Sunset-sunrise characteristics of sporadic layers of ionization in the lower ionosphere observed by the method of resonance scattering of radio waves from artificial periodic inhomogeneities of the ionospheric plasma

Abstract

We present the results of studying the sporadic layers of ionization in the lower ionosphere observed in the sunset-sunrise time during the summer months of 2000 and 2001. Measurements were performed at the "Sura" heating facility of the Radiophysical Research Institute (Nizhny Novgorod, Russia). Based on the analysis of the altitude-time dependences of the amplitude, relaxation time, and phase of the scattered signal, we obtain new data on the formation and dynamics of the evening and nighttime mid-latitude sporadic E layer, present the results of measuring the velocity of the plasma vertical motion, and estimate the relative molecular mass and total number density of metal ions whose pile-up due to the wind shear can cause the formation of the observed sporadic layers.

New Results of Studying the Lower Ionosphere by the Method of Resonance Scattering of Radio Waves from Artificial Periodic Inhomogeneities

“…It was found that the number densities of atmospheric (NO + and O + 2 ) and metal ions depend on the altitude gradient dV/dh of the vertical velocity and the electron number density N s at the maximum of the E s layer. The estimates performed for June 15, 2001 yielded the number densities N m ∼ 7.3 · 10 3 −10 4 cm −3 and N a ∼ (5.3−8) · 10 4 cm −3 of metal and atmospheric ions, respectively, for sporadic layers at the altitudes h ∼ 100−113 km [6]. These values of the total number density of metal ions agree well with the results of lidar and rocket-based measurements.…”

“…Within the framework of the concept that the mid-latitude sporadic E s layer is formed of long-lived metal ions, a method was proposed for determining the molecular mass of these ions, i.e., their sort and concentration, from the altitude dependence of the API relaxation time [6].…”

“…The influence of sporadic ionization on the scattered signal is manifested as a local increase in its amplitude A, which sometimes rises by 30−40 dB, at the altitudes of the E s layer [6]. Obviously, an increase in the signal amplitude is due to an increase in the coefficient of reflection from the E s layer.…”

“…If the critical frequencies of the E s layer and the E region are known, then it is possible to estimate simultaneously the influence of both the refractive index n and the relative molecular mass of metal ions on the relaxation time of the scattered signal: τ Es /τ = (n E /n Es ) 2 (M m /M a ), where M m and M a are the effective molecular masses of metal and atmospheric ions, respectively [6]. Thus, determining the relaxation-time ratio τ Es /τ in the experiment, one can estimate the relative molecular mass of metal ions.…”

Results of studying the sporadic E layer by the method of resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma

“…The method of resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma, which was developed as a complex technique for diagnostics of the ionosphere and neutral atmosphere, has been used for a study of the inhomogeneous structure of the lower ionosphere and sporadic ionization layers for about a decade [1][2][3][4][5][6]. Artificial periodic inhomogeneities are formed in the field of a high-power standing radio wave resulting from the interference of the wave incident on and the wave reflected from the ionosphere.…”