Ulyanov O.M., Shevtsova A.I., Yerin S.M. «Determination of the rotation measure value sign when receiving a single linear polarization of the pulsar radio emission» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 253-267 (2020)

Purpose: The studies of pulsars allow enriching our knowledge in determination of parameters of both the exotic electron-positron plasma in the pulsar magnetosphere with strong magnetic field and the ordinary ion-electron plasma of the interstellar medium, which exists in a weak magnetic field. To determine the parameters of the both plasma types it is reasonable to use polarization characteristics of a pulsed radio emission of pulsars. An accurate determination of these characteristics is quite a complex problem. For its solving, primarily we have to determine two parameters of the propagation medium – its dispersion and rotation measures. Their absolute values can be determined with the relative precision of 10-4, but the problem of rotation measure value sign determination arises. This sign depends on the interstellar magnetic field direction along the line of sight. Hear, a new method of rotation measure value sign determination is proposed. Design/methodology/approach: Muller polarization matrices are usually used for determination of such a propagation parameter as the rotation measure absolute value. When only one linear polarization is received, using of these matrices allows quite accurate determining the absolute value of the rotation measure, but not the sign of this parameter due to a certain symmetry of these matrices with respect to the direction of the linear polarization rotation plane. If we complement the system of equations, which determines the rotation measure value, with some new additional components, which take into account the contributions of the Earth ionosphere and magnetosphere to the rotation measure value, one can notice that this contribution is always positive in the Southern magnetic hemisphere (the majority of the Northern geographical hemisphere) and is always negative in the Northern magnetic hemisphere (the majority of the Southern geographical hemisphere). Moreover, the absolute value of this contribution is maximal at noon and minimal at midnight, when the concentration of ions in the Earth ionosphere is maximal and minimal, respectively. Accounting for these regularities allows to determine not only the absolute value of the rotation measure, but also its sign by means of two independent time-shifted estimations of the observed absolute value of this parameter for various ionization degrees of the Earth ionosphere. Findings: We show that using of additional equations, which take into account the contribution of the Earth ionosphere and magnetosphere to the value of the rotation measure parameter, allows full determination of this parameter accounting for the sign of this value even for the antennas, which can record a single linear polarization only. This approach allows to determine all polarization parameters of the pulsar radio emission as well as of the pulsed or continuum polarized radio emission of other cosmic sources. Conclusions: The paper presents the results of measurement of the rotation measure for the two closest to the Earth pulsars, namely J0814+7429 (B0809+74), J0953+0755 (B0950+08), and the comparison of the proposed technique for this parameter determination with other existing techniques.

Gorbunov A.A., Ryabov M.I., Sukharev A.L., Bezrukovs V.V. «Periodic and sporadic variations in the spectral flux density of the Cas A supernova remnant» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 268-275 (2020)

Purpose: Based on the long-term study data in all radio spectrum ranges, the nature of deviations of spectral flux density of the Cas A supernova remnant from the tendency of its secular decrease is considered. The aim of this work is determining the presence of quasiperiodic variations and sporadic changes in the Cas A spectral radiation flux density depending on frequency. Design/methodology/approach: The main database is using the published results obtained with the method of absolute measurements of the Cas A spectral radiation flux density in a wide range from millimeter to decimeter wavelengths, as well as the results obtained with the method of relative measurements of the ratio of the flux densities of the Cas A supernova remnant and radio galaxy Cyg A, this latter being used as a reference source in the meter wavelength range. For making comparison with the aforesaid data obtained with different methods, the results of a long-term monitoring (since 1987) of the variation of the ratio of the spectral flux densities of Cas A and Cyg A made with the URAN-4 radio telescope of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine at 25 MHz were used. Findings: As a result of the analysis of the observed data for the Cas A radiation flux density in the entire radio wavelength range, the existence of quasiperiodic variations in the range from millimeter to meter wavelengths within 2 to 9 years has been noted. The reason for the detected quasiperiodic variations can be the processes in the Cas A remnant itself. In the decameter wavelength range, according to monitoring data obtained with the URAN-4 radio telescope, the seasonal-diurnal and long-term variations are noted, being associated with changes in the ionosphere state in the solar activity cycle, with some weak appearance of the secular decrease of the Cas A radiation flux. The presence of sporadic variations in the ratio of the spectral flux densities of Cas A and Cyg A is associated with the effect of the increased solar activity. For explaining the lowering of the Cas A spectral flux density to the Cyg A level and maintaining the excess of the Cas A flux at decameter waves, the quasi-simultaneous observations made with radiotelescopes for different wavelength ranges will be required. Conclusions: The evolution of the Cas A supernova remnant remains the focus of interest of current research efforts. An intriguing moment was the discovery of a point X-ray source in the center of radio source Cas A as a possible supernova remnant. The role of this source in the Cas A radio flux secular decrease and in its variations needs to be clarified. A detailed analysis of the long-term data and making quasi-simultaneous observations will allow to reveal the processes occurring in the radio source itself and to determine the influence of the ionosphere state on the results of measurements. A joint program is suggested for observations of Cas A and Cyg A flux variations with the RT-32 and RT-16 radio telescopes, the LOFAR element of the Ventspils International Radio Astronomy Center (Latvia), and the URAN, UTR-2 and GURT radio telescopes of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine.

