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1.
M. A. Livshits I. V. Zimovets D. V. Golovin B. A. Nizamov V. I. Vybornov I. G. Mitrofanov A. S. Kozyrev M. L. Litvak A. B. Sanin V. I. Tretyakov 《Astronomy Reports》2017,61(9):791-804
The study of nonstationary processes in the Sun is of great interest, and multi-wavelength observations and the registration of magnetic fields have been carried out using both ground-based telescopes and several specialized spacecraft in near-Earth orbits in recent years. However, the acquisition of new, reliable information on their hard X-ray radiation remains necessary, in particular, if the corresponding spacecraft provide additional information, e.g., in regard to flare observations from directions other than the Sun–Earth direction. This paper presents a catalog of powerful solar flares registered by the High Energy Neutron Detector (HEND) designed at the Space Research Institute of the Russian Academy of Sciences. HEND is mounted onboard the 2001Mars Odyssey spacecraft. It operated successfully during the flight to Mars and is currently operating in near-Mars orbit. Apart from neutrons, HEND is sensitive to hard X-ray (up to 300 keV) and gamma-ray radiation (above 300 keV). This radiation is registered by two scintillators: an outer one that is sensitive to photons above 40 keV and an inner one sensitive to photons above 200 keV. The catalog was created using a new procedure for calibration of the data. For the most powerful 60 solar flares in the visible and far sides of the Sun (for a terrestrial observer), time profiles of the flare radiation summed over all channels of the X-ray, and in some cases the gamma-ray, bands are provided, as well as spectra and characteristics of power-law fits. The results of previous studies of the Sun using HEND and the potential for further use of these data are discussed. 相似文献
2.
M. A. Livshits D. V. Golovin L. K. Kashapova I. G. Mitrofanov A. S. Kozyrev M. L. Litvak A. B. Sanin V. I. Tret’yakov W. Boynton K. Shinohara D. Hamara 《Astronomy Reports》2011,55(6):551-560
A detailed study of two major solar flares that occurred in Group 10786 at the time of its disappearance behind the western limb is presented. The flares of July 14, 2005 were previously studied fairly poorly, as no RHESSI hard X-ray observations were available for themaxima of the twomost powerful of these flares. Observations carried out using the HEND equipment (on the Mars Odyssey spacecraft) developed at the Institute for Space Research in Moscow are used here to fill this gap. In the first flare, an intense, impulsive burst occurred at 07:23 UT, about 1.5 h after the onset of a weak, prolonged event. While processes in the neighborhood of the northern spot dominated in the flares of July 5–9, a powerful impulsive energy release on July 14 emerged when the flare process that originated in the North reached the southern spot. Our analysis of the flare activity of this medium-sized group reveals a gradual enhancement of the flare activity and a strong interaction between the acceleration above the magnetic-field neutral line and in the immediate vicinity of the spots. At the time of the culmination of the flare activity in the group on July 13 and 14, the pattern of nonstationary processes changes: fast coronal mass ejections form after a series of impulsive energy-release events. Spacecraft observations of the burst of July 14 after 11 UT at points separated in longitude (on RHESSI and Mars Odyssey) revealed clear anisotropy of the flare emission at energies exceeding 80 keV. 相似文献
3.
V. I. Vybornov M. A. Livshits L. K. Kashapova I. G. Mitrofanov D. V. Golovin A. S. Kozyrev M. L. Litvak A. B. Sanin V. I. Tret’yakov W. Boynton K. Shinohara D. Hamara 《Astronomy Reports》2012,56(10):805-812
Observations of the hard X-ray and radio event of October 27, 2002 are analyzed. This flare was observed from near-Martian orbit by the HEND instrument developed at the Space Research Institute of the Russian Academy of Sciences and installed on the Mars Odyssey satellite. Although this powerful flare was observed far over the eastern solar limb, the extended source associated with the flare was detected by RHESSI at energies up to about 60 keV. The eruptive event was observed in the radio at the Nobeyama Radio Observatory. The properties of the X-ray radiation are used to calculate the spectrum of the accelerated electrons responsible for the observed radiation, assuming that the target is thick for a Martian observer and thin for a terrestrial observer. The results are compared with the results of radio observations. The conditions for electron propagation in the corona are discussed. 相似文献
4.
