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21.
A. Chandrasekhar Reddy Jatin Rathod Girija Rajaram Radharani Alyana D. S. Misra C. G. Patil M. Y. S. Prasad A. G. Ananth 《Journal of Astrophysics and Astronomy》2008,29(1-2):313-317
In view of the renewed interest in the study of energetic particles in the outer radiation belt of the earth, we feel it will be helpful in looking for the energy dependence of the electron energy spectrum at geostationary orbit. This may give us some insight into how we can safeguard geostationary satellites from functional anomalies of the deep dielectric charging type, which are caused by charge accumulation and subsequent discharge of relativistic electrons. In this study we examine whether there is any energy dependence in relativistic electron enhancements at geosynchronous altitudes during solar energetic proton events of 2005. 相似文献
22.
Dynamic groundwater resources of National Capital Territory,Delhi: assessment,development and management options 总被引：4，自引：2，他引：2
Rana Chatterjee B. K. Gupta S. K. Mohiddin P. N. Singh Shashank Shekhar Rajaram Purohit 《Environmental Earth Sciences》2009,59(3):669-686
Groundwater is one of the important source of water supply to meet the requirements of National Capital Territory (NCT) of
Delhi, India which is a fast developing urban conglomeration. An assessment of dynamic groundwater resources of NCT Delhi
has been attempted based on the methodology known as Ground Water Resources Estimation Methodology—1997. The methodology includes
assessment of annual replenishable groundwater resources using water level fluctuation approach and empirical norms, estimation
of the annual quantity of groundwater withdrawal and categorization of the assessment units based on the status of groundwater
utilization and water level trend. Annual replenishable groundwater resources of NCT Delhi is about 297 million cubic meter
(mcm) while the annual groundwater draft is about 480 mcm. This is because of over-exploitation of replenishable resources
in seven out of nine districts of the Capital Territory. Based on the assessment of dynamic groundwater resources, a broad
groundwater management plan has been proposed in this paper. This include augmentation of groundwater resources through rain
water harvesting schemes to be implemented on a large scale, regulation on groundwater withdrawal in vulnerable areas, development
of Yamuna flood plain aquifer and declaration of Delhi ridge as groundwater sanctuary. 相似文献
23.
Mita Rajaram B. P. Singh N. Nityananda A. K. Agrawal 《Geophysical Journal International》1979,56(1):127-138
Summary. Transient geomagnetic variations like SSCs, Bays, Sq and storm-time variations show anomalously large Z amplitudes at the three permanent magnetic observatories in India under the equatorial electrojet. Our earlier studies have shown that these anomalies cannot be explained in terms of the usual coastal effect. Another unique feature of this area is the small equatorial enhancement of all magnetic fluctuations, which still remains to be completely understood. It is also noticed that Z/H ratio at Annamalainagar is very large for night-time variations but becomes insignificant for day-time fluctuations, whereas no such large difference is seen at Trivandrum, the other coastal station. All the above features have been explained here by introducing the presence of a conducting channel in the lower crust or upper mantle between India and Sri Lanka Island. The anomalies of the equatorial electrojet in the Indian region thus do not necessitate the conducting surface of the mantle to be deeper in this area as has been suggested by earlier workers. A less conducting mantle in the Indian region otherwise could be difficult to incorporate in the present theories of mantle convection when this area is known to be tectonically active. The presence of the conducting channel is further confirmed by analogue model experiments of Papamastorakis. We further observe that the equatorial electrojet does have an associated internal part in the Indian region. 相似文献
24.
Anomalies in total field, horizontal, and vertical components over the Indian region derived from MAGSAT measurements have been inverted through the ridge-regression method, basically to test: (1) the application of the method in deriving a stable estimate of crustal magnetisation, and (2) the relative amount of information on crustal magnetisation contained in scalar vis-a`-vis vector data. Results show that the instabilities in magnetisation solution that appear when Mayhew's conventional method is applied in low latitudes could be removed through the ridge-regression technique. It was also noticed that magnetisation distribution estimated through the inversion of the total field(B) does not relate well with the geological features in the equatorial region. Inversion of theZ-anomaly alone gives realistic results for the equatorial region but not over higher latitudes. We conclude that a joint inversion ofX- andZ-anomalies provides a magnetisation estimate consistent with known geological features both for equatorial and higher latitudes. 相似文献
25.
Bhaswati Bhattacharyya Rajaram Nityananda 《Monthly notices of the Royal Astronomical Society》2008,387(1):273-278
We present a simple method for determination of the orbital parameters of binary pulsars, using data on the pulsar period at multiple observing epochs. This method uses the circular nature of the velocity space orbit of Keplerian motion and produces preliminary values based on two one-dimensional searches. Preliminary orbital parameter values are then refined using a computationally efficient linear least-squares fit. This method works for random and sparse sampling of the binary orbit. We demonstrate the technique on (i) the highly eccentric binary pulsar PSR J0514−4002 (the first known pulsar in the globular cluster NGC 1851) and (ii) 47 Tuc T, a binary pulsar with a nearly circular orbit. 相似文献
26.