Luo Y., Chernogor L.F., Garmash K.P. «Geomagnetic effect of Turkish earthquake of January 24.2020» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 276-289 (2020)

Purpose: The main cause of geomagnetic disturbances are cosmic sources, processes acting in the solar wind and in the interplanetary medium, as well as large celestial bodies entering the terrestrial atmosphere. Earthquakes (EQs) also act to produce geomagnetic effects. In accordance with the systems paradigm, the Earth–atmosphere–ionosphere–magnetosphere system (EAIMS) constitute a unified system, where positive and negative couplings among the subsystems, as well as feedbacks and precondition among the system components take place. The mechanisms for the action of EQs and processes acting in the lithosphere on the geomagnetic field are poorly understood. It is considered that the EQ action is caused by cracking of rocks, fluctuating motion in the pore fluid, static electricity discharges, etc. In the course of EQs, the seismic, acoustic, atmospheric gravity waves (AGWs), and magnetohydrodynamic (MHD) waves are generated. The purpose of this paper is to describe the magnetic effects of the EQ, which took place in Turkey on 24 January 2020. Design/methodology/approach: The measurements are taken with the fluxmeter magnetometer delivering 0.5–500 pT sensitivity in the 1–1000 s period range, respectively, and in a wide enough studied frequency band within 0.001 to 1 Hz. The EM-II magnetometer with the embedded microcontroller digitizes the magnetometer signals and performs preliminary filtering over 0.5 s time intervals, while the external flash memory is used to store the filtered out magnetometer signals and the times of their acquisition. To investigate quasi-periodic processes in detail, the temporal variations in the level of the H and D components of the geomagnetic field were applied to the systems spectral analysis, which makes use of the short-time Fourier transform, the wavelet transform using the Morlet wavelet as a basis function, and the Fourier transform in a sliding window with a width adjusted to be equal to a fixed number of harmonic periods. Findings: The train of oscillations in the level of the D component observed 25.5 h before the EQ on 23 January 2020 is supposed to be associated with the magnetic precursor. The bidirectional pulse in the H component observed on 24 January 2020 could be due to the piston action of the EQ, which had generated an MHD pulse. The quasi-periodic variations in the level of the H and D components of the geomagnetic field, which followed 75 min after the EQ, were caused by a magnetic disturbance produced by the traveling ionospheric disturbances due to the AGWs launched by the EQ. The magnetic effect amplitude was estimated to be close to 0.3 nT, and the quasi-period to be 700–900 s. The amplitude of the disturbances in the electron density in the AGW field was estimated to be about 8% and the period of 700-900 s. Damping oscillations in both components of the magnetic field were detected to occur with a period of approximately 120 s. This effect is supposed to be due to the shock wave generated in the atmosphere in the course of the EQ. Conclusions: The magnetic variations associated with the EQ and occurring before and during the EQ have been studied in the 1–1000 s period range.