I. V. Zimovets 《Astronomy Reports》2010,54(7):657-674
An analysis is presented for the class-M9.3 solar flare of November 6, 2004, whose decay phase displayed weakly damped harmonic
oscillations of the predominantly thermal X-ray flux detected by the RHESSI spacecraft (at energies ≲25 keV). The period of
these oscillations was ≈78 s, and their characteristic decay time ≈100 min. Similar quasi-periodic pulsations were observed
in the decimeter-centimeter radio flux (pulsations of a type-IV radio outburst), but were less pronounced in the non-thermal
hard X-ray flux (≳25 keV). The area of the quasi-stationary X-ray source, which was located primarily at the apex of a set
of flare loops (≲15 keV) that were cooled primarily via thermal conduction, was found to be in anti-phase with the oscillating
X-ray flux it emitted. The observed oscillations are interpreted as harmonic modulations of the radiation flux emitted by
the heated thermal flare-loop plasma, due to the global, standing, sausage mode of fast magnetoacoustic waves excited in the
loop. 相似文献
5.
This work continues earlier statistical analyses of catalogued proton events in cosmic rays. The spectra of proton enhancements identified from the logarithm of the ratio of the proton fluxes with energies exceeding 100 and 10 MeV, δ = log(F 100/F 10), are studied focusing on 172 powerful events with favorable conditions for escaping from the corona and subsequent propagation in the interplanetary space. The δ distribution for the flares is Gaussian, with a comparatively weak spread in δ. The distribution maximum corresponds to an excess of the 10 MeV flux over the 100 MeV flux by a factor of 30. The fact such a frequent spectrum does exist supports the idea that both soft and hard protons are efficiently accelerated, probably by a single mechanism that operates during the explosive phases of the flares. The sizes of the loops of M2-X4 flares observed by the Yohkoh Hard X-Ray Telescope at energies exceeding 50 keV indicate low heights for the main acceleration regions. There is some excess over the Gaussian distribution for “softer” events. Some post-eruptive phenomena can be clearly distinguished in these events, and they display a correlation between δ and the total flare duration. Thus, there are two sources of the particle acceleration operating at low and high altitudes during the explosive and post-eruptive phases of the solar flares, respectively. The second source, which is manifested through some prolonged flares and filament-ejection phenomena, accelerates protons only to energies of 10–30 MeV. 相似文献
6.
V. V. Nazarenko 《Astronomy Reports》2008,52(1):40-52
Three-dimensional numerical hydrodynamical modeling of a radiative wind and accretion disk in a close binary system with a compact object is carried out, using the massive X-ray binary LMC X-3 as an example. This system contains a precessing disk, and may have relativistic jets. These computations show that an accretion disk with a radius of about 0.20 (in units of the component separation) forms from the radiative wind from the donor when the action of the wind on the central source is taken into account, when the accretion rate is equal to the observed value (about 3.0 × 10?8 M ⊙/year, which corresponds to the case when the donor overflows its Roche lobe by nearly 1%). It is assumed that the speed of the donor wind at infinity is about 2200 km/s. The disk that forms is geometrically thick and nearly cylindrical in shape, with a low-density tunnel at its center extending from the accretor through the disk along the rotational axis. We have also modeled a flare in the disk due to short-term variations in the supply of material through the Lagrange point L1, whose brightnesses and durations are able to explain flares in cataclysmic variables and X-ray binaries. The accretion disk is not formed when the donor underfills its Roche lobe by 0.5%, which corresponds to an accretion rate onto the compact object of 2.0 × 10?9 M ⊙/year. In place of a disk, an accretion envelope with a radius of about 0.03 forms, within which gas moves along very steep spiral trajectories before falling onto the compact object. As in the accretion-disk case, a tunnel forms along the rotational axis of the accretion envelope; a shock forms behind the accretor, where flares occur in a compact region a small distance from the accretor at a rate of about six flares per orbital period, with amplitudes of about 10 m or more. The flare durations are two to four minutes, and the energies of individual particles at the flare maximum are about 100–150 keV. These flares appear to be analogous to the flares observed in gamma-ray and X-ray burst sources. We accordingly propose a model in which these phenomena are associated with massive, close X-ray binary systems with component-mass ratios exceeding unity, in which the donor does not fill its Roche lobe. Although no accretion disk forms around the compact object, an accretion region develops near the accretor, where the gamma-ray and X-ray flares occur. 相似文献
7.
