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271.
Neeraj Singh Bankoti Navin Chandra Joshi Bimal Pande Seema Pande Wahab Uddin Kavita Pandey 《New Astronomy》2011,16(4):269-275
This paper presents the study of normalized north–south asymmetry, cumulative normalized north–south asymmetry and cumulative difference indices of sunspot areas, solar active prominences (at total, low (?40°) and high (?50°) latitudes) and Hα solar flares from 1964 to 2008 spanning the solar cycles 20–23. Three different statistical methods are used to obtain the asymmetric behavior of different solar activity features. Hemispherical distribution of activity features shows the dominance of activities in northern hemisphere for solar cycle 20 and in southern hemisphere for solar cycles 21–23 excluding solar active prominences at high latitudes. Cumulative difference index of solar activity features in each solar cycle is observed at the maximum of the respective solar cycle suggesting a cyclic behavior of approximately one solar cycle length. Asymmetric behavior of all activity features except solar active prominences at high latitudes hints at the long term periodic trend of eight solar cycles. North–south asymmetries of SAP (H) express the specific behavior of solar activity at high solar latitudes and its behavior in long-time scale is distinctly opposite to those of other activity features. Our results show that in most cases the asymmetry is statistically highly significant meaning thereby that the asymmetries are real features in the N–S distribution of solar activity features. 相似文献
272.
Koijam Manihar Singh 《Astrophysics and Space Science》2010,325(1):127-135
Some new interesting solutions, the dynamics, behaviour and phenomena of rotating charged perfect fluid models are investigated,
and their physical and geometrical properties are studied in order to substantiate the possibility of the existence of such
astrophysical bodies in this Universe. The nature and role of the metric rotation Ω(r,t) as well as that of the matter rotation ω(r,t) are studied for uniform and non-uniform motions. The reactions of the gravitational and charged fields with respect to the
rotational motion are studied and possible results are explored for real astrophysical situations, and in some solutions we
find the spatial restrictions on the models for realistic conditions. Rotating models which are expanding are obtained in
which the rotational motions are decaying with time. 相似文献
273.
Twelve Recent benthic foraminiferal species hitherto not reported from the east and west coasts of India are presented and
illustrated. They are, namely- Bolivina semicostata, Elphidium subgranulosum, Hanzawaia nipponica, Planorbulina variabilis, Pseudononion japponicum, Reussella
haizumensis, Rosalina bradyi, Adelosina sp., Lagina sp. A, Lagina sp. B, Uvigerina sp. A and Uvigerina sp. B. 相似文献
274.
M. Chandra Singh P. Kundal R. A. S. Kushwaha 《Journal of the Geological Society of India》2010,76(6):573-586
Oligocene-Miocene deposits of Bhuban and Boka Bil Formations, Surma Group, Manipur Western Hill consist of well preserved
ichnofossil assemblages. These formations are represented by eight lithofacies such as Massive sandstone (Sm), Rippled marked
argillaceous sandstone (Sr), Wavy laminated sandstone-siltstone-silty shale (Sw), Laminated shale (Fl), Massive mudstone (Fm),
Trough cross-bedded sandstone (St), Lenticular laminated sandstonesiltstonesilty shale (Sll) and Laminated to massive sandstone-siltstone
(Ssc). Fifteen ichnospecies were identified, which further categories into Skolithos, Cruziana, and Skolithos/Cruziana ichnofacies. Overall distribution pattern and behavioural nature of the ichnoassemblage and sedimentological attributes suggests
that the sediments of Bhuban and Boka Bil Formations were deposited under frequent fluctuating sea level, moderate to strong
energy condition, subtidal to lower intertidal environment, rich in organic nutrients. 相似文献
275.
To study the characteristic of plasma bubbles in the topside ionosphere during the solar minima, we have analyzed a large
database of post-sunset plasma density measurement acquired during ∼5104 equatorial crossings made by Defense Meteorological
Satellite Program (DMSP) F14 in 2005. On 675 of these crossings, equatorial plasma bubbles (EPBs) events were observed as
intervals of depleted and irregular plasma densities that degrade communication and navigation signals. We have analyzed these
EPB events to study their distributions with month, season and longitude. To test for possible dependence of EPB occurrence
at topside altitudes on the level of magnetic activity, we compared the distributions of one year database with those of Kp
index at the time of equatorial crossings by the DMSP satellites. We also examined the response of the evening sector, low-latitude
ionosphere during eight magnetic storms with minimum Dst ≤ −100 nT. We observed that EPBs occurred regularly during geomagnetic
storms, especially in the initial and main phases but can be suppressed sometimes for days, after prolonged activity during
recovery phases. These results are discussed according to the other reported results. 相似文献
276.
R. T. Ratheesh Kumar Tanmay K. Maji Rajesh R. Nair 《Journal of Earth System Science》2010,119(5):717-730
Indian Ocean subduction zone is one of the most active plate margins of the globe as evident from its vast record of great
magnitude earthquake and tsunami events. We use Bouguer admittance (Morlet isostatic response function) in Sumatra-Java subduction
zones comprising both the subduction and over-riding plates to determine the lithospheric mechanical strength variations.
We determine effective elastic thickness (T
e
) for five oceanic windows (size 990 × 990 km2) by analyzing the admittance using Bouguer gravity and bathymetry data. The results show bimodal T
e
values < 20 km for Sumatra and 20−40 km for Java. The lower bimodal values obtained for Sumatra appears to correlate well
with the zones of historical seismicity. This is in sharp contrast with Java subduction zone, which shows higher T
e
values (20–40 km) and apparently associated with low magnitude earthquakes. We suggest a strong and wide interseismic coupling
for Sumatra between the subducting and over-riding plates, and deeper mantle contributing to low strength, shallow focus —
high magnitude seismicity and vice versa for Java, leading to their seismogenic zonation. 相似文献
277.
