Search

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. Key words: UTR-2; Sun; decameter radio emission; radio bursts; corona

Purpose: Theoretical studies of sensitivity fluctuations of a phased array antenna element for the GURT radio telescope of the new generation caused by seasonal changes of the ground parameters. Design/methodology/approach: A mathematical model of an active antenna represented as a two-port network, whose electrical parameters are described with the scattering matrix and the noise parameters – with the covariation matrix of noise wave spectral densities was used for studying the GURT phased array antenna element composed of a dipole and a low-noise amplifier (LNA). Such a model allows a correct analysis of a signal-to-noise ratio at the active antenna output accounting for all internal and external noise sources. Findings: A numerical analysis of the GURT radio telescope phased array antenna element characteristics was made in a wide frequency range of 8 to 80 MHz. It was found that the seasonal fluctuations of permittivity and conductivity of the ground, which make about 8 and 6 dB correspondingly, mostly affect the dipole efficiency and its impedance matching with the LNA. Variations of both parameters reach 3 dB but have the opposite sign, therefore their effect upon the active antenna sensitivity is mostly compensated. As a result, it is shown that the seasonal fluctuations of the ground parameters do not result in the substantial active antenna sensitivity variations, which lay in about the 0.5 dB range, and only at the lowest frequencies grow to about the 1.5 dB value. Conclusions: The research efforts made have shown that the seasonal fluctuations of the ground electrophysical parameters result in small variations of the sensitivity of the GURT phased ±0.75 dB, which cannot array antenna element, not exceeding affect the quality of radio-astronomy observations considerably. The results of this work can be useful in the development and researches of the ground active phased array antennas designed for operation in the meter and decameter wavelength ranges.

УДК 520.272.2:621.396.677.494 PACS number: 95.55.-Jz Предмет и цель работы: Создание радиотелескопа на основе антенной системы МАRК-4В, которая была разработана для телекоммуникационных приложений, определение возможностей использования лучеводной антенной системы в широкополосном многодиапазонном режиме работы и оценка характеристик антенны с помощью радиоастрономических измерений. Методы и методология: Комплексный анализ всех систем МАRК-4В дает возможность выделить блоки и узлы, которые подлежат замене или модернизации. Анализ конструкции рефлектора и субрефлектора, лучевода, гофрированного рупора и волноводной системы позволяет определить возможные частотные диапазоны работы создаваемого радиотелескопа. Установка широкополосного приемника с предусмотренной возможностью калибровки по охлаждаемой и неохлаждаемой нагрузке позволяет определить температуру антенной системы. Наведение антенны на калибровочные источники и запись сканов за счет вращения Земли исключает систематические ошибки или погрешности системы наведения. Таким образом определяется ширина диаграммы направленности и эффективная площадь радиотелескопа. Результаты: Произведен анализ конструкции антенны и определены первоочередные этапы реконструкции антенной системы МАRК-4В. Демонтированы узкополосные передатчик и приемник диапазона С и установлен широкополосный приемник (диапазон 4.6÷5.1 ГГц ) с детектором и возможностью изменения времени интегрирования сигнала. По результатам наблюдений сделаны первоначальные оценки температуры шумов системы, которые позволяют надеяться на то, что радиотелескоп РТ-32 (г. Золочев, Львовская обл., Украина) совместно с охлаждаемым приемником будет обладать низкими собственными шумами. Рассчитана и установлена новая система наведения антенны, с помощью которой в С диапазоне проведены астрономические тесты ширины диаграммы направленности ( ≈ 7.2 ′ ) и уровня ее боковых лепестков (–12.5 дБ), эффективной площади ( ≈ 680 м 2 ) и коэффициента использования поверхности ( ≈ 0.84 ). Заключение: Выполненные измерения и расчеты показывают, что на базе антенной системы МАRК-4В возможно создать высокоэффективный радиоастрономический инструмент. Разработанные на данный момент системы приема и наведения для радиотелескопа РТ-32 свидетельствуют о высоком потенциале украинской науки. Дальнейшая кооперация научных исследований и высоких технологий приведет к созданию эффективного украинского радиотелескопа сантиметрового диапазона. Ключевые слова: антенна, излучатель, интерферометрия, поляризация, радиоастрономия, радиоисточник, радиотелескоп, сервер, стандарт частоты Статья поступила в редакцию 11.03.2019 Radio phys. radio astron. 2019, 24(2): 87-116 СПИСОК ЛИТЕРАТУРЫ 1. Woodburn L., Natusch T., Weston S., Thomasson P., Godwin M., Granet C., and Gulyaev S. Conversion of a New Zealand 30-metre telecommunications antenna into a radio telescope. Publ. Astron. Soc. Aust. 2015. Vol. 32. id. e017. DOI: 10.1017/pasa.2015.13 2. Petrov L., Natusch T., Weston S., McCallum J., Ellingsen S., and Gulyaev S. First scientific VLBI observations using New Zealand 30 meter radio telescope WARK30M. Publ. Astron. Soc. Pac. 2015. Vol. 127, No. 952. P. 516–522. DOI: 10.1086/681965 3. Yonekura Y., Saito Y., Sugiyama K., Soon K. L., Momose M., Yokosawa M., Ogawa H., Kimura K., Abe Y., Nishimura A., Hasegawa Y., Fujisawa K., Ohyama T., Kono Y., Miyamoto Y., Sawada-Satoh S., Kobayashi H., Kawaguchi N., Honma M., Shibata K. M., Sato K., Ueno Y., Jike T., Tamura Y., Hirota T., Miyazaki A., Niinuma K., Sorai K., Takaba H., Hachisuka K., Kondo T., Sekido M., Murata Y., Nakai N., and Omodaka T. The Hitachi and Takahagi 32 m radio telescopes: Upgrade of the antennas from satellite communication to radio astronomy. Publ. Astron. Soc. Jpn. 2016. Vol. 68, Is. 5. id. 74. DOI: 10.1093/pasj/psw045 4. Venter M. and Bolli P. Electromagnetic analysis and preliminary commissioning results of the shaped dual-reflector 32-m Ghana radio telescope. IOP Conf. Ser. Mater. Sci. Eng. 2018. Vol. 321, Is. 1. id. 12003. DOI: 10.1088/1757-899X/321/1/012003 5. Imbriale W. A. Evolution of the Deep Space Network 34-m diameter antennas. IEEE Aerospace Conference Proceedings. (March 21–28, 1998. Snowmass). Snowmass, CO, USA, 1998. Vol. 3. P. 403–430 DOI: 10.1109/AERO.1998.685847 6. Imbriale W. A. Large Antennas of theDeep Space Network. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2003. 320 p. 7. Mizusawa M. and Kitsuregawa T. A Beam-waveguide Feed Having a Symmetric Beam for Cassegrain Antennas. IEEE Trans. Antennas Propag. 1973. Vol. 21, Is. 6. P. 884–886. DOI: 10.1109/TAP.1973.1140628 8. Korolev A. M., Zakharenko V. V., and Ulyanov O. M. Radio astronomy ultra-low-noise amplifier for operation at 91 cm wavelength in high RFI environment. Exp. Astron. 2016. Vol. 41, Is. 1-2. P. 215–221. DOi: 10.1007/s10686-015-9466-x 9. Konovalenko A., Sodin L., Zakharenko V., Zarka P., Ulyanov O., Sidorchuk M., Stepkin S., Tokarsky P., Melnik V., Kalinichenko N., Stanislavsky A., Koliadin V., Shepelev V., Dorovskyy V., Ryabov V., Koval A., Bubnov I., Yerin S., Gridin A., Kulishenko V., Reznichenko A., Bortsov V., Lisachenko V., Reznik A., Kvasov G., Mukha D., Litvinenko G., Khristenko A., Shevchenko V. V., Shevchen-ko V. A., Belov A., Rudavin E., Vasylieva I., Miroshnichenko A., Vasilenko N., Olyak M., Mylostna K., Skoryk A., Shevtsova A., Plakhov M., Kravtsov I., Volvach Y., Lytvinenko O., Shevchuk N., Zhouk I., Bovkun V., Antonov A., Vavriv D., Vinogradov V., Kozhin R., Kravtsov A., Bulakh E., Kuzin A., Vasilyev A., Brazhenko A., Vashchishin R., Pylaev O., Koshovyy V., Lozinsky A., Ivantyshin O., Rucker H. O., Panchenko M., Fischer G., Lecacheux A., Denis L., Coffre A., Griesmeier J.-M., Tagger M., Girard J., Charrier D., Briand C., and Mann G. The modern radio astronomy network in Ukraine: UTR-2, URAN and GURT. Exp. Astron. 2016. Vol. 42, Is. 1. P. 11–48. DOI: 10.1007/s10686-016-9498-x 10. Zakharenko V., Konovalenko A., Zarka P., Ulyanov O., Sidorchuk M., Stepkin S., Koliadin V., Kalinichenko N., Stanislavsky A., Dorovskyy V., Shepelev V., Bubnov I., Yerin S., Melnik V., Koval A., Shevchuk N., Vasylieva I., Mylostna K., Shevtsova A., Skoryk A., Kravtsov I., Volvach Y., Plakhov M., Vasilenko N., Vasylkivskyi Y., Vavriv D., Vinogradov V., Kozhin R., Kravtsov A., Bulakh E., Kuzin A., Vasilyev A., Ryabov V., Reznichenko A., Bortsov V., Lisachenko V., Kvasov G., Mukha D., Litvinenko G., Brazhenko A., Vashchishin R., Pylaev O., Koshovyy V., Lozinsky A., Ivantyshyn O., Rucker H. O., Panchenko M., Fischer G., Lecacheux A., Denis L., Coffre A., and Gries-meier J.-M. Digital Receivers for Low-Frequency Radio Telescopes UTR-2, URAN, GURT. J. Astron. Instrum. 2016. Vol. 5, Is. 4. id. 1641010. DOI: 10.1142/S2251171716410105

