Residual Electric Field Research Articles

Runaway and wave-induced currents

The present understanding (May 1983) of current drive by lower hybrid waves in Tokamak plasmas is reviewed with particular stress on the theory. First, the classical model of Fisch and its variants are discussed in light of recent experimental data. It is argued that these simple models do not account for most of the features of the results obtained. Next, effects of runaways on current generation are considered. It is shown that runaways, resulting from a residual ohmic electric field, may play an important role. Further, the mechanism of runaway-current sustainment, as proposed by LIU et al. (1982b) is re-examined. It is shown that, for a realistic range of parameters, this mechanism does not allow a significant current to be sustained. Finally, some results of a recently-developed numerical code, which include the evolving electron distribution function, ray tracing and transport, are briefly noted. It is concluded that none of the existing theories can be used to interpret satisfactorily all the experimental observations.

Measurement of Electric Fields at a Dielectric/Electrode Interface Using an Acoustic Transducer Technique

A newly developed electro-acoustic transducer technique is applied to the measurement of electric field intensity at a dielectric/electrode interface. This report describes the principles of this new technique as applied to: the residual electric field intensity by a sheet charge and its location in PET film, to the amount of residual charge density and its polarity in PET thermal electret, and to the electric field intensity at electrode surfaces, including the effects of homo-charge injected from electrodes for PET, PS, and PE films, hetero-charge generated from impurities in epoxy resin, and dipole polarization in PVDF film and tricresyl-phosphate liquid.

Effects of ion sputtering on semiconductor surfaces

Ion beam sputtering has been combined with Auger spectroscopy to study the effects of ion beams on semiconductor surfaces. Observations on the mass dependence of ion selective sputtering of two component systems are presented. The effects of ion implantation are explained in terms of atomic dilution. Experimental data are presented that illustrate the superposition of selective sputtering and implantation effects on the surface composition. Sample reduction from electron and ion beam interaction is illustrated. Apparent sample changes which one might observe from the effects of residual gas contamination and electric fields are also discussed.

Thermospheric response to a magnetic substorm

A computer model is used to simulate the winds and temperature variations in the thermosphere which result from auroral region electric currents during a large isolated magnetic substorm. A disturbance propagates with a speed of 750 m/s poleward and equatorward, with an amplitude of about 200 m/s in the north-south velocity and about 100 K in the temperature at 400-km altitude. The amplitude decays relatively little before the disturbance reaches the equator. The time history of the disturbance is roughly that of a single sinusoid whose period increases with horizontal distance from the source and with decreasing altitude. East-west winds of over 400 m/s at 400-km altitude are created in the auroral region itself by the ion drag mechanism. The spatial distribution of these ion drag winds is significantly affected by momentum convection, so that a simple interpretation in terms of local ion drag forces is generally not sufficient. A residual electric field of about 5 mV/m remains after the substorm source is turned off, due to the dynamo effect of the ion drag winds. Vertical velocities up to about 40 m/s are produced inside the auroral region, primarily by the fact that the heated air is more buoyant than the air outside. Comparison of our simulation with numerous observations shows generally good agreement.

725. Significance of the glowing region near the cathode and residual electric field in it for existence of glow discharge: P Bause, Wiss Z Techn Hochsch Ilmenau, 17 (3), 1971, 97–113 (in German)

725. Significance of the glowing region near the cathode and residual electric field in it for existence of glow discharge: P Bause, Wiss Z Techn Hochsch Ilmenau, 17 (3), 1971, 97–113 (in German)

Ionic forces and membrane phenomena

When a membrane containing diffusible ions is perturbed by an electric field, osmotic and electric relaxation forces are developed. These are calculated for an infinitesimal impulse perturbation. The force characteristics are dependent on the shape of the fixedcharge distribution. The electric force is proportional to the concentration difference, while the osmotic force is proportional to the second derivative of the chemical potential. The residual electric field gives rise to membrane reactance. With two diffusible cations having different concentrations and mobilities, two decaying potential terms are obtained. Under certain conditions these may be represented as due to a real RLC electric circuit. If the mobility of a diffusible cation varies in the membrane, it is possible for the osmotic force to cancel the electric. The case is examined for mobility inversely proportional to the negative fixed charge density, and the requisite charge distribution calculated. It appears that this effect may be of importance in explaining the activity of the axonal membrane. Boundary forces are examined in detail in the Appendices, including the effect of lack of equilibrium. Force relationships are calculated for the uniform fixed-charge membrane.