Plasma weakly ionized

A major point of importance is that the electron energy balance, and therefore the average electron energy, in weakly ionized plasmas is independent of electron density. As a consequence, the energy balance can be treated on a per electron basis. From equation (15) the total power density can be established by multiplying by the product of electron and neutral densities. 

In addition to the neutral atmospheric flux of particles, a cold, weakly ionized plasma exists in LEO. The ionospheric plasma density varies dramatically with altitude and latitude. Near the equator at an altitude of 300 km, peak plasma densities and temperatures are 10 cm and 2000 K,... 

The problems involved in modelling weakly ionized plasmas in molecular gases, operated at pressures below about 100 mbar and with average electron energies in the range 0.5—3 eV, are typically those of non-equilibrium systems. 

One notices that 1) all processes start from the ground vibro-electronic state of H2. 2) rotational excitation and thermalization effects of electron- electron interactions have not been included. In fact rotational excitation is important at values of the reduced field E/N lower than those considered in the calculations and electron-electron interactions can be neglected in weakly ionized plasmas (ionization degree Zi 10 5). 

The study of the ionosphere has largely been performed by observation of the properties of radio wave propagation through this medium. In this work we will not attempt to present an exhaustive study of the interaction of electromagnetic waves and a weakly ionized plasma, nor... 

THE BOLTZMANN EQUATION AND TRANSPORT COEFFICIENTS OF ELECTRONS IN WEAKLY IONIZED PLASMAS... 

Weakly ionized plasmas are complex systems involving several interacting particle components. In the simplest case, they consist largely of unexcited atoms, i.e., neutral gas particles, and to a lesser extent of electrons and positive ions. 

The electrons in weakly ionized plasmas generally undergo two basic impacts, namely, the action of an electric (and possibly of an additional magnetic) field and the interaction with heavy particles in binary elastic and inelastic collisions (Desloge, 1966 Shkarofsky et al., 1966 Golant et al, 1980). 

The different microphysical processes—the field action and the various binary collision processes—in which the electrons are involved in a weakly ionized plasma lead to a complex redistribution of the electrons in their phase space, i.e., their combined coordinate and velocity space. 

Commonly this equation and Eq. (35) are used to determine the normalized isotropic distribution. Consideration of Eq. (36) shows that various quantities of the collision processes and a few plasma parameters are involved in its coefficients and naturally have an immediate impact on its solution. With respect to the atomic data of the various collision processes, these are the momentum-transfer cross section Q (U), the total cross sections Qj U), the corresponding excitation or dissociation energies of the ground-state atoms or molecules, and the mass ratio m jM. With regard to the plasma parameters, the electric field strength E and the density N of the atoms or molecules occur, but only in the form of the reduced field strength E/N. All these quantities have to be known for a specific weakly ionized plasma in order to determine the isotropic distribution MU) by solving Eq. (36). 

To illustrate the behavior of electron kinetic quantities in steady-state conditions, weakly ionized plasmas in neon and molecular nitrogen are considered as typical representatives of atomic and molecular gas plasmas. 

By the preceding representations, an attempt has been made to give, on the basis of the electron Boltzmann equation, an introduction to the kinetic treatment of the electron component in steady-state, time-dependent, and space-dependent plasmas and to illustrate by selected examples the large variety of electron kinetics in anisothermal weakly ionized plasmas. 

The Boltzmann Equation and Transport Coefficients of Electrons in Weakly Ionized Plasmas, R. Winkler... 

The temperatiue difference between electrons and heavy neutral particles due to Joule heating in the collisional weakly ionized plasma is conventionally proportional to the sqirare of the ratio of the electric field ( ) to the pressure p). Only in the case of small values of E/p do the temperatiues of electrons and heavy particles approach each other. Thus, this is a basic requirement for local thermodynamic equilibrium (LTE) in plasma. Additionally, LTE conditions require chemical equilibrium as well as restrictions on the gradients. The LTE plasma follows the maj or laws of equilibrium thermodynamics and canbe characterized by a single temperature at each point of space. Ionization and chemical processes in such plasmas are determined by temperature (and only indirectly by the electric fields through Joule heating). The quasi-equilibrium plasma of this kind is usually called thermal plasma. Thermal plasmas in nature canbe represented by solar plasma (Fig. 1-4). 

Although the relationship between different plasma temperatures in non-thermal plasmas canbe quite sophisticated, it canbe conventionally presented in the collisional weakly ionized plasmas as > E > E Ti Tq. Electron temperature (Te) is the highest in the system, followed by the temperature of vibrational excitation of molecules (TV). The lowest temperature is usually shared in plasma by heavy neutrals (To, temperature of translational... 

Eletsky, A.V, Palkina, L.A., Smirnov, B.M. (1975), Transport Phenomena in Weakly Ionized Plasma, Atom-Izdat, Moscow. 

Typical property ranges for weakly ionized plasmas at low pressure (10 Torr) are ... 

For weakly ionized plasmas of molecular species, the radical species can outnumber the ions but are still fewer than the number of neutrals. 

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