Imaging Fabry-Pérot observations of [OI] 6300 Å emission in the coma of Halley's comet 1982i     

C. Debi Prasad  J. N. Desai 《Earth, Moon, and Planets》1989,44(2):191-195

The observation of [OI] 6300 » emission in the coma of Halley's comet 1982i, using the imaging Fabry-Pérot spectrometer, was carried out from Gurushikhar (2439N, 7243E, 1700m altitude), Mt. Abu, India on March 15, 1986 (R = 0.90 AU, = 0.96 AU). The analysis of the interferogram show the absence of the differential velocity of neutral oxygen above 5 km s^–1.  相似文献   

Are traditional and modern forestry institutions complementary or do they prescribe contradictory rights in Trans-Himalayan Nepal? A lesson to be learned for REDD+ implementation     

Dilli Prasad Poudel 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(1):13-26

Rights to forest products are difficult to decide in situations when traditional management institutions exist parallel to formal ones. Such situations raise the question of whether the institutions are complementary or prescribe contradictory rights and management principles. Based on a household survey and key informant interviews, the article focuses on how diverging management principles can be harmonized to satisfy national forestry goals in Nepal. Villages in the Trans-Himalayan district of Mustang used to manage forests according to their traditional institutions but after 1993 they were included in a new management regime called Conservation Area Management Committees (CAMCs). The findings revealed that the villagers appreciated development initiatives undertaken by the CAMCs but three disjunctions regarding forest management existed between the CAMCs and traditional institutions: there was a disjunction between the two sets of rules for forest resource utilization; there were role dilemmas of local residents who were entrusted with CAMC implementation; and there were spatial disjunctions when formal administrative forest borders did not coincide with customary ones. The simultaneous existence of two institutions thus blurred the rights to forest resources. The author concludes that knowledge of the disjunction between parallel institutions is vital for accommodating new management schemes such as REDD+.  相似文献   

Study of cosmic ray intensity in relation to the interplanetary magnetic field and geomagnetic storms for solar cycle 24     

Chandni Mathpal  Lalan Prasad  Meena Pokharia  Chandrashekhar Bhoj 《Astrophysics and Space Science》2018,363(8):177

In the present study, we investigate the association of cosmic ray intensity (CRI) with various solar wind parameters (i.e. solar wind speed V, plasma proton temperature, plasma proton density), interplanetary magnetic field (IMF B), geomagnetic storms (GSs), averaged planetary A-index (Ap index) and sun spot number (SSN) for the period 2009–2016 (solar cycle 24) by using their daily mean average. To find the association of CRI with various solar wind parameters, GSs, IMF B, Ap index and SSN, we incorporate the analysis technique by superposed-epoch method. We have observed that CRI decreases with the increase in IMF B. Moreover the time-lag analysis has been performed by the method of correlation coefficient and observed a time lag of 0 to 2 day between the decrease in CRI and increase in IMF B. In addition, we show that the CRI is found to decrease in a similar pattern to disturbance storm time (Dst index) for most of the period of solar cycle 24. The high and positive correlation is found between CRI and Dst index. The CRI and Ap index are better anti-correlated to each other than CRI and IMF. CRI and SSN are positively correlated with each other. Solar wind parameters such as solar wind speed V is a CR-effective parameter while plasma proton temperature and plasma proton density are not CR-effective parameters. The indicated parameters such as Dst index, Ap index, IMF B and solar wind parameters such as solar wind speed V, plasma proton temperature, plasma proton density shows a kind of irregular variations for solar cycle 23 and 24 while CRI and SSN shows distinct behaviour for the two cycle.  相似文献   

A comparative study of geomagnetic storms for solar cycles 23 and 24     

Meena Pokharia  Lalan Prasad  Chandrasekhar Bhoj  Chandni Mathpal 《Journal of Astrophysics and Astronomy》2018,39(5):53

The aim of this paper is to investigate the association of the geomagnetic storms with the magnitude of interplanetary magnetic field IMF (B), solar wind speed (V), product of IMF and wind speed (\(V \cdot B)\), Ap index and solar wind plasma density (\(n_{\mathrm{p}})\) for solar cycles 23 and 24. A Chree analysis by the superposed epoch method has been done for the study. The results of the present analysis showed that \(V \cdot B\) is more geoeffective when compared to V or B alone. Further the high and equal anti-correlation coefficient is found between Dst and Ap index (? 0.7) for both the solar cycles. We have also discussed the relationship between solar wind plasma density (\(n_{\mathrm{p}})\) and Dst and found that both these parameters are weakly correlated with each other. We have found that the occurrence of geomagnetic storms happens on the same day when IMF, V, Ap and \(V \cdot B\) reach their maximum value while 1 day time lag is noticed in case of solar wind plasma density with few exceptions. The study of geomagnetic storms with various solar-interplanetary parameters is useful for the study of space weather phenomenon.  相似文献   