Rajesh K. Srivastava Sisir K. Mondal V. Balaram Gulab C. Gautam 《Mineralogy and Petrology》2010,98(1-4):329-345
Boninite-norite (BN) suites emplaced in an intracratonic setting in Archaean Cratons, are reported from many parts of the world. Such high-Mg low-Ti siliceous rocks are emplaced during Neoarchaean-Paleoproterozoic. The Archaean central Indian Bastar Craton also contains such a boninite-norite suite, which occurs in the form of dykes and volcanics. The spatial and temporal correlation of these high-Mg low-Ti siliceous rocks with similar rocks occurring around the northern Bastar and Dharwar Cratons probably represent a Bastar-Dharwar Large Igneous Province during the Neoarchaean-Paleoproterozoic. Platinum group element (PGE) abundances in these rocks provide constraints on their geochemical evolution during the Neoarchaean-Paleoproterozoic. The PGE geochemistry of the boninite-norite suite from the southern part of the central Indian Bastar Craton is presented to understand their behaviour during magma fractionation. In primitive mantle-normalized plots all samples have similar PGE fractionated patterns that are enriched in Pd, Pt and Rh relative to Ru. The Pd/Ru ratios for eight samples range from 2.0 to 7.0 which is higher than primitive mantle (primitive mantle Pd/Ru ≈1.2). The Pd/Pt ratios range between 0.2–2.5 with an average value of 0.7 which is near chondritic (primitive mantle Pd/Pt ≈0.5). PGE variations in these rocks together with those of major and other trace elements are consistent with a model involving olivine fractionation along with chromite as a cotectic phase. The Pt fractionation from Pd and Rh is controlled by both olivine and chromite crystallization at an early stage during high temperature crystal fractionation when the Pt was strongly compatible and Pd and Rh were incompatible. Strong negative correlations of the S content with iron and TiO2 plus lithophile element contents of the rock suggest a decrease of the S solubility in the parental high-Mg magma and separation of an immiscible sulfide liquid with decreasing temperature. Palladium plus other available chalcophile elements (e.g., Re, Au, Ag) have been fractionated in this immiscible sulfide liquid after considerable olivine fractionation of the magma. 相似文献
278.
Rohit Mehra Sandeep Kumar Rajendra Sonkawade N. P. Singh Komal Badhan 《Environmental Earth Sciences》2010,59(5):1159-1164
The activity concentration and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (232Th, 226Ra and 40K) were determined in soil samples collected from ten different locations of Sirsa district of Haryana, using HPGe detector
based on high-resolution gamma spectrometry system. The range of activity concentrations of 226Ra, 232Th and 40K in the soil samples from the studied areas varies from 19.18 Bq kg−1 (Moriwala) to 40.31 Bq kg−1 (Rori), 59.43 Bq kg−1 (Pipli) to 89.54 Bq kg−1 (Fatehpur) and 223.22 Bq kg−1 (Moriwala) to 313.32 Bq kg−1 (SamatKhera) with overall mean values of 27.94, 72.75 and 286.73 Bq kg−1 respectively. The absorbed dose rate calculated from activity concentration of 226Ra, 232Th and 40K ranges between 8.84 and 18.58, 37.02 and 55.78, and 9.24 and 12.97 nGy h−1, respectively. The total absorbed dose in the study area ranges from 60.40 to 82.15 nGy h−1 with an average value of 70.12 nGy h−1. The calculated values of external hazard index (H
ex) for the soil samples of the study area range from 0.36 to 0.49 with an average value of 0.42. 相似文献
279.
Marine Geophysical Research - 相似文献
280.
Birendra Nath Ghosh Narinder Kumar Sharma Nurnabi Meherul Alam Raman Jeet Singh Gopal Prasad Juyal 《山地科学学报》2014,11(5):1208-1217
On farm bio-resource recycling has been given greater emphasis with the introduction of conservation agriculture specifically withclimate change scenarios in the mid-hills of the north-west Himalaya region(NWHR). Under this changing scenario, elevation, slope aspect and integrated nutrient management(INM) may affect significantly soil quality and crop productivity. A study was conducted during 2009-2010 to 2010-2011 at the Ashti watershed of NWHR in a rainfed condition to examine the influence of elevation, slope aspect and integrated nutrient management(INM) on soil resource and crop productivity. Two years of farm demonstration trials indicated that crop productivity and soil quality is significantly affected by elevation, slope aspect and INM. Results showed that wheat equivalent yield(WEY) of improved technology increased crop productivity by -20%-37% compared to the conventional system. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-17%. North aspect and higher elevation increased crop productivity by 15%-25% compared to south aspect and low elevation(except paddy). Intercropping of maize with cowpea and soybean enhanced yield by another 8%-15%. Irrespective of slope, elevation and cropping system, the WEY increased by -30% in this region due to INMtechnology. The influence of elevation, slope aspect and INM significantly affected soil resources(SQI) and soil carbon change(SCC). SCC is significantly correlated with SQI for conventional(R2 = 0.65*), INM technology(R2 = 0.81*) and for both technologies(R2 = 0.73*). It is recommended that at higher elevation.(except for paddy soils) with a north facing slope, INM is recommended for higher crop productivity; conservation of soil resources is recommended for the mid hills of NWHR; and single values of SCC are appropriate as a SQI for this region. 相似文献