Аверкиев Н.С., Bersuker I.B., Гудков В.В., Жевстовских И.В., Сарычев М.Н., Zherlitsyn S., Yasin S., Коростелин Ю.В., Суриков В.Т. «Определение параметров эффекта Яна–Теллера в примесных кристаллах с помощью ультразвуковых исследований» Журнал экспериментальной и теоретической физики, 156, № 1, с. 87-97 (2019)

Для кристаллов с примесными ионами в трехкратно вырожденном электронном T-состоянии разработан метод определения как симметрийных свойств деформаций, так и типа эффекта Яна–Теллера. Метод основан на расчетах изотермического вклада примесной подсистемы в упругие модули кристалла, поглощение и скорость нормальных мод для всех трех возможных задач: T⊗, T⊗t₂ или T⊗ (c+t₂). Проведено сравнение результатов расчета с экспериментальными данными. Эффективность метода продемонстрирована на примере кристалла CdSe:Cr²⁺. Установлено, что центр CrSe₄ описывается в рамках задачи T⊗e. Определены параметры адиабатического потенциала основного состояния.

Chengming T., Baolin T., Yihua Ya., Wei W., Linjie Ch., Fei L., Yujiang D. «Fine structure events in microwave emission during solar minimum» Солнечно-земная физика, 5, № 2, с. 4-10 (2019)

The solar minimum is a period with a relatively smaller number of sunspots and solar eruptions, and has been less studied before. Since the radio signal rapidly responds to the change of solar plasma and magnetic field, we perform a comprehensive analysis of high resolution spectrum data from SBRS and MUSER: 1) a search for solar radio bursts of different kinds in recent solar minima (2007–2009 and 2016–2018); 2) an analysis of several typical radio burst events, negative and positive drifting bursts, for example the November 22, 2015 and August 29, 2016 events; superfine spectral structure events with mini-flares and even without sunspots, for example the March 28, 2008 and July 04, 2017 events. These results show that there were many radio bursts with a fine structure during solar minima. These events occurred not only in powerful flares, but also in faint flares (class C and B by GOES) or even without flares, but in regions related to weak brightenings or ejecta. We assume that the weak solar radio bursts observed by telescopes with high sensitivity and low interference will help us to understand the basic physical characteristics of small-scale solar eruptions.

Sha Li., Yihua Ya., Zhijun Ch., Wei W. «Comparing simulated results of folded and unfolded log-periodic antenna used for observing the Sun» Солнечно-земная физика, 5, № 2, с. 49-54 (2019)

There are two antenna arrays located in Mingantu Spectral Radio Heliograph (MUSER). MUSER-I and MUSER-II cover the frequency band ranging from 0.4 to 2 GHz and from 2 to 15 GHz respectively. A third antenna array covering 30–240 MHz will be established in the coming years. A log-periodic antenna is one of the choices for MUSER low frequency band; it radiates structures capable of maintaining consistent impedance characteristics over a wide bandwidth. Due to the ability of achieving high gain, it is widely used in many broadband applications. In this program, folded and unfolded log-periodic antennas are simulated for the Meridian project. In order to improve its return loss, this antenna is optimized with the width of each pole and the height of the substrate. This optimized process has been implemented in the simulated software HFSS.

Jun Ch., Yihua Ya., Dong Zh., Long Xu. «Scale sequentially CLEAN for MingantU SpEctral Radioheliograph» Солнечно-земная физика, 5, № 2, с. 55-62 (2019)

MingantU SpEctral Radioheliograph (MUSER) is a solar-dedicated radio heliograph, adopting aperture synthesis technique to image the Sun in the frequency range of 0.4 GHz to 15 GHz. MUSER has extremely high spatial resolution, temporal resolution, and frequency resolution beyond those of contemporary devices of the same category. For aperture synthesis, the number of antennas is limited, so sparse sampling of Fourier components is actually obtained for solar observation, which corresponds to the situation that a clean image is convolved by a dirty beam with strong sidelobe in a spatial domain. Thus, the deconvolution, such as CLEAN, is generally required for imaging the aperture synthesis to remove artifacts caused by the convolving dirty beam. The traditional Hogbom CLEAN is based on the assumption that an observed object is only composed of point sources. This assumption does not hold for solar observation, where the solar disk is an extended source containing complex structures and diffuse features. In this paper, we make the first attempt to employ scale sequentially CLEAN for MUSER imaging, including Multi-Resolution CLEAN and Wavelet CLEAN. The experimental results demonstrate that the scale sequentially CLEAN, especially wavelet CLEAN, is superior to the traditional CLEAN algorithm in smaller number of iterations and improved image quality. We provide optimized wavelet parameters to further improve the performance of wavelet CLEAN.

Leonovich A.S., Quigang Z., Kozlov D.A., Yongfu W. «Alfven waves in the magnetosphere generated by shock wave/plasmapause interaction» Солнечно-земная физика, 5, № 2, с. 11-16 (2019)

We study Alfven waves generated in the magnetosphere during the passage of an interplanetary shock wave. After shock wave passage, the oscillations with typical Alfven wave dispersion have been detected in spacecraft observations inside the magnetosphere. The most frequently observed oscillations are those with toroidal polarization; their spatial structure is described well by the field line resonance (FLR) theory. The oscillations with poloidal polarization are observed after shock wave passage as well. They cannot be generated by FLR and cannot result from instability of high-energy particle fluxes because no such fluxes were detected at that time. We discuss an alternative hypothesis suggesting that resonant Alfven waves are excited by a secondary source: a highly localized pulse of fast magnetosonic waves, which is generated in the shock wave/plasmapause contact region. The spectrum of such a source contains oscillation harmonics capable of exciting both the toroidal and poloidal resonant Alfven waves.

Chengming T., Baolin T., Yihua Ya., Wei W., Linjie Ch., Fei L., Yujiang D. «Fine structure events in microwave emission during solar minimum» Солнечно-земная физика, 5, № 2, с. 4-10 (2019)

The solar minimum is a period with a relatively smaller number of sunspots and solar eruptions, and has been less studied before. Since the radio signal rapidly responds to the change of solar plasma and magnetic field, we perform a comprehensive analysis of high resolution spectrum data from SBRS and MUSER: 1) a search for solar radio bursts of different kinds in recent solar minima (2007–2009 and 2016–2018); 2) an analysis of several typical radio burst events, negative and positive drifting bursts, for example the November 22, 2015 and August 29, 2016 events; superfine spectral structure events with mini-flares and even without sunspots, for example the March 28, 2008 and July 04, 2017 events. These results show that there were many radio bursts with a fine structure during solar minima. These events occurred not only in powerful flares, but also in faint flares (class C and B by GOES) or even without flares, but in regions related to weak brightenings or ejecta. We assume that the weak solar radio bursts observed by telescopes with high sensitivity and low interference will help us to understand the basic physical characteristics of small-scale solar eruptions.