Charging of a conducting sphere moving in a weakly ionized gas under an arbitrarily oriented external uniform electric field

A charging conducting sphere moving in a weakly ionized gas is investigated. An external uniform electric field is applied with arbitrary orientation relative to the gas flow. The ion current is obtained analytically and investigated numerically in ballistic assumption. It is shown that charging regimes depend not only on the net charge of the sphere but also on the gas flow type, and the parameter ξ_± – the ratio of ion drift velocity far from the sphere to the gas velocity. The cases |ξ_±|<1 and |ξ_±|>1 yield two different charging regimes for Stokes and potential flows. For the potential flow, the ion current has been found analytically in continuous ξ_±-parameter space. The stationary charge of an isolated sphere is also calculated numerically as a function of α. It achieves maximum magnitudes in direct (α=0) and back (α=π) flows respectively.     

Condensation mode instability in a heat-releasing weakly ionized gas in a magnetic field

Linear equations and dispersion relations describing the condensation mode in weakly ionized plasma with heat release, being in an external magnetic field, are derived. The conditions of the instability onset of the condensation mode of the ion component are found.     

Electron-ion interaction in a weakly ionized gas

The effective electron-ion collision frequency has been measured in a weakly ionized gas. Results are in good agreement with classical theories for the electron-ion interaction in plasmas.     

Ion waves in a partially ionized gas in an external electric field

The propagation of longitudinal acoustic waves in the ion gas in an external electric field is studied theoretically. The results are compared with properties of waves in space without the external field. The phase velocities, damping factors and the influence of parameters of the gas on the properties of ion waves is discussed.In conclusion, the author would like to express his thanks to Prof. J. Kracík DrSc., for valuable advice and suggestions.     

Incoherent scattering of electromagnetic waves by a weakly ionized plasma layer

Institute of Theoretical Physics of the Ukrainian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 12, pp. 1327–1341 December, 1990     

Dissipation of energy of low-frequency waves in a weakly ionized gas

The properties of low-frequency waves in a slightly ionized gas are discussed on the basis of the Boltzmann transport and Maxwell equations. Special attention is paid to decay mechanisms forcing the gas to thermal equilibrium. It is shown that the collisional exchange of energy between ions and neutral atoms may considerably influence the dispersion equations of several modes of oscillations.The author wishes to thank Mrs. E. Dosoudilová for executing the numerical computations.     

Kinetic approach to the propagation of electromagnetic waves in a weakly ionized plasma

Summary High-frequency wave phenomena in a partially ionized plasma are analysed in the frame of the kinetic theory without resorting to perturbation techniques. In particular, we obtain the electron distribution function in an external electric field alternating in both time and position, and then the electrical conductivity and the dispersion relation. Corrections to the results of the macroscopic theory are evaluated up to any desired order.

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Riassunto Il fenomeno della propagazione di un'onda elettromagnetica in un plasma parzialmente ionizzato è analizzato nell'ambito della teoria cinetica. Il metodo proposto consente di ricavare la funzione di distribuzione degli elettroni senza dover ricorrere a tecniche perturbative. Si riportano le espressioni esatte della conducibilità elettrica e della legge di dispersione e, quindi, le correzioni da apportare ai risultati ottenuti con la teoria macroscopica.

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Резюме В рамках кинетической теории анализизируется явление распространения электромагнитных волн в частично ионизованной плазме. Предложенный метод позволяет получить электронную функцию распределения во внешнем электрическом поле без использования теории возмущений. Затем определяются электрическая проводимость и дисперсионное соотношение. Поправки к резулятатам макроскопической теории оцениваются в любом желаемом порядке.

     

High-frequency perturbations of coupled gravitational and electromagnetic fields in a weakly ionized dust

Wavelike perturbations of a system consisting of a gravitational and an electromagnetic field and a dust with a small ionized component are studied. By using the spin coefficient formalism we expand the perturbations of the various quantities characterizing the system into asymptotic series. The whole dynamics of high-frequency waves is shown to be governed by four propagation equations for the expansion coefficients of the tetrad components and of perturbations of the Weyl tensor and Maxwell tensor in each order of the expansion. The perturbations of all the other variables can be derived without integration. The propagation equations are explicitly derived and discussed in the zeroth-order (geometrical optics) and in the first-order approximation. The influence of dust and plasma on the propagation is considered in the first-order equations.     