Solar wind is a set of flows with different parameters (the speed, the exponent of the spectrum of heterogeneities, the width, etc.). A bimodal character of the speed distribution of the solar wind was determined in spaceborne experiments. The measurements onboard the Ulysses spacecraft confirmed that the bimodal structure of solar wind continues to persist at relatively large distances from the Sun (to several astronomical units). However, there is one more possibility to determine the stream structure of solar wind. This is the method of interplanetary scintillations. The purpose of the paper is to reconstruct the stream structure of solar wind beyond the Earth’s orbit using the data on interplanetary scintillations obtained at two observational sites. The experiments were carried out at decameter wavelengths, since they are rather strongly scattered by the rarefied interplanetary plasma beyond the Earth’s orbit. The experimental data on interplanetary scintillations analyzed in this work were obtained in synchronous observations with the UTR-2 and URAN-2 radio telescopes. The parameters of solar wind and its stream structure were determined by comparison of the characteristics of interplanetary scintillations measured in the experiment (the dependences of the harmonic velocity of the cross-spectrum of scintillations and the power spectra) to those calculated with the models. To separate the interplanetary and ionospheric scintillations, the spectral, spatial, and frequency criteria were used. The results of this analysis show that solar wind beyond the Earth’s orbit consists of several streams that replace each other on the line of sight toward the radio source. These investigations prove the reliability and efficiency of the interplanetary scintillation method for reconstructing the stream structure of solar wind.

International audience; Cutting edge astrophysical studies require more and more observing time at low-frequency radio telescopes, which is limited and quite expensive. Modern digital signal processing systems still unable to provide affordable computational and storage resources to allow simultaneous beamforming in a wide frequency range for multiple studies. Low-frequency radio telescopes of a new generation are very flexible and could be split into subarrays or groups of subarrays for some studies which do not require large antenna effective area and high directivity. In this paper we make a survey of astrophysical studies in the frequency range 8-80 MHz using a rather small part of the low-frequency radio telescope GURT - the subarray of 25 active antennas.

Lightning was detected by Voyager 2 at Uranus and Neptune, and weaker electrical processes also occur throughout planetary atmospheres from galactic cosmic ray (GCR) ionisation. Lightning is an indicator of convection, whereas electrical processes away from storms modulate cloud formation and chemistry, particularly if there is little insolation to drive other mechanisms. The ice giants appear to be unique in the Solar System in that they are distant enough from the Sun for GCR-related mechanisms to be significant for clouds and climate, yet also convective enough for lightning to occur. This paper reviews observations (both from Voyager 2 and Earth), data analysis and modelling, and considers options for future missions. Radio, energetic particle and magnetic instruments are recommended for future orbiters, and Huygens-like atmospheric electricity sensors for in situ observations. Uranian lightning is also expected to be detectable from terrestrial radio telescopes., Revised version for Space Science Reviews

УДК 524.354.4, 52-17 PACS numbers: 97.60.Gb, 98.38.Am Предмет и цель работы: Самой сложной задачей исследования транзиентных сигналов является доказательство их космического происхождения. В декаметровом диапазоне не существует ни одного радиотелескопа, который по эффективной площади (а значит, и по мгновенной чувствительности) хотя бы приближался к параметрам УТР-2. Это исключает возможность подтверждения космического происхождения низкоинтенсивных сигналов на каком-либо другом независимом радиотелескопе данного диапазона. Поэтому важность проведения всевозможных тестов для проверки возможного помехового происхождения сигналов-кандидатов нельзя переоценить. В работе проводится анализ распределений характеристик обнаруженных транзиентных сигналов и поиск возможных низкоинтенсивных помех в данных декаметрового обзора пульсаров и источников транзиентного излучения северного неба. Методы и методология: Обработка данных обзора с целью поиска симметричных по времени запаздывания помех из-за мерцаний на неоднородностях ионосферной плазмы, имеющих частотно-временные зависимости, которые похожи на дисперсионное запаздывание в межзвездной среде. Результаты: Сравнение распределений таких характеристик, как сигнал/шум и мера дисперсии, показывает существенное отличие продетектированных в проводимом обзоре сигналов от гипотетических помех, которые имели бы такое же значение смещения нижних частот рабочего диапазона по отношению к верхним, но вместо запаздывания характеризовались бы опережением. Эти различия подтверждают гипотезу о том, что обнаруженные в проводимом обзоре транзиентные сигналы порождаются источниками космического радиоизлучения. Заключение: Расширение конуса радиоизлучения различных типов нейтронных звезд, большое угловое и временное рассеяние в декаметровом диапазоне может объяснить детектирование большого количества одиночных сигналов с уникальными значениями мер дисперсии, т. е. ряда источников транзиентого излучения. Ключевые слова: обзор, одиночный импульс, помеха, мера дисперсии, мерцания, декаметровый диапазон Статья поступила в редакцию 19.04.2018 Radio phys. radio astron. 2018, 23(2): 79-93 СПИСОК ЛИТЕРАТУРЫ 1. Захаренко В. В. Спорадическое излучение радиоастрономических источников и его исследование в декаметровом диапазоне. Радиофизика и радиоастрономия . 2011. Т. 16, № 2. С. 121–134. 2. Zakharenko V. V., Kravtsov I. P., Vasylieva I. Y., Mykhailova S. S., Ulyanov O. M., Shevtsova A. I., Skoryk A. O., Zarka P., and Konovalenko O. O. Decameter pulsars and transients survey of the northern sky. Status, first results, multiparametric pipeline for candidate selection. Odessa Astronomical publications . 2015. Vol. 28, Is. 2. P. 252–255. DOI: https://doi.org/10.18524/1810-4215.2015.28.71047 3. Захаренко В. В., Кравцов И. П., Васильева Я. Ю. Декаметровый обзор северного неба с целью поиска пульсаров и источников транзиентного излучения. Параметры индивидуальных импульсов. Радиофизика и радиоастрономия . 2017. Т. 22, № 1. C. 31–44. DOI: https://doi.org/10.15407/rpra22.01.031 4. Vasylieva I. Y., Zakharenko V. V., Zarka P., Ulyanov O. M., Shevtsova A. I., and Seredkina A. A. Data processing pipeline for decameter pulsar/transient survey. Odessa Astronomical publications . 2013. Vol. 26, Is. 2. P. 159–161. 5. Vasylieva I. Y., Zakharenko V. V., Konovalenko A. A., Zarka P., Ulyanov O. M., Shevtsova A. I., and Skoryk A. O. Decameter Pulsar/Transient Survey of Northern Sky. First results. Радиофизика и радиоастрономия . 2014. Т. 19, № 3. С. 197–205. DOI: https://doi.org/10.15407/rpra19.03.197 6. Vasylieva I. Y. (2015). Pulsars and transients survey, and exoplanet search at low-frequencies with the UTR-2 radio telescope: methods and first results. Phd Thesis ed. Observatoire de Paris . URL: h https://tel.archives-ouvertes.fr/tel-01246634 7. Kravtsov I. P., Zakharenko V. V., Vasylieva I. Y., Mykhailova S. S., Ulyanov O. M., Shevtsova A. I., and Skoryk A. O. Parameters of the transient signals detected in the decameter survey of the Northern sky. Odessa Astronomical publications . 2016. Vol. 29. P. 179–183. DOI: https://doi.org/10.18524/1810-4215.2016.29.85210 8. Petroff E., Keane E. F., Barr E. D., Reynolds J. E., Sarkissian J., Edwards P. G., Stevens J., Brem C., Jameson A., Burke-Spolaor S., Johnston S., Bhat N. D. R., Chandra P.,Kudale S., and Bhandari S. Identifying the source of perytons at the Parkes radio telescope. Mon. Not. R. Astron. Soc . 2015. Vol. 451, Is. 4. P. 3933–3940. DOI: https://doi.org/10.1093/mnras/stv1242 9. Zakharenko V. V., Vasylieva I. Y., Konovalenko A. A., Ulyanov O. M., Serylak M., Zarka P., Griessmeier J.-M., Cognard I., and Nikolaenko V. S. Detection of decametre-wavelength pulsed radio emission of 40 known pulsars. Mon. Not. R. Astron. Soc . 2013. Vol. 431, Is. 4. P. 3624–3641. DOI: https://doi.org/10.1093/mnras/stt470 10. Cordes J. M. and McLaughlin M. A. Searches for fast radio transients. Astrophys. J . 2003. Vol. 596, Is. 2. P. 1142–1154. DOI: https://doi.org/10.1086/378231 11. Maan Yogesh. Discovery of Low DM Fast Radio Transients: Geminga Pulsar Caught in the Act. Astrophys. J . 2015. Vol. 815, Is. 2. id. 126. DOI: https://doi.org/10.1088/0004-637X/815/2/126 12. Keane E. F., Bhattacharyya B., Kramer M., Stappers B. W., Bates S. D., Burgay M., Chatterjee S., Champion D. J., Eatough R. P., Hessels J. W. T., Janssen G., Lee K. J, van Leeuwen J., Margueron J., Oertel M., Possenti A., Ransom S., Theureau G., and Torne P. A Cosmic Census of Radio Pulsars with the SKA. Proceedings of the Conference “Advancing Astrophysics with the Square Kilometre Array (AASKA14)” (June 9-13, 2014. Giardini Naxos). Giardini Naxos, Italy, 2014. id. PoSAASKA14)040. 13. Manchester R. N., Hobbs G. B., Teoh A., and Hobbs M. The Australia Telescope National Facility Pulsar Catalogue. Astron. J . 2005. Vol. 129, Is. 4. P. 1993–2006. DOI: https://doi.org/10.1086/428488 14. Cordes J. M. Observational limits on the location of pulsar emission regions. Astrophys. J . Part 1. 1978. Vol. 222. P. 1006–1011. DOI: https://doi.org/10.1086/156218 15. Keane E. F. and Kramer M. On the birthrates of Galactic neutron stars. Mon. Not. R. Astron. Soc . 2008. Vol. 391, Is. 4. P. 2009–2016. DOI: https://doi.org/10.1111/j.1365-2966.2008.14045.x 16. Malofeev V. M., Malov O. I., and Teplykh D. A. Radio emission from AXP and XDINS. Astrophys. Space Sci . 2007. Vol. 308, Is. 1–4. P. 211–216. DOI: https://doi.org/10.1007/s10509-007-9341-y