In many Precambrian provinces the understanding of the tectonic history is constrained by limited exposure and aeromagnetic data provide information below the surface cover of sediments,water,etc.and help build a tectonic model of the region.The advantage of using the aeromagnetic data is that the data set has uniform coverage and is independent of the accessibility of the region.In the present study,available reconnaissance scale aeromagnetic data over Peninsular India are analyzed to understand the magnetic signatures of the Precambrian shield and suture zones thereby throwing light on the tectonics of the region.Utilizing a combination of differential reduction to pole map,analytic signal,vertical and tilt derivative and upward continuation maps we are able to identify magnetic source distribution,tectonic elements,terrane boundaries,suture zones and metamorphic history of the region.The magnetic sources in the region are mainly related to charnockites,iron ore and alkaline intrusives.Our analysis suggests that the Chitradurga boundary shear and Sileru shear are terrane boundaries while we interpret the signatures of Palghat Cauvery and Achankovil shears to represent suture zones.Processes like metamorphism leave their signatures on the magnetic data:prograde granulites(charnockites)and retrograde eclogites are known to have high susceptibility.We fnd that charnockites intruded by alkali plutons have higher magnetization compared to the retrogressed charnockites.We interpret that the Dharwar craton to the north of isograd representing greenschist to amphibolite facies transition,has been subjected to metamorphism under low geothermal conditions.Some recent studies suggest a plate tectonic model of subductionecollisioneaccretion tectonics around the Palghat Cauvery shear zone(PCSZ).Our analysis is able to identify several west to east trending high amplitude magnetic anomalies with deep sources in the region from Palghat Cauvery shear to Achankovil shear.The magnetic high associated with PCSZ may represent the extruded high pressureeultra high temperature metamorphic belt(granulites at shallow levels and retrogressed eclogites at deeper levels)formed as a result of subduction process.The EW highs within the Madurai block can be related to the metamorphosed clastic sediments,BIF and mafc/ultramafc bodies resulting from the process of accretion. 相似文献
27.
On April 25, 2015, Nepal was struck by the MW7.8 Gorkha earthquake followed by an intense aftershock sequence. It was one of the most destructive earthquakes in the Himalayan arc, causing more than 8900 fatalities. In this study, we analyzed the dataset (429 events, magnitude of completeness (Mc) ≥ 4.2 local magnitude) of the first 45 days after the Gorkha earthquake to estimate the seismicity parameters b-value, D-value, and p-value. We used the maximum likelihood method to estimate the b-value and Omori-Utsu parameters, whereas the correlation integral method was applied to estimate the fractal dimension (D-value). The analysis was carried out using running and sliding window techniques. The lowest b-value (0.57 ± 0.04) and the highest D-value (1.65 ± 0.02) were computed at the time of the Gorkha earthquake, after which the b-value significantly increased to a maximum of 1.57. It again dropped to 0.93 at the time of the major aftershock on May 12, 2015. The D-value showed an initial quick drop and then decreased in a wavy pattern until the end of the study period, indicating the clustering and scattering of earthquakes in a fault region. The b-value contour map identified the eastern part of the study area as a high stress region (b = ～0.8), implying that the stress shifted to that region. The D-value contour map reveals that the seismogenic structure shifted from linear to planar in the region. The rate of aftershock decay (p = 0.86 ± 0.04) for a short period reflects that the level of stress decreased rapidly. This study helps to understand the level of stress and seismicity pattern of a region, which could be useful for aftershock studies. 相似文献
28.
The Magnetosphere-Solar Wind boundary is treated as a tangential discontinuity between collisionless plasma described by C.G.L. equations. An estimate is made, analytically, of the minimum shear speed required to render the interface unstable for propagation in any arbitrary direction. It is found that even systems, which are, for all shear speeds, stable towards propagation parallel to the field, are rendered unstable by propagation away from the field, in some velocity domain. Numerical evaluations for parameters characteristic of the Solar wind-Magnetosphere boundary show that the interface could be unstable even under relatively quiet conditions. 相似文献
29.
The paper considers wave coupling for an arbitrary direction of propagation on the basis of single fluid hydromagnetic equations appropriate for a rarefied plasma. The analysis is used to study the transfer of solar wind momenta into the magnetosphere. It is found that wave refraction is significant only during disturbed conditions for waves travelling with the wind. Enhanced reflection of waves might be important even under quiet conditions in the flanks of the magnetosphere. 相似文献
30.
Prem Kumar Rajaram 《Singapore journal of tropical geography》2003,24(3):290-306
In September 2001, Australia effected a "Pacific Solution" to its "refugee problem": the interception and transfer of "unauthorised boat arrivals" to processing centres in the Pacific Third World. These centres were agreed to by poor countries that were approached precisely because of their vulnerability and dependence upon Australia, in exchange for increases in aid. Australia thereby created a regional refugee problem and, in so doing, Australian seignorage also demands that the laws of those sovereign countries be placed in stasis so that people not convicted of a crime may be detained indefinitely. The Pacific region, in effect, came to be mapped in terms of its utility to Australia, both downplaying and concealing complex economic, social and political issues. This essay studies the Pacific Solution as a means of Australian "emplacement" in the Pacific and on refugee identity/bodies. Both refugee identity and the Pacific Third World are assessed in terms of their utility in serving as sites for Australian emplacement, whereby and wherein the borders of Australia are reinforced, to the detriment of extant "local" emplacements. 相似文献