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601.
K. Chandrashekhar S. Krishna Prasad D. Banerjee B. Ravindra Daniel B. Seaton 《Solar physics》2013,286(1):125-142
The Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard the PRoject for OnBoard Autonomy-2 (PROBA2) spacecraft provides images of the solar corona in EUV channel centered at 174 Å. These data, together with the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO), are used to study the dynamics of coronal bright points. The evolution of the magnetic polarities and associated changes in morphology are studied using magnetograms and multi-wavelength imaging. The morphology of the bright points seen in low-resolution SWAP images and high-resolution AIA images show different structures, whereas the intensity variations with time show similar trends in both SWAP 174 Å and AIA 171 Å channels. We observe that bright points are seen in EUV channels corresponding to a magnetic flux of the order of 1018 Mx. We find that there exists a good correlation between total emission from the bright point in several UV–EUV channels and total unsigned photospheric magnetic flux above certain thresholds. The bright points also show periodic brightenings, and we have attempted to find the oscillation periods in bright points and their connection to magnetic-flux changes. The observed periods are generally long (10?–?25 minutes) and there is an indication that the intensity oscillations may be generated by repeated magnetic reconnection. 相似文献
602.
Prakash Chauhan M Mohan S R Nayak R R Navalgund 《Journal of the Indian Society of Remote Sensing》2002,30(1-2):87-94
In-situ chlorophyll concentration data and remote sensing reflectance (Rrs) measurements collected in six different ship campaigns in the Arabian Sea were used to evaluate the accuracy, precision, and suitability of different ocean color chlorophyll algorithms for the Arabian Sea. The bio-optical data sets represent the typical range of biooptical conditions expected in this region and are composed of 47 stations encompassing chlorophyll concentration, between 0.072 and 5.90 mg m-3, with 43 observations in case I water and 4 observations in case II water. Six empirical chlorophyll algorithms [i.e. Aiken-C, POLDER-C, OCTS-C, Morel-3, Ocean Chlorophyll-2 (OC2) and Ocean Chlorophyll-4 (OC4)] were selected for analysis on the Arabian Sea data set. Numerous statistical and graphical criterions were used to evaluate the performance of these algorithms. Among these six chlorophyll algorithms two chlorophyll algorithms (i.e. OC2 and OC4) performed well in the case I waters of the Arabian Sea. The OC2 algorithm, a modified cubic polynomial function which uses ratio of Rrs490 nm and Rrs555 nm (where, Rrs is remote sensing reflectance), performed well with r2=0.85; rms =0.15. The OC4 algorithm, a four-band (443, 490, 510, 555 nm), maximum band ratio formulation was found best on the basis of statistical analysis results with r2=0.85 and rms=0.14. Both OC2 and OC4 algorithms failed to estimate chlorophyll inTrichodesmium dominated waters. The OC2 algorithm was preferred over OC4 algorithm for routine processing of the OCM data to generate chlorophyll-a images, as it uses a band ratio of 490/555 nm and atmospheric correction is more accurate in 490 nm compared to 443 nm band, which is used by OC4 algorithm. 相似文献
603.
Massimiliano Galeazzi Meng Chiao Michael R. Collier Thomas Cravens Dimitra Koutroumpa Kip D. Kuntz Susan Lepri Dan McCammon Frederick S. Porter Krishna Prasai Ina Robertson Steve Snowden Youaraj Uprety 《Experimental Astronomy》2011,32(2):83-99
The Diffuse X-rays from the Local galaxy (DXL) mission is an approved sounding rocket project with a first launch scheduled around December 2012. Its goal is to identify and separate the X-ray emission generated by solar wind charge exchange from that of the local hot bubble to improve our understanding of both. With 1,000 cm2 proportional counters and grasp of about 10 cm2 sr both in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-min flight what cannot be achieved by current and future X-ray satellites. 相似文献
604.
