Учреждения:
1 - ФГОУ ВПО Южный федеральный университет», 344090, г. Ростов-на-Дону, ул. Зорге, 5
2 - ФГБНУ Научно-исследовательский радиофизический институт

Аннотация:
Представлены результаты первых экспериментов по исследованию неоднородной структуры экваториальной ионосферы на трассе Лейвертон (Австралия) - Ростов-на-Дону протяженностью 11790 км с помощью нового инструмента - ЛЧМ ионозонда-радиопеленгатора, позволяющего одновременно проводить измерения дистанционно-частотных (ДЧХ), амплитудно-частотных (АЧХ) и угловых в диапазоне частот (УЧХ) - т.е. ключевых характеристик ионосферного КВ канала во всем диапазоне частот прохождения радиосигналов на выбранных трассах.

Ключевые слова: загоризонтная радиолокация, ионосфера, ЛЧМ зондирование.

Сведения об источниках финансирования: -

Institutions:
1 - Federal State Educational Institution of Higher Professional Education Southern Federal University, 5 Sorge St., Rostov-on-Don, 344090
2 - FSBI Scientific Research Radiophysical Institute

Abstract
In the ionospheric research a great attention is given to studying formation and existence features of equatorial spread F (ESF). The ESF is a complex phenomenon of night equatorial ionosphere with plasma instabilities hierarchy resulting at favorable ionospheric and termospheric conditions for electronic concentration irregularities generation of wide spectrum of scales. Equatorial irregularities render essential influence at work of communication and navigating systems causing amplitude and phase fluctuations of radio signals.
In the report the research results concerning the inhomogeneous structure of equatorial ionosphere Laverton (Aus-tralia) Rostov-Don path at distance 117900 km with help of new tool LFM ionosonder-radiodirection finder are pre-sented. This tool allows measuring all key parameters ionospheric HF channel (distance-frequency-characteristic (DFC), amplitude-frequency-characteristic (AFC) and angle-frequency-characteristic (AnFC)) in entire range of fre-quencies of radio signals passage. In experiment our tool is used as over-the-horizon LFM HF radar bistatic conditions.
Measurements were carried out in 2010-2012. During evening and night time for the given path abnormal signals were registered as several tracks at frequencies above maximum observed frequency (MOF) of a direct signal (NOF=13,6 MHz) occupying interval of frequencies ~9,8-15,1MHz. Though abnormal signals contained a spreading component, basically these signals have been located on delays: 42,6-43,8 ms, 44-45,2 ms and 46,8-48 ms and azimuth angles of arrival: 85-91, 81-84,7 and 72-79 respectively. Azimuth angle of arrival of a direct signal makes 115. Positioning of areas responsible for occurrence of scattering signals was carried out on the basis of modeling in view of DFC and AnFC measurements.
It is shown that area responsible for formation scattering signals looks like quasi-periodic structure extended ap-proximately in north-southern direction with spatial quasi-period between crests ~400-700 km. This area falls at region in the vicinity of geomagnetic equator. We believe that nature of signals is connected with radio waves scattering from traveling ionospheric disturbances (TIDs). Such quasi-periodic structures are the ionospheric response of atmospheric gravitational waves (AGW). Results of many experimental and theoretical works indicate the essential role of AGW in equatorial irregularities initiation accompanying ESF phenomenon. It is marked that the modulation by wave disturb-ance of electronic density gradient reduces a threshold of development of the Rayleigh-Taylor plasma instability and results to the formation of equatorial irregularities.

Keywords: over-the-horizon HF radiolocation, ionosphere, LFM sounding.

Information about sources of financing: -