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1.
The Siberian Solar Radio Telescope: the current state of the instrument,observations, and data 总被引：2，自引：0，他引：2
Grechnev V.V. Lesovoi S.V. Smolkov G. Ya. Krissinel B.B. Zandanov V.G. Altyntsev A.T. Kardapolova N.N. Sergeev R.Y. Uralov A.M. Maksimov V.P. Lubyshev B.I. 《Solar physics》2003,216(1-2):239-272
The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in
1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument
has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec.
Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar
disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe
the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors
limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk
solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright
points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive
prominences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument.
We compare SSRT observations at 5.7 GHz, including computed `light curves', both morphologically and quantatively, with observations
made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray
observations, and dynamic radio spectra. 相似文献
2.
A type IV radio burst accompanied by several normal- and reverse-drifting type III bursts, multiple long-term quasi-periodic pulsations and spikes was observed with the radio spectrometers (1.0–2.0 and 2.6–3.8 GHz) at National Astronomical Observatories of China (NAOC) on 23 September 1998. In combination with the images of Siberian Solar Radio Telescope (SSRT) of Russia, the complex and multiple magnetic structures inferred from the radio bursts reveal the existence of both large-scale and small-scale magnetic structures. This event suggests that the geometries of coronal magnetic fields contain multiple discrete electron acceleration/injection sites at different heights, and extended open and closed magnetic field lines. It can be shown that the energetic electrons gain access to open, diverging and closed field lines thus producing different types of radio bursts. From the characteristics of position, polarization, dispersion and displacement of the sources, the model of the type IV event is supported, which involves synchrotron emission from the electrons confined by the rapid scattering through the interaction of hydromagnetic wave with particles. 相似文献
3.
Data on the visible angular sizes of sources of microwave subsecond pulses (MSPs) obtained using the Siberian Solar Radio Telescope are analyzed assuming a dominant role for scattering on small-scale electron-density inhomogeneities in the solar corona. The observed dependence of the angular sizes of MSPs on the distance from the solar-disk center confirms that the MSP sources are localized in low layers of the solar corona. Both absolute and fractional levels of small-scale electron-density fluctuations have been estimated. These estimates suggest that flicker-noise-type turbulence power spectra are formed in the lower corona, and are preserved in the solar-wind acceleration region. A composite dependence of the scattering angle of a sounding radio wave on distance from the Sun is presented. 相似文献
4.
5.
The so-called zebra structures in radio dynamic spectra, specifically their frequencies and frequency drifts of emission stripes,
contain information on the plasma parameters in the coronal part of flare loops. This paper presents observations of zebra
structures in a microwave range. Dynamic spectra were recorded by Chinese spectro-polarimeters in the frequency band close
to the working frequencies of the Siberian Solar Radio Telescope. The emission sources are localized in the flare regions,
and we are able to estimate the plasma parameters in the generation sites using X-ray data. The interpretation of the zebra
structures in terms of existing theories is discussed. The conclusion has been arrived at that the preferred generation mechanism
of zebra structures in the microwave range is the conversion of plasma waves to electromagnetic emission on the double plasma
resonance surfaces distributed across a flare loop. 相似文献
6.
V. V. Zharkova N. S. Meshalkina L. K. Kashapova A. T. Altyntsev A. A. Kuznetsov 《Geomagnetism and Aeronomy》2011,51(8):1029-1040
The kinetics of beam electron precipitation from the top of a loop into the solar atmosphere with density gradients and an
increasing magnetic field have been generally described. The Fokker-Planck equations are solved with regard to Coulomb collisions
and the effect of the electric field induced by this beam. The photon spectra and polarization degree in hard X-ray (10–300
keV) and microwave (1–80 GHz) emissions are simulated under different assumptions regarding the beam electron distribution
function. The simulation results are compared with the flare observations on March 10, 2001, and July 23, 2002, visible at
different position angles. It has been indicated that the coincidence of the theoretical photon spectra with simultaneous
observations of the hard X-ray and microwave emissions of these flares is the best for models that not only take into account
collisions, but also the electric field induced by electron fluxes propagating in flare loops with very weakly or moderately
converging magnetic fields. 相似文献
7.