A. E. Vol’vach A. M. Kutkin M. G. Larionov L. N. Vol’vach A. Lakhteenmaki M. Tornikoski J. Tammi P. Savolainen M. F. Aller H. D. Aller M. Sasada 《Astronomy Reports》2014,58(2):71-77
Flux-density variations of the quasar S0528+134 (Nimfa) are analyzed based on long-term monitoring at five radio frequencies between 4.8 and 37 GHz, performed at the Crimean Astrophysical Observatory, the Metsähovi Radio Observatory of Aalto University, and the University of Michigan Radio Astronomy Observatory. The dynamics of a powerful flare in 1996 are analyzed using gamma-ray (0.1–300 GeV), X-ray (2–10 keV, 15–50 keV), and radio observations. The delays of the flare between different spectral ranges and between different radio wavelengths have been measured. The dependence for the delays at different radio wavelengths relative to the X-ray and optical flares is established based on long-term observations in the X-ray, optical, and radio obtained from 2004 to 2013. Multi-frequency monitoring in the radio is used to estimate the orbital and precession periods in the binary supermassive black hole system S0528+134 and the physical characteristics of this system. 相似文献
8.
Regular photometric observations of the two active flare stars EV Lac and AD Leo were carried out in 1996–1999. We have compared the location of the intrinsic radiation of the strongest flares in UBVRI two-color diagrams with those predicted by various models for the radiation sources. Our statistical analysis of flares in EV Lac confirms the 7.5-year activity cycle reported earlier. 相似文献
9.
A. E. Vol’vach L. N. Vol’vach A. M. Kut’kin M. G. Larionov M. Villata K. M. Panteri A. Lahteenmaki M. Tornikoski P. Savolainen G. Tammi A. F. Aller H. D. Aller S. G. Sergeev V. T. Doroshenko Yu. S. Efimov S. A. Klimanov S. V. Nazarov G. V. Borman A. B. Pushkarev V. I. Zhdanov E. V. Fedorova I. B. Vavilova N. G. Chesnok 《Astronomy Reports》2011,55(7):608-615
Long-term monitoring data at five radio frequencies from 4.8 to 37 GHz obtained at the Crimean Astrophysical Observatory, Metsahovi Radio Observatory of Aalto University, and the University of Michigan Radio Astronomy Observatory are used to analyze variations of the flux of the Active Galactic Nucleus (AGN) 3C 454.3. The dynamical characteristics of the three latest powerful flares from 2004 to 2010 are analyzed in detail. Observations in the gamma-ray (0.1–300 GeV), X-ray (2–10 kev, 15–50 keV), and optical are also used. Delays in the development of flares at different frequencies are derived. An empirical frequency dependence for the delays of flares from the gamma-ray to the radio is determined, which can be fit using a logarithmic low and remains the same from flare to flare. The physical characteristics of the central region of the AGN 3C 454.3 are used to estimate the size of its Strömgren sphere, taking into account the relevant mechanisms for heating and cooling the medium, as well as the adopted laws for the variation of the density and temperature with distance from the source of ionization. A model for the location of the radiation regions in the jet at various frequency ranges during the development of flares is proposed. 相似文献
10.
An analysis of the dynamics of the electron temperature of the solar atmosphere in regions where solar flares appear is presented. The temperatures are estimated from the emission in spectral lines of ions with various degrees of ionization. The emission of ionized helium and highly ionized iron was used. Images of preflare states and of flares from the archive of the American SDO spacecraft are analyzed. A solar flare is usually preceded by the registration of a bright glowing structure above the action region, with a temperature exceeding that of the corona. This preflare structure (~1010 cm) is identified with the development of a system of currents, which, according to numerical simulations, is responsible for the accumulation of energy above the active region before the flare. After several tens of hours of a slow increase in the brightness of the preflare glow in the 94 Å iron (FeXVIII) line, the emission in the 193 Å line of FeXXIV increases sharply, indicating a flare-like growth of the temperature up to at least 20 MK. This growth of the emission coincides with the onset of the solar flare. The observed dynamics of the emission in spectral lines of highly ionized ions is consistent with an electrodynamic model of a solar flare based on the accumulation of magnetic energy in a current sheet above the active region and the explosive release of the stored energy. Studies of mechanisms for solar flares are of special importance in connection with the discovery of solar cosmic rays. Information from the worldwide network of neutron monitors and from the GOES spacecraft has made it possible to firmly state that the source of solar rays is solar flares, not shocks generated by such flares. It cannot be ruled out that a similar mechanism, not shocks, is also responsible for the acceleration of cosmic rays in the Galaxy. 相似文献
11.
12.
