Exact solution of the equation for the problem of diffuse reflection and transmission with a scattering function ω0(1 +x cos⊙) by the method of laplace transform and theory of linear singular integral equation

Neutrinos couple through a weak neutral current to the density of matter, in particular to the neutron density. Density fluctuations, or phonons, in the neutron fluid may be emitted or absorbed by neutrinos passing through the matter. At high densities, temperatures and neutrino energies the neutrino mean free paths for phonon emission and absorption can be 10⁶ cm. Significant changes in the neutrino momentum and energy accompany these processes. We present a model calculation for neutrino scattering by phonons, and representative numerical results for the neutrino mean free path and mean energy and momentum changes fork _B T andE _v both ranging from 1 to 27 MeV.Research supported by the National Research Council of Canada.     

Exact solution of the equation of radiative transfer for semi-infinite plane-parallel isotropic scattering atmosphere with scattering albedo ω0 ≤ 1 by a method based on Laplace transform and Wiener-Hopf technique

By performing the one-sided Laplace transform on the scalar integro-differential equation for a semi-infinite plane-parallel isotropic scattering atmosphere with a scattering albedo ₀ 1, an integral equation for the emergent intensity has been derived. Application of the Wiener-Hopf technique to this integral equation will give the emergent intensity. The intensity at any optical depth for a positive scattering angle is also derived by inversion. The intensity at any optical depth for a negative scattering angle is also derived in terms of Cauchy's principal value using Plemelj's formulae.     

Exact solution of the transport equation for radiative transfer with scattering albedo ωO < 1 using the Laplace transform and the Wiener-Hopf technique and an expression ofH-function

We have considered the transport equation for radiative transfer to a problem in semi-infinite non-conservative atmosphere with no incident radiation and scattering albedo ₀ < 1. Usint the Laplace transform and the Wiener-Hopf technique, we have determined the emergent intensity and the intensity at any optical depth. We have obtained theH-function of Dasgupta (1977) by equating the emergent intensity with the intensity at zero optical depth.     

A comparative study of Hα-flares of different visual features in relation to radio bursts and sunspots

Solar H-flares now reported with their distinctive visual features have been statistically examined for a period of about eight years in relation to their different characteristics, flare-burst and flare-sunspot association. Important results obtained are: (i) Integrated intensity changes from the highest to the lowest values in the order F, H, E, and D flare type, whereas, impulsiveness in the order H, F, E, and D type, (ii) Flare-burst association is frequency dependent and is highest and lowest for H and D types respectively in almost all the frequencies, (iii) Most of the flares of D, E, and F types are associated with sunspots of _p , _p , and configurations having field strength 1500–2500 G, while that of H type with _p and configurations having field strength 1000–2000 G.     

Multiple forecasts of kharif rice in orissa state-four year experience of fasal pilot study

Considering the requirement of multiple pre-harvest crop forecasts, the concept of Forecasting Agricultural output using Space, Agrometeorology and Land based observations (FASAL) has been formulated. Development of procedure and demonstration of this technique for four in-season forecasts for kharif rice has been carried out as a pilot study in Orissa State since 1998. As the availability of cloud-free optical remote sensing data during kharif season is very poor for Orissa state, multi-date RADARSAT SCANSAR data were used for acreage estimation of kharif rice. Meteorological models have been developed for early assessment of acreage and prediction of yield at mid and late crop growth season. Four in-season forecasts were made during four kharif seasons (1998-2001); the first forecast of zone level rice acreage at the beginning of kharif crop season using meteorological models, second forecast of district level acreage at mid growth season using two-date RADARSAT SCANSAR data and yield using meteorological models, third forecast at late growth season of district level acreage using three-date RADARSAT SCANSAR data and yield using meteorological models and revised forecast incorporating field observations at maturity. The results of multiple forecasts have shown rice acreage estimation and yield prediction with deviation up to 14 and 11 per cent respectively. This study has demonstrated the potential of FASAL concept to provide inseason multiple forecasts using data of remote sensing, meteorology and land based observations.     

Periodicity in the Basal Component of Radio Emission During Maximum and Minimum Solar Activity

The basal component of radio emission is the radio intensity obtained after subtracting the sunspot-dependent (magneto-active) component from the observed flux and finally deducting the steady part from this subtracted value. The periodicity of this basal component of solar radio emission in the frequency band 0.245–15.4 GHz was studied both for the solar maximum (1980 and 1991) and minimum (1975 and 1986) periods. A constant periodicity of 35 days was observed in the entire radio band under study during the periods of maximum solar activity, whereas the periodicity fluctuates harmonically with frequency during the minimum periods, giving rise to an average time period of approximately 54 days.     

Some studies of the growth of monsoon disturbances

The structure of the monsoon depression and the observed flow features prior to and at the time of monsoon depression formation (composite of 15 depressions) are examined. The composite monsoon depression (transient eddy) has a scale of 25° longitude and extends up to 300 mb and has the greatest intensity at 700 mb. It shows north-north-east to south-south-west tilt in the lower levels indicating that it may draw upon zonal kinetic energy for its growth. The disturbance has lower temperatures to its west and tilts westwards with height indicating that eddy available potential energy is not converted from zonal available potential energy by large scale advection. There appears to be a reduction of vertical shear at the time of formation of monsoon depressions and this possibly aids cumulus convection. The profiles of potential vorticity indicate extremes (i) in the upper troposphere and (ii) at several midtropospheric levels in the region of the monsoon trough indicating the possibility of combined barotropic-baroclinic instability. Using multi-level quasi-geostrophic model and employing the eigen-value technique it is shown that the monsoon zonal current is notbaroclinically unstable. A barotropic stability analysis is also done for monsoon zonal current in the lower and middle tropospheres. It yields very slowly growing unstable modes at lower tropospheric levels with wave lengths of 2500 km and 5000 km.     

On the tectonics of Asia

This report describes an interpretation of the tectonics of central Asia made from seismic and geologic data. It is suggested that central Asia is not a tectonically passive unit, as previously proposed by others, responding solely to the convergence of the Indian plate with Asia. We postulate that the tectonics of central Asia can be represented by the motion of a few continental blocks which are influenced by spreading from the Baikal rift zone as well as compression due to the collision of the Indian plate. Here, a block is defined as a tectonic unit, within a continental plate, with boundaries delineated by broad zones of high seismicity with respect to the interior of the unit. Five tectonic units are postulated for central Asia. These are: the Siberian block, the East and West China blocks, the Southeast Asian block; and the Indian plate. An unusual phenomenon is noted along the boundary between the Siberian and West China blocks. There is general horizontal crustal compression along this boundary from the Hindu Kush north-eastward to the southern tip of Lake Baikal; however, there is general horizontal extension eastward from Lake Baikal through the Stanovoy range. Thus the West China block, to the south of this boundary, seems to be turning clockwise about a point near the southern tip of Lake Baikal. The major known faults within this block, which strike mainly northwest-southeast, may be interpreted as shear zones where interior stresses, due to the block rotation, are released. We cannot support this suggestion with an analytical model because of the uncertainties in various model parameters and geometries. The suggested model gives a possible explanation of why India, to the south of the Himalayas, is almost completely aseismic while the regions to the north and northeast have higher seismicity.