We have analyzed three flare events with subsecond structures in hard X-rays (CGRO/ BATSE) and 17 GHz data (Nobeyama radioheliograph). It was shown that microwave subsecond brightenings (SSB) were generated by directly precipitating electrons with energy of 100–200 keV from tiny regions close to footpoints. In two events, when high correlation between microwaves and X-rays was observed, the SSB can be interpreted in terms of gyrosynchrotron emission. Plasma emission seems to be a more credible explanation of the spontaneous pulses in the event when poor correlation with X-rays was observed. 相似文献
8.
The problem of strong polarization of the zebra-type fine structure in solar radio emission is discussed. In the framework of the plasma mechanism of radiation at the levels of the double plasma resonance, the polarization of the observed radio emission may be due to a difference in rates of plasma wave conversion into ordinary and extraordinary waves or different conditions of escaping of these waves from the source. In a weakly anisotropic plasma which is a source of the zebra-pattern with rather large harmonic numbers, the degree of polarization of the radio emission at twice the plasma frequency originating from the coalescence of two plasma waves is proportional to the ratio of the electron gyrofrequency to the plasma frequency, which is a small number and is negligible. Noticeable polarization can therefore arise only if the observed radio emission is a result of plasma wave scattering by ions (including induced scattering) or their coalescence with low-frequency waves. In this case, the ordinary mode freely leaves the source, but the extraordinary mode gets into the decay zone and does not exit from the source. As a result, the outgoing radio emission can be strongly polarized as the ordinary mode. Possible reasons for the polarization of the zebra pattern in the microwave region are discussed. 相似文献
9.
Sergey V. Lesovoi Alexander T. Altyntsev Eugene F. Ivanov Alexey V. Gubin 《中国天文和天体物理学报》2014,(7):864-868
Here we briefly present some design approaches for a multifrequency 96-antenna radioheliograph. The configuration of the array antenna, transmission lines and digital receivers is the main focus of this work. The radioheliograph is a T-shaped centrally condensed radiointerferometer operating in the frequency range 4–8 GHz.The justification for the choice of such a configuration is discussed. The signals from antennas are transmitted to a workroom by analog optical links. The dynamic range and phase errors of the microwave-over-optical signal are considered. The signals after downconverting are processed by digital receivers for delay tracking and fringe stopping. The required step of delay tracking and data rates are considered. Two 3-bit data streams(I and Q) are transmitted to a correlator with the transceivers embedded in Field Programmed Gate Array chips and with PCI Express cables. 相似文献
10.
V. V. Grechnev V. G. Kurt I. M. Chertok A. M. Uralov H. Nakajima A. T. Altyntsev A. V. Belov B. Yu. Yushkov S. N. Kuznetsov L. K. Kashapova N. S. Meshalkina N. P. Prestage 《Solar physics》2008,252(1):149-177
The famous extreme solar and particle event of 20 January 2005 is analyzed from two perspectives. Firstly, using multi-spectral
data, we study temporal, spectral, and spatial features of the main phase of the flare, when the strongest emissions from
microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin
of solar energetic particles (SEP) arriving at Earth, i.e., acceleration in flares, or shocks ahead of coronal mass ejections (CMEs). Our analysis shows that all electromagnetic emissions
from microwaves up to 2.22 MeV line gamma-rays during the main flare phase originated within a compact structure located just
above sunspot umbrae. In particular, a huge (≈ 105 sfu) radio burst with a high frequency maximum at 30 GHz was observed, indicating the presence of a large number of energetic
electrons in very strong magnetic fields. Thus, protons and electrons responsible for various flare emissions during its main
phase were accelerated within the magnetic field of the active region. The leading, impulsive parts of the ground-level enhancement
(GLE), and highest-energy gamma-rays identified with π
0-decay emission, are similar and closely correspond in time. The origin of the π
0-decay gamma-rays is argued to be the same as that of lower-energy emissions, although this is not proven. On the other hand,
we estimate the sky-plane speed of the CME to be 2 000 – 2 600 km s−1, i.e., high, but of the same order as preceding non-GLE-related CMEs from the same active region. Hence, the flare itself rather
than the CME appears to determine the extreme nature of this event. We therefore conclude that the acceleration, at least,
to sub-relativistic energies, of electrons and protons, responsible for both the major flare emissions and the leading spike
of SEP/GLE by 07 UT, are likely to have occurred nearly simultaneously within the flare region. However, our analysis does
not rule out a probable contribution from particles accelerated in the CME-driven shock for the leading GLE spike, which seemed
to dominate at later stages of the SEP event.
S.N. Kuznetsov deceased 17 May 2007. 相似文献