M. N. Lovkaya 《Astronomy Reports》2013,57(8):603-610
The fine temporal structure of two flares observed on the red-dwarf flare star AD Leo on February 4, 2003 with the 1.25-m telescope of the Crimean Astrophysical Observatory in a rapidphotometry mode is studied. One flare lasted approximately 5 min and another was longer than 8 min. The amplitudes in the U band were 1.65 m and 1.76 m . A detailed color analysis shows that the flare parameters at the maximum brightnesses corresponded to blackbody radiation with temperatures of approximately 14 000 and 13 000 K, enabling the monitoring of temperature — the rapid cooling of flare plasma near the flare maxima—for the first time. During 1.5 and 3.5 min at the maxima, the flares radiated as blackbodies, but these behaved as optically thick plasmas in the Balmer continuum on the second half of the descending branches. At the end of the first flare, the plasma became optically thin in the Balmer continuum; the final stage of the second flare was not observed. The flare areas at the luminosity maxima were 2.1 × 1018 and 3.0×1018 cm2 in a blackbody approximation, or 0.07%and 0.11%of the visible stellar disk. The occurrence of quasi-periodic brightness pulsations during red-dwarf flares on time scales of approximately ten seconds is confirmed. 相似文献
13.
M. A. Livshits I. Yu. Grigoryeva I. I. Myshyakov G. V. Rudenko 《Astronomy Reports》2016,60(10):939-948
Multi-wavelength observations and magnetic-field data for the solar flare of May 10, 2012 (04: 18 UT) are analyzed. A sign change in the line-of-sight magnetic field in the umbra of a small spot has been detected. This is at least partly associated with the emergence of a new magnetic field. A hard X-ray flare was recorded at almost the same time, and a “sunquake” was generated by the impact of the disturbance in the range of energy release on the photosphere. A sigmoid flare was recorded at the beginning of the event, but did not spread, as it usually does, along the polarity inversion (neutral) line. SDO/HMI full vectormagnetic-fieldmeasurements are used to extrapolate the magnetic field of AR 11476 into the corona, and to derive the distribution of vertical currents jz in the photosphere. The relationship between the distribution of currents in the active region and the occurrence of flares is quite complex. The expected “ideal” behavior of the current system before and after the flare (e.g., described by Sharykin and Kosovichev) is observed only in the sigmoid region. The results obtained are compared with observations of two other flares recorded in this active region on the same day, one similar to the discussed flare and the other different. The results confirm that the formation and eruption of large-scale magnetic flux ropes in sigmoid flares is associated with shear motions in the photosphere, the emergence of twisted magnetic tubes, and the subsequent development of the torus instability. 相似文献
14.
Interactions of particles accelerated in solar flares with matter in the solar atmosphere give rise to neutrons, which are efficiently captured on hydrogen nuclei as they are slowed to thermal velocities. This capture is accompanied by the emission of a gamma-ray with energy 2.223 MeV. Observational data for the temporal profiles of the gamma-ray fluxes in this line are used to study the plasma-density distribution in the solar atmosphere during the flares of December 16, 1988, March 22, 1991, and November 6, 1997. This analysis is based on comparisons between the observations and profiles computed taking into account a number of parameters describing the generation and transport of the flare neutrons in atmospheric layers of various densities. In three cases studied, the density of the material in the photosphere below the flare region is enhanced compared to the density in an unperturbed part of the solar atmosphere at the same height. In the case of the December 16, 1988 flare, we are able for the first time to relate the profile of the 2.223 MeV line with the shape of the accelerated particle (proton) spectrum. This opens new possibilities for studies of particle acceleration on the Sun based on observations of flare gamma-ray emission. 相似文献
15.
The ion composition of fluxes of charged particles in interplanetary space with energies ∼0.03–10 MeV/nucleon are studied
during quiet periods in the 23rd solar-activity cycle using data from the ACE spacecraft. Apart from the activity minimum,
the Fe/O ratio during such periods corresponds to either the relative abundances of ions in particle fluxes accelerated in
solar flares or the mean abundances of elements in the solar corona. At the cycle minimum, this ratio takes on values characteristic
for the solar wind. These results indicate that the background fluxes of low-energy particles in the phases of the growth,
maximum, and decay of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal
energies and particles accelerated in small impulsive solar flares. The particle fluxes from such flares are distinguished
by an enhanced abundance of iron ions. 相似文献
16.
Regularities have been searched for in the dynamics of characteristics of flare solar radiation during the development of the active region NOAA 0069 in the interval of August 14–24, 2002. The SONG (Solar Neutrons and Gamma rays) instrument onboard the Russian CORONAS-F Solar Observatory recorded hard X-ray and gamma-ray radiation in nine of the 30 flares of class above C5 in this active region within the indicated time interval. It was obtained that, in accordance with the development of the active region, the X- and gamma-ray flux tended to increase at the flare maxima while the hard X-ray spectral index tended to decrease; flares with a harder radiation spectrum occurred in the sunspot umbra, i.e., in the region with the strongest magnetic fields. 相似文献
17.
