共查询到20条相似文献，搜索用时 46 毫秒
1.
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
2.
This paper continues the cycle of authors’ works on the detection of precursors of large flares (M5 and higher classes) in active regions (ARs) of the Sun by their microwave radiation and magnetographic characteristics. Generalization of the detected precursors of strong flares can be used to develop methods for their prediction. This paper presents an analysis of the development of NOAA AR 12242, in which an X1.8 flare occurred on December 20, 2014. The analysis is based on regular multiazimuth and multiwavelength observations with the RATAN-600 radio telescope in the range 1.65–10 cm with intensity and circular polarization analysis and data from the Solar Dynamics Observatory (SDO). It was found that a new component appeared in the AR microwave radiation two days before the X-flare. It became dominant in the AR the day before the flare and significantly decreased after the flare. The use of multiazimuth observations from RATAN-600 and observations at 1.76 cm from the Nobeyama Radioheliograph made it possible to identify the radio source that appeared before the X-flare with the site of the closest convergence of opposite polarity fields near the neutral line in the AR. It was established that the X-flare occurred 20 h after the total gradient of the magnetic field of the entire region calculated from SDO/HMI data reached its maximum value. Analysis of the evolution of the microwave source that appeared before the X-flare in AR 12242 and comparison of its parameters with the parameters of other components of the AR microwave radiation showed that the new source can be classified as neutral line associated sources (NLSs), which were repeatedly detected by the RATAN-600 and other radio telescopes 1–3 days before the large flares. 相似文献
3.
We discuss the results of a study of microwave radiation from three flare-active regions??NOAA 10300, 10930, and 11158??with powerful eruptive events (X-class flares and coronal mass ejections) recorded on July 15, 2002; December 13, 2006; and February 15, 2011, when the regions were in the central part of the disk. There exists evidence of a ??-configuration in the structure of the photospheric magnetic field formed one or two days prior to the eruptive process as a result of the emergence of a new magnetic flux and shifting movements of the sunspots and accompanied by changes in the spectral characteristics of the microwave radiation of the active regions (ARs), which suggests the development of a peculiar radio source. The analysis of these regions continues a series of studies of eruptive events carried out at RATAN-600 in the 1980s?C1990s and gives a reason to conclude that early detections of peculiar sources in the microwave radiation of ARs, which are essentially areas of high energy release in the solar atmosphere, can be used as a factor in predicting powerful eruptive (geoeffective) processes on the Sun. 相似文献
4.
A weak active region (NOAA 11158) appeared on the solar disk near the eastern limb. This region increased rapidly and, having reached the magnetic flux higher than 1022 Mx, produced an X-class flare. Only weak field variations at individual points were observed during the flare. An analysis of data with a resolution of 45 s did not indicate any characteristic features in the photospheric field dynamics during the flare. When the flux became higher than 3 × 1022 Mx, active region NOAA 10720 produced six X-class flares. The field remained quiet during these flares. An increase in the magnetic flux above ～1022 Mx is a necessary, but not sufficient, condition for the appearance of powerful flares. Simple active regions do not produce flares. A flare originates only when the field distribution in an active region is complex and lines of polarity inversion have a complex shape. Singular lines of the magnetic field can exist only above such active regions. The current sheets, in the magnetic field of which the solar flare energy is accumulated, originate in the vicinity of these lines. 相似文献
5.
L. K. Kashapova S. Kh. Tokhchukova D. A. Zhdanov V. M. Bogod G. V. Rudenko 《Geomagnetism and Aeronomy》2013,53(8):1021-1024
We present the results of a study of the subsecond pulses (SSPs) registered in the microwaves during the C2.4 solar flare. The event occurred on August 10, 2011, in the 11236 active region near the western limb and reached a maximum at 0935 UT. Subsecond pulses were registered by RATAN-600 for the first time when this flare reached its maximum. The fact of detection of SSPs was confirmed by simultaneous observations carried out with a spectropolarimeter at the Radio Astrophysical Observatory, Institute of Solar-Terrestrial Physics. A former analysis of the emission nature of the main flare source revealed the presence of a high-temperature (T > 30 MK) source that determined both the microwave and X-ray emission parameters of this event. We have compared the temporal variations of the SSPs microwave emission with the variations of the plasma parameters (temperature and emission measure) taken from observations with the FERMI space telescope with a subsecond time resolution. The obtained results suggest that the nature of SSP generation, as well as of the flare itself, was determined by the high-temperature source. 相似文献
6.
T. I. Kaltman V. M. Bogod A. G. Stupishin L. V. Yasnov 《Geomagnetism and Aeronomy》2013,53(8):1030-1034
The physical conditions in the low corona and chromosphere of solar active regions are studied. A diagnostics technique based on multiwave observations in the centimeter range, photospheric magnetic field extrapolation, and radioemission calculations has been applied. The calculated spatial and spectral structure of the radioemission has been compared with RATAN-600 spectral-polarization observations with a high spatial resolution. The effect of the plasma physical parameters on the emission structure character in a complex magnetic field topology in active regions is analyzed. Modeling of the spectral singularities at a quasi-periodic propagation of the radioemission is presented. 相似文献
7.
