Effects Of Dust Temperature Research Articles

Effects of dust temperature and radiative heat-loss functions on the magnetogravitational instability of viscoelastic dusty plasma

The effects of dust temperature and radiative heat-loss functions on the instability of selfgravitating homogeneous viscoelastic dusty plasma have been studied using the modified GH model. A general dispersion relation representing the dust temperature, radiative heat-loss functions, magnetic field, thermal conductivity and relaxation time parameters are obtained using the normal mode analysis method in the linearized perturbation equations system. Jeans criteria that represent the onset of instability of selfgravitating medium are obtained under the limits; when the medium behaves like a viscous liquid (strongly coupled limit) and a Newtonian liquid (weakly coupled limit) for some limiting cases. The effects of various parameters on the Jeans instability criteria and on the growth rate of selfgravitating viscoelastic dusty plasma have been discussed. It is found that the dust temperature and radiative heat-loss functions modify the instability criterion by reducing the critical wave number.

HERSCHEL EXTREME LENSING LINE OBSERVATIONS: [C ii] VARIATIONS IN GALAXIES AT REDSHIFTS z = 1–3*

ABSTRACT We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel. The [C ii] luminosity in this sample ranges from 8 × 107 L ⊙ to 3.7 × 109 L ⊙ (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

Existence and stability of modulated dust-acoustic wave packets in the presence of nonthermal ions

The effects of dust temperature and energetic (nonthermal) ions are incorporated in the study of modulated instability of dust-acoustic (DA) waves in a dusty plasma containing warm adiabatic dust grains, isothermal electrons and hot ions obeying a nonthermal distribution. Based on the multiple space and time scales perturbation, a nonlinear Schrödinger equation is derived with a solution showing a new relationship between the modulated DA wave packets and ion nonthermality. It is shown that as the population of fast ions increases, the transition from stable dark envelope solitons to unstable ones shifts to the smaller wavelength regions. The instability growth rate reduces owing to the presence of nonthermal ions. It is also found that the effects of dust temperature and electron concentration modify the criteria for the modulational instability of DA waves. The results could be useful for understanding the properties of modulated wave packets and their evolution in space and laboratory dusty plasmas, such as those in and around the Earth’s foreshock.

Arbitrary amplitude dust-acoustic solitary waves in a dusty plasma with flat-topped ion distribution

The properties of arbitrary amplitude dust-acoustic (DA) solitary waves (SWs) in a dusty plasma containing warm adiabatic dust fluid, isothermal electrons and ions following flat-topped velocity distribution is studied by the pseudo-potential approach. The effects of dust temperature and flat-trapped ions are found to significantly modify the basic features of DA-SWs as well modify the parametric regime for the existence of rarefactive solitary waves. The pseudo-potential for small amplitude limit is also analytically analyzed, and the numerical results are found to agree with analytical results.

Dust-acoustic shock formation in adiabatic hot dusty plasmas with variable charge

Shocklike structure can be formed after a certain transient time due to the self-steepening of the negative potential. In order to have a monotonic or oscillatory shock wave, it is known that a source of dissipation is needed. In this study, we considered the variation of dust charge as a source of dissipation. By using the reductive perturbation technique, the nonlinear Burgers equation is derived and the shocklike solution is determined. The effects of dust temperature on different characteristics of dust-acoustic shock structure are discussed. It is found out that the dust thickness is not affected by dust temperature. By considering a dusty plasma system with a set of parameters, it is shown that there exists a specific dust critical temperature Tdc which gives maximum height for the dust-acoustic shock structure. The effects of the plasma species temperature on shock formation are also investigated.

Effects of flat-topped ion distribution and dust temperature on small amplitude dust-acoustic solitary waves and double layers in dusty plasma

The combined effects of the flat-topped ion distribution and dust temperature are incorporated in the study of small but finite amplitude dust-acoustic (DA) solitary waves (SWs) as well double layers (DLs) in an unmagnetized dusty plasma. Due to the flat-trapped ions, our plasma model admits only rarefactive localized structures. It is found that the effects of dust temperature and resonant particles significantly modify the criteria for the existence of DA SWs and DLs, as well as significantly modify their basic properties.

Effects of dust temperature and trapped ions on the formation of dust-acoustic solitary waves

The effects of dust temperature and trapped ions are incorporated in the study of dust-acoustic solitary waves. An energy integral equation involving the Sagdeev potential is derived, and the basic properties of large amplitude solitary structures are investigated. It is shown that the effects of dust temperature, resonant ions and equilibrium free electron density significantly change the regions of the existence of large amplitude solitary waves. Expanding the Sagdeev potential to include higher-order nonlinearities of electric potential, an exact steady state solution is also obtained which confirms the possibility of dust-acoustic soliton in the small amplitude limit. Furthermore, two asymptotic cases of the stationary solution are found which are related to the contribution of trapped ions.

