Radio echo in the turbulent corona and simulations of solar drift-pair radio bursts

Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pair parameters are qualitatively analyzed and compared with the newly developed Monte Carlo ray-tracing technique simulating radio-wave propagation in the inhomogeneous anisotropic turbulent solar corona. The results suggest that drift-pair bursts can be formed due to a combination of refraction and scattering processes, with the trailing component being the result of turbulent reflection (turbulent radio echo). The formation of drift-pair bursts requires an anisotropic scattering with the level of plasma density fluctuations comparable to that in type III bursts, but with a stronger anisotropy at the inner turbulence scale. The anisotropic radio-wave scattering model can quantitatively reproduce the key properties of drift-pair bursts: the apparent source size and its increase with time at a given frequency, the parallel motion of the source centroid positions, and the delay between the burst components. The trailing component is found to be virtually cospatial and following the main component. The simulations suggest that drift-pair bursts are likely to be observed closer to the disk center and below 100 MHz due to the effects of free–free absorption and scattering. The exciter of drift pairs is consistent with propagating packets of whistlers, allowing for a fascinating way to diagnose the plasma turbulence and the radio emission mechanism

The efficiency of electron acceleration during the impulsive phase of a solar flare

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a lack of observational constraints related to conditions in the primary acceleration region itself. Accelerated electrons with energies above $\sim$20~keV are revealed by hard X-ray (HXR) bremsstrahlung emission, while accelerated electrons with even higher energies manifest themselves through radio gyrosynchrotron emission. Here we show, for a well-observed flare on 2017~September~10, that a combination of \emph{RHESSI} hard X-ray and and SDO/AIA EUV observations provides a robust estimate of the fraction of the ambient electron population that is accelerated at a given time, with an upper limit of $\sim 10^{-2}$ on the number density of nonthermal ($\ge 20$~keV) electrons, expressed as a fraction of the number density of ambient protons in the same volume. This upper limit is about two orders of magnitude lower than previously inferred from microwave observations of the same event. Our results strongly indicate that the fraction of accelerated electrons in the coronal region at any given time is relatively small, but also that the overall duration of the HXR emission requires a steady resupply of electrons to the acceleration site. Simultaneous measurements of the instantaneous accelerated electron number density and the associated specific electron acceleration rate provide key constraints for a quantitative study of the mechanisms leading to electron acceleration in magnetic reconnection events.Comment: 5 figures, 10 page

Cold Solar Flares I. Microwave Domain

We identify a set of ~100 "cold" solar flares and perform a statistical analysis of them in the microwave range. Cold flares are characterized by a weak thermal response relative to nonthermal emission. This work is a follow up of a previous statistical study of cold flares, which focused on hard X-ray emission to quantify the flare nonthermal component. Here we focus on the microwave emission. The thermal response is represented by the soft X-ray emission measured by the GOES X-ray sensors. We obtain spectral parameters of the flare gyrosynchrotron emission and investigate patterns of the temporal evolution. The main results of the previous statistical study are confirmed: as compared to a "mean" flare, the cold flares have shorter durations, higher spectral peak frequencies, and harder spectral indices above the spectral peak. Nonetheless, there are some cold flares with moderate and low peak frequencies. In a majority of cold flares, we find evidence suggesting the presence of the Razin effect in the microwave spectra, indicative of rather dense flaring loops. We discuss the results in the context of electron acceleration efficiency

Millimeter and X-Ray Emission from the 5 July 2012 Solar Flare

The 5 July 2012 solar flare SOL2012-07-05T11:44 (11:39 – 11:49 UT) with an increasing millimeter spectrum between 93 and 140 GHz is considered. We use space and ground-based observations in X-ray, extreme ultraviolet, microwave, and millimeter wave ranges obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager, Solar Dynamics Observatory (SDO), Geostationary Operational Environmental Satellite, Radio Solar Telescope Network, and Bauman Moscow State Technical University millimeter radio telescope RT-7.5. The main parameters of thermal and accelerated electrons were determined through X-ray spectral fitting assuming the homogeneous thermal source and thick-target model. From the data of the Atmospheric Imaging Assembly/SDO and differential-emission-measure calculations it is shown that the thermal coronal plasma gives a negligible contribution to the millimeter flare emission. Model calculations suggest that the observed increase of millimeter spectral flux with frequency is determined by gyrosynchrotron emission of high-energy (≳300 ≳300  keV) electrons in the chromosphere. The consequences of the results are discussed in the light of the flare-energy-release mechanisms.</p

DYNAMICS OF BIOCHEMICAL INDICES OF BLOOD SERUM IN RABBITS UNDER THE INFLUENCE OF PHOTOTHERAPY AFTER LOCAL SKIN THERMAL BURN

The article presents data on the dynamics of some biochemical indices in blood serum of rabbits (total protein, alanine aminotransferase, ureal, creatinine, total cholesterol, glucose) during phototherapy of local skin thermal injury using "Bioprone", "Rikta", "Azor", OKN-11M, BOP-4 devices in 5-15 days after wounding. Obtained data testifies to the development of the response of an organism in the form of metabolic processes aimed at the maintenance of constant internal environment but expressed less that at vast burns. Course of phototherapy quite effectively but without distinct differentiation by the method of therapy has positive effect on the normalization of biochemical indices of blood serum

Comparative morphological evaluation of the effectiveness of some practices of light therapy in wound healing (experimental testing)