Purpose: Theoretical and experimental investigations of noise temperature of a subarray being a part of the active phased array for the GURT – a low frequency radio telescope of new generation. Design/methodology/approach: A mathematical model of the active phased array is developed in the form of a cascade connection of two noisy multiport networks, one of which is associated with the dipole array antenna placed over imperfect ground, and the other with the beam-forming network. The electrical parameters of these multiport networks are described by the scattering matrices, and the noise parameters – by the covariance matrix of the spectral densities of noise waves. The calculation expressions are obtained which allow analyzing the GURT subarray noise temperature with correct account for all internal noise sources and their mutual correlation which is caused by interaction of dipoles in the array. Findings: Numerical and experimental studies of the noise temperature at the subarray output of the GURT active phased antenna array have been performed. These studies made it possible to estimate the relation between the external and internal noise temperatures in a wide frequency range from 8 to 80 MHz when scanning the subarray beam in the upper hemisphere. It is shown that the external noise temperature at the subarray output is more than 6 dB higher than the internal one in the bandwidth of about 65 MHz. Good agreement between the results of calculation and experiment is obtained, that validates the developed model of the GURT subarray and the effectiveness of the proposed technique for numerical analysis of its parameters. Conclusions: The studies described here confirm the possibility of effective use of this subarray as the base cell of a large phased antenna array for the low frequency radio telescope, as well as the standalone antenna of the radio telescope when radio astronomical observations do not require high angular resolution. The results of this work can be useful in the development and studies of active phased antenna arrays for the decameter and meter wave ranges.

PACS numbers: 95.55.Jz, 95.30.-k, 95.55.-n Purpose: overview of the main results of half a century activities of Ukraine (with emphasis on the last decade) in the field of decameter radio astronomy, presenting a number of astrophysical discoveries in the study of the Solar system, Galaxy and Metagalaxy, demonstration of favorable prospects for the Ukrainian and world-wide low-frequency radio astronomy. Design/methodology/approach: The world-largest Ukrainian decameter wavelength radio telescopes UTR-2, URAN, GURT in comprehensive studies of various astrophysical objects in the Universe, as well as special techniques of radio astronomy observations, providing high sensitivity, resolution, dynamic range, noise immunity and research efficiency were applied. Findings: Extensive search efforts and long-term monitoring studies of low-frequency radio emission were made with the best parameters of the experiments for the Sun, planets, solar wind, interstellar medium, galactic background and of extended objects, pulsars, transients, radio galaxies, and quasars. New objects and phenomena in the Universe were opened, in particular, the regions of the cold interstellar medium with ionized carbon, and the corresponding spectral lines of recordly high excited atoms at levels more than 1000, found 40 earlier unknown at low frequencies pulsars, electrostatic discharges in theatmosphere of Saturn, ultra-slim space-frequency-temporal structures of continuous, pulsed and sporadic radio emission of objects in the Solar system, Galaxy and Metagalaxy. Conclusions: The main achievements of the national radio astronomy at decameter and meter wavelengths are shown. The world’s largest radio telescopes UTR-2, URAN-1...URAN-4, GURT are created, upgraded, and implemented in ground monitoring, which made many astrophysical discoveries recognized by the world scientific community. Ukrainian radio telescopes are indispensable, fully popular and included in the ground and ground-space radio astronomy network and widely used in international studies. There are favourable prospects for further development of Ukrainian and international low-frequency radio astronomy – one of the most important areas of modern astronomical science. Key words: low frequency radio astronomy, decameter and meter bands of radio waves, radio telescope, Solar System, Galaxy, Metagalaxy Manuscript submitted 16.11.2017 Radio phys. radio astron. 2018, 23(1): 3-23 REFERENCES 1. KONOVALENKO, A. A., 2005. Low-Frequency Radio Astronomy Prospects. Radio Phys. Radio Astron . vol. 10, special is., pp. S86–S114 (in Russian). 2. KONOVALENKO, A., SODIN, L., ZAKHARENKO, V., ZARKA, P., ULYANOV, O., SIDORCHUK, M., STEPKIN, S., TOKARSKY, P., MELNIK, V., KALINICHENKO, N., STANISLAVSKY, A., KOLIADIN, V., SHEPELEV, V., DOROVSKYY, V., RYABOV, V., KOVAL, A., BUBNOV, I., YERIN, S., GRIDIN, A., KULISHENKO, V., REZNICHENKO, A., BORTSOV, V., LISACHENKO, V., REZNIK, A., KVASOV, G., MUKHA, D., LITVINENKO, G., KHRISTENKO, A., SHEVCHENKO, V. V., SHEVCHENKO, V. A., BELOV, A., RUDAVIN, E., VASYLIEVA, I., MIROSHNICHENKO, A., VASILENKO, N., OLYAK, M., MYLOSTNA, K., SKORYK, A., SHEVTSOVA, A., PLAKHOV, M., KRAVTSOV, I., VOLVACH, Y., LYTVINENKO, O., SHEVCHUK, N., ZHOUK, I., BOVKUN, V., ANTONOV, A., VAVRIV, D., VINOGRADOV, V., KOZHIN, R., KRAVTSOV, A., BULAKH, E., KUZIN, A., VASILYEV, A., BRAZHENKO, A., VASHCHISHIN, R., PYLAEV, O., KOSHOVYY, V., LOZINSKY, A., IVANTYSHIN, O., RUCKER, H. O., PANCHENKO, M., FISCHER, G., LECACHEUX, A., DENIS, L., COFFRE, A., GRIEsMEIER, J.-M., TAGGER, M., GIRARD, J., CHARRIER, D., BRIAND, C. and MANN, G., 2016. The modern radio astronomy network in Ukraine: UTR-2, URAN and GURT. Exp. Astron . vol. 42, is. 1, pp. 11–48. DOI: https://doi.org/10.1007/s10686-016-9498-x 3. ZAKHARENKO, V., KONOVALENKO, A., ZARKA, P., ULYANOV, O., SIDORCHUK, M., STEPKIN, S., KOLIADIN, V., KALINICHENKO, N., STANISLAVSKY, A., DOROVSKYY, V., SHEPELEV, V., BUBNOV, I., YERIN, S., MELNIK, V., KOVAL, A., SHEVCHUK, N., VASYLIEVA, I., MYLOSTNA, K., SHEVTSOVA, A., SKORYK, A., KRAVTSOV, I., VOLVACH, Y., PLAKHOV, M., VASILENKO, N., VASYLKIVSKYI, Y., VAVRIV, D., VINOGRADOV, V., KOZHIN, R., KRAVTSOV, A., BULAKH, E., KUZIN, A., VASILYEV, A., RYABOV, V., REZNICHENKO, A., BORTSOV, V., LISACHENKO, V., KVASOV, G., MUKHA, D., LITVINENKO, G., BRAZHENKO, A., VASHCHISHIN, R., PYLAEV, O., KOSHOVYY, V., LOZINSKY, A., IVANTYSHYN, O., RUCKER, H. O., PANCHENKO, M., FISCHER, G., LECACHEUX, A., DENIS, L., COFFRE, A. and GRIEs-MEIER, J.-M., 2016. Digital Receivers for Low-Frequency Radio Telescopes UTR-2, URAN, GURT. J. Astron. Instrum . vol. 5, is. 4, id. 1641010. DOI: https://doi.org/10.1142/S2251171716410105 4. KONOVALENKO, A. A., YERIN, S. M., BUBNOV, I. N., TOKARSKY, P. L., ZAKHARENKO, V. V., ULYANOV, O. M., SIDORCHUK, M. A., STEPKIN, S. V., GRIDIN, A. O., KVASOV, G. V., KOLIADIN, V. L., MELNIK, V. M., DOROVSKYY, V. V., KALINICHENKO, M. M., LITVINENKO, G. V., ZARKA, P., DENIS, L., GIRARD, J., RUCKER, H. O., PANCHENKO, M., STANISLAVSKY, A. A., KHRISTENKO, A. D., MUKHA, D. V., REZNICHENKO, O. M., LISACHENKO, V. N., BORTSOV, V. V., BRAZHENKO, A. I., VASYLIEVA, I. Y., SKORYK, A. O., SHEVTSOVA, A. I. and MYLOSTNA, K. Y., 2016. Astrophysical studies with small low-frequency radio telescopes of new generation. Radio Phys. Radio Astron . vol. 21, no. 2, pp. 83–131 (in Russian). DOI: https://doi.org/10.15407/rpra21.02.083 5. KONOVALENKO, A. A., 2017. I. S. Shklovsky and Low-Frequency Radio Astronomy. Radio Phys. Radio Astron . vol. 22, no. 1, pp. 7–30 (in Russian). DOI: https://doi.org/10.15407/rpra22.01.007

