Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

Experimental determination of the D-region ionosphere effective recombination coefficients Appleton has shown the analogy between the EC change in the ionosphere and behavior of a linear inductive chain [ Appleton , 1953]. Having differentiated the equation (1) on time, he has received the equation: d l, + 2 a *> ". d, - d, <2 » Comparing it with the equation describing an inductive chain d 2I ^ R d l _ \ de d t2 L dt L dt where I -the electric current flowing through the circuit with resistance of R and inductance of L under the influence of the electromotive force s, one can see the analogy between l/(2acff«e) in the equation (2), describing the ionosphere, and L/R which is the time constant in the equation (3), describing the electric chain. Thus, it is possible to expect that the extremum of the EC profile will be reached through the period x = l/(2aeff/te) after reaching of the extremum by the electron formation speed q. By the analogy with the constant of time L/R of the electric chain Appleton called reaction of the ionosphere to an ionization process as the ionosphere sluggishness with the characteristic constant of time x = l/(2oeffne), which different researchers call as "sluggishness" [Appleton, 1953; Ratcliffe, Weekes, 1963], "relaxation time" [Alpert, 1972; Appleton, 1953] or simply "ionospheric time constant" [Appleton, 1953; Ivanov et al., 2012]. This consideration can be applicable for the processes during a solar eclipse. At the eclipse maximum the electron formation speed q (ionization speed) becomes a minimum one, but at the same time the EC at the chosen height continues to decrease and it reaches the minimum only after some time. This temporary delay between the eclipse maximum (the ionization speed minimum) and the minimum of the EC profiles is defined as x =1 / (2aeffrteq). Thus, knowing the temporary delay between an eclipse maximum and a minimum of the EC profile at the chosen ionosphere height, it is possible to determine the ERC c^ff for this height by the formula: а эфф= 1/{2тея), (4) where г - a temporary delay between the maximum of an eclipse and a minimum of the EC profile; neq - the EC at the time of the minimum of an electron formation speed. For the place of observations parameters of the maximum of a solar eclipse can be determined precisely using astronomical year-books of the Institute of Applied Astronomy RAS, see, for example, [Astronomical Yearbook, 2014]. The minimum of the EC is found from the experimental EC profile at the chosen height. If during an eclipse observations were made at several heights, then there was an opportunity to find values of ERC for each of these heights. 3. Method and facility o f partial reflections The most effective research method of the D-region of the ionosphere is the method of partial reflections (MPR) offered in the early fifties by Gardner and Pawsey [1953]. This method has obtained further development [Belrose, Burke, 1964]. It represents radar sounding of the lower ionosphere in the band of decameter waves. The method is rather simple one in realization and allows receiving data on the EC and parameters of irregularities at the heights o f the lower ionosphere. The cornerstone of the MPR is radiation of ordinary and extraordinary waves in the form of the alternating impulses or linearly polarized wave at frequencies in the range from 2 to 8 MHz and the separate receiving of radio waves dispersed by irregularities of the ionospheric plasma [Rapoport, 1972]. For determination of parameters of the environment, according to MPR, measurements of amplitudes or difference of absorption along trajectories of spreading of ordinary and extraordinary radio waves (the method of differential absorption) are widely used [Belikovich et al., 2004]. The facility of partial reflections of the Polar Geophysical Institute for research of the lower ionosphere consists of the transmitter, the receiver, the transduced phased array and the automated system of data sampling. It is located at the observatory "Tumanny" (69.0N, 35.7E). Key parameters and the technique of processing of signals are specified in the work [Tereshchenko et al., 2003]. Technical characteristics of the radar: working frequencies - 2.60- 2.72 MHz; transmitter power in an impulse - about 60 kW; impulse duration - 15 microsec; sounding frequency - 2 Hz. The antenna array consists of 38 couples of crossed dipoles, occupies the space of 105 m2 and has directional pattern width on the level of half power about 20°. Alternatively two circular polarization are received which are amplified by the receiver of direct amplification with the band of 40 kHz. Registration of signal amplitudes can be Time. UT Figure 1. The two-dimensional picture of the electron concentration distribution on time and height in the day of the eclipse on 20 March 2015 88