Electromagnetic Ion Cyclotron Waves in Multi-Ions Hot Anisotropic Plasma in Auroral Acceleration Region-Particle Aspect Approach     

Soniya Patel  P. Varma  M. S. Tiwari 《Earth, Moon, and Planets》2012,109(1-4):29-41

Using particle aspect approach, the effect of multi-ions densities on the dispersion relation, growth rate, perpendicular resonant energy and growth length of electromagnetic ion cyclotron wave with general loss-cone distribution function in hot anisotropic multi-ion plasma is presented for auroral acceleration region. It is observed that higher He⁺ and O⁺ ions densities enhance the wave frequency closer to the H⁺ ion cyclotron frequency and growth rate of the wave. The differential heating of He⁺ ions perpendicular to the magnetic field is enhanced at higher densities of He⁺ ions. The waves require longer distances to achieve observable amplitude by wave-particle interactions mechanism as predicted by growth length. It is also found that electron thermal anisotropy of the background plasma enhances the growth rate and reduces the growth length of multi-ions plasma. These results are determined for auroral acceleration region.  相似文献   

Statistical evaluation of PM<Subscript>10</Subscript> and distribution of PM<Subscript>1</Subscript>, PM<Subscript>2.5</Subscript>, and PM<Subscript>10</Subscript> in ambient air due to extreme fireworks episodes (Deepawali festivals) in megacity Delhi     

S. Tiwari  D. M. Chate  M. K. Srivastava  P. D. Safai  A. K. Srivastava  D. S. Bisht  B. Padmanabhamurty 《Natural Hazards》2012,61(2):521-531

Temporal variation of PM₁₀ using 2-year data (January, 2007–December, 2008) of Delhi is presented. PM₁₀ varied from 42 to 200 μg m⁻³ over January to December, with an average 114.1 ± 81.1 μg m⁻³. They are comparable with the data collected by Central Pollution Control Board (National Agency which monitors data over the entire country in India) and are lower than National Ambient Air Quality (NAAQ) standard during monsoon, close to NAAQ during summer but higher in winter. Among CO, NO₂, SO₂, rainfall, temperature, and wind speed, PM₁₀ shows good correlation with CO. Also, PM₁₀, PM_2.5, and PM₁ levels on Deepawali days when fireworks were displayed are presented. In these festive days, PM₁₀, PM_2.5, and PM₁ levels were 723, 588, and 536 μg m⁻³ in 2007 and 501, 389, and 346 μg m⁻³ in 2008. PM₁₀, PM_2.5, and PM₁ levels in 2008 were 1.5 times lower than those in 2007 probably due to higher mixing height (446 m), temperature (23.8°C), and winds (0.36 ms⁻¹).  相似文献   

Area Change and Thickness Variation over Pensilungpa Glacier (J&;K) using Remote Sensing     

Arvind Chandra Pandey  Swagata Ghosh  M. S. Nathawat  Reet Kamal Tiwari 《Journal of the Indian Society of Remote Sensing》2012,40(2):245-255

Accurate representations of the Earth’s surface in the form of digital elevation models (DEMs) are essential for a variety of applications in glaciological and remote-sensing research. In the present study area change and thickness variation over Pensilungpa glacier was attempted using remote sensing approach. It can be remarked that a net loss of 9.23 sq. km. which is 38% of the glacier area mapped in 1962 indicate a drastic change over the glacier area during 1962–2007. Estimation of glacier thickness change on Pensilungpa glacier based on ASTER DEM (2003) and Survey of India (SOI) contour based DEM (1962) indicated increase in the glacier elevation in the accumulation zone mainly by 30 to 90 m and similar reduction by 30 to 90 m in the ablation zone.  相似文献   

Biostratigraphy and depositional environment of the Miocene limestone bed of Baripada,Mayurbhanj district,Odisha: Foraminiferal,sedimentological and bulk organic geochemical evidences     