Study of Geomagnetic Storms and Solar and Interplanetary Parameters for Solar Cycles 22 and 24     

Meena Pokharia  Lalan Prasad  Chandrashekhar Bhoj  Chandni Mathpal 《Solar physics》2018,293(9):126

The aim of this paper is to investigate the association of geomagnetic storms with the component of the interplanetary magnetic field (IMF) perpendicular to the ecliptic (\(Bz\)), the solar wind speed (\(V\)), the product of solar wind speed and \(Bz\) (VBz), the Kp index, and the sunspot number (SSN) for two consecutive even solar cycles, Solar Cycles 22 (1986?–?1995) and 24 (2009?–?2017). A comparative study has been done using the superposed epoch method (Chree analysis). The results of the present analysis show that \(Bz\) is a geoeffective parameter. The correlation coefficient between Dst and \(Bz\) is found to be 0.8 for both Solar Cycles 22 and 24, which indicates that these two parameters are highly correlated. Statistical relationships between Dst and Kp are established and it is shown that for the two consecutive even solar cycles, Solar Cycles 22 and 24, the patterns are strikingly similar. The correlation coefficient between Dst and Kp is found to be the same for the two solar cycles (?0.8), which clearly indicates that these parameters are well anti-correlated. For the same studied period we found that the SSN does not show any relationship with Dst and Kp, while there exists an inverse relation between Dst and the solar wind speed, with some time lag. We have also found that VBz is a more relevant parameter for the production of geomagnetic storms, as compared to \(V\) and \(Bz\) separately. In addition, we have found that in Solar Cycles 22 and 24 this combined parameter is more relevant during the descending phase as compared to the ascending phase.  相似文献   

Unmelted cosmic metal particles in the Indian Ocean          下载免费PDF全文

Mokkapati Shyam Prasad  N. G. Rudraswami  Agnelo A. De Araujo  Vijay D. Khedekar 《Meteoritics & planetary science》2017,52(6):1060-1081

Fe‐Ni metal is a common constituent of most meteorites and is an indicator of the thermal history of the respective meteorites, it is a diagnostic tool to distinguish between groups/subgroups of meteorites. In spite of over a million micrometeorites collected from various domains, reports of pure metallic particles among micrometeorites have been extremely rare. We report here the finding of a variety of cosmic metal particles such as kamacite, plessite, taenite, and Fe‐Ni beads from deep‐sea sediments of the Indian Ocean, a majority of which have entered the Earth unaffected by frictional heating during atmospheric entry. Such particles are known as components of meteorites but have never been found as individual entities. Their compositions suggest precursors from a variety of meteorite groups, thus providing an insight into the metal fluxes on the Earth. Some particles have undergone heating and oxidation to different levels during entry developing features similar to I‐type cosmic spherules, suggesting atmospheric processing of individual kamacites/taenite grains as another hitherto unknown source for the I‐type spherules. The particles have undergone postdepositional aqueous alteration transforming finally into the serpentine mineral cronstedtite. Aqueous alteration products of kamacite reflect the local microenvironment, therefore they have the potential to provide information on the composition of water in the solar nebula, on the parent bodies or on surfaces of planetary bodies. Our observations suggest it would take sustained burial in water for tens of thousands of years under cold conditions for kamacites to alter to cronstedtite.  相似文献   

Evolution and paleobiogeography of mangroves     

Jyoti Srivastava  Vandana Prasad 《Marine Ecology》2019,40(6)