The article provides information on the efficiency of thermal injury healing in animals (rabbits) under light therapy with «Bioptron», «Ricta», «Azor», 0KN-11M, BOP-4. An analysis has been done of the results of the morphological and planimetric research within 5-15 days after wounding. The factual data received have led to the conclusion that it is advisable to combine different physiotherapeutic practices in wound treatment. Synchronization of processes of an epitelization and maturing of granulyatsionny fabric allowed to recommend for appointment different lengths of waves of optical range in a certain sequence, beginning from ultra-violet beams of short, average range, then laser radiation of an infrared, red range, and also their combination, then to continue influence by the polarized light through standard periods (courses)

Study of Integrated Light Spectra of 48 Globular Clusters in the Galaxy M31

В работе определены возрасты, содержания элементов Fe, Ca, Mg, C, Mn, Ti, Cr и впервые удельные содержания гелия (Y) для 48 шаровых скоплений галактики M31. Получены значения металличности в диапазоне [Fe/H] = −2.0 ...−0.7 dex. Скопления оказались старше 10 млрд лет. Мы обсуждаем полученные содержания элементов в сравнении с данными из литературы для скоплений M31 и звезд нашей Галактики.The age, abundances of the elements Fe, Ca, Mg, C, Mn, Ti, Cr and, for the first time, specific helium abundance (Y) are determined for 48 globular clusters of the M31 galaxy. The metallicity values were obtained in the range [Fe/H] = −2.0 ... − 0.7 dex. The clusters appear to be older than 10 billion years. We discuss the determined elemental abundances in comparison with the literature data for globular clusters in M31 and stars in our Galaxy.Работа частично поддержана грантом Министерства науки и высшего образования Российской Федерации № 075-15-2022-262 (13.МНПМУ.21.0003)

Наблюдения Солнца на радиотелескопе РТ-7.5 МГТУ им. Н.Э. Баумана и моделирование миллиметрового излучения солнечной вспышки 2 апреля 2017 года

Presently, in the territory of Russia active millimeter solar observations are under way via Bauman Moscow State Technical University (BMSTU) RT-7.5 radio telescope (Shustikov et al., 2015, Smirnova et al., 2016; Rozanov 1981; Smirnova et al., 2013; Ryzhov et al., 2014). Rozanov 1981; Smirnova et al. 2013; Рыжов и др. 2014). A radio telescope antenna of the 7.75 m diameter with its unique receiving equipment mounted for frequencies of 93 and 140 GHz, (3.2 and 2.2 mm) allows observing the Sun in the mode of tracking area, or scanning, simultaneously at two frequencies. Such observations are a source of the most valuable information on flares - the most powerful solar activity effects. It is impossible to understand a nature of the energy release mechanisms in the solar flares when there is no adequate diagnosis of physical parameters of plasma and magnetic fields. Meanwhile, sub-THz (0.1-1 THz) radio observations make it possible to diagnose the most inaccessible areas for the Sun researchers, i.e. the chromosphere. The ground-based observations in the millimeter range are rare because of high sensitivity requirements for receiving equipment and significant atmosphere disturbances, while the appropriate space projects are just under development. The paper objective is to investigate a nature of the sub-THz emission from the flare with the positive spectral tilt recorded on the RT-7.5 radio telescope on April 2, 2017. To solve this problem, we used observations in the x-ray, ultraviolet, and microwave ranges. Based on the model of the flare Machado et.al. (1980) Chromosphere, a coronal plasma contribution to the millimeter radio emission has been estimated. This approach allows us not only to take a fresh look at the results obtained earlier, but also makes it possible to diagnose in-depth the physical parameters of the flare plasma.В настоящее время на территории России активно проводятся миллиметровые наблюдения Солнца на радиотелескопе РТ-7.5 МГТУ им. Н.Э. Баумана (Шустиков и др. 2015; Смирнова и др. 2016; Rozanov 1981; Smirnova et al. 2013; Рыжов и др. 2014). Антенна радиотелескопа диаметром 7,75 м с установленной на ней уникальной приемной аппаратурой для частот 93 и 140 ГГц, (3.2 и 2.2 мм) позволяет наблюдать Солнце в режиме ведения области, или сканирования, одновременно на двух частотах. Такие наблюдения являются источником ценнейшей информации о вспышках — наиболее мощных проявлениях солнечной активности. Понять природу механизмов энерговыделения в солнечных вспышках без адекватной диагностики физических параметров плазмы и магнитных полей невозможно. Между тем суб-терагерцовые (0.1-1 TГц) радионаблюдения позволяют диагностировать наиболее труднодоступную область для исследователей Солнца - хромосферу. Наземные наблюдения в миллиметровом диапазоне проводятся редко из-за высоких требований к чувствительности приемной аппаратуры и значительных атмосферных помех, в то время как соответствующие космические проекты находятся лишь на стадии разработки. Цель данной работы – исследовать природу суб-терагерцового излучения вспышки с положительным наклоном спектра 02 апреля 2017 г., зарегистрированной на радиотелескопе РТ-7.5. Для решения поставленной задачи использовались наблюдения в рентгеновском, ультрафиолетовом и микроволновом диапазонах. На основе модели вспышечной хромосферы Machado et.al. (1980), оценен вклад корональной плазмы в миллиметровое радиоизлучение. Такой подход позволяет не только по-новому взглянуть на полученные ранее результаты, но и дает возможность провести углубленную диагностику физических параметров вспышечной плазмы