We have begun an investigation of the possible origins of considerable of powerful solar flares. This effect is manifest, first and foremost, in the existence of high-temperature plasma in flare loops over many hours. Analysis of the soft X-ray emission in two energy bands detected by the GOES satellites for about 20 powerful solar flares reveals long time intervals during the decay phase when the source temperature decreases, in general, exponentially. The characteristic time t i for a decrease in the temperature by a factor of ten is 3–10 hours for most powerful events. In addition, another interval of very slow decrease with a characteristic time t i of tens of hours can be identified in some cases. We found a gradual change in the dependence of the temperature on the square root of the emission measure for the source as a whole, which characterizes the transition from purely coronal processes to powerful flares with a prolonged inflow of plasma from the chromosphere. Modeling the energy balance in a loop can yield the requirements for the source of plasma heating in a long-lived arch system. A necessary condition for the development of prolonged flares seems to be a powerful coronal mass ejection, which initiates the formation of a source of plasma heating at coronal heights. Our analysis shows that a considerable fraction of the energy is often released in the region of the cusp, and that systems of giant coronal arches rising to heights of about 100 000 km above the limb are formed in most prolonged events (called dynamical flares in the terminology of Svestka). 相似文献
18.
M. A. Kharinov V. K. Konnikova A. V. Ipatov I. A. Ipatova A. K. Erkenov 《Astronomy Reports》2020,64(4):350-362
The presented observation results of the blazar J0238+1636 were obtained in: 2014–2019 with the RATAN-600 radio telescope from the Special Astrophysical Observatory of the Russian Academy of Sciences at 2.3, 4.8, 8.2, 11.2, and 21.7 GHz; and 2015–2017 with the 32-m Zelenchuk and Badary radio telescopes of the Institute of Applied Astronomy of the Russian Academy of Sciences at 4.84 and 8.57 GHz. Two flares were detected on the long-term light curve. The time scale for variability on the rising branch of the first flare is τvar = 0.5 year, and the upper limit for the linear and angular sizes of the emitting region at 21.7 GHz are 0.3 pc and 0.05 mas, respectively. The brightness temperature is Tb ≥ 2.6 × 1013 K, and the Doppler factor is δ ≥ 3. In three sets of the source’s daily observations, which lasted up to three months each, no significant variability on the day-to-day scale was found after subtracting the long-term variability. In the RT-32 data, the intraday variability (IDV) was found at a frequency of 4.84 GHz in three out of 15 sessions and at 8.57 GHz in two out of 13 sessions. The characteristic times for variability are 4−5 hours. 相似文献
19.
M. A. Livshits A. M. Urnov F. F. Goryaev L. K. Kashapova I. Yu. Grigor’eva T. I. Kal’tman 《Astronomy Reports》2011,55(10):918-927
Results of simultaneous measurements of radiation fluxes from post-eruption arcades on the Sun at 171, 195, 284, and 304 ?
(from STEREO spacecraft data) and at radio wavelengths (from the RATAN-600 radio telescope) are presented. An original probabilistic
approach developed earlier by Urnov was used to determine the differential emission measure. This method requires no regularization,
and the obtained results do not depend on the choice of the temperature grid. This approach has yielded the differential measure
of emission at temperatures approximately from 0.3 to 15 MK. The subsequent calculation of thermal magnetobremsstrahlung in
a multi-temperature model with the magnetic field decreasing with height produces a spectrum similar to that observed on RATAN-600.
Thus, in many non-stationary events with modest powers, a thermal multi-temperature model is quite able to explain the emission
of post-eruption arcade systems, and it is not necessary to invoke the emission of accelerated particles. The proposed model
enables direct estimation of the ratio of the magnetic and gas pressures at the tops of post-eruption arcades, and determination
of the conditions required for the origin of secondary nonstationary processes in the decay stage of the main flare. 相似文献
20.
M. R. Kundu 《Journal of Earth System Science》1984,93(3):201-225
We review high spatial resolution microwave observations of solar active regions, coronal loops and flares. Observations of
preflare active regions are presented; in particular we discuss the interpretations of reversal of polarization at the flare
site and the role of newly emerging flux in triggering the onset of flares. We discuss the spatial locations of microwave
burst emitting regions; loops or arcades of loops appear to be the sites of flare energy release in microwave bursts. We provide
direct observational evidence of magnetic reconnection as the primary cause of acceleration of electrons in microwave bursts. 相似文献