As deduced from the data with high spatial resolution obtained at the radio heliographs of the Siberian Solar Radio Telescope
(SSRT, 5.7 GHz) and the Nobeyama radio heliograph (NoRH, 17 GHz), radio brightness centers in the distribution of the Stokes
parameter I are shifted relative to the distribution of the parameter V 1–2 days before an intense flare. It has been shown that this phenomenon can be related to the behavior of quasi-stationary
sources over the inversion line of the radial component of the magnetic field (neutral-line associated sources (NLSs)). These
sources have a brightness temperature up to 106 K and a circular polarization up to 90%. The origination of NLSs is associated
with the outflow of a new magnetic flux into the atmosphere of an active region that is a classical factor of the flare activity.
Therefore, an NLS is a precursor of power solar flares and can be used as a forecast factor. Owing to the high resolution
of the SSRT, the deviation of the observed polarization distribution of microwave radiation of the active region from the
normal one within the solar disk zone containing the active region can be used as a precursor of the preflare state of the
active region. As a result, the single-frequency Tanaka-Enome criterion is modified. The use of the data from two radio heliographs
(SSRT and NoRH) allows us to propose a two-frequency criterion of normal longitudinal zones that is more efficient for short-term
forecasting of solar flares. Preflare features associated with the displacement of brightness centers in I and V, which is manifested as the transformation of NLSs into spot sources, are fine attributes added to forecast according to
the two-frequency criterion. This is illustrated by an example of active region 10930, which produced power proton flares
on December 6 and 13, 2006. 相似文献
8.
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
9.
The correlation between the pulsed and smooth components of ultraviolet radiation and hard X-rays from solar flares has been
interpreted on the basis of the time behavior of the energy flux penetrating from the magnetic field reconnection region to
the boundary of the heated region. It has been shown that the time behavior of the primary flare energy flux is easily reconstructed
from the time profile of the intensity of hard X-rays, and the time profile of the intensity of ultraviolet radiation represents
the release of the flare energy in the flare transient layer. The smooth or pulsed component of the ultraviolet radiation
depends on the form of the primary energy release. Information on the dynamics of the heating process and the formation and
equalization of the gas pressure in the flare transient layer has been obtained from the observed temperature dependence of
the emission measure. The described scheme explains the set of flare phenomena and the correlation between hard X-rays with
pulsed ultraviolet bursts. 相似文献
10.
The correlation between the pulsed and smooth components of ultraviolet radiation and hard X-rays from solar flares has been interpreted on the basis of the time behavior of the energy flux penetrating from the magnetic field reconnection region to the boundary of the heated region. It has been shown that the time behavior of the primary flare energy flux is easily reconstructed from the time profile of the intensity of hard X-rays, and the time profile of the intensity of ultraviolet radiation represents the release of the flare energy in the flare transient layer. The smooth or pulsed component of the ultraviolet radiation depends on the form of the primary energy release. Information on the dynamics of the heating process and the formation and equalization of the gas pressure in the flare transient layer has been obtained from the observed temperature dependence of the emission measure. The described scheme explains the set of flare phenomena and the correlation between hard X-rays with pulsed ultraviolet bursts. 相似文献
11.
The morphological peculiarities of the 1N (N09W22) two-ribbon spotless flare on March 16, 1981, as well as its connection
with a magnetic field, have been considered. In contrast to major flares of the active region, this spotless flare is characterized
by a large-scale development process, a large distance from the magnetic neutral line, and the absence of the spread of the
ribbons. The development of the flare had four periods. At the beginning of each period, a sharp increase in the brightness
of the flare was observed along with a simultaneous decrease in the area of the flare ribbons. The areas of the ribbons varied
synchronously during all of the periods. However, the situation changed abruptly near the maximum: the area of one of the
ribbons increased, whereas the area of the other ribbon decreased. In our opinion, this behavior is a manifestation of real
physical processes in the flare source and was a precursor of the beginning of the flare decay. The magnetic field and its
topology, as well as the cellular structure of the chromosphere, were primarily responsible for the evolution of the flare.
Almost all of the mottles and bright parts of the flare were localized in the immediate vicinity of magnetic hills with field
intensities from 80 to 250 G. The main structural elements of the flare have been identified. A phenomenon called the tunnel
effect has been revealed: the flare progresses inside a tunnel formed by the system of dark arch structures (filaments). The
results indicate that spotless flares apparently constitute a specific class of flare phenomena and the study of them is of
great interest for understanding of the origin of solar flares. 相似文献
12.
13.