Ajoy K. Bhaumik  Joydeep Paikray  Jagadish Dutta  Arijit Mitra  Devleena Tiwari  Dattatray J. Patil 《Journal of the Geological Society of India》2017,90(4):437-446

Baripada Marine Beds (BMB) have been studied extensively in terms of its mega fossil content. However, not much has been discussed about the foraminiferal content and the organic matter assemblage in these beds. The fossiliferous sequence of BMB consists of sandstone, shale and limestone units. The present study is persued on the limestone unit of BMB. Foraminiferal, thin section and rock-eval pyrolysis studies were performed on the 33 surface samples collected from five sections of Jamdapal and Mukurmatia region along the Budhabalang river bank. Foraminifera are less abundant in the samples of Jamdapal, whereas Mukurmatia is comparatively rich. First appearance datum of Globorotalia menardii[ranges since middle Miocene (12.6 Ma); FAD at planktic foraminiferal zone N12] and last appearance datum of Neogloboquadrina continuosa [ranges between early Miocene (23.2 Ma) to late Miocene (8.3 Ma); FAD at planktic foraminiferal zone N4B and LAD at N16] together suggest that the limestone unit was deposited in between 12.6 to 8.3 Ma within the upper Miocene. Also, the association of shallow water benthic foraminifera (Species of Ammonia, Asterorotalia, Bolivina, Buliminella, Cibicides, Challengerella, Criboelphidium, Cribononion, Elphidium, Hanzawaia, Nonionella) and planktic foraminifera (Globigerina falcoensis, Globigerina woodi, Globorotalia menardii, Neogloboquadrina continuosa) together with oyster bank and shark teeth suggest deposition of limestone within well oxygenated, tropical, shallow water, open marine condition (within 40m water depth). Lithological and thin section studies together with global sea level fluctuation history advocate that upper Miocene marine transgression promoted the formation of this unit. Bulk organic geochemical data obtained by the rock-eval pyrolysis studies on selected samples indicate a low total organic carbon (TOC), with low hydrogen index (HI), high oxygen index (OI). The organic facies is characterised by type-IV kerogen with major contribution from near shore terrestrial plants. This also suggests deposition in shallow, oxygenated environments that did not promote significant accumulation and preservation of organic content in sediments.  相似文献   

Co-seismic gravity changes in the Koyna-Warna region: Implications of mass redistribution     

K. N. D. Prasad  N. Srinivas  A. E. Meshram  A. P. Singh  V. M. Tiwari 《Journal of the Geological Society of India》2017,90(6):704-710

Koyna-Warna Region (KWR) is one of the known sites for reservoir triggered seismicity. The continued triggered seismicity over the five decades is restricted to a region of about 600–700 sq. km, which provides a unique opportunity to monitor geophysical anomalies likely to be associated with seismicity of the region. Present study confers temporal gravity changes recorded by gPhone and GRACE satellite and interprets observed changes in conjunction with seismological, geodetic (cGPS) observations and groundwater level measurements. GRACE data suggest that seasonal vertical deformation due to hydrological loading is ～ 2 cm, which corroborates with continuous GPS observations. Seasonal hydrological loading of the region, which is in a phase of reservoir loading, might be influencing the critically stressed KWR leading to the seasonal seismicity of the region. The gPhone gravity data distinctly show co-seismic gravity signals for eight earthquakes of M_w > 2 and gravity anomalies show positive correlation on a logarithmic scale with earthquake released energy. To investigate the cause of gravity changes, an estimate is made for 14^th April 2012 earthquake for M_w 4.8 using fault dislocation model. The recorded gravity changes of 189 μGal by gPhone located at a distance of 28 km from the hypocentre is much more than the estimate of ～0.1 μGal calculated for M_w 4.8 Koyna earthquake. Therefore, it is inferred that co-seismic gravity signals for eight earthquakes are primarily caused due to redistribution of mass at shallow depth.  相似文献   

Groundwater modeling of Hiranyakeshi watershed of Ghataprabha sub-basin     

Nagraj S. Patil  N. L. Chetan 《Journal of the Geological Society of India》2017,90(3):357-361