Purpose: The goal of the work is improving the efficiency of interferometric studies of cosmic radio sources at decameter waves. Design/methodology/approach: The URAN interferometer network observations are made usually at frequencies of 20 and 25 MHz with the recorded bandwidth of 250 kHz. The URAN receivers provide an effective software filtering of interferences and reducing the redundancy of stored information during the recording. A software package developed for the URAN performs the further data synchronization and correlation, calculates the visibility functions, and determines the angular structure of studied objects. We propose to expand significantly the frequency range of observations and increase the number of frequency channels recorded simultaneously using the DSPZ digital receivers for signal recording. A number of narrower bands can then be chosen from the entire frequency range of 8 to 32 MHz of the recorded signals. The further filtering of narrow-band interference, reduction of bit capacity and further data processing are performed with the URAN software package. Findings: To implement this approach, we developed the software which singles out the narrow bands from a broadband signal and converts data storage formats and synchronization marks used in DSPZ to the form used in URAN receivers for information recording. We have observed the 3C380 quasar using the URAN-2 interferometer with the baseline of 153 km with simultaneous recording of signals with the DSPZ and URAN receivers. The data synchronization reliability at the interferometer sites, the efficiency of the interference removal automatic algorithm in a low-frequency part of the decameter range, the coincidence of the results obtained with the DSPZ and URAN were checked during observations. The paper also analyzed the possibility of expansion of the recorded data bandwidth to improve the sensitivity of observations. We considered the factors limiting the bandwidth at the decameter wavelengths and the conditions in which its expanding is possible are noted. Conclusions: The results obtained demonstrate the effectiveness of using the DSPZ receivers for the URAN interferometers. The flexibility of the proposed approach increase the number of observational frequencies to improve the accuracy of determining the angular structure models of the sources, expand the frequency range of the observations and increase the sensitivity of the studies.

Purpose: Proving of the high astrophysical significance of the low-frequency radio astronomy (decameter and adjacent hectometer and meter wavelengths), demonstration of the priority results of the Ukrainian low-frequency radio astronomy as well as significant contribution of I. S. Shklovsky to its development. Design/methodology/approach: The requirements to characteristics of high efficiency radio telescopes UTR-2, URAN, GURT and to sensitive and interference immune observational methods at low frequencies are formulated by using the theoretical analysis and astrophysical predictions including those I. S. Shklovsky’s. Findings: New generation radio telescopes UTR-2, URAN, GURT are created and modernized. New observational methods at low frequencies are introduced. Large-scale investigations of the Solar system, Galaxy and Methagalaxy are carried out. They have allowed to detect new objects and phenomena for the continuum, monochromatic, pulse and sporadic cosmic radio emission. The role of I. S. Shklovsky in the development of many low-frequency radio astronomy directions is noted, too. Conclusions: The unique possibilities of the low-frequency radio astronomy which gives new information about the Universe, inaccessible with the other astrophysical methods, are shown. The progress of the low-frequency radio astronomy opens the impressive possibilities for the future. It includes modernization of the largest radio telescopes UTR-2, URAN, NDA and creation of new instruments GURT, NenuFAR, LOFAR, LWA, MWA, SKA as well as making multi-antenna and ground-space experiments. The contribution of outstanding astrophysicist of the XX century I. S. Shklovsky to this part of actual astronomical science is evident, claiming for attention and will never be forgotten.

Purpose: Making analysis of variations of fast and slow solarwind parameters at distances from the Sun of about 1 AU and more. Design/methodology/approach: The method of Feynman pathintegrals is applied to calculate the temporal spectra and dispersion dependences of the drift velocity of interplanetary scintillations. The calculated spectra and dispersion dependences have been compared with the experimental ones to determine the solar wind parameters. Findings:The parameters of fast and slow solar wind are determined and obtained data analyzed by the results of observations with the UTR-2 and URAN-2 radio telescopes made in 2003–2011. Based on these results, the empirical radial dependences of the turbulence spectra for fast and slow solar wind have been built. Conclusions: The slow solar wind turbulence is shown on the average corresponding to the Kolmogorov law of hydrodynamic turbulence. The turbulence of fast quasi-stationary solar wind is well described by the Iroshnikov–Kraichnan magnetohydrodynamic turbulence.

Ukraine has scientific and technical potential to construct a spacecraft and payloads for exploration of the Moon in collaboration with other interested countries. In this paper we propose a double mission that consists of two parts: (1) orbiter exploration from an elongated orbit with a pericenter over the north pole (100 km above the surface) and the apocenter over the south pole (altitude about 3000 km), and (2) exploration with a lander located on the lunar farside near the south pole in the surroundings of the crater Braude. The lander carries five antennas for radio astronomy observations from hundreds of KHz to 40 MHz. The farside landing is necessary to provide effective shielding electromagnetic noises from the Earth, including aurora and lighting radiation. The lander communicates with the relay satellite in a high portion of the orbit; the orbiter is equipped with scientific payloads for investigation of the lunar surface. In the mode of a radio spectrometer, the radio antennas may study solar flares of various types, coronal mass ejections, Jupiter radio emission (L and S bursts), and Saturn (lightning and kilometer radio emission). Overlapping frequencies in the range of 10–40 MHz will allow coordination with terrestrial radio telescopes of IRA NAS, Ukraine (UTR-2, GURT), whose operation is limited by the Earth ionosphere. The absence of terrestrial noise allows us to approach the solution of the problem of searching for cosmological effects associated with the line of neutral hydrogen at Z = 50 … 100. The lander panoramic camera equipped with color and polarization filters provides important observations of horizon glow caused by the effect of electrostatic levitation of the lunar dust. For the orbital module we suggest remote-sensing instruments, which had not previously been used in space exploration of the Moon. The expected spatial resolution of the data will be about 100 m for the northern hemisphere. The equipment should include instruments, prototypes of which are already available in science organizations of Ukraine. These include an infrared spectrometer to map the abundance of OH/H2O compounds in the lunar soil. A HiRes camera operating in two spectral bands is suggested for mapping structural and mineralogical characteristics of young surface formations. The 3-mm radar, working in a squint mode, will not only map the radio brightness of the surface, which characterizes its roughness, but also improve the lunar topographic model with a spatial resolution of 100 m.

Context.We discuss the origin of quasi-harmonic emission bands that have been observed in the dynamic spectra of the Jovian decameter emission.Aims.We aim to show that the interpretation of the observed structure can be based on the effect of double plasma resonance (DPR) at ion cyclotron harmonics.Methods.According to the proposed model, in the extended source in the upper ionosphere of Jupiter, where the DPR condition is satisfied for one of the ion cyclotron frequency harmonics, the ion cyclotron waves are effectively excited at the frequency of the lower hybrid resonance. The observed electromagnetic radiation with a quasi-harmonic structure arises due to scattering of ion cyclotron waves by supra-thermal electrons.Results.Based on the VIP4 magnetic field model, we determine the longitudes at which the source of the considered radiation can be located. The obtained estimates of the plasma density and its height distribution in the source, as well as the energies of emitting ions and scattering electrons provide information about the plasma parameters in the upper ionosphere of Jupiter. Furthermore, these estimates are in good agreement with the observational data.