Luo Y., Chernogor L.F. «Electromagnetic effects of acoustic and atmospheric gravity waves in the near-earth atmosphere» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 290-307 (2020)

Purpose: Acoustic and atmospheric gravity waves (AAGW) are generated by many natural and anthropogenic sources. The AAGW propagation at ionospheric heights is accompanied by the generation of disturbances in the magnetic and electric fields. The plasma presence plays a crucial role. The mechanisms for generating electrical and magnetic disturbances in the near-Earth atmosphere by the AAGW have been studied much worse. Therefore, the validation of the capability to generate electromagnetic disturbances in the near-Earth atmosphere by the AAGW is an urgent problem. The purpose of this paper is to describe the mechanism for generating disturbances in the electric and magnetic ields in the near-Earth atmosphere under the action of AAGW and to estimate the amplitudes of these disturbances for various AAGW sources. Design/methodology/approach: The impact of a series of highenergy ources often results in the generation of synchronous disturbances in the acoustic and geoelectric (atmospheric) fields, when an approximate proportionality between the pressure amplitude and the amplitude of the disturbances in the atmospheric electric field is observed to occur. Based on the observational data and making use of the Maxwell equations, the theoretical estimates of the disturbances in the electric and magnetic ields have been obtained. Findings: Simplified expressions have been obtained for estimating the amplitudes of the electric and magnetic fields under the action of the AAGW generated by natural and manmade sources. The amplitudes of the electric and magnetic fields generated by the AAGW of natural and manmade origin, which travel in the near-Earth atmosphere, have been calculated. The amplitudes of the AAGW generated electric and magnetic ields are shown to be large enough to be detected with the existing electrometers and fluxmeter magnetometers. The magnitudes of the amplitudes of the electric and magnetic fields generated in the near-Earth atmosphere under the action of AAGW are large enough to trigger coupling between the subsystems in the Earth–atmosphere–ionosphere–magnetosphere system. Conclusions: The estimates and not numerous observations are in good agreement.

Komendant V.H. «On the character of an artificial satellite drag under various states of solar and geomagnetic activity» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 308-323 (2020)

Purpose: The artificial satellites drag in the atmosphere remains an urgent problem to date. In this work, the artificial satellites data are used in order to study the atmosphere state under various manifestations of solar and geomagnetic activity. The selected satelites were moving uncontrollable being good indicators of the upper atmosphere state. The B-star (drag term) drag coefficient is used in this work. This term is used in the SGP and SDP models to take into account the resistance of the atmosphere to the satelite orbital motion. The data of the drag of two artificial satellites, one moving in elliptical and the other in circular orbits at midlatitudes (orbital plane angles of 58°-60°) were considered. These data include the end of the 23rd solar activity cycle, as well as the growth, the maximum and the decay phases of the 24th solar cycle (years 2005–2017). Seven periods of anomalous drag of the satellites were analyzed. They are: 4 monthly periods (two in 2005 and two in 2011) and 3 yearly periods (within 19.07.2014 to 22.08.2015), five-year long (2005–2010) and six-year long (2011–2017) periods. Design/methodology/approach: The periodogram analysis was made. This allowed to reveal the periodic processes in changes in the state of the atmosphere of different duration. The correlation coefficients of the B-star drag term with the indices of solar and geomagnetic activity were calculated. The analysis of extreme drag of the satellites in the periods of the increased solar and geomagnetic activity (intervals of observation lasting a month) was made. Findings: Using the solar and geomagnetic data we found that some month-long part of the anomalous drag periods were followed by flares on the Sun and the arrival of the coronal mass ejections into the near-Earth space. At time intervals of yearlong observations the highest values (0.5-0.7) were obtained for the coefficients of the B-star parameter correlation with the solar activity indices – solar radiation at the wavelength of 10.7 cm, F10.7, and Lyman alpha radiation, Lα. At monthly time intervals, the largest values of the correlation coefficients were obtained for the B-stars with the electron fluxes with energies above 0.6 and 2 MeV, E, (0.3–0.5), the Lyman alpha radiation, Lα, (0.58–0.73 for a сircular orbit satellite), and the solar constant, TSI, (0.3–0.6), as well as the geomagnetic storms intensity index, Dst , (0.66–0.69). Periodogram calculations show the presence of a whole spectrum of periods in the deceleration of a circular orbit satellite and a dedicated period for an elliptical orbit satellite. Conclusions: The B-star drag term dependences on the indices of solar and geomagnetic activity during some periods of their intensification for the 23–24 cycles of solar activity are considered. The periodogram analysis made together with the analysis of the conditions and parameters of space weather allows to see the general and more detailed picture of the solar and geomagnetic activity influence on the change in the motion of the satellite in the atmosphere. The B-star drag term helps to consider only the atmosphere influence on the artificial satellite movement in the near-Earth space.

