Tessellation of SoHO magnetograms

A gradient based algorithm which divides arbitrary images into non-overlapping surface filling tiles of opposite polarity is used to study the flux and size distributions of large scale magnetic flux concentrations in solar and heliospheric observatory (SoHO) magnetograms. The mean absolute flux and size of the concentrations at the considered scale is found to be about 1.7 × 10¹⁸Mx and 5.2Mm for both polarities. The form of the flux distribution is characterized by a skewness of α₃ = 4.9 and a kurtosis of α₄ = 42.8. The fall in the distribution in the range 6.5 × 10¹⁷ Mx to 5×10¹⁸ Mx is described by an exponential fit, in agreement with a model for the sustenance of quiet region flux.     

An Experimental Evidence Of Non-Ducted Propagation During Daytime From The Esd Whistler Observations At Low Latitude Ground Station Jammu

The propagationmechanism of low latitude daytime whistlers is investigated on the basis of ground measurements made continuously during daytime in North India at Jammu (geomag. lat. 22°26°N;L = 1.17). On February 14, 1998 extremely small dispersion (ESD) whistlers with dispersion varying from 5–10 sec^1/2 in surprisingly large numbers were recorded at Jammu during daytime in the late afternoon. The results of a study of the characteristics of ESD whistlers are presented and the discussion indicates that ESD whistlers recorded are the VLF waves radiated from the return stroke of the lightning discharge launched at the ionosphere with different initial wave normal angles, propagated upwards under eitherquasi-longitudinal conditions or pro-longitudinal whistler mode, turned around at different heights due to quasi-transverse propagation and received at Jammu with the dispersion of the order of 5–10 sec^1/2. The validity of this suggestion has been tested by performing actualray-tracing computations in thepresence of equatorial anomaly model. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Century of Solar Ca <Emphasis Type="SmallCaps">ii</Emphasis> Measurements and Their Implication for Solar UV Driving of Climate

Spectroheliograms and disk-integrated flux monitoring in the strong resonance line of Ca ii (K line) provide the longest record of chromospheric magnetic plages. We compare recent reductions of the Ca ii K spectroheliograms obtained since 1907 at the Kodaikanal, Mt. Wilson, and US National Solar Observatories. Certain differences between the individual plage indices appear to be caused mainly by differences in the spectral passbands used. Our main finding is that the indices show remarkably consistent behavior on the multidecadal time scales of greatest interest to global warming studies. The reconstruction of solar ultraviolet flux variation from these indices differs significantly from the 20th-century global temperature record. This difference is consistent with other findings that, although solar UV irradiance variation may affect climate through influence on precipitation and storm tracks, its significance in global temperature remains elusive.     

Initial mass functions of Wolf-Rayet stars

On the basis of evolutionary tracks on the HR diagram the lower limit of initial mass functions for Wolf-Rayet stars are estimated. The lower limit to the initial masses of the Wolf-Rayet stars seems to be 20M and in this respect there is no significant difference between the WN and WC stars.     

Effect of rotational and tidal distortions on the periods of small adiabatic oscillations of stellar models

Kopal's method of representing the inner structure of a rotationally and tidally-distorted star by a rotationally-and tidally-distorted Roche model has been used in conjunction with an averaging concept introduced by Kippenhahn and Thomas of representing the equipotential surfaces of a rotationally and tidally distorted stellar model by the equipotential surfaces of an equivalent spherical model to determine the combined effects of rotation and tidal distortion on the periods of small adiabatic oscillations of a stellar model.     

A self-similar flow in Generalized Roche model with increasing energy

The self-similar flow of a gas, moving under the gravitational attraction of a central body of fixed mass behind a spherical shock wave driven out by a propelling contact surface into quiet solar wind region, is investigated. The total energy content between the inner expanding surface and the shock front increases with time. In the last section we briefly pose the self-similar isothermal flow of a gas behind a spherical shock wave.     

Self-similar solutions for the blast wave problem in radiative gasdynamics,I

Similarity solutions, describing the flow of a perfect gas behind spherical shock waves, are investigated including the radiation heat flux. The shock is assumed to be propagating in a medium at rest. Shock radius varies exponentially with time and density is inversely proportional to fifth power of the shock radius immediately ahead of the shock front.     

The onset of shock wave in an electrically conducting and radiating gas

The present work applies the method of characteristics to study the behaviour of planar and cylindrical wave-heads propagating through a perfectly electrically conducting and thermally radiating inviscid gas under the optically thin limit in the presence of a transverse magnetic field. The true nonlinear progress of the flow variable gradients at the wavefront is predicted and the critical distance at which the characteristics pile up at the wavefront to form a shock wave is obtained. It is investigated as to how the effects of radiative flux, the magnetic field strength and the specific heat ratio influence the process of steepening or flattening of the characteristic wavefront.     

Hall effects on heat and mass transfer flow through porous medium

Effects of Hall current on free convection and mass transfer flow through a porous medium bounded by a vertical surface has been analysed. The problem is solved analytically. The velocity profiles are shown on graphs. Effects ofm (Hall parameter).K ^* (permeability parameter), and Sc (Schmidt number) on velocity are discussed.