PACS number: 84.40.Ba Purpose: theoretical and experimental investigations of sensitivity by the signal-to-noise ratio criterion active antenna used as a phased array element of the GURT radio telescope of new generation. Design/methodology/approach: A mathematical model of active antenna is proposed, the technique of its application for calculation of the active phased array element sensitivity being described. Findings: Numerical and experimental studies of the temperatures of external and internal noises at the active phased array element output of the GURT radio telescope are carried out, as well as element sensitivity estimated over a wide frequency range from 10 to 80 MHz. Conclusions: The obtained agreement between the results of computation and experiment points to correctness of the proposed technique of calculating the sensitivity of active antennas, and the results of studies of the phased array element confirm the possibility of its effective use in construction of the antenna system for the GURT radio telescope. Key words: radio telescope, phased antenna array, active antenna, signal-to-noise ratio Manuscript submitted 15.02.2016 Radio phys. radio astron. 2016, 21(1): 48-57 REFERENCES 1. KRAUS, J. D., 1966. Radio Astronomy . New York, USA: McGraw-Hill. 2. DE VOS, M., GUNST, A. W. and NIJBOER, R., 2009. The LOFAR Telescope: System Architecture and Signal Processing. IEEE Proc . vol. 97, is. 8, pp. 1431–1437. DOI: https://doi.org/10.1109/JPROC.2009.2020509 3. ELLINGSON, S.,W., CLARKE, T. E., COHEN, A., CRAIG, J., KASSIM, N. E., PIHLSTROM, Y., RICKARD, L. J. and TAYLOR, G. B., 2009. The Long Wavelength Array. IEEE Proc . vol. 97, is. 8, pp. 1421–1430. DOI: https://doi.org/10.1109/JPROC.2009.2015683 4. ZARKA, P., TAGGER, M., DENIS, L., GIRARD, J. N., KONOVALENKO, A., ATEMKENG, M., ARNAUD, M., AZARIAN, S., BARSUGLIA, M., BONAFEDE, A., BOONE, F., BOSMA, A., BOYER, R., BRANCHESI, M., BRIAND, C., CECCONI, B., CELESTIN, S., CHARRIER, D., CHASSANDE-MOTTIN, E., COFFRE, A., COGNARD, I., COMBES, F., CORBEL, S., COURTE, C., DABBECH, A.,. DAIBOO, S, DALLIER, R., DUMEZ-VIOU, C., EL KORSO, M. N., FALGARONE, E., FALKOVYCH, I., FERRARI, A., FERRARI, C., FERRIERE, K., FEVOTTE, C., FIALKOV, A., FULLEKRUG, M., GERARD E., GRIEsMEIER, J.-M., GUIDERDONI, B., GUILLEMOT, L., HESSELS, J.,. KOOPMANS, L, KONDRATIEV, V., LAMY, L., LANZ, T., LARZABAL, P., LEHNERT, M., LEVRIER, F., LOH, A., MACARIO, G., MAINTOUX, J.-J., MARTIN, L., MARY, D., MASSON, S., MIVILLE-DESCHENES, M.-A., OBEROI, D., PANCHENKO, M., PANDEY-POMMIER, M., PETITEAU, A., PINCON, J.-L., REVENU, B., RIBLE, F., RICHARD, C., RUCKER, H. O., SALOME, P., SEMELIN, B., SERYLAK, M., SMIRNOV, O., STAPPERS, B., TAFFOUREAU, C., TASSE, C., THEUREAU, G., TOKARSKY, P., TORCHINSKY S., ULYANOV, O., VAN DRIEL, W., VASYLIEVA, I., VAUBAILLON, J., VAZZA, F., VERGANI, S., WAS M., WEBER, R. and ZAKHARENKO V., 2015. NenuFAR: Instrument Description and Science Case. In: 10th International Conference on Antenna Theory and Techniques Proceedings . 21– 24 April 2015,Kharkiv,Ukraine, pp. 13–18. DOI: https://doi.org/10.1109/ICATT.2015.7136773 5. KONOVALENKO A. A., FALKOVICH I. S., GRIDIN A. A., TOKARSKY P. L. and YERIN S. N., 2012. UWB Active Antenna Array for Low Frequency Radio Astronomy. In: 6th International Conference on Ultrawideband and Ultrashort Impulse Signals Conference Proceedings . 17–21 Sept. 2012, Sevastopol, Ukraine, pp. 39–43. DOI: https://doi.org/10.1109/UWBUSIS.2012.6379725 6. IVASHINA M. V., MAASKANT R. and WOESTENBURG B., 2008. Equivalent System Representation to Model the Beam Sensitivity of Receiving Antenna Arrays. IEEE Antennas Wireless Propag. Lett . vol. 7, pp. 733–737. DOI: https://doi.org/10.1109/LAWP.2008.2006917 7. WIJNHOLDS S. J. and VAN CAPPELLEN W. A., 2011. Insitu antenna performance evaluation of the LOFAR phased array radio telescope. IEEE Trans. Antennas Propag . vol. 59, no. 6, pp. 1981–1989. DOI: https://doi.org/10.1109/TAP.2011.2122225 8. ELLINGSON, S. W., 2011. Sensitivity of Antenna Arrays for Long-Wavelength Radio Astronomy. IEEE Trans. Antennas Propag . vol. 59, no. 6, pp. 1855–1863. DOI: https://doi.org/10.1109/TAP.2011.2122230 9.SAZONOV, D. M., 2015. Multielement antenna systems. The matrix approach . Moscow: Radiotechnika-Press Publ. (in Russian). 10. TOKARSKY, P. L., 2006. Matrix Model of a Dissipative Antenna Array. Radiotekhnika. All-Ukr. Sci. Interdep. Mag . is. 146, pp. 156–170 (in Russian). 11. RAZEVIG, B. D. (ed.), POTAPOV, Yu. V. and KURUSHIN, A. A., 2003. Design of microwave devices using Microwave Office . Moskow: SOLON-Press Publ. (in Russian). 12. BABAK, L. I., 1980. Determination of microwave circuits noise characteristics. Radiotekhnika i Elektronika . vol. 25, no. 11, pp. 2380–2384 (in Russian). 13. KRYMKIN, V. V., 1971. The spectrum of background lowfrequencyradio emission. Radiophysics and Quantum Electronics . vol. 14, is. 2, pp. 161–164. DOI: https://doi.org/10.1007/BF01031395 14. MARKOV, G. T. and SAZONOV, D. M., 1975. Aerials , 2nd ed., Moscow: Energiya Publ. (in Russian). 15. 4nec2 – NEC based antenna modeler and optimizer by Arie Voors [online]. Available from: http://www.qsl.net/4nec2/

We report about new observations of solar 'drift pair' (DP) bursts by means of the UTR-2 radio telescope at frequencies 10-30 MHz. Our experimental data include both 'forward' and 'reverse' bursts with high frequency and time resolution. The records of 301 bursts, observed in 10-12 July of 2015, are investigated. The main properties of these bursts (frequency bandwidth, central frequency and others) have been analysed. In this report our main attention is paid to the comparison of our observations with the similar observations of decametre DPs performed earlier during 13-15 July of 2002 in the same frequency range. Common features of DPs in the two different pieces of data samples have been found. This may indicate the possible presence of stability in the frequency-time properties of decametre DPs from one cycle of solar activity to another.

In the report the tools and methods of observations of radio recombination lines which are carried out atInstituteofRadio Astronomyof theNationalAcademy of Sciences ofUkraineusing the world’s largest decameter radio telescope UTR-2 (arrays “South – North” and “East – West”) are described. The low-frequency radio recombination lines can be used as effective means of the low-density partially ionized interstellar medium diagnostic. However, low intensities of the lines and high level of interferences makes such investigations very difficult and impose high requirements to equipment. Observations are carried out with the 4096-channel digital correlometer and new generation digital spectral processors with 8192 spectral channels. Currently, the systematic observations of radio recombination lines have been carried out in the directions of remnants of supernova stars, Galactic plane, nebulas and dust clouds. Experiments aimed to finding the redshifted line of neutral hydrogen HI which arises in the cosmological epochs of reionization in the range 8 – 32 MHz are carried out. The carbon radio recombination lines have been detected in the direction of Cassiopeia A in the broad range of frequencies from 20 to 32 MHz. The carbon radio recombination line, corresponding to the transitions to atomic level with number of 1009 (these corresponds to the Bohr size of atom near0,1 mm) have been registered.

© 2018 International Union of Radio Science URSI. In the paper we present the preliminary results of analysis of the solar Type IIIb bursts properties observed on June 14, 2012. Namely the parameters of their fine structure known as striae are studied in the continuous frequency band 8 - 32 MHz. It is shown that durations and instantaneous frequency bandwidths depend on the observing frequency. Notably, bandwidth increases and duration decreases with the frequency. The comparative analysis of the decameter spikes and striae is also performed. ispartof: 2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018 ispartof: 2nd URSI Atlantic Radio Science Meeting (AT-RASC) location:SPAIN, Meloneras date:28 May - 1 Jun 2018 status: published

The present state of solar wind investigations by IPS (interplanetary scintillations) observations at decameter wavelengths is discussed. Radio telescopes, equipment and methods which are used in these experiments are shown. We also describe some interesting results devoted to the long term monitoring of the solar wind beyond Earth’s orbit, the detection of the large scale disturbances associated with active processes at the Sun and the reconstructions of the solar wind stream structure. Emphasis is placed on perspectives of low frequency IPS investigations which are particularly connected with the creation of the Giant Ukrainian Radio Telescopes (GURT) and UTR-2 – URAN – GURT – LOFAR collaboration.

We report the systematic analysis of zebra-like fine spectral structures in decametric frequency range of Jovian radio emission. Observations were performed by the large ground-based radio telescope URAN-2 during three observation campaigns between, Sep., 2012, and May, 2015. In total, 51 zebra pattern (ZP) events were detected. These rare fine radio features are observed in frequency range from 12.5 to 29.7 MHz as quasi-harmonically related bands of enhanced brightness. ZPs are strongly polarized radio emission with a duration from 20 s to 290 s and flux densities ~105−106 Jy (normalized to 1 AU), that is, 1–2 orders lower than for Io-decametric radio emission (DAM). Occurrence of the events does not depend on the position of Io satellite but is strongly controlled by the Jovian central meridian longitude (CML). ZPs are mainly detected in two active sectors of Jovian CMLs: 100∘ to 160∘ for Northern sources (right-handed polarized) and 300∘ and 60∘ (via 360∘) for the Southern sources (left-handed). The frequency interval between neighboring stripes is from 0.26 to 1.5 MHz and in most cases this interval increases with frequency. We discussed the double plasma resonance with electrons or ions as a possible source of the ZPs. The performed analysis of the observations allows us to conclude that the observed ZPs are a new type of narrow band spectral structures in the Jovian DAM.

On April 7, 2011 a CME was observed originating above the AR NOAA 1176, located behind the solar limb. This CME was associated with type IV burst, type II bursts and groups of J-bursts and type III bursts. Groups of J-bursts and type III bursts were observed from 10:50 to 11:20 UT. There was a group of J-bursts from 10:52 to 10:57 UT, originating from accelerated electrons propagating along high magnetic loops connected with the active region NOAA 1176. The group of type III bursts continued from 11:00 to 11:20 UT. There were a lot of spikes and type IIIb bursts with polarizations up to 80% during the group of type III bursts. Type IV burst began at 11:20 UT at 32 MHz and continued for more than 3 hours. Its maximum flux was about 200 s.f.u., and the polarization achieved 40%. There were 3 type II bursts superimposed by type IV burst. Their drift rates were approximately 0, 10 kHz/s, 25 kHz/s, and it appears that they were radio emissions from different regions of the spherical shock produced by the CME. All type II bursts consisted of tadpoles with ”heads” and ”tails”. Their durations were 4 s and 2 s, and their polarizations were about 10% and 40%, correspondingly. The frequency bands of the ”tails” was up to 10 MHz. Their frequency drift rates could be positive and negative ones, and their absolute values changed from 0.4 MHz/s to 4 MHz/s. Previously we found that decameter type IV bursts oscillated with periods of tens of minutes. The type IV burst observed on April 7, 2011 showed oscillations also. Fourier and wavelet analyses showed periods of about 40 minutes for both fluxes and polarizations. Moreover, it turned out that these periods decreased with time with rates of 0.03–0.07. Interpretations of all decameter phenomena are discussed.

