Radio Physics and Radio Astronomy

Number 1, 2021

5-73
THE FOUNDER OF THE DECAMETER RADIO ASTRONOMY IN UKRAINE ACADEMICIAN OF NAS OF UKRAINE SEMEN YAKOVYCH BRAUDE IS 110 YEARS OLD: HISTORY OF CREATION AND DEVELOPMENT OF THE NATIONAL EXPERIMENTAL BASE FOR THE LAST HALF CENTURY

Authors: O. O. Konovalenko, V. V. Zakharenko, L. M. Lytvynenko, O. M. Ulyanov, M. A. Sidorchuk, S. V. Stepkin, V. A. Shepelev, P. Zarka, H. O. Rucker, A. Lecacheux, M. Panchenko, Yu. M. Bruck, P. L. Tokarsky, I. M. Bubnov, S. M. Yerin, V. L. Коliadin, V. M. Melnik, M. M. Kalinichenko, O. O. Stanislavsky, V. V. Dorovskyy, O. D. Khristenko, V. V. Shevchenko, O. S. Belov, A. O. Gridin, O. V. Antonov, V. P. Bovkun, O. M. Reznichenko, V. M. Bortsov, G. V. Kvasov, L. M. Ostapchenko, M. V. Shevchuk, V. A. Shevchenko, Ya. S. Yatskiv, I. B. Vavilova, I. S. Braude, Y. G. Shkuratov, V. B. Ryabov, G. I. Pidgorny, A. G. Tymoshevsky, O. O. Lytvynenko, V. V. Galanin, M. I. Ryabov, A. I. Brazhenko, R. V. Vashchishin, A. V. Frantsuzenko, V. V. Koshovyy, O. L. Ivantyshyn, A. B. Lozinsky, B. S. Kharchenko, I. Y. Vasylieva, I. P. Kravtsov, Y. V. Vasylkivsky, G. V. Litvinenko, D. V. Mukha, N. V. Vasylenko, A. I. Shevtsova, A. P. Miroshnichenko, N. V. Кuhai, Ya. M. Sobolev, N. O. Tsvyk

Abstract

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Purpose: A historical review of the experimental baselopment of low-frequency radio astronomy in Ukraine, its foundation half a century ago by an outstanding scientist S.Ya. Braude to the current state. Design/methodology/approach: The constant progress of electronic, computer and digital technologies, information and telecommunication technologies, theory and practice of antenna and receiving systems design, which introduction enriched the hardware and methodological ideology of construction and usage of the UTR-2, URAN, and GURT radio telescopes, have been used. Findings: The worldwide most effective national experimental radio astronomy means, the UTR-2, URAN, and GURT decameter-meter wave radiotelescopes, have been created and improved. The best combination of the systems main parameters: sensitivity; frequency band; spatial, frequency and temporal resolutions; noise immunity; uniformity of amplitude-frequency and space-frequency characteristics and multifunctionality has been provided. Conclusions: For the half a century of radio astronomical scientific and technical at the Institute of Radio Astronomy of NAS of Ukraine, the high astrophysical informativeness of the low-frequency radio astronomy and the possibility of creating a highly efficient experimental base – giant radio telescopes of decameter-meter wavebands have been proved. Today, the Ukrainian radio telescopes are well known and recognized world-wide being indispensable and most in demand by the scientific community. The founder of the decameter radio astronomy in Ukraine, the eminent scientist Semen Yakovych Braude was not mistaken when he decided to start radio astronomical explorations. The memory of him will always remain in the minds and hearts of many generations

74-89
EXPLORATION OF THE SOLAR DECAMETER RADIO EMISSION WITH THE UTR-2 RADIO TELESCOPE

Authors: V. N. Melnik, A. A. Konovalenko, V. V. Dorovskyy, A. Lecacheux, H. O. Rucker, M. V. Shevchuk

Abstract

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Purpose: The overview of the scientifi c papers devoted to the study of the solar decameter radio emission with the world’s largest UTR-2 radio telescope (Ukraine) published for the last 50 years. Design/methodology/approach: The study and analysis of the scientifi c papers on both sporadic and quiet (thermal) radiation of the Sun recorded with the UTR-2 radio telescope at the decameter wavelength range. Findings: The most signifi cant observational and theoretical results of the solar radio emission studies obtained at the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine for the last 50 years are given. Conclusions: For the fi rst time, at frequencies below 30 MHz, the Type II bursts, Type IV bursts, S-bursts, drift pairs and spikes have been recorded. The dependences of these bursts parameters on frequency within the frequency band of 9 to 30 MHz were obtained. The models of their generation and propagation were suggested. Moreover, for the fi rst time the fi ne time-frequency structures of the Type III bursts, Type II bursts, Type IV bursts, U- and J-bursts, S-bursts, and drift pairs have been observed due to the high sensitivity and high time-frequency resolutions of the UTR-2 radio telescope. The super-fi ne structure of Type II bursts with a “herringbone” structure was identifi ed, which has never been observed before. New types of bursts were discovered: “caterpillar” bursts, “dog-leg” bursts, Type III bursts with decay, Type III bursts with changing drift rate sign, Type III-like bursts, Jb- and Ub-bursts, etc. An interpretation of the unusually high drift rates and drift rates with alternating signs of the Type III-like bursts was suggested. Based on the dependence of spike durations on frequency, the coronal plasma temperature profi le at the heliocentric heights of 1.5–3RS was determined. Usage of the heliographic and interferometric methods gave the possibility to start studies of the spatial characteristics – sizes and locations of the bursts emission sources. Thus, it was shown that at the decameter band, the Type III burst durations were defi ned by the emission source linear sizes, whereas the spike durations were governed by the collision times in the source plasma. It was experimentally proved that the effective brightness temperatures of the sources of solar sporadic radio emission at the decameter band may reach values of 1014–1015 K. In addition, it was found that the radii of the quiet Sun at frequencies 20 and 25 MHz are close to the distances from the Sun at which the local plasma frequency is equal to the corresponding observed frequency of radio emission in the Baumbach–Allen model.