Internal wave characteristics in the eastern Arabian Sea during summer monsoon     

P G K Murthy  G S Sharma  V V James  K V Suseela 《Journal of Earth System Science》1992,101(4):317-327

The time series BT profiles and surface winds and atmospheric pressure, collected in the deep waters off Ratnagiri and Karwar during summer monsoon were utilized to document the characteristics of internal waves (IW). Low-frequency (≤2, cycle per day (cpd)) IW off Ratnagiri are found to propagate at 83 cm/s with wavelengths of 45 km and wave heights upto 40 m. These parameters for high-frequency (>2 cpd) IW off Karwar correspond to 99 cm/s, 3 km and 23 m. The IW off Karwar appear to leave the station at 70° (±10°) (measured from the horizontal). The data sets were further analysed to address the harmonic composition of the IW and identify the possible sources for the observed IW fields. Power spectra of the IW indicated energy peaks at inertial (0·6 cpd) and tidal (1 and 2 cpd) frequencies off Ratnagiri and in the high-frequency band of 0·5–2·0 cycles per hour off Karwar. The coherence between the IW and wind/tide is found to be good at several frequencies within the IW spectrum. This feature probably suggests tides as a source for the IW of tidal frequencies and winds and tides as a joint source for the IW at the remaining frequencies.  相似文献   

Reflection and transmission ofSH waves in an initially stressed medium consisting of a sandy layer lying over a fluid-saturated porous solid     

M. D. Sharma  M. L. Gogna 《Pure and Applied Geophysics》1993,140(4):613-628

Biot's theory is employed to study the reflection and transmission ofSH waves in a sandy layer lying over a fluid-saturated porous solid half-space. The entire medium is considered under constant initial stress. Effects of sandiness, initial stress, anelasticity and viscosity of the interstitial fluid on the partitioning of energy are studied. In the presence of initial stress the incident wave starts attenuating when incider beyond a certain angle (depending upon the amount of initial stress), even if the medium is perfectly clastic. Anelasticity of the solid layer results in the dissipation of energy during transmission. The direction of attenuation vector of incident wave affects the dissipation energy to a large extent. Effect on partitioning of energy reverse at incidence after the critical angle. A complete account of energy returmed back to the underlying half-space and that which is dissipated in the overlying layer has been discussed analytically as well as numerically.  相似文献   

The versatility of digital linear filters used in computing resistivity and EM sounding curves—comments     

S.P. Sharma 《Journal of Applied Geophysics》1993,30(4)

  相似文献   

Propagation ofSH-waves in a heterogeneous visco-elastic layer overlying a homogeneous voigt medium     

Arabinda Biswas 《Pure and Applied Geophysics》1969,76(1):100-106

Summary The propagation ofSH-waves in a vosco-elastic layer having variable material properties has been studied to explain the damping phenomenon of the wave motion. The damping coefficient may be calculated and the effect of heterogeneity on such type of wave motion may be observed from the obtained frequency equation.  相似文献   

Abundance enhancements of silicon to iron in solar energetic particles and their implications     

M. N. Vahia  S. Biswas  N. Durgaprasad 《Astrophysics and Space Science》1988,149(2):241-254

Differential energy spectra of low abundant elements between silicon and iron of energetic solar particles (SEP) in the August 4, 1972 event were measured in the energy region of 10 to 40 MeV amu^–1 using rocket-borne Lexan detectors. The relative abundances of elements were determined and abundance enhancements, i.e., SEP/photospheric ratios, and their energy dependence were derived in 10–40 MeV amu^–1 interval. It is found that there are four types of abundance enhancements as a function of energy as follows: (a) silicon, iron, and calcium show fairly strong energy dependence which decreases with increasing energy and at 20–40 MeV amu^–1 reaches photospheric values; (b) in case of sulphur enhancement factors are independent of energy and the values are close to unity; (c) argon shows energy independent enhancements of about 3 to 4 in 10–40 MeV amu^–1; (d) titanium and chromium show weakly energy-dependent, but very high abundance enhancement factor of about 10 to 40. These features are to be understood in terms of the atomic properties of these elements and on the physical conditions in the accelerating region. These are important not only for solar phenomena but also to gain insight into the abundance enhancements of cosmic-ray heavy nuclei.on leave from Tata Institute of Fundamental Research, Bombay, India.  相似文献   

On the energy dependence of the ratio of Li,Be and B to C,N, O and F nuclei in the primary cosmic rays     

