Electron Density Profile Measurements Research Articles

Observed redistribution of E-region ionization by neutral winds

Sequential measurements of electron density profiles are compared with the ionization drift velocities derived from simultaneously obtained neutral wind velocities. The measurements resulted from a series of 5 rocket flights launched at Wallops Island during a 6-hr period in the morning of 22 February 1968. The electron density profiles were measured with a Langmuir probe during rocket ascent and the wind profiles were determined from vapor trails released during descent. The computed ion drift velocities describe accurately the upper portion of the electron density profiles which are characterized by a slowly descending layer of enhanced electron density. The small and slowly varying drift velocities in the lower E-region cannot be so simply related to the complex structure observed in the electron density. The data from the upper portion of the electron density profiles are used to calculate the value of the recombination coefficient. This value compares well with laboratory measurements.

Comparison of A3-absorption measurements at 1.f. and rocket measured D-region profiles

The paper is concerned with the comparison of ground-based absorption results at low frequencies and available rocket measurements of D-region electron density profiles at comparable solar zenith angles in the same season. Full-wave treatment is used. In spite of considerable longitude and latitude differences between these measurements, there is reasonable agreement between computed and observed absorption, if the rocket measured electron density and collision frequency profiles are used.

Boundary-layer structure in a shock-generated plasma flow: Part 2. Experiments using a new quantitative schlieren technique

The shock-tube side-wall boundary layer in a 1 eV, high-density argon plasma was studied experimentally using anew, simple, quantitative schlieren technique. The angular refraction of light which enters the shock-tube test section parallel to a side wall and passes through typically 1 mm thick boundary layers was determined in two separate wavelengths. This was done by measuring the displacements of two shadows formed by two thin wires placed in the point source light, which is reflected non-centrally by a concave spherical mirror. The experiments were of exploratory nature only, but clearly demonstrated the feasibility of the new technique in analysing plasma-boundary-layer flows. Measured electron density profiles in the high-temperature region of the sidewall boundary layers agreed within experimental errors with those calculated from the equilibrium-boundary-layer theory.

RADIAL DENSITY PROFILE AND CRITICAL MAGNETIC FIELD MEASUREMENT FOR THE HELICAL INSTABILITY IN A HOLLOW PLASMA COLUMN

The characteristics of the current convective instability in a hollow plasma column are described. Langmuir probe measurements of the radial form of the perturbed electron density reveal that the rotating helix is concentrated towards the outer wall of the discharge vessel. The instability has been shown to occur at a lower critical magnetic field for a hollow plasma cell than for a regular positive column cell of the same dimensions. Neither of these features are considered in previous theoretical work. For both the regular and the hollow positive column, the use of measured electron density profiles in numerically evaluating a stability criterion is shown to give improved agreement between theory and experiment.

Ion Kinetics in the Lower Ionosphere

ABSTRACTA comprehensive re-examination is made of the ion kinetics of the lower ionosphere in the light of recent space measurements of solar XUV radiation, ion composition and electron density profiles, and laboratory measurements of rate constants. The ionic chemistries of the ions NO+, O+2, N+2 and O+ are discussed. An approach in terms of the individual ionic chemistries and the recognition of NO+ abundance below 80 km., introduce some fundamental changes in the equations governing lower ionospheric ionization. Laboratory coefficients are found to be generally consistent with the data excepting for the process N+2 + O2 → O+2 + N2. For the process O+2 + N2 → NO+ + NO, for which laboratory observations give only an upper limit, a value of 1 × 10−18 cm.3/s. is inferred. A value of 3×10−8 cm.3/s. is obtained for the dissociative recombination coefficient of NO+.

Time and Space-Resolved Electron Densities in a Theta Pinch at Various Distances along the Discharge Axis

The influence of the finite length of the discharge coil on the axial behaviour of a theta pinch plasma column is investigated by measuring electron density profiles at various distances from the midplane of the coil along the discharge axis. The resulting line densities were then checked by an independent method. For a parallel trapped magnetic field it was possible in this way to measure end losses and also the collection rate of the contraction wave in the case of an antiparallel trapped magnetic field.

Sounding the ionosphere by incoherent scatter at very high frequencies

Based on the ideas of Rayleigh and Thomson, incoherent-scatter radar was conceived primarily to measure electron-density profiles. However, completely unexpected results revealed the much greater potentialities of the technique.