We study a unique fine structure in the dynamic spectrum of the solar radio emission discovered by the UTR-2 radio telescope (Kharkiv, Ukraine) in the frequency band of 20 – 30 MHz. The structure was observed against the background of a broadband type IV radio burst and consisted of parallel drifting narrow bands of enhanced emission and absorption on the background emission. The observed structure differs from the widely known zebra pattern at meter and decimeter wavelengths by the opposite directions of the frequency drift within a single stripe at a given time. We show that the observed properties can be understood in the framework of the radiation mechanism by virtue of the double plasma resonance effect in a nonuniform coronal magnetic trap. We propose a source model providing the observed frequency drift of the stripes.

The calculation technique results of numerical analysis of parameters of active phased antenna array (APAA) of the Giant Ukrainian Radio Telescope (GURT) of decameter and meter wavelengths which is being built now nearby Kharkiv at the area of S. Ya. Braude Radio Astronomy Observatory of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine are presented. The technique is based on the matrix theory of antenna arrays which combines an electromagnetic approach to analysis of radiators array with the methods of microwave multiport theory for the APAA feed network description. The results of numerical calculation of the APAA effective area and its gain, which in case of passive array is associated with its efficiency, are given and analyzed for a wide scan range within 10 to 80 MHz.

Features of sporadic decameter solar radio emission associated with some active regions according to observations made with radio telescope UTR-2 on August 1, 2014 are considered. Analysis of characteristics of type IV bursts, fiber-bursts and type III bursts, which were preceded and followed by type IV bursts, was carried out. Similarity of origins of fiber-bursts and type III bursts. By the frequency drift rate, they are distributed by statistically independent groups. Each group of bursts and that of type IV bursts were identified with radio emission from a particular active region. The plasma parameters in these regions and their variations while generating type IV bursts are estimated. Key words: group of active regions, decameter wavelength range, type IV bursts, fiber bursts, type III bursts, identification, generation regions, plasma parameters Manuscript submitted 07.05.2014 Radio phys. radio astron. 2014, 19(4): 295-306 REFERENCES 1. BOISCHOT, A., 1958. Etude du rayonnement radioelectrique solairesur 169 MHz e l'aide d'un grand interferometre a reseau. Ann. d'Astrophys ., vol. 21, pp. 273. 2. GINZBURG, V. L. and ZHELEZNIAKOV, V. V., 1959. On the Possible Mechanisms of Sporadic Solar Radio Emission (Radiationin an Isotropic Plasma). Astron. Zh. (Sov. Astron), vol. 35, pp. 694–705. 3. MELNIK, V. N., RUCKER, H. O. and KONOVALENKO, A. A., 2008. Solar Type IV Bursts at Frequencies 10–30 MHz. In: PINGZHI WANG, ed. Solar Physics Research Trends. New York: Nova Science Pub., pp. 287–325. 4. ZAQARASHVILI, T. V., MELNIK, V. N., BRAZHENKO,A. I., PANCHENKO, M., KONOVALENKO, A. A., FRANZUZENKO, A. V., DOROVSKYY, V. V. and RUCKER, H. O., 2013. Radio seismology of the outer solar corona. Astron. Astrophys, vol. 555, id. A55. DOI: 10.1051/0004-361/201321548 5. MELNIK, V. N., KONOVALENKO, A. A., BRAZHENKO, A. I., RUCKER, H. O., DOROVSKYY, V. V., ABRANIN, E. P., LECACHEUX, A. and LONSKAYA, A. S., 2010. Bursts in emission and absorption as a fine structure of Type IV bursts. Astrophysics and Cosmology after Gamow: Proc. 4th Gamow International Conf. Astrophysics and Cosmology After Gamow and the 9th Gamow Summer School "Astronomy and Beyond: Astrophysics, Cosmology, Radio Astronomy, High Energy Physics and Astrobiology". AIP Conference Proceedings, vol. 1206, pp. 450–454. DOI: https://doi.org/10.1063/1.3292553 6. BOIKO, A. I., MELNIK, V. N., KONOVALENKO, A. A., ABRANIN, E. P., DOROVSKYY, V. V. and RUCKER, H. O., 2012. Decametric radio bursts associated with the 13 July 2004 CME event at frequencies 10–30 MHz. Adv. Astron. Space Phys. , vol. 2, no. 1. pp. 76–78. 7. BRAZHENKO, A. I., MELNIK, V. N., KONOVALENKO, A. A., ABRANIN, E. P., DOROVSKYY, V. V., VASHCHISHIN, R. V., FRANTZUSENKO, A. V. and RUCKER, H. O., 2010. Observations of the Solar Continuum Radio Emission at Decameter Wavelengths. Astrophysics and Cosmology after Gamow: Proc. 4th Gamown International Conf. Astrophysics and Cosmology After Gamowand the 9th Gamow Summer School "Astronomyand Beyond: Astrophysics, Cosmology, Radio Astronomy, High Energy Physics and Astrobiology". AIP Conf. Proc, vol. 1206, pp. 440–444. DOI: https://doi.org/10.1063/1.3292551 8. BRAUDE, S. Y., MEGN, A. V. and SODIN, L. G., 1978. Decameter wave band radio telescope UTR-2. In: Anteny . Moscow, USSR: Svyaz'. no. 26, pp. 3–14 (in Russian). 9. Student. The probable error of a mean. 1908. Biometrika , vol. 6. no. 1, pp. 1–25. 10. GOPALSWAMY, N., 2004. A Global Picture of CMEs in the Inner Heliosphere. In: G. Poletto and S. Suess, ed. The Sun and the Heliosphere as an Integrated system. Astrophys. Space Sci. Libr . Dordrecht: Kluwer Acad. Publ., vol. 317, pp. 201–250. DOI: https://doi.org/10.1007/978-1-4020-2831-1_8 11. HARTZ, T. R., 1969. Type III solar radio noise bursts at hectometer wavelengths. Planet. Space Sci. , vol. 17, no. 2, pp. 267–287. DOI: https://doi.org/10.1016/0032-0633(69)90044-0 12. MELNIK, V. N., KONOVALENKO, A. A., RUCKER, H. O., RUTKEVYCH, B. P., DOROVSKYY, V. V., ABRANIN, E. P., BRAZHENKO, A. I., STANISLAVSKY, A. A. and LECACHEUX, A., 2008. Decameter Type III like bursts. Sol. Phys. , vol. 250, no. 1, pp. 133–145. DOI: https://doi.org/10.1007/s11207-008-9166-z 13. MELNIK, V. N., KONOVALENKO, A. A., RUCKER, H. O., BOIKO, A. I., DOROVSKYY, V. V., ABRANIN, E. P. and LECACHEUX, A., 2011. Observations of Powerful Type III Bursts in the Frequency Range 10-30 MHz. Sol. Phys ., vol. 269, no. 2, pp. 335–350. DOI: https://doi.org/10.1007/s11207-010-9703-4

The paper is devoted to the analysis of the unusual event observed on 14 June 2012 in the frequency range 8–42 MHz. During this event the radiation flux changed stepwise two times. Assuming that these changes of radiation flux could be associated with the changes of the coronal plasma parameters (temperature, magnetic field) and using spikes as a tool for the determination of those parameters we traced how the temperature and magnetic field varied during the time of observations. According to the model proposed in the paper the magnetic field was about 1.9 G and the temperature varied in the range of 0.1–0.6 × 106 K at the heights 1.6–3.3 solar radii.

