The major lightning regions and associated casualties over India

Natural Hazards - Lightning, a climate-related highly localized natural phenomenon, claims lives and damage properties. These losses could only be reduced by the identification of active seasons...     

Spherical shock waves in viscous magnetogasdynamics

The point-source, spherical magnetogasdynamics shock wave moving into a constant density -law gas is considered in the limit of infinite shock strength, from the point of view of the Richtmyer-Von Neumann viscosity technique. Numerical solutions of this problem has been obtained in viscous and non-viscous regions. A similarity solution of this problem is shown to exist. We have shown that field variables change rapidly when the magnetic field is imposed in both the viscous and the non-viscous regions.Supported by CSIR, New DeIhi under the grant No. 7157/287/81-DMR-I.     

Viscous Damping of Non-Adiabatic MHD Waves in an Unbounded Solar Coronal Plasma

The damping of MHD waves in solar coronal magnetic field is studied taking into account thermal conduction and compressive viscosity as dissipative mechanisms. We consider viscous homogeneous unbounded solar coronal plasma permeated by a uniform magnetic field. A general fifth-order dispersion relation for MHD waves has been derived and solved numerically for different solar coronal regimes. The dispersion relation results three wave modes: slow, fast, and thermal modes. Damping time and damping per periods for slow- and fast-mode waves determined from dispersion relation show that the slow-mode waves are heavily damped in comparison with fast-mode waves in prominences, prominence–corona transition regions (PCTR), and corona. In PCTRs and coronal active regions, wave instabilities appear for considered heating mechanisms. For same heating mechanisms in different prominences the behavior of damping time and damping per period changes significantly from small to large wavenumbers. In all PCTRs and corona, damping time always decreases linearly with increase in wavenumber indicate sharp damping of slow- and fast-mode waves.     

Qualitative analysis of two-fluid FRW cosmological models

This paper focuses attention on a qualitative analysis of the evolution of two-fluid flat FRW cosmological models.In the first model one of the fluid represents matter content of the universe comoving with respect to the another fluid that is the cosmic microwave background radiation (CMBR), these two fluids are interacting.The first model is most relevant to describe the scenario before the recombination epoch when matter and radiation were in an interactive phase and the photons was bound to electron through Thomson scattering. The second model describe two noninteracting fluids where the matter is comoving to the space-time coordinates and the CMBR is moving axially, relative to the matter thus modeling the relative velocity between galaxies and the CMBR (Phys. Rev. Lett. 39:898–901, 1977). This model portray the cosmic evolution in the postrecombination epoch when the two-fluid are noninteracting.In this epoch the photons got themselves free to form the CMBR being observed presently.      

Growth and decay of sonic discontinuities in non-equilibrium magnetogasdynamics

The phenomenon associated with sonic discontinuities in non-equilibrium magnetogasdynamics has been studied by the use of singular surface theory. The fundamental differential equations for growth and decay of sonic discontinuities have been formulated for general class of relaxing gas applying compatibility conditions for surface of discontinuity in continuum mechanics. This class of equations have been solved completely and for particular case of plane. We have also obtained the critical time at which sonic wave terminates in shock wave.     

Fault rupture directivity of large earthquakes in Himalaya

The paper examines the predominant fault rupture directivity during large earthquakes in different sectors of the Himalaya which influences strong ground motion and damage scenario. The nature of the faulting of earthquakes vis-à-vis their rupture directivity has been discussed. It is found that the rupture directivity near the Indo-Eurasian plate boundary varies from place to place i.e. either along the strike direction of the faults or at right angles to it. The secondary meizoseismal areas as observed for 1505 Dharchula, 1803 Uttarakhand, 1905 Kangra earthquakes in the Himalaya and 2001 Bhuj earthquake in stable continental region suggest that they are a fairly good indicator of predominant rupture directivity since the latter accentuates the site response up to a longer distance. The resulting larger ground motions, therefore, need to be incorporated in the design of engineering structures by suitable modifications in the BIS code.