Ion acoustic solitary waves in plasma with nonthermal electron,positron and warm ion

In this paper, the characteristics of ion acoustic solitary waves are studied in plasmas containing warm ion fluid, non-thermally distributed electron and positron. We study the effects of non-thermal electrons and ion temperature on solitons by Pseudo-potential method and show that the parametric region where ion acoustic solitons can exist is modified. We also obtain linear dispersion relation by using the standard normal-modes analysis.     

Ion acoustic solitons of KdV and modified KdV equations in weakly relativistic plasma containing nonthermal electron,positron and warm ion

In this paper, the ion-acoustic solitons in a weakly relativistic electron-positron-ion plasma have been investigated. Relativistic ions, Maxwell-Boltzmann distributed positrons and nonthermal electrons are considered in collisionless warm plasma. Using a reductive perturbation theory, a Korteweg-de Vries (KdV) equation is derived, and the relativistic effect on the solitons is studied. It is found that the amplitude of solitary waves of the KdV equation diverges at the critical values of plasma parameters. Finally, in this situation, the solitons of a modified KdV (mKdV) equation with finite amplitude is derived.     

Arbitrary amplitude electron-acoustic solitary waves in the presence of excess superthermal electrons

The problem of arbitrary amplitude electron-acoustic solitary (EAS) waves in a plasma having cold fluid electrons, hot superthermal electrons and stationary ions is addressed. The domain of their allowable Mach numbers enlarges as the spectral index κ increases revealing therefore that the “maxwellisation” process of the hot component favors the propagation of the EAS waves. As the superthermal character of the plasma is increased, the potential pulse amplitude increases while its width is narrowed, i.e, the superthermal effects makes the electron-acoustic solitary structure more spiky. As the spectral index κ decreases, the hot electrons are locally expelled and pushed out of the region of the soliton’s localization. A decrease of the fractional number density of the hot electrons relative to that of the cold ones number density would lead to an increase of the depth as well as the width of the localized EAS wave. Our results should help to understand the salient features of large amplitude localized structures that may occur in the plasma sheet boundary layer and may provide an explanation for the strong spiky waveforms that have been observed in auroral electric fields.     

Exact relativistic plasma waves in an electron–positron plasma

Electrostatic plasma waves in an adiabatic electron–positron plasma are investigated nonperturbatively. It is shown that quasistationary large-amplitude waves with smooth as well as highly peaked profiles can appear. In the peaked waves, the electron and positron peaks may be separated by large distances, but no completely isolated soliton-like structures were found.     

Head-on collision of dust-acoustic solitary waves in an adiabatic hot dusty plasma with external oblique magnetic field and two-temperature ions

In the present paper, the characteristics of the head-on collision between two dust-acoustic solitary waves (DASWs) in an adiabatic dusty plasma consisting of variable negatively charged dust grains, isothermal electrons and two-temperature isothermal ions in the presence of an external oblique magnetic field are investigated. Using the extended Poincaré–Lighthill–Kuo (PLK) method, the Korteweg–de Vries (KdV) equations and the analytical phase shifts after the head-on collision of two solitary waves are derived. The effects of the magnetic field and its obliqueness, two different type of isothermal ions and the dust particles adiabaticity are discussed. It is found that these factors significantly affect the phase shifts.     

Dust ion-acoustic solitary and shock waves in a dusty plasma with non-thermal electrons

A theoretical investigation of the one dimensional dynamics of nonlinear electrostatic dust ion-acoustic (DIA) waves in an unmagnetized dusty plasma consisting of ion fluid, non-thermal electrons and fluctuating immobile dust particles has been made by the reductive perturbation technique. The basic features of DIA solitary and shock waves are studied by deriving the Korteweg-de Vries (KdV) and KdV Burger equations, respectively. It is shown that the special patterns of nonlinear electrostatic waves are significantly modified by the presence of the non-thermal electron component. In particular, the rarefactive solitary and shock structures are found with smaller amplitude in comparison to the isothermal case. The transition from DIA solitary to shock waves is also studied which is related to the contributions of the dispersive and dissipative terms. It is found that the dust charge fluctuation is a source of dissipation, and is responsible for the formation of the dust ion-acoustic shock waves. Furthermore, the dissipative effect becomes important and may prevail over that of dispersion as the population of non-thermal electrons present decreases. The present investigation may be of relevance to electrostatic solitary structures observed in many space dusty plasma, such as Saturn’s E-ring.     

