Dominant Energy Loss Research Articles

Inductive electric field of a time-dependent ring current

The inductive electric field generated by a time-dependent symmetric ring current has been investigated. The symmetric ring current was modelled by a population of protons drifting in a magnetic dipole field. The interaction of these protons with ion-cyclotron waves was assumed to be the dominant energy loss process for the ring current protons, at least under certain conditions. The calculation, with spectral densities for the ion-cyclotron waves that are based on experimental data, showed that an azimuthal inductive electric field of as much as 0.25 mV/m can be produced by this mechanism. Furthermore there is evidence that if the spectral density of the waves is substantially larger than the one adopted here, the electric field might increase to the order of 1.0 mV/m or more.

Longitudinal magnetoresistance in the Extreme Quantum Limit in nonparabolic semiconductors

We calculate the Longitudinal Magnetoresistance in the Extreme Quantum Limit (ħΩ c ⪡ k B T) for a nondegenerate n-type InSb sample at low temperatures when the dominant energy and momentum loss mechanisms are the el-acoustic phonon and the el-ionized impurity interactions. The magnetic field dependence of the effective mass which is due to the nonparabolic nature of the conduction band as well as the energy and magnetic field dependence of the relaxation time are incorporated in the analysis. Analytical results are presented for both nondegenerate and degenerate samples when individual scattering mechanisms are operative. In general nonparabolicity causes an enhancement in the Longitudinal Magnetoresistance and changes the nature of its magnetic field dependence as compared to the case of a parabolic conduction band.

On the Steady Flow of Gas from the Nuclei of Seyfert Galaxies

Heating of gas energy released during explosive events produces hot winds in Seyfert nuclei. Steady-state solutions indicate that supersonic velocities up to about 800 km per sec are obtainable. Lyman continuum radiation emitted by the wind ionizes and maintains temperature of cooler gas clouds seen in emission, and dominates energy losses during early stages of expansion. A study of stability of the thermal equilibrium state leads to a two-component model: a hot stable phase (the wind), in pressure equilibrium with a cooler stable phase (clouds). Extreme variations in cloud electron densities are a consequence of the steep decrease with radius of external pressure. Cloud dynamics are related to the radius of formation and internal parameters. Permitted lines of H are emitted by high-density clouds formed at the base of the wind, while forbidden lines arise in radially moving clouds, produced throughout the wind.

Warm electron effects in GaAs at low temperatures

The field impact ionization of shallow donors in n-type GaAs at low temperatures gives rise to non-ohmic conduction effects. This has been observed in both vapour and liquid phase grown epitaxial GaAs at temperatures between 4.2 K and 20 K. At fields greater than 10 V cm-1 the complete ionization of the donors gives a known carrier concentration which allows the electron mobility as a function of electric field to be investigated. The results have been interpreted in terms of polar mode scattering, being the dominant energy loss process for fields greater than 10 V cm-1, and ionized impurity scattering, being the mobility limiting process. Excellent qualitative and quantitative agreement has been obtained between the experimental and theoretical mobilities.

Energy relaxation of warm holes in p-type tellurium

Measurements of the warm hole energy relaxation time of Te in the temperature range between 150°K and 190°K are reported. Experimental data were obtained using a microwave harmonic mixing method. These energy relaxation times are compared with calculated values assuming polar optical scattering as being the dominant energy loss mechanism in this temperature range. Furthermore, deviations from Ohm's law applying weak and medium d.c. fields to Te samples have been investigated and will be discussed.