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31.
The lifetimes and spatial scales of emission network cells in the solar chromosphere were studied from a nearly continuous sequence of Caii K filtergrams, obtained from Antarctica. The temporal autocorrelation function (ACF) was calculated for spatially-aligned windows from the time sequence of filtergrams. The lifetime of network cells was found to be dependent on the activity of the region. The estimated lifetimes are 24–34 hours for quiet-region cells and 58–61 hours for active-region cells. The temporal ACF shows prominent undulations in some of the quiet-region windows. The spatial ACF reveals the periodicity of the emission network in quiet regions. 相似文献
32.
The first optical signatures of plasmapause associated processes were gleaned from the daytime auroral emissions monitored
from Maitri, the Indian station in Antarctica, using the newly built, ground-based, Multiwavelength Daytime Photometer (MWDPM).
The plasmapause boundary inferred from these measurements conforms well with the known empirical relationship with the geomagnetic
indexKp. The measurements made at 391.4, 486.1, 557.7 and 630.0 nm emissions revealed significant day-to-day variations in their
spatial and temporal extents. These preliminary results are presented and discussed. 相似文献
33.
R. S. Dwivedi A. N. Singh K. K. Raju 《Journal of the Indian Society of Remote Sensing》1981,9(2):33-40
Measuring spectral reflectance of soils in situ which simulates measurements made from aircraft and by satellite scanner system has become an integral part of soil mapping using remote sensing techniques. A preliminary study has been conducted to measure the spectral reflectance of some typical red and black soils of India using a field radiometer (EXOTECH-100-A) and to study the changes in specrtral reflectance patterns due to tillage and crop and non-crop cover, The spectral reflectance were measured in four different pands of electromagnetic spectrum—two in visible (0.5-0.6μ and 0.6-0.7μ) and two in infrared (0.7-0.8μ and 0.8-1.0μ) region. Spectral reflectance curves were drawn from these values which helped in understanding the spectral separability and mixing of various red and black soil types. Black soils having grass cover showed maximum reflectance value followed by ploughed one and bare counterparts whereas, the order of decrease in spectral reflectance of red soils was bare soils> ploughed soil> soils with grass cover. 相似文献
34.
Magnetic properties, namely intensity of natural remanent magnetisation (NRM) and magnetic susceptibility, of mafic and ultramafic formations of Eastern Ghats belt in the Godavari Districts, Andhra Pradesh are studied. The formations sampled for the study are, iron-ore, chromite-ore, amphibolite, gabbro, charnockite and khondalite gneiss. Mineralogical differences in iron-ore and the degree of martitisation are reflected in magnetic susceptibility. NRM and susceptibility of chromite-ore are feeble. The gabbro exhibits strong magnetic properties because of its contiguity with iron formation. The Koenigsberger ratio is found to indicate relative palaeomagnetic stability. 相似文献
35.
G. Lakshminarayana C. Manikyamba Tarun C. Khanna Prachiti P. Kanakdande K. Raju 《Journal of the Geological Society of India》2010,75(6):807-819
The Rajahmundry Traps of the Krishna Godavari Basin (K-G Basin) consist of three distinct basalt flows interbedded with two
intertrappean sedimentary horizons, which in turn are underlain by the late Cretaceous fossiliferous limestone bed (infratrappean)
and overlain by the Cenozoic Rajahmundry Formation (conglomerate/sandstone). Among the three, the lower flow is characterized
by the presence of the physical volcanological features such as rootless cones, tumuli and dyke like forms along with single
to multitier columnar and radial jointing. The middle and upper flows are simple, massive and vesicular and exhibit spheroidal
weathering. Physical volcanological features and lithological attributes indicate that the lower flow was formed by an explosive
volcanic activity in hydrous environment, followed by sub aerial eruption to form the middle and upper flows. The fossiliferous
limestone bed is a representative horizon for the K-T boundary mass extinction caused due to intense volcanism. Intertrappean
sediments exhibit weathered soil profiles (palaeosols) with limestone beds denoting a distinct time gap during various phases
of lava eruption. Evaluation of the palaeogeographic scenario of the Krishna and Godavari Rivers does not provide any evidence
for the existence of Cretaceous palaeovalley which would have provided pathway for lava transportation from the Deccan volcanic
province of western India to the K-G Basin situated along the east coast. The present study opens up an alternative approach
to explain the origin of basalt flows at Rajahmundry. In all probability the lavas could be intrabasinal. NW-SE and NESW faults
or their intersection zones are probable pathways for lava eruption in the K-G Basin. 相似文献
36.
