Minimum Of Electron Density Research Articles

Deductions of daytime electron density profiles from VLF measurements over a middle latitude path during quiet conditions

The first order mode phase velocity ( v) is assumed only to be a function of zenith angle (χ) along the 8200 km VLF path from Hawaii to Cambridge, Mass. (U.S.A.). On this assumption c v (cos χ) is constructed from VLF phase measurements on 10.2 kHz averaged over 10 days in May 1969. By calculating the phase velocity for a number of electron density profiles, an example is given of a set of electron profiles which could describe the development of electron density profiles of the C- and D-regions during the day. The minimum in VLF phase frequently observed immediately after sunrise is explained by filling up the minimum in electron density between the ionospheric C- and D-layer.

The magnetospheric plasmapause and the electron density trough at the alouette i orbit

The location of the magnetospheric plasmapause or ‘knee’ and the position of the electron density minimum or ‘trough’ at the orbit of the Alouette I satellite near 1000 km have been derived from whistler data and from topside ionograms respectively. A statistical study of the dependence of both knee and trough positions on the degree of magnetic disturbance and on local time during the Summer of 1963 reveals that, in general, within the statistical scatter, the geomagnetic field lines on which each occur are the same. During the local night, the equatorial radial distance to the centre of the plasmapause is described by the relation: R p = 5.64 − (0.78 ± 0.12) √ K p Earth radii, whereas the field line through the centre of the electron density trough is best described by the equation: L T = 5.64 − (1.09 ± 0.22) √ K p . It is inferred that the plasmapause in the magnetosphere and the trough near the exospheric base are related phenomena, and that a sharp decrease of plasma density occurs beyond a particular field line, the position of which depends on local time and on the degree of geomagnetic activity. For magnetically quiet conditions ( K p = 0), this line of force corresponds to L≅ 5.6 near midnight, whereas for moderate magnetic activity ( K p = 3) its L value is approximately 4. The radial distance at which this field line crosses the equatorial plane decreases at a rate of approximately 0.1 Earth radii/hr throughout the local night. The geomagnetic latitude at which the field line concerned reaches an altitude of 1000 km is approximately 57° at 02.00 LT for K p ≅ 3, and decreases at a rate of 1.8° ± 0.4° per unit increase of K p .

Surface Studies of Solids by Total Reflection of X-Rays

Analysis of the shape of the curve of reflected x-ray intensity vs glancing angle in the region of total reflection provides a new method of studying certain structural properties of the mirror surface about 10 to several hundred angstroms deep. Dispersion theory, extended to treat any (small) number of stratified homogeneous media, is used as a basis of interpretation.Curves for evaporated copper on glass at room temperature are studied as an example. These curves may be explained by assuming that the copper (exposed to atmospheric air at room temperature) has completely oxidized about 150A deep. If oxidation is less deep, there probably exists some general reduction of density (e.g., porosity) and an electron density minimum just below an internal oxide seal. This seal, about 25A below the nominal surface plane, arrests further oxidation of more deeply-lying loose-packed copper crystallites.All measurements to date have been carried out under laboratory atmospheric conditions which do not allow satisfactory separation or control of the physical and chemical variables involved in the surface peculiarities. The method, under more controlled conditions of preparation and treatment of the surface, promises to be useful.