Mean sea level determination from satellite altimetry

The primary experiment on the Geodynamics Experimental Ocean Satellite‐3 (GEOS‐3) is the radar altimeter. This experiment's major objective is to demonstrate the utility of measuring the geometry of the ocean surface, i.e., the geoid. Results obtained from this experiment so far indicate that the planned objectives of measuring the topography of the ocean surface with an absolute accuracy of ±5 m can be met and perhaps exceeded. The GEOS‐3 satellite altimeter measurements have an instrument precision in the range of ±25 cm to ±50 cm when the altimeter is operating in the “short pulse”; mode. After one year's operations of the altimeter, data from over 5,000 altimeter passes have been collected. With the mathematical models developed and the altimeter data presently available, mapping of local areas of ocean topography has been realized to the planned accuracy levels and better. This paper presents the basic data processing methods employed and some interesting results achieved with the early data. Plots of mean sea surface heights as inferred by the altimeter measurements are compared with a detailed 1^o × 1° gravimetric geoid.     

Heat and mass transfer of an oscillatory flow with Hall current,II

An analysis of Hall current on the combined effects of thermal and mass diffusion of an electrically conducting liquid past an infinite vertical porous plate is performed. Analytical expressions for the transient velocity, the transient temperature in the boundary layer and the skin-friction on the plate are derived. The effects of various parameters on the velocity, temperature, shearing stresses and rate of heat transfer are shown by graphs and tables.     

Study of high and low amplitude wave trains of cosmic ray diurnal variation during solar cycle 23

A detailed study has been conducted on the long-term changes in the diurnal variation of cosmic rays in terms of high and low amplitude wave trains event (HAEs/LAEs) during the period 1996–2008 (solar cycle 23), using the neutron monitor data from Kiel neutron monitoring station. As such, 17 HAE and 48 LAE cases have been detected and analyzed. These HAEs appear quite dominantly during the declining phase as well as near the maximum of the solar activity cycle 23. In contrast, the low amplitude events (LAEs) are inversely correlated with solar activity cycle. In fact, LAEs appear quite dominantly during the minimum phase of the solar activity. When we compare our results for diurnal phase with that observed on an annual average basis, we notice no significant diurnal phase shift for HAEs as well as for LAEs. Moreover, we find that the high-speed solar wind streams (HSSWS) do not play any significant role in causing these variations. These results are discussed on the basis of that observed in earlier cycles.     

Seismotectonic and liquefaction studies of an industrial site in Northern India

Foundation soil of the proposed fertiliser complex in Northern India is examined for its susceptibility to liquefaction during an earthquake. Information on geotectonic set up and earthquake occurrences in the region around the site is used for defining the earthquake parameters of the ground motion. The effective peak ground acceleration for the site is estimated to be of the order of 0.15 g. Laboratory tests were carried out on soil samples obtained from the site on a horizontal vibration table. The test results were used in determining the possibility of liquefaction employing the methodology developed at the Department of Earthquake Engineering, University of Roorkee. About 10 m of a thick soil layer below the top 1.5 m stiff clay is likely to liquefy. Remedial measures used at the site to counter the possibility of liquefaction are mentioned.     

High pressure-temperature studies on an olivine tholeiite and a tholeiitic picrite from the pavagarh region,Gujarat, India

Experimental studies have been performed on an olivine tholeiite and tholeiitic picrite at pressure and temperature ranges of 20–40 kb and 1200–1300°C. The lower and upper limits of basalt-eclogite transition zone for tholeiitic picrite are 23 kb and 31·67 kb at 1200°C, and 24·67 kb and 33·67 kb at 1300°C, whereas for olivine tholeiite, these are 27 kb and 32·33 kb at 1200°C, and 28·70 kb and 33·70 kb at 1300°C. While the assemblages for both samples below the transition region are Pl+Px+Mt, they are Pl+Gt+Px+Mt within it. The eclogite field has Gt+Px+Mt. The ratio of garnet to plagioclase increases from the transition zone to the eclogite field and with the disappearance of plagioclase, the percentage of garnet increases to 30 in the eclogite field. Comparison of our results with previous studies on basalt-eclogite transition shows that the transition zone found by us occurs at higher pressure-temperature conditions. Seismic studies of the region below the Deccan Traps show an increase in velocity (1–4%) at depth. It is suggested that after partial melting, during ascent of the basaltic liquid, a significant portion of it crystallizes within the upper mantle as pockets of eclogite. As eclogite is more dense than peridotite, their presence should cause a similar increase in the seismic velocity below the Deccan area.     

Impact of LULC change on the runoff,base flow and evapotranspiration dynamics in eastern Indian river basins during 1985–2005 using variable infiltration capacity approach

As a catchment phenomenon, land use and land cover change (LULCC) has a great role in influencing the hydrological cycle. In this study, decadal LULC maps of 1985, 1995, 2005 and predicted-2025 of the Subarnarekha, Brahmani, Baitarani, Mahanadi and Nagavali River basins of eastern India were analyzed in the framework of the variable infiltration capacity (VIC) macro scale hydrologic model to estimate their relative consequences. The model simulation showed a decrease in ET with 0.0276% during 1985–1995, but a slight increase with 0.0097% during 1995–2005. Conversely, runoff and base flow showed an overall increasing trend with 0.0319 and 0.0041% respectively during 1985–1995. In response to the predicted LULC in 2025, the VIC model simulation estimated reduction of ET with 0.0851% with an increase of runoff by 0.051%. Among the vegetation parameters, leaf area index (LAI) emerged as the most sensitive one to alter the simulated water balance. LULC alterations via deforestation, urbanization, cropland expansions led to reduced canopy cover for interception and transpiration that in turn contributed to overall decrease in ET and increase in runoff and base flow. This study reiterates changes in the hydrology due to LULCC, thereby providing useful inputs for integrated water resources management in the principle of sustained ecology.     

Effect of the presence of a conducting channel between India and Sri Lanka Island on the features of the equatorial electrojet

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.     

Vertical component MAGSAT anomalies and Indian tectonic boundaries

MAGSAT vertical component (Z-component) of crustal anomalies are correlated for the first time with major geological and tectonic boundaries/features of the Indian subcontinent. A prominent ‘low’ is consistently observed on all the profiles centred between 19° and 23° latitudes over the broad Peninsular ‘high’. The other conspicuous ‘low’ indicated from the present work is confined to the region above Sarda depression (29° N to 31° N) in the foothills of Himalayas. Interesting magnetic signatures are identified over the Narmada-Son rift and Godavari graben.     

Garnet-staurolite-mica schist from Rangli Rangliot,Eastern Himalaya: Constraints from phase equilibria and Thermobarometry

Rangli Rangliot is an integral part of lesser Himalaya. The area around Rangli Rangliot consists of garnetstaurolite-mica schist and it is characterized by mineral assemblage garnet-biotite-muscovite-staurolite-quartz± plagioclase. Different reaction textures are of particular interest as they reflect discontinuous or continuous reactions under changing physical conditions. The relative X_Mg in the minerals varies in the order: muscovite> biotite> staurolite> garnet, and the X_Mn decreases in the order: garnet>staurolite>biotite>muscovite. The P-T evolution of the garnet-staurolite-mica schist has been constrained through the use of internally consistent TWEEQU programme and Perple_X software in the KFMASH model system. The combination of these two approaches demonstrates that the garnet-staurolite-mica schist experienced peak pressure and temperature at 5.8 kbar and 590 °C. The proposed clockwise P-T path implies that rocks from the study area could have resulted from thickened continental crust undergoing decompression.