S. Biswas 《Astrophysics and Space Science》1969,5(1):59-67

A critical study of all available data on the energy dependence of the ratio ff the intensities of Li, Be, and B to C, N, O and F nuclei (L/M-ratio) in cosmic rays is made. It seems that in a recent experiment by Von Rosenvingeet al. (1969), the flux of M-nuclei has come out higher in the energy interval of 200–400 MeV/nucleon and that of L-nuclei lower in the energy interval 400–600 MeV/nucleon; as a result they obtained a value of the ratio of L/M which is about 50% lower than all other investigators. The results of all other studies yield the best estimate of the ratio of L/M as 0.26±0.03, 0.41±0.03 and 0.26±0.02 in the energy interval 50–150, 200–600 and>1500 MeV/nucleon respectively.  相似文献   

Diffuse X-ray background measurements in the energy range 2–18 keV     

A. S. Prakasarao  D. P. Sharma  U. B. Jayanthi  U. R. Rao 《Astrophysics and Space Science》1971,10(1):150-155

Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 _–3.3 ^+4.3 E ^{–1.73±0.15} photons/cm²-sec-keV-ster the spectrum being much flatter than that observed at higher energies.  相似文献   

Major Element, REE, and Other Trace Element Behavior in Amphibolite Weathering under Semiarid Conditions in Southern India     

Sharma A  Rajamani V 《The Journal of geology》2000,108(4):487-496

A body of komatiitic amphibolite, an enclave within the Archean high-grade orthogneisses in southern India, shows mild chemical weathering under semiarid conditions. Along fractures, chemical weathering has advanced (Chemical Index of Alteration &sqbl0;CIA&sqbr0;=53; CIA of fresh rock approximately 26) to the extent that secondary Mg-Fe-Al clay minerals have formed and the rock has turned brownish red, soft, and fine grained. The weathering process has resulted in the mobilization and redistribution of the so-called immobile elements Fe, Al, Ti, and REE effected by the nature of secondary mineral formation (talc vs. aluminous clay minerals) and also possibly by soil microbes. In the initial stages of secondary mineral formation, there is a small loss of Fe, Al, and REE (noticeably Eu). However, in the fracture zone as well as in the incipiently altered zone, there is significant REE enrichment, probably affected by a different precipitation mechanism. Mobilized REE may have come from a minor alteration of clinopyroxene.  相似文献   

Mapping of fault rupture of the 28 may 2004 iran earthquake (mw= 6.2) using satellite image     

M. Sharifikia  C. S. Dubey  B. K. Sharma  M. Chaudhry  P. K. Champati Ray 《Journal of the Indian Society of Remote Sensing》2006,34(4):423-430

  相似文献   

The behavior of natural and anthropogenic osmium in the Hudson River-Long Island Sound estuarine system     

Karl K. Turekian  Mukul Sharma 《Geochimica et cosmochimica acta》2007,71(17):4135-4140

The extent to which riverine Os is trapped in a temperate estuary was the aim of this study. The behavior of Os through the Hudson River, East River and the Long Island Sound (LIS) system is addressed using both natural Os and anthropogenically mobilized Os. The Os concentration ([Os]) and isotopic composition (¹⁸⁷Os/¹⁸⁸Os) of the Mid-Atlantic Bight as inferred from the analysis of a water sample of 31‰ salinity (S) at Vineyard Sound, MA are 46 fM and 1.070, respectively. In comparison, the Hudson River at Newburgh, NY has [Os] = 68 fM and ¹⁸⁷Os/¹⁸⁸Os = 1.265. The Os concentration of the East River at the Whitestone Bridge is 51 fM and remains essentially constant proceeding eastward in the LIS despite the increase of salinity from 20‰ towards the higher value of the Mid-Atlantic Bight. The ¹⁸⁷Os/¹⁸⁸Os ratio of water at Whitestone Bridge is 0.945 and increases eastward through the Sound to 0.979 at 7 km and then to 1.019 at 39.6 km. The behavior of Os through LIS appears to be conservative at S > 20‰. On the basis of Os concentration and isotopic composition we infer that anthropogenic Os is being added to the East River through sewers with the likely isotopic ratio of ∼0.13 and that about 24% of riverine Os must be removed at S ? 20‰. There is a net transport of about 0.4-1 mole of anthropogenic Os per year from the East River into the LIS. The residence time of Os in the ocean at present must be about 39,000 years, unless an independent source of supply of Os can be identified.  相似文献