2. Installation Parameters and Method of Studies

[4]  The method of partial reflections is one of the ground-based methods of quantitative studies of the flare effects in the lower ionosphere [Mitra, 1974]. The characteristics and structural scheme of the measuring partial reflections installation of PGI were described by Tereshchenko et al. [2003]. The installation is located in the vicinity of Tumanny town of the Murmansk Region (69.0o N, 35.7o E). The observations were conducted at frequencies of 2.65-2.78 MHz at the pulse power of the transmitter about 60 kW and pulse duration of 15  m s. The reception of the scattered signals was conducted by receiving-transmitting antenna with the directivity diagram of 19 times 22o at the half-power level. Two circular polarizations were received in turn and were amplified by the receiver with the band of 40 kHz. The registration of the signal amplitudes was performed in the height interval 50-146 km. The step of the data reading was 1.5 km. The receiving instrumentation was equipped by a quick-operating multichannel analog-digital transformer and computer for reception, processing, and analysis of the data. The amplitudes of the ordinary and extraordinary components of the signal were averaged over every minute at all registered altitudes. These data were used for the general estimation of the observation results and then were averaged over time intervals 5-15 min. Using the averaged data, the electron concentration profile Ne(h) was calculated by the method of differential absorption of radio waves described by Belikovich et al. [2003a].

[5]  To obtain the concentration as a function of height in the differential absorption method [Belrose and Burke, 1964], the difference in absorption along the trajectory of propagation of ordinary and extraordinary waves is used. It is assumed that the electron collision frequency vertical profile is known from some other independent data. The method makes it possible to calculate the vertical profile with a vertical shift of pm 1-2 km relative to the corresponding profile of the amplitudes of the scattered signal.

[6]  Extra geophysical equipment was used at carrying out the measurements: the installation for ionospheric drift measurements on the basis of the space diversity reception of the scattered signal, magnetometer, and riometer at a frequency of 32 MHz.


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