Groundwater modeling is an effective tool for managing the groundwater resource and to predict for the future. There is a need for proper quantification of the scarce water resources that are under threat because of the population explosion, industrialization, urbanization and climate change. More than 60% of India is underlained by hard rock aquifers. The Hiranyakeshi watershed of Ghataprabha sub-basin, chosen for the study is also under hard rock aquifer and faces severe groundwater problems. This is due to majority of the agricultural and industrial activities in the watershed depend on the groundwater. A 3-D groundwater flow model, viz. Visual MODFLOW was used for the study with two conceptual layers. The first layer is a weathered zone which is about 20-30m from the top, followed by a second layerof fractured zone which is about 30-40m from the first. The model was simulated for a period of seven years (2008-2014), under transient case. The results from the modeling shows that for the next 10 years the water table is believed to decrease more than 50m in the study area. To overcome this critical stage, the present draft should be reduced by nearly 50%.  相似文献   

Sensitivity Studies of Convective Schemes and Model Resolutions in Simulations of Wintertime Circulation and Precipitation over the Western Himalayas     

P. Sinha  P. R. Tiwari  S. C. Kar  U. C. Mohanty  P. V. S. Raju  S. Dey  M. S. Shekhar 《Pure and Applied Geophysics》2015,172(2):503-530

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Phase Space Structure, Attractor Dimension, Lyapunov Exponent and Nonlinear Prediction from Earth’s Atmospheric Angular Momentum Time Series   总被引：8，自引：0，他引：8  

R. K. Tiwari  K. N. N. Rao 《Pure and Applied Geophysics》1999,156(4):719-736

--On a short time scale, Atmospheric Angular Momentum (AAM) has been demonstrated to be essentially the sole excitation source of LOD variations. The LOD variation, therefore, merely reflects the AAM variation (LOD as proxy for AAM). The study of the nonlinear nature of AAM variability (e.g., its orbital complexity, dimensionality and extreme sensitivity to the initial conditions) may provide a physical premise for theoretical modelling of the earth-atmosphere-ocean system. Analysis of the high quality of detailed daily LOD/AAM variations time series, spanning the period of 1962-1992, reveals a non-zero and low positive Lyapunov exponent value which suggests possible evidence of deterministic chaos in the underlying dynamics. Application of modern nonlinear prediction techniques capable of distinguishing chaos and random fractals to the data set, further support the above findings and render a predictive time limit of approximately 12-15 days. A low dimensional strange attractor and a low average Lyapunov exponent suggest a low level of unpredictability and stability in the system dynamics. It is argued here that a possible source of the raised entropy in LOD/AAM systems possibly stems from a conceivable nonlinear interaction between the seasonal cycle and inter- or intra-annual fluctuations due to thermodynamics properties of the atmosphere-ocean system.  相似文献   

Static charged dust distributions: Sources of purely electromagnetic origin     

R. N. Tiwari  Saibal Ray 《Astrophysics and Space Science》1991,182(1):105-110

The present work is a continuation of our earlier work on the charged dust sources of purely electromagnetic origin for static axisymmetric and static spherically-symmetric fields. Here we have extended the above work to the case of generalized static metric and have shown that a static charged dust distribution, irrespective of any symmetry conditions, can be only of purelly electromagnetic origin. Incidentally, it follows from this result itself that the Weyl-Majumdar-Papapetrou class of static charged dust sources, which form an important class of astrophysical systems, are also of purely electromagnetic origin.  相似文献   

Inhomogeneous Plane Symmetric Models in a Scalar-Tensor Theory     

Shri Ram  S.K. Tiwari 《Astrophysics and Space Science》1998,259(1):91-97

For the general plane symmetric metric, some exact solutions of Einstein field equations in the scalar tensor theory developed by Saez and Ballestev are presented in vaccum and in the presence of stiff fluid. The physical and kinematical features of the models are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献