Comment on “Head-on collision of electron acoustic solitary waves in a plasma with nonextensive hot electrons”

In a recent paper “Head-on collision of electron acoustic solitary waves in a plasma with nonextensive hot electrons” (Astrophys. Space Sci. 338:271–278, 2012) Eslami, Mottaghizadeh and Pakzad deal with the problem of the head-on collisions between two weakly nonlinear electron-acoustic solitary waves. Unfortunately, their treatment is deficient and leads to erroneous conclusions.     

Self-gravitational instability of rotating viscous Hall plasma with arbitrary radiative heat-loss functions and electron inertia

The effects of arbitrary radiative heat-loss functions and Hall current on the self-gravitational instability of a homogeneous, viscous, rotating plasma has been investigated incorporating the effects of finite electrical resistivity, finite electron inertia and thermal conductivity. A general dispersion relation is obtained using the normal mode analysis with the help of relevant linearized perturbation equations of the problem, and a modified Jeans criterion of instability is obtained. The conditions of modified Jeans instabilities and stabilities are discussed in the different cases of our interest. We find that the presence of arbitrary radiative heat-loss functions and thermal conductivity modifies the fundamental Jeans criterion of gravitational instability into a radiative instability criterion. The Hall parameter affects only the longitudinal mode of propagation and it has no effect on the transverse mode of propagation. For longitudinal propagation, it is found that the condition of radiative instability is independent of the magnetic field, Hall parameter, finite electron inertia, finite electrical resistivity, viscosity and rotation; but for the transverse mode of propagation it depends on the finite electrical resistivity, the strength of the magnetic field, and it is independent of rotation, electron inertia and viscosity. From the curves we find that the presence of thermal conductivity, finite electrical resistivity and density-dependent heat-loss function has a destabilizing influence, while viscosity and magnetic field have a stabilizing effect on the growth rate of an instability. The effect of arbitrary heat-loss functions is also studied on the growth rate of a radiative instability.     

Modulational instability of ion-acoustic waves in electron–positron–ion plasmas

The stability of modulation of ion-acoustic waves in a collisionless electron–positron–ion plasma with warm adiabatic ions is studied. Using the Krylov–Bogoliubov–Mitropolosky (KBM) perturbation technique a nonlinear Schrödinger equation governing the slow modulation of the wave amplitude is derived for the system. It is found that for given set of parameters having finite ion temperature ratio (T _i /T _e ) the waves are unstable for the values of k lying in the range k _min<k<k _max. On increasing the ion temperature ratio (T _i /T _e ), it is found that k _min and k _max, both decreases and product PQ increases. The range of unstable region shifts towards the small wave number k, as temperature ratio (T _i /T _e ) increases. The positron concentration and temperature ratio of positron to electron, change the unstable region slightly. As positron concentration increases both k _min and k _max for modulational instability increases and maximum value of the product PQ shifts towards the larger value of k.     

Kadomtsev–Petviashvili equation for solitary waves in warm dense astrophysical electron-positron-ion plasmas

Theoretical investigation is carried out to understand the dynamics and stability of three dimensional ion solitary waves propagating in dense plasma comprising of ultra-relativistic degenerate electrons and positrons and warm ions. A linear dispersion relation is derived which shows a strong dependence of wave on positron concentration (through the change of density balance) and ion-to-degenerate electron temperature ratio. A nonlinear Kadomtsev-Petviashvili equation is derived by employing the reductive perturbation technique and solved analytically and the conditions for existence of stable solitary waves are found. The analysis reveals that only compressive solitary waves exist in the system. Effects of the change of density balance and Fermi temperature ratios are studied in detail, both analytically and numerically. Furthermore, the conditions for stable solitary waves are discussed by using energy consideration method. The numerical results are also presented by using the parameters consistent with the degenerate and ultrarelativistic astrophysical plasmas.     

Charged particles’ areas of three-dimensional motions in a system of two magnetic stars

We study the parametric evolution of the regions where three-dimensional motions of a charged particle are allowed in the combined electromagnetic field produced by two rotating magnetic stars. We discuss the changes in the topology of the zero-velocity surfaces, as well as in the trapping regions of the particle motion for various values of the dipoles’ magnetic moments.     

Solitary solution and energy for the Kadomstev–Petviashvili equation in two temperatures charged dusty grains

The nonlinear properties of small amplitude dust-acoustic solitary waves (DAWs) in a homogeneous unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions have been investigated. A reductive perturbation method was employed to obtain the Kadomstev-Petviashvili (KP) equation. The effects of the presence of charged hot and cold dust grains on the nature of DAWs were discussed. Moreover, the energy of two temperatures charged dusty grains were computed. The present investigation can be of relevance to the electrostatic solitary structures observed in various space plasma environments.     

