EDDINGTON'S “Internal Constitution of the Stars” was published in 1926 and gives what now ranks as a classical account of his own researches and of the general state of the theory at that time. Since then, a tremendous amount of work has appeared. Much of it has to do with the construction of stellar models with different equations of state applying in different zones. Other parts deal with the effects of varying chemical composition, with pulsation and tidal and rotational distortion of stars, and with the precise relations between the interior and the atmosphere of a star. The striking feature of all this work is that so much can be done without assuming any particular mechanism of stellar energy-generation. Only such very comprehensive assumptions are made about the distribution and behaviour of the energy sources that we may expect future knowledge of their mechanism to lead mainly to more detailed results within the framework of the existing general theory. An Introduction to the Study of Stellar Structure By S. Chandrasekhar. (Astrophysical Monographs sponsored by The Astrophysical Journal.) Pp. ix+509. (Chicago: University of Chicago Press; London: Cambridge University Press, 1939.) 50s. net.

An Introduction to the Study of Stellar Structure

13. 벼잎선충의 약제처리 방법별 방제 효과

Visible-light photocatalytic activity of TiO2/ZnS nanocomposites prepared by homogeneous hydrolysis

Collisions with electrons from several sources are common throughout planetary atmospheres. While in most circumstances direct electron impact is less significant than solar radiation, electron collisions have a major influence on the chemistry driven by both photon and particle impact. This review addresses electron collisions in atmospheres, with emphasis on cases where electron impact drives, enhances, or otherwise interacts with chemical processes. Understanding of atmospheric processes typically involves computational simulation based on theory, remotely-sensed atmospheric data, atomic and molecular physics data and chemical reaction rates. These and the modelling techniques will therefore also be covered. An example of current and future work on electron impact on the hydroxyl radical (OH) is presented, where applications in both atmospheric studies and plasma medicine are important.

Electron collisions in atmospheres

The micrometeoroid population within 10 Earth radii (60,000 km) has been observed by the HEOS 2 dust experiment between 7 February 1972 and 2 August 1974. A total of 431 particles has been observed. Of those 90 particles are classified as random, the rest as particle bursts. The random particles only show a slight increase (factor 3) in flux within 10 Earth radii, compared to the deep space flux at 1 AU and this is interpreted as being due to the gravitational field of the Earth. The bursts are divided into groups and swarms according to their time profiles. The 19 recorded groups are observed both within 10 Earth radii and above, again with a slight increase below 60,000 km. The 15 recorded swarms are exclusively observed within 10 Earth radii. The total micrometeoroid flux in this region is enhanced by 2–3 orders of magnitude. The interpretation is that larger bodies in the 10–10 6 g mass range of the type III fireballs are disintegrating while travelling through the Earth's auroral zones. The fragmentation process proposed is that of electrostatic disruption. This leads to one (or several) swarm(s) of small individual particles, which originally made up the flurry type (cometary) parent body.

Micrometeoroids within ten earth radii.

We study the influence of ion beam and charged dust impurity on the propagation of dust ion-acoustic (DIA) solitary wave (SW) in an unmagnetized plasma consisting of Boltzmann distributed electrons, positive ions, positive ion beam and negatively charged immobile dusts in a double plasma device. On interacting with an ion beam, the solitary wave is bifurcated into a compressive fast and a rarefactive slow beam mode, and appears along with the primary wave. However, there exists a critical velocity of the beam beyond which the amplitude of the fast solitary wave starts diminishing and rarefactive slow beam mode propagates with growing amplitude. Whereas, the presence of charged dust impurity in the plasma reduces this critical beam velocity and a substantial modification in the phase velocity of the slow beam mode is observed with increasing dust density. Furthermore, the nonlinear wave velocity (Mach number) as well as the width of the compressive solitons are measured for different beam velocity and dust density, and are compared with those obtained from the K-dV equation. The experimental results are found in a well agreement with the theoretical predictions.

Characteristics of ion-acoustic solitary wave in a laboratory dusty plasma under the influence of ion-beam

We study the influence of ion beam and charged dust impurity on the propagation of dust ion-acoustic solitary wave in an unmagnetized plasma consisting of Boltzmann distributed electrons, positive ions, positive ion beam, and negatively charged immobile dusts in a double plasma device. On interacting with an ion beam, the solitary wave is bifurcated into a compressive fast and a rarefactive slow beam mode, and appears along with the primary wave. However, there exists a critical velocity of the beam beyond which the amplitude of the fast solitary wave starts diminishing and rarefactive slow beam mode propagates with growing amplitude. Whereas, the presence of charged dust impurity in the plasma reduces this critical beam velocity and a substantial modification in the phase velocity of the slow beam mode is observed with increasing dust density. Furthermore, the nonlinear wave velocity (Mach number) as well as the width of the compressive solitons are measured for different beam velocity and dust density, and are compared with those obtained from the K-dV equation. The experimental results are found in a well agreement with the theoretical predictions.

In this report, the investigation of the properties of dust acoustic (DA) solitary wave propagation in an adiabatic dusty plasma including the effect of the non-thermal ions and trapped electrons is presented. The reductive perturbation method has been employed to derive the modified Korteweg–de Vries (mK-dV) equation for dust acoustic solitary waves in a homogeneous, unmagnetized, and collisionless plasma whose constituents are electrons, singly charged positive ions, singly charged negative ions, and massive charged dust particles. The stationary analytical solution of the mK-dV equation is numerically analyzed and where the effect of various dusty plasma constituents DA solitary wave propagation is taken into account. It is observed that both the ions in dusty plasma play as a key role for the formation of both rarefactive as well as the compressive DA solitary waves and also the ion concentration controls the transformation of negative to positive potentials of the waves.

Modified Korteweg–de Vries equation in a negative ion rich hot adiabatic dusty plasma with non-thermal ion and trapped electron

Using the well-known reductive perturbation technique, the three-dimensional (3D) Burgers equation and modified 3D Burgers equation have been derived for a plasma system comprising of non-thermal i...

Dust acoustic shock waves in arbitrarily charged dusty plasma with low and high temperature non-thermal ions

A rigorous investigation is presented on the propagation characteristics of non-linear dust acoustic (DA) waves in an unmagnetized dusty plasma system containing non-thermal and vortex-like ions and Maxwellian electrons under the effect of a fluctuating charged dust fluid. The three-dimensional (3D) Burgers' equation and a new form of a lower degree modified 3D Burgers' equation with their analytical solutions are derived to study the features of shock waves in such plasmas. The effect of the population of non-thermal ions, the vortex-like ion parameter as well as the temperature ratios of ions and electrons on the evolution of shock waves in the presence of dust charge fluctuation is presented. This theoretical investigation might be effectively utilized to unveil the nature of many astrophysical plasma environments (Saturn's spokes etc.) where such plasmas are reported to have existed.

http://iopscience.iop.org/article/10.1088/1009-0630/17/4/02/pdf

M. K. Deka

Papers

Characteristics of ion-acoustic solitary wave in a laboratory dusty plasma under the influence of ion-beam

Characteristics of ion-acoustic solitary wave in a laboratory dusty plasma under the influence of ion-beam

Modified Korteweg–de Vries equation in a negative ion rich hot adiabatic dusty plasma with non-thermal ion and trapped electron

Dust acoustic shock waves in arbitrarily charged dusty plasma with low and high temperature non-thermal ions

Dust Acoustic Shock Waves with Non-Thermal and Vortex-Like Ions in Dusty Plasma