18,681 research outputs found
Study of dominating parameters of high speed solar plasma streams in relation to cosmic ray and geomagnetic storms
The high speed solar wind streams observed near Earth are generally associated with the solar features, such as solar flares and coronal holes. Past studies of these streams from the two sources have revealed distinctly different effects on cosmic ray intensity, whereas the effect is similar for geomagnetic disturbances. Moreover, the effect of the magnitude of the high speed streams (V) and its rate of increase (dv/dt) has also been a subject of investigation to understand their relative contribution in producing geomagnetic disturbances. From the analysis of some of the fast streams presented here, it is difficult to predict, which one of the two (V, dv/dt) is more effective in producing geo-magnetic disturbances. Further, in most of the cases, no substantial decrease in cosmic ray intensity is observed
Cumulative effect of Forbush decreases in the heliospheric modulation during the present solar cycle
A monthly Forbush decrease index (Fd-I) is generated and it is compared with the observed long term chnges in the cosmic ray intensity near earth at energies greater than or equal to 1 Gev over 1976-83. Significant correlation is observed between the two except for 1978. Such an effect is also seen in the correlation plot between the solar flare index (SFI) and Fd-I
Chiral Symmetry Breaking and Pion Wave Function
We consider here chiral symmetry breaking through nontrivial vacuum structure
with quark antiquark condensates. We then relate the condensate function to the
wave function of pion as a Goldstone mode. This simultaneously yields the pion
also as a quark antiquark bound state as a localised zero mode in vacuum. We
illustrate the above with Nambu Jona-Lasinio model to calculate different
pionic properties in terms of the vacuum structure for breaking of exact or
approximate chiral symmetry, as well as the condensate fluctuations giving rise
to mesons.Comment: latex, revtex, 16 page
Constraints on nuclear matter parameters of an Effective Chiral Model
Within an effective non-linear chiral model, we evaluate nuclear matter
parameters exploiting the uncertainties in the nuclear saturation properties.
The model is sternly constrained with minimal free parameters, which display
the interlink between nuclear incompressibility (), the nucleon effective
mass (), the pion decay constant () and the meson
mass (). The best fit among the various parameter set is then
extracted and employed to study the resulting Equation of state (EOS). Further,
we also discuss the consequences of imposing constraints on nuclear EOS from
Heavy-Ion collision and other phenomenological model predictions.Comment: 10 pages, 8 figure
Head-on infall of two compact objects: Third post-Newtonian Energy Flux
Head-on infall of two compact objects with arbitrary mass ratio is
investigated using the multipolar post-Minkowskian approximation method. At the
third post-Newtonian order the energy flux, in addition to the instantaneous
contributions, also includes hereditary contributions consisting of the
gravitational-wave tails, tails-of-tails and the tail-squared terms. The
results are given both for infall from infinity and also for infall from a
finite distance. These analytical expressions should be useful for the
comparison with the high accuracy numerical relativity results within the limit
in which post-Newtonian approximations are valid.Comment: 25 pages, 2 figures, This version includes the changes appearing in
the Erratum published in Phys. Rev.
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