We reviewed the geological record of mangroves based on fossil pollen, fruits, and wood evidence of Nypa, Avicennia, Sonneratia, Rhizophoraceae, and mangrove associates to trace the origin, distribution, extinction, and range contraction of paleo‐mangroves during the Late Cretaceous–Miocene time. Our study region covers paleocoastal areas of Indo‐West Pacific (IWP) and Atlantic East Pacific (AEP) region. First, we compiled the mangrove fossil records from the Late Cretaceous till Miocene and identified the migration pattern for Nypa, Avicennia, Sonneratia, Rhizophoraceae members, and mangrove associates such as Acrostichum, Wetherellia, Pelliciera, Aegiceras, Heritiera, Excoecaria, and Barringtonia. Second, we interpreted the paleoclimate shifts which caused the dispersal/extinction of this specialized ecosystem. Lastly, we proposed the future consequences of mangrove diversity for restoration and conservation strategies. First mangroves appeared during the Late Cretaceous, 100–65 Ma, since then their evolution is closely related to sea‐level changes in geological times. The oldest geological record of Nypa palm which prefers broad ecological tolerance is a good example for pantropical distribution of mangroves. High sea‐level and humid climate offered sufficient coastal regions and climate for the development of 12 genera of mangroves in nine families and subsequent proliferation into newer areas during early to middle Eocene (~50–40 Ma). The Eocene/Oligocene boundary crisis heralds the beginning of a biogeographical split between the present‐day eastern and western provinces of mangroves with records of Sonneratia, Rhizophora, Pelliciera, Barringtonia, and Acrostichum. However, during Oligocene and Middle Miocene mangroves occupied the present geographical position with addition of Nypa, Avicennia, and Excoecaria species. Re‐evaluation of Cenozoic records suggests that the climatic conditions of Late Paleocene, end of Eocene, and middle Pliocene were the driving force that led to the evolution and expansion of mangrove flora. During the Neogene, latitudinal contraction, extinction, and migration of mangroves led to the present bipartite distribution. The Himalayan uplift and establishment of Asian summer monsoon toward Late Neogene further affected the coastal dynamics which tailored the mangrove distribution of the Indian subcontinent. Loss of ecological habitats and local extinction forming disjunct distribution of mangroves during the Quaternary have also affected its overall biogeography.  相似文献   

Erratum to: Use of remote sensing in characterization and management of Dhamni micro-watershed of Chandrapur District of Maharashtra     

Elvis A. Shukla  Jagdish Prasad  M.S.S. Nagaraju  Rajeev Srivastava  D.L. Kauraw 《Journal of the Indian Society of Remote Sensing》2009,37(2):334

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Investigation of the generation and propagation of low frequency internal waves: A case study for the east coast of India     

A.D. Rao  S.V. Babu  K.V.S.R. Prasad  T.V. Ramana Murty  Y. Sadhuram  D.K. Mahapatra 《Estuarine, Coastal and Shelf Science》2010

SAR (Synthetic Aperture Radar) images in the northwest Bay of Bengal indicate the existence of internal waves and their occurrence and intensity is topography dependent as indicated by in-situ data and satellite information. To complement and comprehend the observations, a three-dimensional Princeton Ocean Model is applied to study the generation and propagation of internal waves. The model domain is configured with a variable curvilinear grid and the input fields comprise bathymetry, initial temperature and salinity, wind stress, air-sea heat flux and tidal information. The numerical investigation indicated a predominant activity of internal waves in the north, and the rationale is three-fold. The first one could be the stable stratification due to fresh water discharge from head-bay major river system, secondly, the significant magnitude/range of the tides and finally, the bathymetry in the coastal waters off Paradip is about 12% shallower compared to that of Visakhapatnam and further south. The cumulative effect of these causes the predominance of internal waves in the north. The core of the energy is essentially in the low-frequency range and the model is able to simulate semi-diurnal and diurnal components reasonably well up to 6 h frequency (0.162 cph).  相似文献   

Production of Bauxite Certified Reference Material (BARC-B1201) for Nine Property Values (Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO,Cr2O3, MgO and LOI) Traceable to SI Units     

Ankam Durga Prasad  Lori Rastogi  Vinod Kumar Verma  Vasudevan Krishna Kumari  Sudhakar Yadlapalli  Kulamani Dash 《Geostandards and Geoanalytical Research》2023,47(3):629-636

The National Centre for Compositional Characterisation of Materials (NCCCM) / Bhabha Atomic Research Centre (BARC) and National Aluminium Company Limited (NALCO), India have produced an Indian origin bauxite certified reference material (CRM), referred to as BARC-B1201, certified for major (Al₂O₃, Fe₂O₃, SiO₂, TiO₂, loss on ignition - LOI) and trace contents (V₂O₅, MnO, Cr₂O₃, MgO). Characterisation was undertaken by strict adherence to ISO Guides. A method previously developed and validated in our laboratory, using single step bauxite dissolution and subsequent quantitation (of Al₂O₃, Fe₂O₃, SiO₂, TiO₂, V₂O_5, MnO, Cr₂O₃ and MgO) by ICP-AES (SSBD ICP-AES) was used for homogeneity studies and an inter-laboratory comparison exercise (ILCE) of the candidate CRM. LOI was determined by thermo-gravimetric analysis. Property values were assigned after an ILCE with participation from seventeen reputed government and private sector laboratories in India. The CRM was certified for nine property values: Al₂O₃, Fe₂O₃, SiO₂, TiO₂, V₂O_5, MnO, Cr₂O₃, MgO and LOI, which are traceable to SI units.  相似文献