Steady-state electric discharge in a weakly ionized gas at thermal equilibrium

The similarity properties of a discharge in a weakly ionized gas at thermal equilibrium are examined. The conditions for a developed discharge are shown to be governed by a dimensionless discharge parameter. An explicit dependence of the discharge parameter on the potential difference, the pressure, and the type of gas is found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 2, No. 4, pp. 116–120, April, 1969.     

Dynamics of heating of weakly ionized plasma in a self-consistent electric field

The dynamics of heating of a weakly ionized plasma in a pulsed discharge with allowance for the back reaction of the currents excited in the plasma on the field is analyzed on the basis of a kinetic equation with the Bhatnagar-Gross-Krook (BGK) model elastic collision integral. It is shown that the nature of the heating depends essentially on the ratio of the frequency of elastic collisions of an electron with neutrals and the plasma frequency. Analytic expressions for the dynamic electron distribution function and its moments are obtained. The limits of applicability of the approximation used are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 12–16, June, 1986.     

Conditions of the occurrence of charge instabilities in weakly ionized plasma flows

The dynamics of the perturbations of a weakly ionized plasma flow is considered in the context of three-fluid hydrodynamics. The conditions of the formation of flow-charge instabilities, which have been obtained in criterial form, are discussed.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 27–31, November, 2004.     

Kerr effect caused by an electric current in a weakly ionized gas

The anisotropy of the velocity distribution caused by an electric current in a fluid leads to a molecular alignment via the non-spherical interaction. This alignment implies a birefringence proportional to the square of the applied electric field just as the ordinary Kerr effect. The kinetic theory of this phenomenon is presented for a lorentzian mixture, viz. a gas of few light charged linear molecules and of many heavy optically isotropic particles. The current-induced contribution to the Kerr effect turns out to be much larger than the contribution which stems from the usually considered orienting influence of the electric field on anisotropic molecules.     

Convection in a weakly ionized plasma

The nonlinear dynamic stability of a weakly ionized plasma is investigated taking into account the spatial effects. Also obtained are the stability criteria.     

Thermal fluctuations of a quantized electromagnetic field in weakly absorbing media

The quantum fluctuations of an electromagnetic field in thermally excited media are calculated using the quantum electrodynamical method of Γ operators and without invoking phenomenological elements. The drawbacks of the standard theory based on the fluctuation-dissipation theorem and on the Matsubara technique of temperature Green’s functions are indicated. The decisive role of the correct consideration of higher order photon-photon correlators and the inadmissibility of their approximation by products of lower order correlators are underlined. It is shown that, contrary to the accepted opinion, the quantum fluctuations of an electromagnetic field cannot be expressed via the refractive indices of media introduced into the theory for the calculation of mean fields. The results obtained are compared with those previously derived using the Matsubara technique for calculation of the Green’s functions of an electromagnetic field in dispersive media under conditions of thermodynamic equilibrium. The previous results are shown to be incorrect at least for media consisting of atoms or molecules with a discrete energy spectrum.     

Screening of a charged particle field in rarefied ionized gas

A self-consistent field of a charged micron-size particle placed in a rarefied ionized gas is created by both free ions moving along infinite trajectories and trapped ions moving in closed orbits. The character of screening of the particle field is analyzed under dynamic conditions in a nonequilibrium plasma where the temperature (or the mean energy) of electrons greatly exceeds the ion temperature. Under these conditions, trapped ions are generated in a restricted region of the particle field where the transitions between closed ion orbits resulting from resonant charge exchange dominate. This leads to a higher number density of trapped ions compared to that of free ions. The parameters of the self-consistent field of the particle and ions are found when free or trapped ions determine the screening of the particle field, and a similarity law is established for a simultaneous variation of the number density of plasma particles and the particle size. In dusty plasmas of the Solar System, which result from the interaction of the solar wind with dust, formation of trapped ions increases the plasma number density compared to that in the solar wind.     

Nonrelativistic anyons in external electromagnetic field

The first-order, infinite-component field equations we proposed before for nonrelativistic anyons (identified with particles in the plane with noncommuting coordinates) are generalized to accommodate arbitrary background electromagnetic fields. Consistent coupling of the underlying classical system to arbitrary fields is introduced; at a critical value of the magnetic field, the particle follows a Hall-like law of motion. The corresponding quantized system reveals a hidden nonlocality if the magnetic field is inhomogeneous. In the quantum Landau problem spectral as well as state structure (finite vs. infinite) asymmetry is found. The bound and scattering states, separated by the critical magnetic field phase, behave as further, distinct phases.