Static charged dust distributions: Sources of purely electromagnetic origin

The present work is a continuation of our earlier work on the charged dust sources of purely electromagnetic origin for static axisymmetric and static spherically-symmetric fields. Here we have extended the above work to the case of generalized static metric and have shown that a static charged dust distribution, irrespective of any symmetry conditions, can be only of purelly electromagnetic origin. Incidentally, it follows from this result itself that the Weyl-Majumdar-Papapetrou class of static charged dust sources, which form an important class of astrophysical systems, are also of purely electromagnetic origin.     

Effect of magnetic activity on ionospheric time delay at low latitude

The purpose of this work is to investigate the effect of magnetic activity on ionospheric time delay at low latitude Station Bhopal (geom. lat. 23.2°N, geom. long. 77.6°E) using dual frequency (1575.42 and 1227.60 MHz) GPS measurements. Data from GSV4004A GPS Ionospheric Scintillation and TEC monitor (GISTM) have been chosen to study these effects. This paper presents the results of ionospheric time delay during quiet and disturbed days for the year 2005. Results show that maximum delay is observed during quiet days in equinoxial month while the delays of disturbed period are observed during the months of winter. We also study the ionospheric time delay during magnetic storm conditions for the same period. Results do not show any clear relationship either with the magnitude of the geomagnetic storm or with the main phase onset (MPO) of the storm. But most of the maximum ionospheric time delay variations are observed before the main phase onset (MPO) or sudden storm commencement (SSC) as compared to storm days.     

Study of momentum transfers within a vegetation canopy

Two models have been developed by applying conditions of continuity between the roughness sublayer and the top of vegetation canopy having constant foliage distribution. Massman's cosh-type of wind profile and Albini's exponential wind profile have been used to derive expressions for shear stress, displacement height and roughness length in analytical forms. The computed results compared with those of Massman models (1987, 1997) show similarity with the present models.     

Exploiting IKONOS and Hyperion data fusion for automated road extraction

We present here the examples that show how fusing data from hyperspectral sensors with data from high spatial resolution sensors can enhance overall road detection accuracy. The fusion of hyperspectral and high spatial resolution data combines their superior respective spectral and spatial information. IKONOS (MSS) and Hyperion images were fused using the principal component analysis (PCA) method. The approach for road extraction integrates multiresolution segmentation and object oriented classification. Road extraction is done from an IKONOS (MSS) image and a Hyperion and IKONOS (MSS) merged image and comparisons are made depending on accuracy and quality measures such as completeness and correctness. This article also emphasises the types of roads which are giving better accuracy of extraction after fusion with hyperspectral image. This can vary because of types of material and condition of roads. The methodology was applied on roads of Dehradun, India.     

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.     

Impact of anthropogenic activity and cyclonic storm on black carbon during winter at a tropical urban city,Pune

Black carbon (BC) aerosols are emitted into the atmosphere as a byproduct of different combustion processes and are reported to be a very strong absorber of solar radiation. In this paper, we present results on BC aerosols over Pune, a tropical urban city in south west India during Diwali festival in the month of November 2010. Daily mean BC showed about 5 % increase on Diwali day compared with preceding and succeeding period with concentrations reaching as high as about 21 μg/m³ in the morning on Diwali day, mainly due to the influence of extensive fireworks. However, the strong winds accompanied by occasional rainfall due to severe cyclonic storm “Jal” formed in the Bay of Bengal on the same day dampened this effect and reduced BC to about 2 μg/m³ within 6 h. There was only 5 % increase in mean BC concentration on Diwali day during 2010 as compared to the average increase of about 17 % during preceding 4 years on Diwali day, mainly due to the impact of weather conditions induced by Jal.     

Use of Remote Sensing and Geospatial Technique for Pre-feasibility Analysis of Rural Water Pipeline Grids

The article outlines a procedure of pre-feasibility analysis of planned rural water supply pipeline grids in India. Usually, these type of pre feasibility studies prior to actual implementation, is carried out based on ground surveys and is time consuming. In this work, we use thematic spatial data, such as geomorphology and landuse–landcover along with digital elevation model (DEM) to carry out the pre-feasibility assessment of proposed pipeline grids. DEM generated from CartoSat-1 stereo data has been used to understand the possible topographic hindrances along the planned pipeline route and optimise the same. Further, topographic data also indicates the possible routes of gravity assisted flow. The geomorphology thematic data interpreted from Resourcesat-1 LISS III imagery is used to identify possible geomorphologic hindrances along the pipeline route. Similarly, landuse–landcover information derived from Resourcesat-2 LISS III images, was used to assess the land use/cover impact of the planed pipeline corridor. This has been demonstrated, in the current article using a hypothetical pipeline route. The activity can be carried in a specially designed geo-spatial interface in NRSC/ISRO Bhuvan geoportal. This type of assessment can prove to be time saving and cost effective at a pre-feasibility stage.     

Cylindrical magnetohydrodynamic model of shock waves with radiation heat flux

Similarity solutions have been obtained for a cylindrical piston advancing with constant speed into a uniform plasma of infinite electrical conductivity and uniform axial magnetic field with heat radiation. The total energy of the expanding wave has been supposed to remain constant. The plasma is assumed to be a perfect grey gas in local thermodynamic equilibrium. To make the discussions less complicated the simplifying assumptions include transparent shock, cool piston neither an emitter nor a reflector and negligible radiation pressure and energy.This research was partially supported by a grant from U.G.C., India.