Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots     

K. Jain  R. W. Komm  I. González Hernández  S. C. Tripathy  F. Hill 《Solar physics》2012,279(2):349-363

The temporal variation of the horizontal velocity in sub-surface layers beneath three different types of active region is studied using the technique of ring diagrams. In this study, we select active regions (ARs) 10923, 10930, 10935 from three consecutive Carrington rotations: AR 10930 contains a fast-rotating sunspot in a strong emerging active region while other two have non-rotating sunspots with emerging flux in AR 10923 and decaying flux in AR 10935. The depth range covered is from the surface to about 12 Mm. In order to minimize the influence of systematic effects, the selection of active and quiet regions is made so that these were observed at the same heliographic locations on the solar disk. We find a significant variation in both components of the horizontal velocity in active regions as compared to quiet regions. The magnitude is higher in emerging-flux regions than in the decaying-flux region, in agreement with earlier findings. Further, we clearly see a significant temporal variation in depth profiles of both zonal and meridional flow components in AR 10930, with the variation in the zonal component being more pronounced. We also notice a significant influence of the plasma motion in areas closest to the rotating sunspot in AR 10930, while areas surrounding the non-rotating sunspots in all three cases are least affected by the presence of the active region in their neighborhood.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987112000059     

Dilip Saha  Vikash Tripathy 《地学前缘(英文版)》2012,3(4):429-444

A lirst report on tuff beds from the Owk Shale in the Proterozoic Kurnool sub-basin in southern India is presented.The rhvolitic lo ihodacitic tuffs,overlying shclfal limestones formed at depths below storm wave base,have rheomorphic features indicative of viscoplaslic flow.and geochemical signatures of rhvolitic to rhyodacitic unwekled to welded tuffs,similar to those described from other Proterozoic intracratonie basins like Vindhvan and Chhattisgarh basins in India.Fragmentary naiure of altered glass with perlitic cracks and local admixture with intrabasinal sediments suggest phreatomagmatic reactions.The widespread and repealed occurrences of felsic luffs in these basins.possibly derived from low degree melting of continental crust.suggest intermittent(ectonothermal instability which likely intluenced hasinal topography and cyclic development of the carbonate platforms.  相似文献   

Molecular evidence for Myripristis jacobus and Scarus taeniopterus new to Bay of Bengal: Sporadic appearance or preliminary colonization?     

Tapan K. Barik  Surya N. Swain  Bijayalaxmi Sahu  Bibarani Tripathy  Usha R. Acharya 《Marine Ecology》2021,42(1):e12632

Individual specimens of Myripristis jacobus Cuvier, 1829 and Scarus taeniopterus Lesson, 1829 were collected from Gopalpur‐on‐sea, Odisha coast, Bay of Bengal. Both the fish samples were assigned species level tags using the conventional taxonomic methods. The capture of both the fish species is of particular interest in that they were new to the Bay of Bengal. Molecular analysis using the mitochondrial cytochrome oxidase subunit I (COI) gene showed high confidence sequence similarity in species identification. The resultant phylogenetic relationships strongly support the monophyly of both the genus with congruent clustering of both the species according to their morphological identification. In addition, the time tree produced is in complete agreement with the recent studies. These studies conclusively prove that both the species might have been originated during the middle to the late Miocene period. Furthermore, both fish species are typical inhabitants of stigmatized coral reefs, confined to the reef regions. These fish species perhaps migrated to the Bengal Bay from the Andaman and Nicobar Islands reef regions because of climatic changes.  相似文献   

Temporal variations in Sr and 87Sr/86Sr of the Ganga headwaters: estimates of dissolved Sr flux to the mainstream     

Gyana Ranjan Tripathy  Vineet Goswami  Sunil Kumar Singh  G. J. Chakrapani 《水文研究》2010,24(9):1159-1171

