Spatially Resolved Microwave Observations of Multiple Periodicities in a Flaring Loop     

E. G. Kupriyanova  V. F. Melnikov  K. Shibasaki 《Solar physics》2013,284(2):559-578

Quasi-periodic pulsations (QPPs) with at least three simultaneously existing spectral components with periods P≥30 s, P≈20 s, and about P≈10 s were detected during the decay phase of a solar flare on 3 July 2002, observed with the Nobeyama Radioheliograph (NoRH). A detailed study of the spatial structure of the Fourier amplitudes of QPPs along a flaring loop has revealed different spatial distributions of the three components. It is shown that the source of the QPPs with period P≥30 s has its maximum amplitude in the inner region of the loop, between the footpoints. QPPs with period P≈20 s are localized at the periphery of the loop, mainly in the outer parts of the footpoints. The spatial distribution of oscillations with period about P≈10 s contains three regions of high QPP amplitudes: two near the footpoints and one in the middle of the flaring region. It is shown that the observed properties of the spectral components are most accurately described by the fundamental, second, and third harmonics of the kink mode standing waves. This is the first identification of the kink mode in flare loops which is based on strict limitations derived from data on the spatial structure of a pulsating flare region.  相似文献   

Sub-terahertz emission from solar flares: The plasma mechanism of chromospheric emission     

V. V. Zaitsev  A. V. Stepanov  V. F. Melnikov 《Astronomy Letters》2013,39(9):650-659

We consider the plasma mechanism of sub-terahertz emission from solar flares and determine the conditions for its realization in the solar atmosphere. The source is assumed to be localized at the chromospheric footpoints of coronal magnetic loops, where the electron density should reach n ≈ 10¹⁵ cm^?3. This requires chromospheric heating at heights h ? 500 km to coronal temperatures, which provides a high degree of ionization needed for Langmuir frequencies ν _p ≈ 200–400 GHz and reduces the bremsstrahlung absorption of the sub-THz emission as it escapes from the source. The plasma wave excitation threshold for electron-ion collisions imposes a constraint on the lower density limit for energetic electrons in the source, n ₁ > 4 × 10⁹ cm^?3. The generation of emission at the plasma frequency harmonic ν ≈ 2ν _p rather than the fundamental tone turns out to be preferred. We show that the electron acceleration and plasma heating in the sub-THz emission source can be realized when the ballooning mode of the flute instability develops at the chromospheric footpoints of a flare loop. The flute instability leads to the penetration of external chromospheric plasma into the loop and causes the generation of an inductive electric field that efficiently accelerates the electrons and heats the chromosphere in situ. We show that the ultraviolet radiation from the heated chromosphere emerging in this case does not exceed the level observed during flares.  相似文献   

Investigation of the parameters of the massive binary X-ray system IGR J17544-2619     

E. A. Nikolaeva  I. F. Bikmaev  S. S. Melnikov  A. I. Galeev  R. Ya. Zhuchkov  E. N. Irtuganov 《Bulletin of the Crimean Astrophysical Observatory》2013,109(1):27-31

The paper presents the results of spectroscopic research of the high-mass X-ray binary IGRJ17544-2619 optical component that were carried out with the RTT-150. The analysis of a long series of spectroscopic observations of the optical star of IGRJ17544-2619 system in 2007–2011 was carried out. Orbital parameters of the system were obtained: γ-velocity of 47 km/s, semiamplitude of radial velocity curve K = 30.5 km/s, eccentricity e = 0.44, longitude of the periastron ω = 142°, and an orbital period of the system of 12.17 days. The lower limit of the compact object mass was found to be equal to M = 2.82M _⊙.  相似文献   

Distribution of the new invader Mnemiopsis sp. and the resident Aurelia aurita and Pleurobrachia pileus populations in the Black Sea in the years 1991-1993     

Mutlu  E.; Bingel  F.; Gucu  A. C.; Melnikov  V. V.; Niermann  U.; Ostr  N. A.; Zaika  V. E. 《ICES Journal of Marine Science》1994,51(4):407-421

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Electromagnetic and corpuscular emission from the solar flare of 1991 June 15: Continuous acceleraton of relativistic particles     

L. G. Kocharov  G. A. Kovaltsov  G. E. Kocharov  E. I. Chuikin  I. G. Usoskin  M. A. Shea  D. F. Smart  V. F. Melnikov  T. S. Podstrigach  T. P. Armstrong  H. Zirin 《Solar physics》1994,150(1-2):267-283

