Density and temperature diagnostics of solar emission lines from Navii and Alix     

P. K. Raju  B. N. Dwivedi  Asheesh K. Gupta 《Solar physics》1994,149(2):289-299

Line intensity ratios of EUV emission lines from Navii and Alix have been considered for electron density and temperature determinations within the chromosphere-corona transition region and the corona. The electron pressure within the emission region has been assumed to be a constant parameter. Theoretical line intensities for these ions have been computed using a model solar atmosphere and compared with the values as observed by ATM ultraviolet spectrometer. The observed intensities correspond to the average quiet-Sun conditions near solar minimum.  相似文献   

The excitation mechanism and the line-to-continuum intensity ratio of the [Fexiv] 5303 Å line in various coronal regions     

K. P. Raju  J. N. Desai 《Solar physics》1993,147(2):255-261

The excitation mechanism of the coronal green line in various coronal regions is studied. The line-to-continuum intensity ratio is calculated using the model electron density values given by Newkirk (1961) and is compared with the observed values. Reasonably good agreement is found between the model calculations and observed values. The model calculations show that collisional excitation is more important in the innermost regions while radiative contribution progressively increases towards outer regions. The individual contributions depend strongly on the activity of the particular coronal region. An increased contribution from collisional excitation is seen in coronal active regions owing to the large electron density. A contour map of the line-to-continuum intensity ratio as derived from the observations, is plotted. At 1.10R the value is about 80 in active regions, 30–40 in coronal streamers, while it is less than 10 in polar regions.  相似文献   

Density dependence of the line emission of boron-like coronal ions     

G. Elwert  P. K. Raju 《Astrophysics and Space Science》1975,38(2):369-375

Assuming steady state conditions, we calculated the occupation of 20 levels of the ion Six as a function of the electron density and temperature taking into account collisional processes and spontaneous radiative ones. Between the two levels of the ground state also the photo-absorption of the corresponding infrared radiation has been considered. The emission of the most important UV-, X- and IR-lines is determined as a function of the electron density and temperature. Intensity ratios are plotted versus electron density. The line emission as a function of the height of the radiating layers is studied for UV- and X-ray lines. The resulting fluxes in earth distance are compared with observations.  相似文献   

Regional gravity and magnetic studies over the continental margin of the central west coast of India     

L. V. Subba Raju  K. A. Kamesh Raju  V. Subrahmanyam  D. Gopala Rao 《Geo-Marine Letters》1990,10(1):31-36

Gravity studies over the continental margin of the central west coast of India show a sediment thickness of 2–3 km on the shelf associated with deeper horst and graben structures, of 6 km in the shelf margin basin, and about 1 km in the deep sea. The upward trend in free-air gravity anomaly toward the deep sea region is interpreted as crustal thinning. Model studies indicate a 25-km-thick crust in the shelf region and a minimum of 18 km in the more offshore region. An abrupt magnetic signature change suggests differential basement depths in the shelf region. Major faulting in the region is confirmed in water depths of approximately 100–200 m.  相似文献   

Theoretical and experimental analysis of tethered buoy instability in gravity waves   总被引：1，自引：0，他引：1  

Sreeram Radhakrishnan  Raju Datla  Richard I. Hires 《Ocean Engineering》2007,34(2):261-274

The motion of a tethered spherical buoy subjected to incident regular waves was measured in a wave tank. Transverse instability was observed when the period of the wave generated was close to one-half of the natural period of the buoy. The transverse instability confirmed as Mathieu type was predominant at the surface but diminished with increase in the depth of submergence. The stable and unstable zones were determined on the Mathieu's instability diagram. Experimental results were in agreement with the predicted zone of instability for a two degree of freedom oscillation problem of Mathieu type which has a periodically varying spring constant.  相似文献   

Ranking of CMIP5-based global climate models for India using compromise programming     

K.?Srinivasa Raju  P.?Sonali  D.?Nagesh KumarEmail author 《Theoretical and Applied Climatology》2017,127(3-4):563-572

In this study, regional patterns of precipitation in Marmara are described for the first time by means of Ward’s hierarchical cluster analysis. Daily values of winter precipitation data based on 19 meteorological stations were used for the period from 1960 to 2012. Five clusters of coherent zones were determined, namely Black Sea-Marmara, Black Sea, Marmara, Thrace, and Aegean sub-regions. To investigate the prevailing atmospheric circulation types (CTs) that cause precipitation occurrence and intensity in these five different rainfall sub-basins, objective Lamb weather type (LWT) methodology was applied to National Centers of Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis of daily mean sea level pressure (MSLP) data. Precipitation occurrence suggested that wet CTs (i.e. N, NE, NW, and C) offer a high chance of precipitation in all sub-regions. For the eastern (western) part of the region, the high probability of rainfall occurrence is shown under the influence of E (SE, S, SW) atmospheric CTs. In terms of precipitation intensity, N and C CTs had the highest positive gradients in all the sub-basins of the Marmara. In addition, although Marmara and Black Sea sub-regions have the highest daily rainfall potential during NE types, high daily rainfall totals are recorded in all sub-regions except the Black Sea during NW types.  相似文献   

In-season time series analysis of Resourcesat-1 AWiFS data for estimating irrigation water requirement     

P.V. Raju  M.V.R. Sesha Sai  P.S. Roy 《International Journal of Applied Earth Observation and Geoinformation》2008,10(2):220-1

