CHANGES IN SUNSPOT AND FLOCCULAR SOURCES OF RADIO EMISSION PRECEDING AN IMPORTANCE 2N FLARE ON 23 AUGUST 1988     

Agalakov  B. V.  Ledenev  V. G.  Lubyshev  B. I.  Nefedyev  V. P.  Yazev  S. A.  Zubkova  G. N.  Kerdraon  A.  Urbarz  H. W. 《Solar physics》1997,173(2):305-318

Based on observations from the Siberian solar radio telescope, and invoking data from other observatories, we investigate preflare changes in the sunspot and floccular sources of radio emission and the development of an importance 2N flare in the chromosphere and corona in the active region on August 23, 1988.It has been ascertained that preflare changes became observable six hours prior to the flare onset and manifested themselves in intense flux fluctuations above the sunspot and in an enhancement of the source emission flux above the flocculus.It is shown that the flare onset is associated with a newly emerged magnetic flux in the form of a pore near the filament and with the appearance of radio sources above the filament. The flare was accompanied by type III radio bursts and a noise storm at meter wavelengths. Coronal mass ejection parameters are estimated from type III burst observations.  相似文献   

Anomalous polarization features of the cyclotron radiation source in the NOAA 7123 active region: The structure, dynamics, and reasons of occurrence     

N. G. Peterova  N. A. Topchilo  L. V. Opeikina  B. V. Agalakov  T. P. Borisevich  B. I. Lubyshev 《Geomagnetism and Aeronomy》2013,53(8):1000-1006

The research results of the unique NOAA 7123 active region (April 1992) are presented; its anomalous polarization features (long-term predominance of O-mode radiation above the central part of the main sunspot) were previously revealed by VLA observations with a resolution of (2–4)” at wavelengths of 3.6 and 6.4 cm (Vourlidas et al., 1997). Additional observations in a wider band of electromagnetic radiation, including, in particular, spectrum-polarization observations performed with the RATAN-600 and SSRT radio telescopes, are considered. The analysis of these data allowed for the conclusion that the anomaly was caused by the presence of a cold substance in the upper coronal layers, starting from the height where (6–7) cm radiation was generated. A possible transportation agent of this substance—Hα filament—one of the bases of which fell on the sunspot’s umbra-penumbra boundary, was found.  相似文献   

The three-dimensional structure of the corona above active region NOAA 9591 from microwave observations     

N. G. Peterova  B. V. Agalakov  T. P. Borisevich  A. N. Korzhavin  B. I. Ryabov 《Astronomy Reports》2006,50(8):679-686

We study the active region NOAA 9591 using observations at 1.92–10.17 cm obtained on two large Russian radio instruments: the RATAN-600 radio telescope and the Siberian Solar Radio Telescope. The active region was associated with an isolated spot at the photospheric level, whose magnetic field had a well-defined Delta configuration. The radio observations show that the structure of the coronal source located above the spot cannot be described in a simple (unipolar) cyclotron model. A comparison with X-ray observations indicates that the three-dimensional structure of the corona above the spot can be represented as a strongly elongated loop whose apex resembles a cusp brightening (a qualitative model for the structure is presented). Unexpectedly, radiation with a high degree of polarization (～25%) was detected far (～100 000 km) from the photosphere. The need for a quantitative model for coronal sources above the strong Delta-configuration magnetic fields, which are known to play an important role in active solar processes (flares, phenomena such as coronal-mass ejections) is outlined. Thanks to its simple morphology, which enabled the identification of a pure Delta configuration, the active region NOAA 9591 provides high-quality observational material for the creation of such a model.  相似文献   

Studying the solar corona above active regions from microwave observations during solar flares recorded by CORONAS-F satellite     

B. V. Agalakov  T. P. Borisevich  N. G. Peterova  B. I. Ryabov  N. A. Topchilo  S. N. Kuznetsov  I. N. Myagkova  B. Yu. Yushkov  K. Kudela 《Geomagnetism and Aeronomy》2006,46(5):547-554

In 2001–2003, 45 flares of hard X ray (HXR) and gamma ray radiation, identified with a particular active region (AR) that produced each event, were recorded during the experiments onboard the Russian Solar Observatory CORONAS-F using the SONG (solar neutrons and gamma ray quanta) instrument. The solar corona structure and dynamics above these ARs is studied on the basis of the microwave observations with two Russian radio telescopes RATAN-600 and Siberian Solar Radio Telescope (SSRT). The results are illustrated using the active region NOAA 9601 and flare of September 5, 2001 (～ 1430 UT) as an example. The flare is interesting because the energy of its gamma radiation exceeded 1 MeV, while its power was only M6.0 in soft X rays. Such a combination of the event characteristics is not too frequent, which indicates that the spectrum of the studied event was rather hard. The type of the source of microwave radiation above NOAA 9601 has been determined. Some properties of this-type sources of a diagnostic value for detecting ARs capable of producing HXR and gamma radiation are indicated.  相似文献