Performance of seven fully coupled models in simulating Indian summer monsoon climatology as well as the inter-annual variability was assessed using multi member 1 month lead hindcasts made by several European climate groups as part of the program called Development of a European multi-model ensemble system for seasonal-to-inter-annual prediction (DEMETER). Dependency of the model simulated Indian summer monsoon rainfall and global sea surface temperatures on model formulation and initial conditions have been studied in detail using the nine ensemble member simulations of the seven different coupled ocean–atmosphere models participated in the DEMETER program. It was found that the skills of the monsoon predictions in these hindcasts are generally positive though they are very modest. Model simulations of India summer monsoon rainfall for the earlier period (1959–1979) are closer to the ‘perfect model’ (attainable) score but, large differences are observed between ‘actual’ skill and ‘perfect model’ skill in the recent period (1980–2001). Spread among the ensemble members are found to be large in simulations of India summer monsoon rainfall (ISMR) and Indian ocean dipole mode (IODM), indicating strong dependency of model simulated Indian summer monsoon on initial conditions. Multi-model ensemble performs better than the individual models in simulating ENSO indices, but does not perform better than the individual models in simulating ISMR and IODM. Decreased skill of multi-model ensemble over the region indicates amplification of errors due to existence of similar errors in the individual models. It appears that large biases in predicted SSTs over Indian Ocean region and the not so perfect ENSO-monsoon (IODM-monsoon) tele-connections are some of the possible reasons for such lower than expected skills in the recent period. The low skill of multi-model ensemble, large spread among the ensemble members of individual models and the not so perfect monsoon tele-connection with global SSTs points towards the importance of improving individual models for better simulation of the Indian monsoon. 相似文献
605.
Regolith mass balance inferred from combined mineralogical, geochemical and geophysical studies: Mule Hole gneissic watershed, South India 总被引:3,自引:0,他引:3
Jean-Jacques Braun Marc Descloitres Jean Riotte Simon Fleury Jean-Loup Boeglin Eva Lacarce M. Sekhar M.S. Mohan Kumar S. Subramanian Bernard Dupré 《Geochimica et cosmochimica acta》2009,73(4):935-24
The aim of this study is to propose a method to assess the long-term chemical weathering mass balance for a regolith developed on a heterogeneous silicate substratum at the small experimental watershed scale by adopting a combined approach of geophysics, geochemistry and mineralogy. We initiated in 2003 a study of the steep climatic gradient and associated geomorphologic features of the edge of the rifted continental passive margin of the Karnataka Plateau, Peninsular India. In the transition sub-humid zone of this climatic gradient we have studied the pristine forested small watershed of Mule Hole (4.3 km2) mainly developed on gneissic substratum. Mineralogical, geochemical and geophysical investigations were carried out (i) in characteristic red soil profiles and (ii) in boreholes up to 60 m deep in order to take into account the effect of the weathering mantle roots. In addition, 12 Electrical Resistivity Tomography profiles (ERT), with an investigation depth of 30 m, were generated at the watershed scale to spatially characterize the information gathered in boreholes and soil profiles. The location of the ERT profiles is based on a previous electromagnetic survey, with an investigation depth of about 6 m. The soil cover thickness was inferred from the electromagnetic survey combined with a geological/pedological survey.Taking into account the parent rock heterogeneity, the degree of weathering of each of the regolith samples has been defined using both the mineralogical composition and the geochemical indices (Loss on Ignition, Weathering Index of Parker, Chemical Index of Alteration). Comparing these indices with electrical resistivity logs, it has been found that a value of 400 Ohm m delineates clearly the parent rocks and the weathered materials. Then the 12 inverted ERT profiles were constrained with this value after verifying the uncertainty due to the inversion procedure. Synthetic models based on the field data were used for this purpose. The estimated average regolith thickness at the watershed scale is 17.2 m, including 15.2 m of saprolite and 2 m of soil cover.Finally, using these estimations of the thicknesses, the long-term mass balance is calculated for the average gneiss-derived saprolite and red soil. In the saprolite, the open-system mass-transport function τ indicates that all the major elements except Ca are depleted. The chlorite and biotite crystals, the chief sources for Mg (95%), Fe (84%), Mn (86%) and K (57%, biotite only), are the first to undergo weathering and the oligoclase crystals are relatively intact within the saprolite with a loss of only 18%. The Ca accumulation can be attributed to the precipitation of CaCO3 from the percolating solution due to the current and/or the paleoclimatic conditions. Overall, the most important losses occur for Si, Mg and Na with −286 × 106 mol/ha (62% of the total mass loss), −67 × 106 mol/ha (15% of the total mass loss) and −39 × 106 mol/ha (9% of the total mass loss), respectively. Al, Fe and K account for 7%, 4% and 3% of the total mass loss, respectively. In the red soil profiles, the open-system mass-transport functions point out that all major elements except Mn are depleted. Most of the oligoclase crystals have broken down with a loss of 90%. The most important losses occur for Si, Na and Mg with −55 × 106 mol/ha (47% of the total mass loss), −22 × 106 mol/ha (19% of the total mass loss) and −16 × 106 mol/ha (14% of the total mass loss), respectively. Ca, Al, K and Fe account for 8%, 6%, 4% and 2% of the total mass loss, respectively.Overall these findings confirm the immaturity of the saprolite at the watershed scale. The soil profiles are more evolved than saprolite but still contain primary minerals that can further undergo weathering and hence consume atmospheric CO2. 相似文献
606.
