Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2013, Vol. 10, No. 4, pp. 154-160
Response of the HF radio wave propagation characteristics to the X-ray flux variations
V.A. Ivanova
1, N.M. Polekh
1, V.I. Kurkin
1, L.V. Chistyakova
1, M.D. Pezhemskaya
1, I.G. Brynko
1, A.I. Orlov
1, A.V. Podlesny
1, Z.P. Dumbrava
2, I.N. Poddelsky
21 Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia
2 Institute of Cosmophysical Researches and Radio Wave Propagation FEB RAS, Paratunka, Kamchatka region, Russia
In this work we carry out the analysis of HF oblique-incidence and quasi-vertical sounding data over paths located in the Siberian and Far Eastern regions. For four M-class solar flares registered on 30.07.2011 (М9.3), 02.08.2011 (М1.4), 04.08.2011 (М9.3) and 09.08.2011 (M2.5) the lowest observed frequencies (LOF) have been evaluated. LOF values characterize signal absorption over the paths. LOF variations for studied days have been compared with LOF variations for 24.07.2011 when there were registered no solar flares and magnetic field was quiet. Sharp LOF increases during investigated X-ray solar flares in comparison with quiet conditions were registered over all paths. In the moment of maximum of X-ray of solar flares (by GOES satellite data) disappearance of reflections from Es- and F1-layers has been observed, HF signals propagation occurred by means of reflections from F2-layer. Thereby as a result of our investigation of response of the HF radio wave propagation characteristics to the X-ray flux variations sharp increase of radio waves absorption and decrease of frequency range during solar flares has been observed.
Keywords: распространение декаметровых радиоволн, наинизшая наблюдаемая частота, всплески рентгеновского излучения, внезапное ионосферное возмущение, high frequency radio wave propagation, lowest observed frequency, X-ray solar flares, sudden ionospheric disturbance
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