Characterization of recharge processes in shallow and deeper aquifers using isotopic signatures and geochemical behavior of groundwater in an arsenic-enriched part of the Ganga Plain   总被引：1，自引：0，他引：1  

Dipankar Saha  U.K. SinhaS.N. Dwivedi 《Applied Geochemistry》2011,26(4):432-443

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On Thermal-Pulse-Driven Plasma Flows in Coronal Funnels as Observed by the Hinode/EUV Imaging Spectrometer (EIS)     

A. K. Srivastava  P. Konkol  K. Murawski  B. N. Dwivedi  A. Mohan 《Solar physics》2014,289(12):4501-4515

Using one-arcsecond-slit-scan observations from the Hinode/EUV Imaging Spectrometer (EIS) on 5 February 2007, we find the plasma outflows in the open and expanding coronal funnels at the eastern boundary of AR 10940. The Doppler-velocity map of Fe?xii 195.120 Å shows the diffuse closed-loop system to be mostly red-shifted. The open arches (funnels) at the eastern boundary of AR exhibit blue-shifts with a maximum speed of about 10?–?15 km?s^?1. This implies outflowing plasma through these magnetic structures. In support of these observations, we perform a 2D numerical simulation of the expanding coronal funnels by solving the set of ideal MHD equations in appropriate VAL-III C initial temperature conditions using the FLASH code. We implement a rarefied and hotter region at the footpoint of the model funnel, which results in the evolution of slow plasma perturbations propagating outward in the form of plasma flows. We conclude that the heating, which may result from magnetic reconnection, can trigger the observed plasma outflows in such coronal funnels. This can transport mass into the higher corona, giving rise to the formation of the nascent solar wind.  相似文献   

Characterization of the atmospheric boundary layer from radiosonde observations along eastern end of monsoon trough of India   总被引：1，自引：0，他引：1  

Sagarika Chandra  Arun K Dwivedi  Manoj Kumar 《Journal of Earth System Science》2014,123(6):1233-1240

In this paper, a comparison of two methods for the calculation of the height of atmospheric boundary layer (ABL), using balloon-borne GPS radiosonde data is presented. ABL has been characterized using vertical profiles of meteorological parameter. The gradient of virtual potential temperature (?? _v ) profile for the determination of mixed layer heights (MLH) and the mean value of turbulent flow depth (TFD) obtained from the vertical profile of Bulk Richardson Number (R _{i B} ) have been used in this study. One-year data have been used for the study. There is large seasonal variability in MLH with a peak in the summer and winter whereas the TFD remained steady throughout the year. Results from the present study indicate that the magnitudes of TFD are often larger than the MLH.  相似文献   

Site suitability analysis for khair(ACACIA CATECHU) in part of doon valley using geoinformatics     

Puneet Dwivedi  S. P. S. Kushwaha  S. Nandy  C. S. Rathore 《Journal of the Indian Society of Remote Sensing》2006,34(2):187-191

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Rainfall-Runoff Modeling using Clustering and Regression Analysis for the River Brahmaputra Basin     

Satanand Mishra  C. Saravanan  V. K. Dwivedi  J. P. Shukla 《Journal of the Geological Society of India》2018,92(3):305-312

In this research, k-means, agglomerative hierarchical clustering and regression analysis have been applied in hydrological real time series in the form of patterns and models, which gives the fruitful results of data analysis, pattern discovery and forecasting of hydrological runoff of the catchment. The present study compares with the actual field data, predicted value and validation of statistical yields obtained from cluster analysis, regression analysis with ARIMA model. The seasonal autoregressive integrated moving average (SARIMA) and autoregressive integrated moving average (ARIMA) models is investigated for monthly runoff forecasting. The different parameters have been analyzed for the validation of results with casual effects. The comparison of model results obtained by K-means & AHC have very close similarities. Result of models is compared with casual effects in the same scenario and it is found that the developed model is more suitable for the runoff forecasting. The average value of R² determined is 0.92 for eight ARIMA models. This shows more accuracy of developed ARIMA model under these processes. The developed rainfall runoff models are highly useful for water resources planning and development.  相似文献   

Electron density from Mg VIII emission lines     

B. N. Dwivedi 《Solar physics》1988,116(2):405-408

Mg VIII emission line intensity ratio I (430.47)/I (436.62) has been studied in detail and is found to be an excellent candidate for diagnosing the quiet Sun and the coronal holes.  相似文献   

Theoretical Ne VI/Mg VI line diagnostics for SUMER     

B. N. Dwivedi  Anita Mohan 《Solar physics》1995,157(1-2):135-140

Theoretical Nevi/Mgvi EUV line emissivity ratios, suitable for density-measurements in various solar features such as active regions, sunspots, umbrae and flare plasmas and to be observed in the SUMER spectral range, are presented and their applications discussed with the help of available observational data.  相似文献   

Nonlinear dynamics of Landau damped kinetic Alfvén waves     

Nidhi Gaur  Navin Kumar Dwivedi  R. P. Sharma 《Astrophysics and Space Science》2012,342(2):407-415

In the present paper we have studied the nonlinear dynamical equation of Landau damped kinetic Alfvén wave (KAW) to investigate the nonlinear evolution of KAW and the resulting turbulent spectra in solar wind plasmas. We have introduced a parameter g which governs the coupling between the amplitude of the pump KAW and the density perturbation. The numerical solution has been carried out to see the dependence on the parameter g in the nonlinear part of our equation. Our results reveal the formation of damped localized structures of KAW as well as steepening of the turbulent spectra by increasing g when damping is taken into account. The power spectra of magnetic field fluctuations indicate the redistribution of energy among the higher wave numbers. Each power spectrum with and without damping splits up into two different scaling ranges, Kolmogorov scaling followed by a steeper scaling. The steepening in the power spectra with Landau damping is more than without Landau damping case (for the same value of g). This type of steeper spectra has also been observed in the solar wind and is attributed to the Landau damping effects.  相似文献   

Application of Artificial Neural Network Model for the Prediction of Suspended Sediment Load in the Large River     

Gaur  Shishir  Mishra  Aryan  Gupta  Anurag  Jain  Arihant  Dave  Apurve  Eslamian  Saied  Dwivedi  S. B.  Graillot  Didier 《Water Resources》2021,48(4):565-575

Water Resources - Predicting the Suspended Sediment Load (SSL) of the river is a very significant and challenging task. Being a non-linearity in the SSL data, it requires a non-linear method to get...  相似文献   

Heliospheric Modulation of Galactic Cosmic Rays During Solar Cycle 23     

Partha Chowdhury  K. Kudela  B. N. Dwivedi 《Solar physics》2013,286(2):577-591

Galactic cosmic rays (GCRs) encounter an outward-moving solar wind with cyclic magnetic-field fluctuation and turbulence. This causes convection and diffusion in the heliosphere. The GCR counts from the ground-based neutron monitor stations show intensity changes that are anti-correlated with the sunspot numbers with a lag of a few months. GCRs experience various types of modulation from different solar activity features and influence space weather and the terrestrial climate. In this work, we investigate certain aspects of the GCR modulation at low cut-off rigidity (R _c≈1 GV) in relation to some solar and geomagnetic indices for the entire solar cycle 23 (1996?–?2008). We separately study the GCR modulation during the ascending phase of cycle 23 including its maximum (1996?–?2002) and the descending phase including its minimum (2003?–?2008). We find that during the descending phase, the GCR recoveries are much faster than those of the solar parameters with negative time-lag. The results are discussed in light of modulation models, including drift effects and previous results.  相似文献