Sobitnyak L.I., Ryabov M.I., Orlyuk M.I., Sukharev A.L., Romenents A.O., Sumaruk Yu.P., Pilipenko A.A. «Analysis of the magnetic storms catalog for monitoring radio source fluxe data with the URAN-4 radio telescope in the Odesa magnetic anomaly zone» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 324-330 (2020)

Purpose: Compilation of a digital catalog of magnetic storms in the Odesa magnetic anomaly zone in order to find the reasons for possible changes in the radiation fluxes of cosmic radio sources, according to observations at the URAN-4 radio telescope. Design/methodology/approach: Since 1987 until now, the radio flux of powerful galactic and extragalactic radio sources has been monitored at the URAN-4 radio telescope of the Odesa Observatory of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine. The monitoring program includes radio galaxies 3C274, 3C405 and supernova remnants 3C144, 3C461. Changes in the radio source flux level are determined by the ionosphere state due to the changes in space weather. At the “Odesa” geomagnetic observatory of the Institute of Geophysics of the National Academy of Sciences of Ukraine, the geomagnetic field measurements have been made since 1948. Simultaneously, the measurements of three elements of the geomagnetic field: horizontal component (H), vertical component (Z) and inclination (D), have been recorded. Findings: Using the “Odesa” geomagnetic observatory data, the digital catalog of magnetic storms was compiled for the measuring period of the powerful space radio source fluxes obtained with the URAN-4 radio telescope. For the magnetic storms monitored during the periods of 1987–1995 and 2000–2009, the date and time are shown for the beginning and the end of the magnetic storm, the magnetic storm duration, the amplitude of the three magnetic field elements, being H, Z, and D, and the magnetic storm type characteristic.The “Odesa” geomagnetic observatory is located near the magnetic anomaly zone. To find the distinctions in manifestations of the geomagnetic activity arisen owing to the magnetic anomaly existence, the geomagnetic disturbances recorded at the “Odesa” and “Moscow” (IZMIRAN, Russia) observatories were compared. It was shown that the total annual duration of the magnetic storms was longer in Odesa than in Moscow. This demonstrates some special role of the magnetic anomaly in the development of geomagnetic disturbances. Conclusions: The digital catalog of magnetic storms in the Odesa magnetic anomaly zone was compiled for the 1987–1995 and 2000–2009 periods. It is also planned to terminate working over the complete catalog of magnetic storms recorded at the “Odesa” observatory for the entire continuous period of monitoring space radio sources at the URAN-4 radio telescope in order to find the manifestations of geomagnetic disturbances impact upon the ionosphere state and changes of intensity in cosmic radio source fluxes. These studies are supplemented by the comparative analysis of the “Odesa” observatory geomagnetic data and the data from some other geomagnetic observatories.

«To the 80-th Anniversary of Ya. S. Yatskiv» Радиофизика и радиоастрономия (Украина), 25, № 4, с. 331-332 (2020)