The effects of Alfvén waves on heating plasma in post-flare loops

In investigating the effects of collision Alfvén waves on the heating of a cool-type solar loop, like the post-flare loop, models are proposed, and the distributions of ion or electron density, temperature, pressure, and wave energy density are simulated. We assumed the magnetic field strength in the loop is about 100 G and found that Alfvén waves can propagate through the whole loop, that is to say, the decay length of collision Alfvén waves which we consider can reach to the height or length of the loop. Thus, the Alfvén wave heating is a considerable heating mechanism in cool loops. And we also found that the variations of density, pressure, and wave energy density are more significant than those of the temperature. In the whole loop, the temperature is of the order of 10⁴ K. In comparison with other parameters, the temperature can be considered as homogeneous; hence, the heat conductive flux in the simulations is omitted.     

Effect of ion temperature on arbitrary amplitude Kinetic Alfvén solitons in a plasma with a q-nonextensive electron velocity distribution

Taking into account of ion temperature effect, existence conditions of arbitrary amplitude solitary Kinetic Alfvén Waves (KAWs) in a plasma with q-nonextensive electrons are investigated by the conventional Sagdeev pseudo potential method. It is found that only solitons with density hump can exist, the amplitude of which depends sensitively on the parameter q, ion temperature ( \(\sigma= \frac{T_{i}}{T_{e}}\) ) and plasma β. There is an upper limit of solitary wave amplitude which decreases with increase of q, σ and β. The amplitude of solitary KAWs is found to increase with increase in ion temperature. The results obtained in the framework of Maxwellian distribution are reproduced when q→1.     

Radiation condensation instability in a plasma with ionization and recombination

In this work, we consider radiation (thermal) instability in a weakly ionized plasma with continuous ionization and recombination. The situation can be visualized in the case of envelopes of planetary nebulae, which are envelopes of ionized plasmas surrounding red giant stars. Various observations report continuous photoionization of these plasmas by the highly energetic streams of photons emanating from the parent star. Recently, it has been shown that thermal instability can be a probable candidate in such plasmas for the existence of small scale structures (viz., striations) whose kinematic age is much smaller than that of the parent nebula. We therefore report a systematic study of these plasmas with photoionization and determine the instability domain. We have shown that the continuous ionization and recombination may lead to modification of the underlying instability, which may limit the size of the small structures that are believed to form from these instabilities, and may thus provide an explanation of the physical processes responsible for the existence of these structures. We further show that in many cases the system bifurcates to an ovserstable (growing wave) state from a condensation instability (monotonic) and vice versa.     

Effect of high relativistic ions on ion acoustic solitons in electron-ion-positron plasmas with nonthermal electrons and thermal positrons

Propagation of ion acoustic solitary waves are studied in e-p-i plasmas containing high relativistic ions, Maxwell–Boltzmann distributed positrons and nonthermal electrons. Reductive perturbation method is used and the Korteweg-de Vries (KdV) equation is derived. The effects of high relativistic ions and nonthermal electrons on soliton characters are studied.     

Inclusion of sdBs in evolutionary population synthesis for binary stellar populations and the application: the determination of photo-z and galaxy morphology

Subdwarf B stars (sdBs) can significantly change the ultraviolet spectra of populations at age t～1 Gyr, and have been even included in the evolutionary population synthesis (EPS) models by Han et al. (Mon. Not. R. Astron. Soc. 380:1098, 2007). In this study we present the spectral energy distributions (SEDs) of binary stellar populations (BSPs) by combining the EPS models of Han et al. (Mon. Not. R. Astron. Soc. 380:1098, 2007) and those of the Yunnan group (Zhang et al. in Astron. Astrophys. 415:117, 2004; Mon. Not. R. Astron. Soc. 357:1088, 2005), which have included various binary interactions (except sdBs) in EPS models. This set of SEDs is available upon request from the authors. Using this set of SEDs of BSPs we build the spectra of Burst, E, S0–Sd and Irr types of galaxies by using the package of Bruzual and Charlot (Mon. Not. R. Astron. Soc. 344:1000, 2003). Combined with the photometric data (filters and magnitudes), we obtain the photometric redshifts and morphologies of 1502 galaxies by using the Hyperz code of Bolzonella et al. (Astron. Astrophys. 363:476, 2000). This sample of galaxies is obtained by removing those objects, mismatched with the SDSS/DR7 and GALEX/DR4, from the catalogue of Fukugita et al. (Astron. J. 134:579, 2007). By comparison the results with the SDSS spectroscopic redshifts and the morphological index of Fukugita et al. (Astron. J. 134:579, 2007), we find that the photo-z fluctuate with the SDSS spectroscopic redshifts, while the Sa–Sc galaxies in the catalogue of Fukugita et al. (Astron. J. 134:579, 2007) are classified earlier as Burst-E galaxies.