A beamforming device for a 5×5-element subarray of receiving phased antenna array of new GURT radio telescope designed to operate within 10 − 70 MHz is presented. The device is composed of six identical units. Each unit contains equal-arm 5:1 combiner with connected to its arms discrete phase shifters based on time delay lines switching principle. Five of these units combine the signals of array elements inside rows of the subarray, whereas the sixth one assembles the combined signals of subarray rows. Operation principle of beamforming unit is described, the results of its computer modeling and performance measurement results are given. The time-delay lines manufacturing errors influence on subarray power parameters is estimated, as well as their fabrication tolerance found. Key words: phase changer, beamformer, phased array, radio-telescope Manuscript submitted 24.04.2014 Radio phys. radio astron. 2014, 19(3): 240-248 REFERENCES 1. KONOVALENKO, A. A., 2005. Low-Frequency Radio Astronomy Prospects. Radio Phys. Radio Astron . vol. 10, special issue, pp. S86–S114 (in Russian) 2. MYLOSTNA, K. Y. and ZAKHARENKO, V. V., 2013.Search and Study of Storm Activity on Saturn and Other Planets of the Solar System. Radio Phys. Radio Astron . vol. 18, no. 1, pp. 12–25 (in Russian). 3. DE VOS, M., GUNST, A. W., and NIJBOER, R., 2009.The LOFAR Telescope: System Architecture and Signal Processing. IEEE Proc. vol. 97, Is. 8, pp. 1431–1437. DOI: https://doi.org/10.1109/JPROC.2009.2020509Source 4. ELLINGSON, S. W., CLARKE, T. E., COHEN, A., CRAIG, J., KASSIM, N. E., PIHLSTROM, Y., RICKARD, L. J., and TAYLOR, G. B., 2009. The Long Wavelength Array. IEEE Proc . vol. 97, is. 8, pp. 1421–1430. DOI: https://doi.org/10.1109/JPROC.2009.2015683 5. GIRARD, J. N., ZARKA, P., TAGGER, M., DENIS, L., CHARRIER, D.,KONOVALENKO, A. A., and BOONE, F., 2012. Antenna design and distribution of the LOFAR super station. Comptes Rendus Physique . vol. 13, Is. 1, pp. 33–37. 6. DEWDNEY, P. E., HALL, P. J., SCHILIZZI, R. T., and LAZIO, T. J. L. W., 2009. The Square Kilometre Array. IEEE Proc . vol. 97, is. 8, pp. 1482–1496 7. KONOVALENKO, A. A., FALKOVICH, I. S., GRIDIN, A. A., TOKARSKY, P. L., and YERIN, S. N., 2012. UWB active antenna array for low frequency radio astronomy. In: Proc. of the VI-thIntern. Conf. on Ultrawide band and Ultrashort Impulse Signals (UWBUSIS'12). Sevastopol (Ukraine). pp. 39–43. DOI: https://doi.org/10.1109/UWBUSIS.2012.6379725 8. BRUCK, Y. M. and INYUTIN, G. A., 1978. Binary digital delay line (phase shifters) for electrically controlled broadband antenna. In: Anteny . Moscow, USSR: Svyaz' Publ., no. 26, pp. 107–121 (in Russian). 9. BRAUDE, S. Y., MEGN, A. V. and SODIN, L. G., 1978. Decameter wave band radio telescope UTR-2. In: Anteny . Moscow, USSR: Svyaz' Publ. no. 26, pp. 3–15 (in Russian). 10. FALKOVICH, I. S., KONOVALENKO, A. A., GRIDIN,A. A., SODIN, L. G., BUBNOV, I. N., KALINI CHENKO, N. N., RASHKOVSKII, S. L., MUKHA, D. V.and TOKARSKY, P. L., 2011. Wide-band high linearity active dipole for low frequency radio astronomy. Exp. Astron .vol. 32, is. 2, pp. 127–145. DOI: https://doi.org/10.1007/s10686-011-9256-z 11. VOSKRESENSKII, D. I., STEPANENKO, V. S., and FILIPPOV, V. S. Microwave devices and antennas. Designing phased arrays . Moscow: Radiotekhnika Publ. (in Russian). 12. Surface-mounting, 1-GHz-Band / 3-GHz-Band, Miniature, DPDT, High-frequency Relay datasheet [online]. Available from:www.omron.com/ecb/products/pdf/en-g6k_2f_rf.pdf. 13. Surface Mount Power Splitter/Combiner SCP-5-1 datasheet [online]. Available from: www.minicircuits.com/pdfs/SCP-5-1.pdf. 14. SHIFRIN, Ya. S., 1970. Questions of statistical antenna theory. Moscow: Sov. radio. Publ. (in Russian). 15. INDENBOM, M. V., 2008. Fluctuations of the directivity pattern of the antenna array for output. Anteny , no. 4, pp. 40–46. 16. MERKULOV, V. V., 1966. By the estimation of emitters CPV system with phase and amplitude distortion. Radiotechnika i elektronika , vol. 11, no. 11, pp. 2066–2069. 17. STEBLIN, V. I. and KLASSEN, V. I., 1981. The method of analysis of statistical characteristics of CPV phased array antenna with random amplitudes and phases of the location of radiators. Radiotechnika i elektronika , vol. 26, no. 3, pp. 524–531. 18. SHIFRIN, Ya. S. and KORNIENKO, L. G., 2000. Statistics field antenna arrays. Anteny , no. 1, pp. 3-26. 19. SAZONOV, D. M., GRIDIN, A. N., and MISHUSTIN, B. A., 1981. Microwave devices . Moscow: Vyshchaya shkola Publ. (in Russian).

The results of radio emission observations for Cassiopeia A source at frequencies 35, 38, 40, 45, 50, 55, 60 and 65 MHz are presented. At these frequencies, the radio-emission flux density ratio between Cassiopeia A and Cygnus A for the epoch of 2014 is obtained. Brief information about the antenna facility and reception equipment used in the measurements is given. At frequencies 35−65 MHz, the radio emission flux of Cassiopeia A is found for the epoch of 2014 by comparison with the well-known flux density of Cygnus A. The intersection frequency of the low-frequency spectra for Cassiopeia A and Cygnus A is experimentally determined. The results obtained by other authors for the secular decrease of the flux density of Cassiopeia A radio emission at 38 MHz are confirmed.

УДК 523.164.42 Описаны некоторые особенности применения спектральной и дисперсионной методик определения параметров солнечного ветра по данным наблюдений межпланетных мерцаний космических радиоисточников в декаметровом диапазоне радиоволн. Указаны характерные ошибки восстановления параметров солнечного ветра в зависимости от методики и модели солнечного ветра. Ключевые слова: межпланетные мерцания, солнечный ветер, спектральная методика, дисперсионная методика Статья поступила в редакцию 21.05.2014 Radio phys. radio astron. 2014, 19(2): 120-125 СПИСОК ЛИТЕРАТУРЫ 1. Hewish A., Scott P. F., and Wills D. Interplanetary Scintillation of Small Diameter Radio Sources // Nature. – 1964. – Vol. 203, Is. 4951. – P. 1214–1217. 2. Hewish A., Dennison P. A., and Pilkington J. D. H. Measurements of the size and motion of the irregularities in the interplanetary medium // Nature. – 1966. – Vol. 209, Is. 5029. – P. 1188–1189. 3. Шишов В. И., Шишова Т. Д. Влияние размеров источника на спектры межпланетных мерцаний. Наблюдения // Астрономический журнал. – 1979. – Т. 56, № 3. – C. 613–622. 4. Бовкун В. П., Жук И. Н. Спектры мерцаний на неоднородностях ионосферы и межпланетной плазмы и возможность их разделения в декаметровом диапазоне радиоволн // Доклады АН УССР. – 1981. – Сер. А, № 6. – С. 69–71. 5. Manoharan P. K. and Ananthakrishnan S. Determination of solar-wind velocities using single-station measurements of interplanetary scintillations // Mon. Not. R. Astron. Soc. – 1990. – Vol. 244. – P. 691–695. 6. Фалькович И. С., Коноваленко А. А., Калиниченко Н. Н., Ольяк М. Р., Гридин А. И., Бубнов И. Н., Браженко А. И., Лекашо А., Рукер Х. О. Первые результаты дисперсионного анализа межпланетных мерцаний в декаметровом диапазоне длин волн // Радиофизика и радиоастрономия. – 2007. – Т. 12, № 4. – С. 350–356. 7. Breen A. R., Coles W. A., and Grall R. R., Klinglesmith M. T., Markkanen J., Moran P. I., Tegid B., and Williams P. J. S. EISCAT measurements of the solar wind // Ann. Geophysicae. – 1996. – Vol. 14. – P. 1235–1245. 8. Калиниченко Н. Н., Фалькович И. С., Коноваленко А. А., Браженко А. И. Разделение межпланетных и ионосферных мерцаний космических источников в декаметровом диапазоне радиоволн // Радиофизика и радиоастрономия. – 2013. – Т. 18, № 3. – С. 210–219. 9. Брауде С. Я., Мень А. В., Содин Л. Г. Радиотелескоп декаметрового диапазона волн УТР-2 // Антенны. – М.: Связь. – 1978. – Вып. 26. – С. 3–14. 10. Мень А. В., Шарыкин Н. К., Захаренко В. В., Булацен В. Г., Браженко А. И., Ващишин Р. В . Радиотелескоп декаметрового диапазона волн УРАН-2 // Радиофизика и радиоастрономия. – 2003. – Т. 8, № 4. – С. 345–356. 11. Бовкун В. П., Жук И. Н. Мерцания космических источников в декаметровом диапазоне радиоволн на неоднородностях межпланетной плазмы и ионосферы // Космическая наука и техника. – 1992. – № 7. – С. 80–91. 12. Фалькович И. С., Калиниченко Н. Н., Гридин А. А., Бубнов И. Н. О возможности широкополосных наблюдений межпланетных мерцаний на декаметровых волнах // Радиофизика и радиоастрономия. – 2004. – Т. 9, № 2. – С. 121–129. 13. Фалькович И. С., Гридин А. А., Калиниченко Н. Н., Бубнов И. Н. Шестнадцатиполосный корреляционный радиометр для наблюдения межпланетных мерцаний // Радиофизика и радиоастрономия. – 2005. – Т. 10, № 4. – С. 392–397. 14. Olyak M. R. Large-scale structure of solar wind and geomagnetic phenomena // J. Atmos. Solar-Terr. Phys. – 2012. – Vol. 86. – P. 34–40. 15. Olyak M. R. The dispersion analysis of drift velocity in the study of solar wind flows // J. Atmos. Solar-Terr. Phys. – 2013. – Vol. 102. – P. 185–191. 16. Калиниченко Н. Н., Коноваленко А. А., Браженко А. И., Соловьев В. В. Корональный выброс массы 15 февраля 2011 г. в межпланетном пространстве и его наблюдения методом мерцаний космических источников в декаметровом диапазоне радиоволн // Радиофизика и радиоастрономия. – 2013. – Т. 18, № 4. – С. 301–308.

