Results of Determining the Electron Number Density in the Ionospheric E Region from Relaxation Times of Artificial Periodic Irregularities of Different Scales

Abstract

We present the first results of determining the electron number density in the ionospheric E region by a novel technique based on the creation of artificial periodic irregularities when the ionosphere is affected by powerful radio emission at two frequencies. Using the results of the measurements performed in October 2006 during heating of the ionosphere by the "Sura" facility radiation at frequencies 4.7 and 5.6 MHz, we obtained the electron number density profiles in an altitude range of 100 to 110 km. Features of the procedure of measurement and calculation of the electron number density are described in detail. It is shown that the method can be used for a study of the irregular structure of the lower ionosphere.

Altitude–time variations in electron number density in the ionospheric E layer

“…To determine the electron-density profile at altitudes 95-125 km, we employ a method implemented in recent years [11][12][13]. For this, periodic structures with two different spatial scales are created almost simultaneously (each 15 s), which is provided by high-power heating of the ionosphere by radio waves with different frequencies.…”

“…The electron number density was determined by the method of resonant scattering of radio waves by artificial periodic irregularities of the ionospheric plasma with respect to relaxation times of the signals scattered by periodic structures with two different spatial scales [11][12][13].…”

Artificial periodic irregularities, wave phenomena in the lower ionosphere, and the sporadic E layer

“…The results of studying the sporadic E layer, which were obtained in the experiment of October 2006, as well as the electron-density profiles obtained in these measurements by the two-frequency method are presented in [11,13,14]. The disadvantages of the above-said measurements include the technical impossibility of using the data about the phase of the scattered signal, which are used to determine the vertical velocity of the plasma motion.…”

“…As a result, for an altitude of 100 km we find ion masses M m = 58 and 44, which are close to the masses of Fe + and Ca + . To determine the molecular mass of positive metal ions at the altitude of the sporadic E layer, we used the profiles of electron density in the sporadic layer and the background E region, which were determined by the two-frequency method using the directions from [10,11]. Figure 6 shows an example of the profile of elec- Fig.…”

“…It was based on the concept of formation of the sporadic layer from long-living metal ions, as well as on measurement of the vertical plasma motion and frequency characteristics of the E s layer. The latter were determined first from the vertical-sounding ionograms and further, from the profile of the electron density, which was determined in the experiments aimed at creating artificial periodic irregularities almost simultaneously at two frequencies, i.e., on two different spatial scales [10,11]. This approach allows one to use the results of measuring the relaxation time of the scattered signal, which depends on the frequency used to create artificial periodic irregularities, for independent determination of the altitude profile of the electron density in the E region of the ionosphere, and the temperature and density of the neutral component.…”