Geological and geotechnical investigations of Loharinag-Pala Hydroelectric Project,Garhwal Himalaya,Uttarakhand 总被引:1,自引:0,他引:1
Ajay K. Naithani A. K. Bhatt K. S. Krishna Murthy 《Journal of the Geological Society of India》2009,73(6):821-836
The project area, forming a part of Bhagirathi valley, exposed rocks classed as central Himalayan crystallines and are medium
to high grade metamorphics. The rock types exposed are feldspathic gneisses, quartz-biotite schists, garnet-biotite schist,
biotite gneisses, migmatites and amphibolites. To design the rock support for the underground structures of desilting chambers,
HRT, surge shaft, pressure shafts, power house, TRT and for the foundations of barrage and intake of desilting chambers, rock
mass classifications was attempted following the methods of Bieniawski Rock Mass Rating (RMR) Classification and Tunnelling
Quality Index (Q) of Barton et al. RMR technique involves collection of data on rock strength, RQD (%), spacing of discontinuities,
condition of discontinuities and groundwater condition, while the ‘Q’ involves collection of data on RQD (%), joint set numbers
(Jn), joint roughness number (Jr), joint alternation number (Ja), joint water reduction factor (Jw) and stress reduction factors
(SRF). The permeability test in the overburden was done by the constant head method, while in the bed rock portion conducted
by packer test. The result indicates that the rock masses of the area fall under the good, fair and poor rock quality. Augen
gneiss of power house area is coming under the category of moderately strong rock as proved by deformability characteristics
and strength parameter. On the basis of above study recommendations have been made for the proper and safe construction of
the project components. 相似文献
607.
The effect of granular pile installation on the modifications induced in loose to medium dense granular deposits is studied.
SPT is the most often used to evaluate the in situ soil properties. Expressions for modified SPT N1 values for different soils, i.e., for different initial SPT N1 values, were determined as functions of replacement ratio from the available field data. Improvements in the ground are presented
in the form of modified or improved SPT N1 values versus replacement ratio charts, which can then be used to design the required degree of treatment for the expected
improvement or to estimate the improved values of treated ground for different initial states of sands. 相似文献
608.
In this paper an attempt has been made to determine the effect of Coriolis force on the shapes of Roche equipotential surfaces
of rotating stars and stars in binary systems. Equations of Roche equipotential surfaces have been obtained for rotating and
binary stars which take into account the effects of Coriolis force besides the centrifugal and gravitational forces. Shapes
of Roche equipotentials and values of Roche limits are obtained for different values of angular velocity of rotation for rotating
stars and for different values of mass ratios for the binary stars. The obtained results have been compared with the corresponding
results in which the effect of Coriolis force has not been considered. 相似文献
609.
Nonradial oscillations of certain models of the generalized Roche series have been investigated numerically to further understand the nature of the eigen-values and the eigen-functions of the modes of nonradial oscillations of stellar models. 相似文献
610.
The averaging technique of Kippenhahn and Thomas (1970) has been used in conjunction with Kopal's method of evaluating various parameters on the Roche equipotentials to determine the effects of rotation and tidal distortions on the periods of small adiabatic radial and nonradial modes of oscillations of polytropic models of the stars. 相似文献