The headwaters of the Ganga (the Alaknanda, Bhagirathi and the Ganga) were analysed for their dissolved major ions, Sr and ⁸⁷Sr/⁸⁶Sr on a biweekly to monthly basis over a period of one year to determine their temporal variations and the factors contributing to them. The concentrations of major ions and Sr show significant seasonal variation with lower values during monsoon period in all the three rivers. A similar trend is also observed for ⁸⁷Sr/⁸⁶Sr and Na*/Ca (Na* = Na_r? Cl_r) suggesting relatively lower contribution of Sr and Na from silicates (which are more radiogenic in Sr) during monsoon. Budget calculations show that silicate derived dissolved Sr (Sr_s) in the river Ganga, Alaknanda and the Bhagirathi varied from 10 ± 4 to 27 ± 11, 7 ± 3 to 30 ± 12, 16 ± 6 to 57 ± 23% of measured Sr respectively with lower values during monsoon. The relative decrease in silicate erosion compared to carbonate during monsoon can result from several factors, these include higher dissolution kinetics of the carbonates, lower water–rock interaction time and availability of larger area for weathering. The annual discharge weighted Sr flux derived from the time series data is higher by ～20% from that based on peak flow Sr, and lower by ～40% compared to that derived from lean flow Sr concentration. The area‐normalized annual flux of dissolved Sr from the Ganga at Rishikesh is about five times its flux at Rajshahi (Bangladesh) and a few other major global rivers, such as the Amazon, indicating higher erosion rate over the Himalaya. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Phytoplankton pigment change as a photoadaptive response to light variation caused by tidal cycle in Ariake Bay,Japan     

Tatsuya Shibata  Sarat C. Tripathy  Joji Ishizaka 《Journal of Oceanography》2010,66(6):831-843

Underwater light environment and photosynthetic accessory pigments were investigated in Ariake Bay in order to understand how change of the pigments occurs in response to the tidal-induced changes in underwater light conditions. We hypothesize that phytoplankton increases photo-protective pigments and decreases light-harvesting pigments under higher light condition in the mixed layer caused by tidal cycle. Contribution rates of non-phytoplankton particles (a _nph (400–700)) for light attenuation coefficient (K _d ) was highest (32–85%), and those of phytoplankton particles (a _ph (400–700)), dissolved organic matter (a _g (400–700)) and water were 6–32, 6–21 and 5–23%, respectively. Mean K _d was higher during the spring tide (0.55 ± 0.23 m⁻¹) than the neap tide (0.44 ± 0.16 m⁻¹), and the K _d difference was caused by the substances resuspension due to the tidal current. In contrast, ratios of photo-protective pigments (diadinoxanthin and diatoxanthin) per chlorophyll a ((DD+DT)/Chl a) were higher during the neap tide (0.10 ± 0.03 mg mg-Chl a ⁻¹) than the spring tide (0.08 ± 0.03 mg mg-Chl a ⁻¹). And there was significant positive correlation between (DD+DT)/Chl a and mean relative PAR in the mixed layer ($ \overline {I_{mix} } $ \overline {I_{mix} } ). Moreover, there was significant negative correlation between ratios of light-harvesting pigments (fucoxanthin) per Chl a (Fuco/Chl a) and $ \overline {I_{mix} } $ \overline {I_{mix} } . These results suggested that phytoplankton in Ariake Bay increase photo-protective pigments and decrease light-harvesting pigments in the higher light condition of less turbid, shallower mixed layer during neap tide than spring tide.  相似文献   

Intracontinental thrusts and inclined transpression along eastern margin of the East Dharwar craton, India     

Dilip Saha  S. Chakraborti  V. Tripathy 《Journal of the Geological Society of India》2010,75(1):323-337

