Oscillation of solar radio emission at coronal acoustic cut-off frequency

Recent SECCHI COR2 observations on board STEREO-A spacecraft have detected density structures at a distance of 2.5--15~R propagating with periodicity of about 90~minutes. The observations show that the density structures probably formed in the lower corona. We used the large Ukrainian radio telescope URAN-2 to observe type IV radio bursts in the frequency range of 8--32~MHz during the time interval of 08:15--11:00~UT on August 1, 2011. Radio emission in this frequency range originated at the distance of 1.5--2.5 R according to the Baumbach-Allen density model of the solar corona. Morlet wavelet analysis showed the periodicity of 80~min in radio emission intensity at all frequencies, which demonstrates that there are quasi-periodic variations of coronal density at all heights. The observed periodicity corresponds to the acoustic cut-off frequency of stratified corona at a temperature of 1~MK. We suggest that continuous perturbations of the coronal base in the form of jets/explosive events generate acoustic pulses, which propagate upwards and leave the wake behind oscillating at the coronal cut-off frequency. This wake may transform into recurrent shocks due to the density decrease with height, which leads to the observed periodicity in the radio emission. The recurrent shocks may trigger quasi-periodic magnetic reconnection in helmet streamers, where the opposite field lines merge and consequently may generate periodic density structures observed in the solar wind.Comment: 10 pages, 6 figures, accepted in A&

Radio seismology of the outer solar corona

Observed oscillations of coronal loops in EUV lines have been successfully used to estimate plasma parameters in the inner corona (< 0.2 R_0, where R_0 is the solar radius). However, coronal seismology in EUV lines fails for higher altitudes because of rapid decrease in line intensity. We aim to use radio observations to estimate the plasma parameters of the outer solar corona (> 0.2 R_0). We use the large Ukrainian radio telescope URAN-2 to observe type IV radio burst at the frequency range of 8-32 MHz during the time interval of 09:50-12:30 UT in April 14, 2011. The burst was connected to C2.3 flare, which occurred in AR 11190 during 09:38-09:49 UT. The dynamic spectrum of radio emission shows clear quasi-periodic variations in the emission intensity at almost all frequencies. Wavelet analysis at four different frequencies (29 MHz, 25 MHz, 22 MHz and 14 MHz) shows the quasi-periodic variation of emission intensity with periods of 34 min and 23 min. The periodic variations can be explained by the first and second harmonics of vertical kink oscillation of transequatorial coronal loops, which were excited by the same flare. The apex of transequatorial loops may reach up to 1.2 R_0 altitude. We derive and solve the dispersion relation of trapped MHD oscillations in a longitudinally inhomogeneous magnetic slab. The analysis shows that a thin (with width to length ratio of 0.1), dense (with the ratio of internal and external densities of > 20) magnetic slab with weak longitudinal inhomogeneity may trap the observed oscillations. Seismologically estimated Alfv\'en speed inside the loop at the height of 1 R_0 is 1000 km/s. Then the magnetic field strength at this height is estimated as 0.9 G. Extrapolation of magnetic field strength to the inner corona gives 10 G at the height of 0.1 R_0.Comment: 12 pages, 10 figures, Accepted in A&

СОСТОЯНИЕ ГОМЕОСТАТИЧЕСКОГО РАВНОВЕСИЯ ОРГАНИЗМА У ВПЕРВЫЕ ВЫЯВЛЕННЫХ БОЛЬНЫХ ТУБЕРКУЛЕЗОМ ЛЕГКИХ ДО НАЧАЛА ЛЕЧЕНИЯ

The conducted studies indicate that before the beginning of antituberculous treatment TB patients with homeostatic equilibrium disorder depending on the phase state of the specific process in the lungs, the expression of the intoxication syndrome, the extent of lung tissue damage and the age of the patients. Increasing of BHE(body homeostatic equilibrium) disfunction rate is followed by upraise of defective adaptive reactions. LLI indicators intend for BHE evaluation, H and R of the formed elements of the white bloodcellsintend to state the degree of BHE disfunction.Проведенными исследованиями установлено, что у больных туберкулезом до начала лечения противотуберкулезными препаратами имеется существенное нарушение ГРО от фазового состояния специфического процесса в легких, от выраженности интоксикационного синдрома, от объема поражения легочной ткани и возраста больных. При нарастании глубины нарушения ГРО у них частота неполноценных типов АР возрастает. Показатели ЛЛИ в клинике предназначены для ориентировочной оценки состояния ГРО, а Н и R ФЭБК - для определения глубины его нарушения

PROGRESS IN THE STUDY OF DECAMETER-WAVELENGTH SOLAR RADIO EMISSION WITH UKRAINIAN RADIO TELESCOPES. Part 2

Subject and Purpose. This part of the paper continues presentation of results of the solar radio emission studies performed with Ukrainian radio telescopes over the past 20 years. The importance is stressed of developing adequate instruments and methods for identifying the nature of decameter-wavelength radio emissions from the Sun. Methods and Methodology. The low frequency Ukrainian radio telescopes UTR-2, GURT and URAN-2 have been used in the project along with other ground- and space based instruments in order to achieve a comprehensive understanding of physical conditions in the solar corona. Results. Special methods and tools have been developed for studying radio frequency burst emissions against the background of strong interference. Unique data have been obtained concerning sources of sporadic radio emissions from the Sun, as well as the contribution from wave propagation effects and the impact of the ionosphere on the results of observations. The most significant observational and theoretical results are presented, obtained in the study of solar low frequency emissions over the past 20 years. Solar radio emissions are shown to be efficient sounding signals not for the solar corona alone but for the Earth’s ionosphere as well, which allows identifying its impact on the results of radio astronomy observations. Conclusions. The Ukrainian radio telescopes of the meter and decameter wavebands currently are unrivaled tools for investigating the Universe in the low-frequency range of radio waves. Owing to their advanced characteristics, they make a significant contribution to the progress of world’s solar radio astronomy