AWiFS sensor on board IRS-P6 (Resourcesat-1), with its unique features—wide swath and 5-day revisit capability provides excellent opportunities to carry out in-season analysis of irrigated agriculture. The study carried out in Hirakud command area, Orissa State indicated that the progression of rice crop acreage could be mapped through analysis of time series AWiFS data set. The spectral emergence pattern of rice crop was found useful to identify the period of rice transplantation and its variability across the command area. This information, integrated with agro-meteorological data, was used to quantify 10-daily canal-wise irrigation water requirement. A comparison with field measured actual irrigation supplies indicated an overall supply adequacy of 88% and showed wide variability at lateral canal level ranging between 18% and 109%. The supply pattern also did not correspond with the chronological variations associated with crop water requirement, supplies were 15% excess during initial part of season (December and January) and were 20.1% deficit during later part of season (February to April). Rescheduling the excess supplies of the initial period could have reduced the deficit to 15% during peak season. The study has demonstrated the usefulness of AWiFS data to generate the irrigation water requirement by mid-season, subsequent to which 38% supplies were yet to be allocated. This would support the irrigation managers to reschedule the irrigation water supplies to achieve better synchronization between requirement and supply leading to improved water use efficiency.  相似文献   

Evaluation of hydrogeochemical processes in the Pleistocene aquifers of Middle Ganga Plain, Uttar Pradesh, India   总被引：4，自引：4，他引：0  

Janardhana Raju Nandimandalam 《Environmental Earth Sciences》2012,65(4):1291-1308

Evaluation of major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting a total of fifty-one groundwater samples in shallow (<25 m) and deep aquifer (>25 m) in the Varanasi area. Hydrochemical facies, Mg-HCO₃ dominated in the largest part of shallow groundwater followed by Na-HCO₃ and Ca-HCO₃ whereas Ca-HCO₃ is dominated in deep groundwater followed by Mg-HCO₃ and Na-HCO₃. High As concentration (>50 μg/l) is found in some of the villages situated in northeastern parts (i.e. adjacent to the concave part of the meandering Ganga river) of the Varanasi area. Arsenic contamination is confined mostly in tube wells (hand pump) within the Holocene newer alluvium deposits, whereas older alluvial aquifers are having arsenic free groundwater. Geochemical modeling using WATEQ4F enabled prediction of saturation state of minerals and indicated dissolution and precipitation reactions occurring in groundwater. Majority of shallow and deep groundwater samples of the study area are oversaturated with carbonate bearing minerals and under-saturated with respect to sulfur and amorphous silica bearing minerals. Sluggish hydraulic conductivity in shallow aquifer results in higher mineralization of groundwater than in deep aquifer. But the major processes in deep aquifer are leakage of shallow aquifer followed by dominant ion-exchange and weathering of silicate minerals.  相似文献   

Impact of anthropogenic activity and cyclonic storm on black carbon during winter at a tropical urban city,Pune     

M. P. Raju  P. D. Safai  P. S. P. Rao  S. Tiwari  P. C. S. Devara 《Natural Hazards》2014,71(1):881-894

Black carbon (BC) aerosols are emitted into the atmosphere as a byproduct of different combustion processes and are reported to be a very strong absorber of solar radiation. In this paper, we present results on BC aerosols over Pune, a tropical urban city in south west India during Diwali festival in the month of November 2010. Daily mean BC showed about 5 % increase on Diwali day compared with preceding and succeeding period with concentrations reaching as high as about 21 μg/m³ in the morning on Diwali day, mainly due to the influence of extensive fireworks. However, the strong winds accompanied by occasional rainfall due to severe cyclonic storm “Jal” formed in the Bay of Bengal on the same day dampened this effect and reduced BC to about 2 μg/m³ within 6 h. There was only 5 % increase in mean BC concentration on Diwali day during 2010 as compared to the average increase of about 17 % during preceding 4 years on Diwali day, mainly due to the impact of weather conditions induced by Jal.  相似文献   

Near surface manifestation of hydrocarbons in Proterozoic Bhima and Kaladgi Basins: Implications to hydrocarbon resource potential   总被引：1，自引：0，他引：1  

M. S. Kalpana  D. J. Patil  A. M. Dayal  S. V. Raju 《Journal of the Geological Society of India》2010,76(6):548-556

Reconnaissance surface geochemical survey for adsorbed soil gas analysis conducted in Proterozoic Bhima and Kaladgi Basins, have revealed occurrence of anomalous concentrations of light gaseous hydrocarbons i.e. C₁ to C₄ (CH₄, C₂H₆, C₃H₈, i-C₄H₁₀ and n-C₄H₁₀) in the near surface soils. The concentrations of C₁ and ΣC₂₊(C₂H₆+C₃H₈+ i-C₄H₁₀+ n-C₄H₁₀) in Bhima and Kaladgi Basins are in the range of 1–2594 ppb and 1 to 57 ppb and 1–1142 ppb and 1–490 ppb, respectively. The carbon isotopic data of adsorbed soil gas methane in few selected samples are in the range of −29.9 to −39‰ (PDB). The evaluation of adsorbed soil gas data indicates that all the gas components are cogenetic and hydrocarbon ratios of C₁/(C₂+C₃) < 10 and C₃/C₁*1000 between 60–500 and 20–60 suggest that the adsorbed gases are derived from oil and gas-condensate zones. The carbon isotopic values of methane further support thermogenic origin of these migrated gases. The concentration distribution of C₁ and ΣC₂₊ in the study areas illustrate C₁ and ΣC₂₊ anomalies near Katamadevarhalli, Andola and Talikota in Bhima Basin and near Kaladgi, Lokapur and north of Mudhol in Kaladgi Basin. The hydrocarbon anomalies near the surface coincide with the favourable subsurface structural features and correlate with existing geochemical and geophysical data in these basins suggesting seepage related anomalies.  相似文献