Hydrogeochemical investigation and groundwater quality assessment of Pratapgarh district,Uttar Pradesh 总被引:3,自引:0,他引:3
Ashwani Kumar Tiwari Abhay Kumar Singh 《Journal of the Geological Society of India》2014,83(3):329-343
Hydogrochemical investigation of groundwater resources of Paragraph district has been carried out to assess the solute acquisition processes and water quality for domestic and irrigation uses. Fifty-five groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, hardness, major anions (F?, Cl?, NO3, HCO3 ?, SO4 2?) and cations (Ca2+, Mg2+, Na+, K+). Study results reveal that groundwater of the area is alkaline in nature and HCO3 ?, Cl?, Mg2+, Na+ and Ca2+ are the major contributing ions to the dissolved solids. The hydrogeochemical data suggest that weathering of rock forming minerals along with secondary contributions from agricultural and anthropogenic sources are mainly controlling the groundwater composition of Pratapgarh district. Alkaline earth metals (Ca2++Mg2+) exceed alkalis (Na++K+) and weak acid (HCO3 ?) dominate over strong acids (Cl?+SO4 2?) in majority of the groundwater samples. Ca-Mg-HCO3 and Ca-Mg-Cl-HCO3 are the dominant hydrogeochemical facies in the groundwater of the area. The computed saturation indices demonstrate oversaturated condition with respect to dolomite and calcite and undersaturated with gypsum and fluorite. A comparison of groundwater quality parameters in relation to specified limits for drinking water shows that concentrations of TDS, F?, NO3 ? and total hardness exceed the desirable limits in many water samples. Quality assessment for irrigation uses reveal that the groundwater is good for irrigation. However, values of salinity, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), %Na and Kelley index are exceeding the prescribed limit at some sites, demanding adequate drainage and water management plan for the area. 相似文献
37.
A major portion of the southern part of the Indian subcontinent is classified as a stable continental region. However, a few segments in this region are punctuated by rifts and shear zones that are seismically active. The Godavari rift that sutures the eastern Dharwar and the Bastar cratons is one such region, prone to seismic hazard. Estimation of the sedimentary thickness in these seismically active regions assumes importance since locales of thick and soft sediments are vulnerable to destruction due to surface waves generated by earthquakes. In the present study, data from five broadband seismological stations are utilized to estimate the average sedimentary thickness of the Godavari region using the difference in travel times of the direct S and converted Sp phases from local earthquakes. The thickness of sediments varies between 0.32 and 4.32 km. Also, the site-specific response in terms of the fundamental resonance frequency and the corresponding amplifications are estimated using the well-established Nakamura technique. The predominant frequencies are in the range of 1.3–4.61 Hz, and the amplifications are higher (>1.5) for the stations inside the Godavari basin. Both the thickness and amplification values clearly indicate that the sediments tend to get thicker toward the center of the basin, in good agreement with the geological distribution of the sedimentary units. 相似文献
38.
Hgbomite, a rare exotic mineral, is found to be associated with the vanadiferous–titaniferous(V-Ti) bearing magnetite bands at Bhakatarhalli, Nuggihalli greenstone belt, western Dharwar Craton, India. We report on a second occurrence of hgbomite from the Dharwar craton in Karnataka, which is the sixth documented occurrence of this mineral from India. We evaluate the chemical characteristics of hgbomite and associated Fe-Ti-minerals in an attempt to identify its formation as a primary hydrothermal mineral in a metamorphosed magnetite layer.We report here the presence of hgbomite as a complex oxide of Fe, Mg, Al and Ti with accessory of Zn, V and Sn. Petrographic studies suggest the(V–Ti) bearing magnetite(Mt) contain spinel, hgbomite, chlorite, martite, ilmenite(Il) and minor amounts of diaspore. The hgbomite displays euhedral to subhedral textures, and is up to 250 μm along the grain boundaries of magnetite and ilmenite. In the samples studied, hgbomite is prismatic, irregular and elongated in shape. The genesis of hgbomite in veins between magnetite and ilmenite implies its precipitation from fluids without involving complicated reactions. Several models were proposed for the formation of hgbomite; however, the subject is still debatable. 相似文献
39.
K. P .Raju J. N. Desai T. Chandrasekhar N. M. Ashok 《Journal of Astrophysics and Astronomy》1991,12(4):311-317
The line intensity of the green coronal line and the continuum intensity are derived from the filter and white light photographs of the solar corona obtained during the 1980 total solar eclipse. Ratio of the line to continuum intensity is plotted against the radial distancer(=R/R0,R 0 is the solar radius), in various position angles. A simple model assuming an electron density dependence of the line and continuum intensities suggests a dominant collisional mechanism for the excitation of the line in the innermost regions (~ 1.4R 0). The measured line to continuum ratio tends to a constant value at different radial distances in different position angles. The constancy of the measured line to continuum ratio indicates significant radiative excitation beyond 1.4 R0, in some of the position angles. 相似文献
40.
Mandal Prantik Srinagesh D. Vijayaraghavan R. Suresh G. Naresh B. Raju P. Solomon Devi Aarti Swathi K. Singh Dhiraj K. Srinivas D. Saha Satish Shekar M. Sarma A. N. S. Murthy YVVBSN 《Natural Hazards》2022,111(3):2241-2260
Natural Hazards - Since the initial collision at 55 Ma, rocks of the Indian crust below the Himalayas have undergone modification chemically and compositionally due to the ongoing... 相似文献