Выдающемуся украинскому ученому, организатору науки и общественному деятелю, академику НАН Украины Ярославу Степановичу Яцкиву исполнилось 80 лет. Родился Я.С. Яцкив 25 октября 1940 в с. Данильча Рогатинского района Ивано-Франковской области в крестьянской семье. В 1960 г.. (В 20-летнем возрасте!) Закончил Львовский политехнический институт по специальности "астрономо-геодезия». Как астроном-наблюдатель работал в Полтавской гравиметрической обсерватории АН УССР. В 1965 г.. Закончил аспирантуру Главной астрономической обсерватории АН УССР и защитил кандидатскую диссертацию. В 1965-1974 гг. – младший научный сотрудник, ученый секретарь, заместитель директора по научной работе ГАО АН УССР. С 1975 г.. И до сих пор - директор этой обсерватории. В 1976 г.. Защитил докторскую диссертацию по специальности "Астрометрия и небесная механика". С 1979 г. – член-корреспондент АН УССР Отделение физики и астрономии, с 1985 г. – академик АН УССР по специальности астрономия. Научные достижения академика Я. С. Яцкива хорошо известны. Он автор и соавтор более 200 научных работ, нескольких книг. Научная тематика этих работ посвящена особенностям вращения Земли, фундаментальной астрометрии, космической геодинамике и космической планетодинамици. Ярослав Степанович был инициатором введения в практику лазерной локации искусственных спутников Земли, радиоинтерферометрии со сверхдлинной базой, радиотехнических наблюдений навигационных спутников и создание в Украине постоянной сети станции ГНСС. В 1980-е гг. Я.С. Яцкив был ответственным за организацию наземного астрономического обеспечения международного проекта "Вега" (исследование Венеры и кометы Галлея), за что получил Государственную премию СССР в области науки и техники. Свою первую Государственную премию УССР получил еще в 1983, а в 2003 г. – Государственную премию Украины. В том же году удостоен премии Рене Декарта ЕС. Кроме этих премий, Я.С. Яцкив получил еще с десяток других престижных премий. За долгую трудовую жизнь Ярослав Степанович получил большое количество наград и отличий. Вот несколько из них: орден "Знак почета" (1982), медаль "Ветеран труда" (1987), орден "За заслуги" III ст. (1987), орден "За заслуги" II ст. (2000), орден Дружбы (РФ, 2001), орден "За заслуги" I в. (2012), орден князя Ярослава Мудрого V в. (2016). Я.С. Яцкив ведет активную научно-организационную деятельность. Он инициатор создания в 1991 году. И бессменный президент Украинской астрономической ассоциации, инициатор создания в 1992г. Национального космического агентства Украины (теперь ГКАУ), соавтор первой Национальной космической программы Украины (1993). Основал в 1994 году. Журнал "Космическая наука и технология". С 1998 г.. Активно работает как член Президиума НАНУ. С 2001 г.. Выполняет обязанности заместителя Председателя Совета по космическим исследованиям. В 2004-2009 гг. Он был вице-президентом Европейского астрономического союза. Руководил подготовкой и выполнением Целевой комплексной программы НАН Украины по научным космическим исследованиям на 2012–2016 гг. Ярослав Степанович выполнял также обязанности Председателя Украинского международного комитета по вопросам науки и культуры при НАНУ (с 1996 г.), Председателя научно-издательского совета НАНУ (с 2002 г.), Председателя Государственной комиссии единого времени и эталонных частот (1996–2010), Президента международной ассоциации украинистов (2005–2008) и является членом Комитета научной терминологии при Президиуме НАНУ (с 2017 г.). Очень велик список почетных званий академика. Вот некоторые из них: почетный член Международной ассоциации геодезии (1991), Астроном 1-й категории Парижской обсерватории (1992), Заслуженный деятель науки и техники Украины (1998), Почетный доктор Национального университета "Львовская политехника" (2005), Почетный доктор Прикарпатского национального университета имени В. Стефаника (2006), Почетный профессор национального педагогического университета имени М.П. Драгоманова (2010), Почетный доктор Харьковского национального университета имени В.Н. Каразина (2011), Почетный доктор Киевского национального университета имени Тараса Шевченко (2015 ), Почетный доктор Одесского национального университета имени И.И. Мечникова (2015), Почетный профессор национального университета "Киево-Могилянская академия" (2016). Как Председатель научно-издательского совета НАН Украины академик Я. С. Яцкив отвечает за решение задач издательской деятельности, развитие полиграфической базы НАН Украины, осуществляет общее руководство издательством "Наукова думка" НАН Украины и Издательским домом "Академпериодика" НАН Украины. Он является главным редактором журналов "Кинематика и физика небесных тел", "Мировоззрение", "Космическая наука и технология", заместителем главного редактора журнала "Наука и инновации", членом редколлегий журналов "Радиофизика и радиоастрономия", "Наука и науковедение", "Мир физики", "Artificial Satellites", "Память веков"и др. Ученый Я.С. Яцкив имеет активную гражданскую позицию. Он стремится объединить демократические силы независимой Украины, участвует в работе Конгресса украинской интеллигенции. Усилия академика направленные на внедрение демократических принципов управления украинской наукой. Очень популярны многочисленные выступления Ярослава Степановича в средствах массовой информации по проблемам науки, астрономической образования и общественной жизни. Где-то далеко в космосе пролетает малая планета 2728, которая носит имя великого украинского астронома – "Яцкив".