Data on X-,γ-ray, optical and radio emission from the 1991 June 15 solar flare are considered. We have calculated the spectrum of protons that producesγ-rays during the gradual phase of the flare. The primary proton spectrum can be described as a Bessel-function-type up to 0.8 GeV and a power law with the spectral index ≈3 from 0.8 up to 10 GeV or above. We have also analyzed data on energetic particles near the Earth. Their spectrum differed from that of primary protons producingγ-ray line emission. In the gradual phase of the flare additional pulses of energy release occurred and the time profiles of cm-radio emission andγ-rays in the 0.8–10 MeV energy band and above 50 MeV coincided. A continuous and simultaneous stochastic acceleration of the protons and relativistic electrons at the gradual phase of the flare is considered as a natural explanation of the data.  相似文献   

On the Eclipses in GW Ori Double System     

S. Lamzin  V. Shevchenko  K. Grankin  S. Melnikov 《Astrophysics and Space Science》1998,261(1-4):167-168

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Spectral Flattening During Solar Radio Bursts At Cm–mm Wavelengths and the Dynamics of Energetic Electrons in a Flare Loop     

V. F. Melnikov  A. Magun 《Solar physics》1998,178(1):153-171

Until recently, most of the information on particle acceleration processes in solar flares has been obtained from hard X-ray and cm-microwave observations. As a rule they provide information on electrons with energies below 300 keV. During recent years it became possible to measure the gamma-ray and millimeter radio emission with improved sensitivities. These spectral ranges carry information on much higher energy electrons. We studied the temporal and spectral behaviour of the radio burst emission at centimeter-millimeter wavelengths (8–50 GHz) by using the data from the patrol instruments of IAP (Bern University). We have analyzed more than 20 impulsive and long duration radio bursts (of 10 s to several 100 s duration).The main finding of the data analysis is the presence of spectral flattening throughout the bursts, which occurs always during the decay phase of flux peaks, at frequencies well above the spectral peak frequency and independently of burst duration. Furthermore, for some of the bursts, the flux maxima at higher frequencies are delayed. These findings can serve as evidence of the hardening of the electron spectrum at energies above some hundreds of keV during the decay phase of cm–mm flux peaks. As a most likely reason for such a hardening we consider Coulomb collisions of energetic electrons continuously injected and trapped in a flaring loop.  相似文献   

Spatial,spectral, and polarization properties of radio emission of the 3 February, 1983 proton flare     

L. M. Bakunin  V. G. Ledenev  V. P. Nefedyev  N. N. Potapov  G. Ya. Smolkov  A. M. Uralov  G. P. Chernov  V. V. Fomichev  V. P. Melnikov  T. S. Podstrigach  O. V. Epifanova  A. V. Khokhlov  Sh. Enome 《Solar physics》1991,135(1):107-129

A complex analysis in different radio ranges of the evolutionary features of the 3 February, 1983 flare (0543-0619-0812 UT) has shown that the flare is a prolonged ( 15 hr) process of energy release and particle acceleration that gradually extends to still greater zones of the active region (AR) magnetosphere in both area and altitude. Observations from the Siberian Solar Radio Telescope obtained at = 5.2 cm indicate that the flare was preceded by quasi-periodical brightness enhancements with a period of 6–7 min of two sources of size 20 and with a brightness temperature of 107 K.During the flare maximum phase, a type II burst with harmonic structure and the subsequent type FC II continuum with fine structure were both observed in the meter band. It has been found that zebra-structure appearances correlate with the H-flare kernel brightenings at loop tops.The observed characteristics of the type II burst and of the type FC II continuum treated in this paper are interpreted in terms of the complex flare flow structure, involving forward and backward shock waves.  相似文献   

The engineering-physical basis of temperature regime regulation of ground massifs in northern construction     

P. I. Melnikov  V. I. Makarov  A. A. Plotnikov 《Engineering Geology》1981,18(1-4):165-174

Artificial ground freezing at low temperatures provides a solution to such complicated problems as strengthening foundations, improvement of their reliability and the provision of the watertightness of the ground.

Ground cooling and freezing directly changes the stress—deformation state of foundations and underground constructions.

Basic diagrams on ways and means of forming low temperature frozen zones of a definite shape in the ground are given in the paper. Peculiarities of the work of the seasonally functioning heat-exchange devices and systems are discussed.

The development and refinements of methods of calculation and long-term forecast of temperature fields in artificially cooled ground massifs is of great importance.

Experimental data on migration phenomena in freezing soils and the methods of the numerical modeling of cooled massifs are discussed.

The paper is illustrated by diagrams, test results and calculation data.  相似文献   

Modeling the distribution of circular polarization degree of microwave emission along the flare loops in event July 19, 2012     

A. S. Morgachev  S. A. Kuznetsov  V. F. Melnikov  J. A. Simões 《Geomagnetism and Aeronomy》2015,55(8):1118-1123

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