of the year 1969. There is no general agreement in the result arrived at by those two methods. The distribution of energy in various magnitude ranges for shallow, intermediate and deep earthquakes have been made. The release of earthquake energy with depth has been studied by dividing the upper 700 kilometres of the earth into layers of 100 kilometres thickness, and calculating the energy for each layer.  相似文献   

Break-up of quasi-periodic motion as an interpretation of white-dwarf variability     

M. K. Das  F. X. Schmider  R. K. Tavakol 《Astrophysics and Space Science》1992,188(1):137-142

High-speed photometric data obtained for a number of white-dwarf stars confirm the presence of subharmonic frequency in their power spectra. As many of these white dwarfs show multiperiodic structures, we show that the break up of quasi-periodic motion results in the appearance of similar subharmonic components in their spectra.  相似文献   

Double layers and collapsible waves in plasmas expected in interplanetary space     

G. C. Das  K. M. Sen 《Earth, Moon, and Planets》1994,64(1):47-53

The propagation of ion-acoustic waves by the augmentation of Kadomtsev-Petviashvili equation are studied in a plasma in relation to that existing in the interplanetary space. We precisely pointed out the causes of occuring the double layers as well as collapsing of the solitary waves in the plasma dynamics.  相似文献   

Spectrum of average flux of the S-component of solar radio emission     

M. K. Das Gupta  S. K. Sarkar 《Solar physics》1971,18(2):276-283

Spectrum of average flux of the S-component of solar radio emission observed during the peak phase of the present solar cycle has been determined statistically. Daily values of the mean solar flux at 606, 1415, 2695, 4995 and 8800 MHz observed at the Sagamore Hill Solar Radio Observatory have been examined. The superposed epoch method (Chree analysis) has been used for determining the true nature of the S-component at all these frequencies. Spectrum has been obtained after elimination of the basic components at the respective frequencies. The important results obtained from the present statistical investigation are: (1) the basic component increases with frequency, (2) the S-component shows a maximum at 4995 MHz (6 cm), (3) the spectrum is independent of the phase of the 27-day cycle and (4) S-components at all the frequencies have slopes which are both more uniform and higher in the ascending phase than those in the descending phase of the 27-day cycle. In the descending phase slopes increase with frequency.  相似文献   

An exact solution of time-dependent equation of transfer of trapped radiation in a finite absorbing medium     

S. K. Bishnu  S. R. Das Gupta 《Astrophysics and Space Science》1987,134(2):261-299

Milne's time-dependent equation of transfer of trapped radiation in finite absorbing medium has been exactly solved by a combination of Das Gupta's modified form of the Wiener-Hopf technique and method of solving boundary value problems in the theory of heat conduction as adopted by Chandrasekhar (1950) to solve the same equation approximately in combination with his method of discrete ordinates. Milne himself had earlier obtained an approximate solution of his equation.  相似文献   

The pulses as a diagnostic technique in the Sun     

G. C. Das 《Astrophysics and Space Science》1980,71(2):353-361

In this paper we discuss a method of finding physical parameters by studying the pulses in the Sun. For the sake of a mathematical approach, we consider an ideal,highly relevant model which could exist in the Sun with the effects of ionization, due to which there will be a continuous formation of ionized particles. It is observed that the pulse originated at the centre of a dipole field propagates along the magnetic field. We derive a dispersion relation for these types of pulses, propagating from the centre to the solar surface. The time taken by the pulse from its source to the solar surface is also estimated, with due account of the ionization effects on the pulse. Without proper account of these effects, the technique employed in determing the physical parameters may lead to error. Temporal and spatial damping of the pulses lead to estimates of the velocity distribution of the ionized particles and of the amplitude of the magnetic field of the wave in pulse.  相似文献   

Dholkata Bauxite Deposit on Metavolcanics, Keonjhar District, Orissa, India     

Bijaya Ketana Nayak  Subir Kumar Das 《Resource Geology》2005,55(1):33-44

Abstract. The Dholkata bauxite deposit of Keonjhar district, Orissa, has developed on the metavolcanics of tholeiitic basalt composition. The weathered profile reveals five distinct altered zones, such as topsoil, laterite, bauxite, lithomarge and altered metavolcanics. The mineralogy of different zones studied in a representative pit shows the association of major mineral constituents like gibbsite, goethite, hematite, kaolinite, limonite and quartz. Gibbsite is the most dominant one followed by goethite and hematite in the bauxite zone. The geochemical study of all weathering zones indicates the geochemical affinity of the elements Ni, Th and U for laterites and Cr, Zr and Hf for bauxites to occur in high quantities. Trend surface maps predict the bauxite zones in the different levels of the deposit. If the zones having A1₂O₃ 35–40 % are blended with high grade ores, the deposit may prove to be a potential one.  相似文献   

Utilization and flow of energy in tropical ecosystem: A test case for two Ox-bow lakes   总被引：1，自引：0，他引：1  

S. K. Das M.Sc.  D. Chakrabarty Ph.D  WBES 《International Journal of Environmental Science and Technology》2006,3(2):141-146

To estimate the rate of organic production, two solar powered tropical natural aquatic systems (Oxbow lakes) have been studied for 24 months. The study of utilization of energy in those two tropical lakes has revealed that herbivores were more efficient in energy utilization than autotrophs. Silver carp and grass carp were found to be most efficient in conversion of energy in the grazing and detritus food chain of these lakes. The efficiency of the system to fish production was found to be 0.05 % of the total available solar radiation. Various forms of life are all accompanied by energy changes, even though no energy is created or destroyed in the studied system.  相似文献