The results of microwave observations of the solar eclipse of March 29, 2006, with the RATAN-600 radiotelescope are presented. The observations were carried out using the northeastern sector of the radiotelescope in a broad wavelength range (1.03, 1.38, 2.70, 6.20, 13.00, and 30.70 cm) in the intensity channel. The aim of the present work is to conduct a comparative analysis of the distributions of brightness temperatures in the solar atmosphere at a distance (ranging from one to two solar radii) from the center of the optical solar disk. The data for the analysis come from the RATAN-600 observations of the solar eclipse of March 29, 2006, earlier observations with the RATAN-600 radiotelescope, and calculations of brightness temperatures that were carried out using the Baumbach-Allen formula which describes the electron density in the solar corona. The differences between the distributions obtained by the above-mentioned methods are discussed. 相似文献
14.
Field variations in the region of the eruptive event on June 7, 2011 are studied based on vector measurements of the photospheric magnetic field by the SDO/HMI instrument. Variations of the modulus (B), the radial (Br) and the transverse (Bt) components of the magnetic induction, and the inclination angle (α) of the field lines to the radial direction from the center of the Sun are analyzed. It is found that, in the part of the flare region near the polarity inversion line (PIL) after the onset of the flare, the magnitude and the transverse component of the magnetic induction as well as the angles α abruptly increase. During the slow rise of filament near its channel, the inclination angles of the field lines decrease. It is shown that diverging flare ribbons are above the regions of the photosphere with local maxima of the field modulus and with deep minima of the inclination angles of the field lines at all stages of their existence over their entire length with the exception of small areas. It is established that the azimuth decreases after the onset of the flare near the PIL of the photospheric magnetic field, which means an increase in the shear. On the contrary, at a distance from the PIL there is a slight decrease in the shear.
相似文献15.
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
16.
The MHD simulations of preflare situation in the corona above the real active region (AR) are performed without any assumptions about the solar flare mechanism. All conditions for simulation are taken from observations. Such approach is directed to understand the flare mechanism. The observed SOHO MDI magnetic maps are used. The special numerical methods are developed and realized in the PERESVET code for numerical simulation in the real time scale. The first results of real time scale MHD simulation during several first minutes are presented. Initiation of current sheet (CS) creation in the vicinity of the magnetic field X-line is shown. The possibilities of real time scale MHD simulation of preflare situation on modern computers using the developed mathematical methods are discussed. 相似文献
17.
Variations in the photospheric magnetic field in the region of solar flares, related to halo coronal mass ejections (HCMEs) with velocities V > 1500, 1000 < V < 1500, and V < 650 km/s, have been studied based on SOHO/MDI data. Using data with a time resolution of 96 min, it has been indicated that on average the ??B L?? and ??|B L|?? field characteristics increase nonmonotonically during 1?C1.5 days before a flare and decrease during 0.5?C1 days after a flare for groups of ejections with V > 1000 km/s for all considered HCME groups. Angle brackets designate averaging of the measured B L magnetic field component and its magnitude |B L| within an area with specified dimensions and the center coincident with the projection onto the region where the flare center field is measured. It has been established that a solar flare related to an HCME originates when the ??B L?? and ??|B L|?? values are larger than the boundary values in the flare region. Based on 1-min data, it has been found for several HCMEs with V > 1500 km/s that the beginning of powerful flares related to ejections is accompanied by rapid impulsive or stepped variations in ??B L?? and ??|B L|?? near the center of a flare with a size of approximately 4.5°. It has been established that the HCME velocity positively correlates with the |??B L??| value at the flare onset. 相似文献
18.
Yu. A. Fursyak 《Geomagnetism and Aeronomy》2016,56(7):930-937
Specific features of the magnetic configuration, morphological structure, dynamics, and evolution of sunspot groups of the current (24th) cycle of solar activity with high flare activity are considered. The gradients of longitudinal magnetic fields at places of δ-configuration are calculated. The main finding is a time delay of 24–30 h between the time when the magnetic field gradient reaches a critical level of 0.1 G/km and the time when the first of powerful flares occurs in the active region. The study is based on data from the SDO and GOES-15 spacecrafts and ground-based solar telescopes (TST-2 at the Crimean Astrophysical Observatory of the Russian Academy of Sciences and the 150-foot telescope at the Mount Wilson Observatory). 相似文献
19.
The spectra of the coronal hole radio emission in solar cycles 23 and 24 have been studied based on RATAN-600 data in the 4–16.5 GHz range at frequencies of 5.7 and 17 GHz and 327 MHz. It has been found that bright features of coronal hole microwave emission at 17 GHz and dark features at 5.7 GHz can exist in coronal holes when the spectral index is 1.25–1.5 in the 6.5–16.5 GHz range; the radio spectrum in this range is flat when coronal holes are indiscernible against the background of a quiet Sun. The possible vertical scale of the solar atmosphere over coronal holes is discussed. 相似文献