Large amplitude dust acoustic solitary waves and double layers in positively charged warm dusty plasma with nonthermal electrons

Large amplitude dust acoustic solitary waves and double layers in a nonthermal plasma consisting of positively charged dust grains, nonthermal electrons, and isothermal ions including the effect of dust temperature have been studied using the Sagdeev potential technique by a computational scheme. The effect of different parameters on the nature of existence of solitary waves and double layers has been investigated to delimit their compositional parameter space. The physics corresponding to the computational result has been pointed out.

Nonlinear oscillations in a magnetized dusty plasma with two-temperature trapped ions

The nonlinear properties of dust-acoustic waves (DAWs) propagating obliquely to an external magnetic field in a dusty plasma comprised of Boltzmannian electrons, two-temperature trapped ions and charged dust grains are investigated. The typical integral form of the Sagdeev potential is examined numerically and is expanded up to the fourth order of the electrostatic potential ϕ to study analytically the nature of the solitary waves whose amplitude tends to zero as the Mach number M approaches its critical value M c. The critical Mach number typically depends on the dust fluid temperature, density and the obliqueness of the wave vector. Only the rarefactive soliton solution as well as the profiles of spiky solitary waves are shown to coexist by the effects of dust temperature, two-temperature trapped ions, obliqueness and the external magnetic field.

Effects of adiabatic hot dust on arbitrary amplitude electrostatic solitary structures in magnetoplasmas

The effects of dust temperature on arbitrary amplitude dust acoustic solitary waves in a homogeneous magnetized plasma are studied. It is found that the dust temperature is destructive for the formation of solitons in magnetized plasmas. This behavior is similar to the case of unmagnetized hot dusty plasmas. However, the soliton amplitude increases with the increase in the obliqueness of the wave propagation. The numerical results are also shown for illustrative purposes.

Modulational instability of dust acoustic waves in dusty plasmas: Modulation obliqueness, background ion nonthermality, and dust charging effects

The oblique modulational instability of dust acoustic (DA) waves in an unmagnetized warm dusty plasma with nonthermal ions, taking into account dust grain charge variation (charging), is investigated. A nonlinear Schrödinger-type equation governing the slow modulation of the wave amplitude is derived. The effects of dust temperature, dust charge variation, ion deviation from Maxwellian equilibrium (nonthermality) and constituent species’ concentration on the modulational instability of DA waves are examined. It is found that these parameters modify significantly the oblique modulational instability domain in the k-θ plane. Explicit expressions for the instability rate and threshold have been obtained in terms of the dispersion laws of the system. The possibility and conditions for the existence of different types of localized excitations are also discussed. The findings of this investigation may be useful in understanding the stable electrostatic wave packet acceleration mechanisms close to the Moon, and also enhances our knowledge on the occurrence of instability associated to pickup ions around unmagnetized bodies, such as comets, Mars, and Venus.

Modeling the Astronomical Silicate Mineralogy: On the Effects of Grain Temperature

The mineralogical composition of dust contains important information regarding the origin and processing of the dust and the physical, chemical, and evolutionary properties of the astrophysical environment where the dust is found. In the literature, the composition of cosmic dust is usually inferred by fitting the observed infrared (IR) emission spectrum with a sum of emission spectra calculated from various individual grain species of different sizes but assuming a single, identical temperature for them. However, we show in this work that these grains of different compositions and/or different sizes, while in thermal equilibrium with the radiation field to which the grains are exposed, achieve different temperatures. The effects of dust temperature on dust compositional studies are demonstrated by showing that the IR emission spectrum calculated from a mixture of grains emitting at different temperatures differs substantially from that of the same grain mixture but with a single, identical temperature. Therefore, the need for obtaining realistic temperatures from realistic cosmic dust analogs is a key to properly interpreting the observational IR emission spectra, e.g., the rich set of data that the Spitzer Space Telescope has been collecting.

The effects of dust temperature and the dust charge variation in a dusty plasma with vortex-like ion distribution

By considering both the dust temperature and the dust charge variation in dusty plasma with vortex-like ion distribution, we obtained a modified Korteweg-de Vries equation. It indicates that the effect of dust charge variation can cause the one-dimensional soliton amplitude to become larger and the dust temperature can cause the soliton amplitude to become larger as well. Moreover, as the dust temperature increases, the soliton amplitude will increase.

Effects of dust temperature and fast ions on gravitational instability in a self-gravitating magnetized dusty plasma

A theoretical investigation has been made of effects of dust temperature, fast (nonthermal) ions, and external magnetic field on gravitational instability in a self-gravitating magnetized hot dusty plasma, which consists of extremely massive, negatively charged hot dust fluid, nonthermally distributed ions, and Boltzmann distributed electrons, where the gravitational force is comparable to or greater than the electrostatic force. The effects of dust temperature, fast ions, and external magnetic field have been found to modify the criterion for this gravitational instability. It has been shown that the growth rate of this gravitational instability decreases with dust temperature, fast ions, and external magnetic field, but increases with the number of free electrons, with the ratio of ion temperature to electron temperature, and with the ratio of dust mass to dust charge. The implications of this result in some astrophysical situations are briefly discussed.