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451.
The propagation of nonlinear waves in a quantum plasma is studied. A quantum magnetohydrodynamic (QHD) model is used to take into account the effects of quantum force associated with the Bohm potential. Using the standard reductive perturbation technique, nonlinear Kadomtsev-Petviashvili (KP) equation is obtained to study the properties of ion acoustic waves (IAWs). For such waves the amplitude of the solitary waves is independent of the quantum parameter H (the ratio of the electron plasmon to electron Fermi energy), whereas the width and energy of the soliton increases with H. 相似文献
452.
Uday Narayan Ghosh Deb Kumar Ghosh Prasanta Chatterjee Mustapha Bacha Mouloud Tribeche 《Astrophysics and Space Science》2013,343(1):265-272
The properties of nonplanar (cylindrical and spherical) ion-acoustic solitary waves (IA SWs) in an unmagnetized, collisionless electron-positron-ion (e-p-i) plasma, whose constituents are q-distributed electrons and positrons and inertial ions, are investigated by deriving the modified Gardner (MG) equation. The well known reductive perturbation method is employed to derive the MG equation. The basic features of nonplanar IA Gardner solitons (GSs) are discussed. It is found that the properties of nonplanar IA GSs (rarefactive and compressive) are significantly affected by the particle nonextensivity. 相似文献
453.
Partha Pratim Ghosh Saibal Ray A. A. Usmani Utpal Mukhopadhyay 《Astrophysics and Space Science》2013,345(2):367-371
The concept of oscillatory Universe appears to be realistic and buried in the dynamic dark energy equation of state. We explore its evolutionary history under the framework of general relativity. We observe that oscillations do not go unnoticed with such an equation of state and that their effects persist later on in cosmic evolution. The ‘classical’ general relativity seems to retain the past history of oscillatory Universe in the form of increasing scale factor as the classical thermodynamics retains this history in the form of increasing cosmological entropy. 相似文献
454.
A Korteweg-de Vries (KdV) equation with a linear Landau damping term describing weakly nonlinear and weakly dispersive ion-acoustic
waves in an electron-positron-ion plasma is derived. It is found that the Landau damping causes the solitary wave amplitude
to decay with time. It is also found that in absence of Landau damping, both linear wave phase velocity and solitary wave
amplitude decrease with the increase of positron density, whereas, both increase with the increase of positron temperature.
On the other hand, the Landau damping rate decreases with the increase of both positron density and temperature. 相似文献
455.
S. K. Ghosh B. Mookerjea T. N. Rengarajan S. N. Tandon R. P. Verma 《Journal of Astrophysics and Astronomy》2001,22(2-3):173-185
Three Galactic star forming regions associated with W3(OH), S209 and S187 have been simultaneously mapped in two trans-IRAS
far infrared (FIR) bands centered at ≈140 and 200μm using the TIFR 100 cm balloon borne FIR telescope. These maps show extended
FIR emission with structures. The HIRES processed IRAS maps of these regions at 12, 25, 60 & 100 ìm have also been presented
for comparison. Point-like sources have been extracted from the longest waveband TIFR maps and searched for associations in
the other five bands. The diffuse emission from these regions have been quantified, which turns out to be a significant fraction
of the total emission. The spatial distribution of cold dust (T < 30 K) for two of these sources (W3(OH) & S209), has been
determined reliably from the maps in TIFR bands. The dust temperature and optical depth maps show complex morphology. In general
the dust around S209 has been found to be warmer than that in W3(OH) region. 相似文献
456.
Uday Narayan Ghosh Prasanta Chatterjee Sanjib Kumar Kundu 《Astrophysics and Space Science》2012,339(2):255-260
The head-on collision of dust acoustic solitary waves are studied in a dusty plasma composed of dust and nonextensive distributed
ions by using the extended version of Poincaré-Lighthill-Kuo (PLK) method. The effect of the nonextensivity on the phase shift
is studied. It is found that the presence of nonextensive distributed ions plays a significant role on the collision of dust
acoustic solitary waves. 相似文献
457.