УДК 523.4-77 Представлены первые исследования тонкой временной структуры радиоизлучения молний на Сатурне, полученные со сверхвысоким временным разрешением (единицы–сотни наносекунд). Установлено, что временная структура молний имеет два характерных масштаба: с длительностью десятки–сотни микросекунд и длительностью в единицы микросекунд. В ходе обработки данных впервые проведен анализ меры дисперсии на пути распространения сигналов молнии от шторма в атмосфере Сатурна до наземного наблюдателя. Ключевые слова: высокое временное разрешение, молнии на Сатурне, тонкая временная структура, дисперсионная задержка, ионосфера, межпланетная среда Статья поступила в редакцию 09.12.2013 Radio phys. radio astron. 2014, 19(1): 10-19 СПИСОК ЛИТЕРАТУРЫ 1. Dyudina U. A., Ingersoll A. P., Ewald S. P., Porco C. C., Fischer G., Kurth W. S., and West R. A. Detection of visible lightning on Saturn // Geophys. Res. Lett. – 2010. – Vol. 37, No. 9. – id. L09205. 2. Farrell W. M, Kaiser M. L., Fischer G., Zarka P., Kurth W. S., and Gurnett D. A. Are Saturn electrostatic discharges really superbolts? A temporal dilemma // Geophys. Res. Lett. – 2007. – Vol. 34, Is. 6. – id. L06202. 3. Konovalenko A. A., Kalinichenko N. N., Rucker H. O., Lecacheux A., Fischer G., Zarka P., Zakharenko V. V., Mylostna K. Y., Griesmeier J.-M., Abranin E. P., Falkovich I. S., Sidorchuk K. M., Kurth W. S., Kaiser M. L., and Gurnett D. A. Earliest recorded ground-based decameter wavelength observations of Saturn’s lightning during the giant E-storm detected by Cassini spacecraft in early 2006 // Icarus. – 2013. – Vol. 224, No. 1. – P. 14–23. 4. Zakharenko V., Mylostna K., Konovalenko A., Zarka P., Fischer G., Griesmeier J.-M., Litvinenko G., Rucker H., Sidorchuk M., Ryabov B., Vavriv D., Ryabov V., Cecconi B., Coffre A., Denis L., Fabrice C., Pallier L., Schneider J., Kozhyn R., Vinogradov V., Mukha D., Weber R., Shevchenko V., and Nikolaenko V. Ground-based and spacecraft observations of lightning activity on Saturn // Planet. Space Sci. – 2012. – Vol. 61, No. 1. – P. 53–59. 5. Zakharenko V. V., Mylostna K. Y., Fischer G., Konovalenko A. A., Zarka P., Griesmeier J.-M., Ryabov B. P., Vavriv D. M., Ryabov V. B., Rucker H., Ravier P., Sidorchuk M. A., Cecconi B., Coffre A., Denis L., Fabrice C., Kozhyn R. V., Mukha D. V., Pallier L., Schneider J., Shevchenko V. A., Vinogradov V. V., Weber R., and Nikolaenko V. S. Identification of Saturn Lightings Recorded by the UTR-2 Radio Telescope and Cassini Spacecraft // Radio Physics and Radio Astronomy. – 2011. – Vol. 2, Is. 2. – P. 93–98. 6. Fischer G., Kurth W. S., Gurnett D. A., Zarka P., Dyudina U. A., Ingersoll A. P., Ewald S. P., Porco C. C., Wesley A., Go C., and Delcroix M. A giant thunderstorm on Saturn // Nature. – 2011. – Vol. 475, No. 7354. – P. 75–77. 7. Kozhin R. V., Vynogradov V. V., and Vavriv D. M. Lownoise, high dynamic range digital receiver/spectrometer for radio astronomy applications // Proc. SMW’07 Symposium. – Kharkiv (Ukraine). – 2007. – P. 736–738. 8. Ryabov V. B., Vavriv D. M., Zarka P., Ryabov B. P., Kozhin R., Vinogradov V. V., and Denis L. A low-noise, high-dynamic range, digital receiver for radio astronomy applications: an efficient solution for observing radio-bursts from Jupiter, the Sun, pulsars, and other astrophysical plasmas below 30 MHz // Astron. Astrophys. – 2010. – Vol. 510. – id. A16. 9. Konovalenko A. A., Falkovich I. S., Rucker H. O., Lecacheux A., Zarka P., Koliadin V. L., Zakharenko V. V., Stanislavsky A. A., Melnik V. N., Litvinenko G. V., Gridin A. A., Bubnov I. N., Kalinichenko N. N., Reznik A. P., Sidorchuk M. A., Stepkin S. V., Mukha D. V., Nikolajenko V. S., Karlsson R., and Thide B. New antennas and methods for the low frequency stellar and planetary radio astronomy // Proc. of PRE VII. – Graz (Austria). – 2010. – P. 521–531. 10. Колядин В. Л. Использование фазовых динамических кросс-спектров для широкополосных радиоастрономических наблюдений: опыт применения на радиотелескопе УТР-2 // Радиофизика и радиоастрономия. – 2011.– Т. 16, № 4. – С. 341–354. 11. Милостная К. Ю., Захаренко B. В. Поиск и исследование грозовой активности на Сатурне и других планетах Солнечной системы // Радиофизика и радиоастрономия. – 2013. – Т. 18, № 1. – С. 12–25. 12. Hankins T. H. Microsecond intensity variations in the radio emissions from CP 0950 // Astrophys. J. – 1971. – Vol. 169. – P. 487–491. 13. Backer D. C., Hama S., Hook S. V., and Foster R. S. Temporal variations of pulsar dispersion measures // Astrophys. J. – 1993. – Vol. 404. – P. 636–642. 14. Открытая база данных. CODE's global ionosphere maps. Available from: ftp://ftp.unibe.ch/aiub/CODE/2012/ 15. Открытая база данных. News and information about the Sun-Earth enviroment. Available from: http:/spaceweather.com/ 16. Открытая база данных. Jet Propulsion Laboratory, Cassini Solstice mission. A new: Lightning Flashing on Saturn. Available from: http://saturn.jpl.nasa.gov 17. Dyudina U. A., Ingersoll A. P., Ewald S. P., Porco C. C., Fischer G., Kurth W., Desch M., Del Genio A., Barbara J., and Ferrier J. Lightning storms on Saturn observed by Cassini ISS and RPWS during 2004–2006 // Icarus. – 2007. – Vol. 190, Is. 1. – P. 545–555. 18. Fischer G., Dyudina U. A., Kurth W. S., Gurnett D. A., Zarka P., Barry T., Delcroixk M., Go C., Peach D., Vandebergh R., and Wesley A. Overview of Saturn lightning observations. H. O. Rucker, W. S. Kurth, P. Louarn, and G. Fischer, editors. Planetary Radio Emissions VII. – Vienna: Austrian Academy of Sciences Press, 2011. – P. 135–144.

International audience; Rapid progress currently takes place in the field of low-frequency radio astronomy in the meter-decameter-hectometer range of wavelengths. It is caused by a radical modernization of the existing radio telescopes, creation of a new generation of instruments, space-borne observations, and by the development of research on all classes of astrophysical objects, including the Solar System. On the other hand, a range of difficulties specific to low-frequency radio astronomy is known, which are caused by technical, methodological, and physical limitations. An effective strategy for overcoming these difficulties is based on synchronous observations using several radio telescopes separated by distances from a few to several thousand kilometers. This provides an opportunity to reduce and identify radio interference and the influence of the propagation media, to increase the sensitivity and resolution, and to solve many problems with higher efficiency. In recent years such simultaneous observations were carried out for the Sun, Jupiter, Saturn, interplanetary medium, pulsars, exoplanets, and transients using the radio telescopes UTR-2, URAN, GURT, NDA, NenuFAR, LOFAR and other. Parallel observations with the space missions WIND, STEREO, Cassini and Juno also facilitate improvement of the quality and reliability of low-frequency radio astronomical experiments.

The third part of the work dealt with the heliograph of the UTR-2 radio telescope description shows that every pixel from the signal received by the corresponding beam of the antenna pattern is the crosscorrelation dynamic spectrum (time-frequency-intensity) measured by the digital spectrum processor in real time. This new generation heliograph allows the solar corona images within 8÷33 MHz with the 4 kHz frequency resolution, time resolution to 1 ms, and for a 90 dB dynamic range. The illustrations of observations of solar corona and other radio sources made in summer of 2010 with the heliograph are demonstrated.

A detailed description of the wideband analog- digital heliograph based on the UTR-2 radio telescope has been suggested. This device operates in the parallel-serial scheme, when five uniformly spaced beams (formed simultaneously) of the antenna pattern scan a given radio source (e. g. solar corona). As a result, the obtained image represents a cadre consisting of 5×8 pixels with the spatial resolution 25′×25′. Every pixel is caused by a signal from the corresponding beam of the antenna pattern.

Context.The Sun’s activity can appear in terms of radio bursts. In the frequency range 8−33 MHz the radio telescope URAN-2 observed special fine structures appearing as a chain of stripes of enhanced radio emission in the dynamic radio spectrum. The chain drifts slowly from 26 to 23 MHz within 4 min. The individual structures consist of a “head” at the high-frequency edge and a “tail” rapidly drifting from the “head” to lower frequencies over an extent of ≈10 MHz within 8 s. Since they resemble the well-known “herring bones” in type II radio bursts, they are interpreted as shock accelerated electron beams.Aims.The electron beams generating these fine structures are considered to be produced by shock drift acceleration (SDA). The beam electrons excite Langmuir waves which are converted into radio waves by nonlinear wave-plasma processes. That is called plasma emission. The aim of this paper is to link the radio spectral data of these fine structures to the theoretical results in order to gain a better understanding of the generation of energetic electrons by shocks in the solar corona.Methods.Adopting SDA for generating energetic electrons, the accelerated electrons establish a beam-like velocity distribution. Plasma emission requires the excitation of Langmuir waves, which is efficient if the velocity of the beam electrons exceeds a few times thermal electron speed. That is the case if the angle between the shock normal and the upstream magnetic field is nearly perpendicular. Hence, the Rankine-Hugoniot relationships, which describe the shock transition in the framework of magnetohydrodynamics, are evaluated for the special case of nearly perpendicular shocks under coronal circumstances.Results.The radio data deduced from the dynamic radio spectrum can be related in the best way to the theoretical results, if the electron beams, which generate these fine structures, are generated via SDA at an almost perpendicular shock, which is traveling nearly horizontally to the surface of the Sun.

International audience

International audience