Recent works suggest Proterozoic plate convergence along the southeastern margin of India which led to amalgamation of the high grade Eastern Ghats belt (EGB) and adjoining fold-and-thrust belts to the East Dhrawar craton. Two major thrusts namely the Vellikonda thrust at the western margin of the Nellore Schist belt (NSB) and the Maidukuru thrust at the western margin of the Nallamalai fold belt (NFB) accommodate significant upper crustal shortening, which is indicated by juxtaposition of geological terranes with distinct tectonostratigraphy, varying deformation intensity, structural styles and metamorphic grade. Kinematic analysis of structures and fabric of the fault zone rocks in these intracontinental thrust zones and the hanging wall and footwall rocks suggest spatially heterogeneous partitioning of strain into various combinations of E-W shortening, top-to-west shear on stratum parallel subhorizontal detachments or on easterly dipping thrusts, and a strike slip component. Although relatively less prominent than the other two components of the strain triangle, non-orthogonal slickenfibres associated with flexural slip folds and mylonitic foliation-stretching lineation orientation geometry within the arcuate NSB and NFB indicate left lateral strike slip subparallel to the overall N-S trend. On the whole an inclined transpression is inferred to have controlled the spatially heterogeneous development of thrust related fabric in the terrane between the Eastern Ghats belt south of the Godavari graben and the East Dharwar craton.  相似文献   

Late time acceleration and role of skewness in anisotropic models     

S. K. Tripathy 《Astrophysics and Space Science》2014,350(1):367-374

We study cosmological models with anisotropy in expansion rates in the context of the recent observations predicting an accelerating universe. In the absence of any anisotropy in the cosmic fluid, it is shown that the role of skewness in directional Hubble rates is crucial in deciding the behavior of the model. We find that incorporation of skewness leads to a more evolving effective equation of state parameter.  相似文献   

Swelling pressure–suction relationship of heavily compacted bentonite–sand mixtures     

Setianto Samingan Agus  Yulian Firmana Arifin  Snehasis Tripathy  Tom Schanz 《Acta Geotechnica》2013,8(2):155-165

This paper presents results of an experimental work to determine a relationship between swelling pressure and suction of heavily compacted bentonite–sand mixtures. For comparison, tests were also carried out on heavily compacted bentonite specimens. A series of swelling pressure tests were performed using multi-step constant-volume method where suction of the specimens tested was reduced in a stepwise manner toward a zero value. The suction reduction was induced using vapor equilibrium and axis-translation techniques. It is shown that compacted specimens did not exhibit any collapse upon suction decrease and exhibited maximum swelling pressures at zero-equilibrium suction. The development of swelling pressure with decreasing suction of the specimens showed threshold suctions below which a further reduction in suction yields an increase in the swelling pressure of the same magnitude. The magnitude of threshold suction was found to be a function of bentonite content in compacted specimens.  相似文献   

Bulk viscous string cosmological models with electromagnetic field     

S. K. Tripathy  S. K. Nayak  S. K. Sahu  T. R. Routray 《Astrophysics and Space Science》2009,321(3-4):247-252

LRS Bianchi type-I string cosmological models are studied in the frame work of general relativity when the source for the energy momentum tensor is a bulk viscous stiff fluid containing one dimensional strings embedded in electromagnetic field. The bulk viscosity is assumed to be inversely proportional to the scalar expansion. The physical and kinematical properties of the models are discussed. The effects of Viscosity and electromagnetic field on the physical and kinematical properties are also investigated.  相似文献   

Bulk viscous barotropic magnetised string cosmological models     

Sunil K. Tripathy  Subodha K. Nayak  Subrat K. Sahu  Tushar R. Routray 《Astrophysics and Space Science》2009,323(3):281-287

Spatially homogeneous and anisotropic LRSBianchi type-I string cosmological models are studied in the frame work of general relativity when the source for the energy momentum tensor is a bulk viscous fluid containing one dimensional strings embedded in a magnetic field. A barotropic equation of state for the pressure and density is assumed to get determinate solutions of the field equations. The bulk viscous pressure is assumed to be proportional to the energy density. The effects of viscosity and electromagnetic field on the properties of the model are investigated. The role of bulk viscosity and electromagnetic field in getting an inflationary phase and in establishing a string phase in the universe is studied.  相似文献