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1.
Studies of the extreme solar proton event of January 20, 2005 intensified the contest over of a long-standing problem: are solar cosmic rays arriving at the Earth accelerated by solar flares or by shocks preceding rapidly moving coronal mass ejections? Among the most important questions is the relationship between the energy spectra of the solar cosmic rays and the frequency spectra of flare microwave bursts. Some studies of previous solar-activity cycles have shown that such a relationship does exist, in particular, for protons with energies of tens of MeV. The present work analyzes this relation using data for 1987–2008. For flare events observed in the western half of the disk, there is a significant correlation between the index δ, which is equivalent to the power-law index of the integrated energy spectrum of 10–100 MeV protons detected near the Earth’s orbit, and radio burst parameters such as a ratio of peak fluxes S at two frequencies (for example, at 9 and 15 GHz) and a microwave peak frequency f m . Proton fluxes with hard (flat) energy spectra (δ ≤ 1.5) correspond to hard microwave frequency spectra (S 9/S 15 ≤ 1 and f m ≥ 15 GHz), while flares with soft radio spectra (S 9/S 15 ≥ 1.5 and f m ≤ 5 GHz) result in proton fluxes with soft (steep) energy spectra (δ ≥ 1.5–2). It is also shown that powerful high-frequency bursts with the hardest radio spectra (f m ≈ 30 GHz) can point at acceleration of significant proton fluxes in flares occurring in strong magnetic fields. These results argue that solar cosmic rays (or at least their initial impulses) are mainly accelerated in flares associated with impulsive and post-eruptive energy release, rather than in shocks driven by coronal mass ejections. 相似文献
2.
The flare source of thermal X-rays above a magnetic arch in the corona arises from the dissipation of the magnetic energy
of the current sheet formed at the reconnection of magnetic-field lines. The sources of hard X-rays emitted from the footpoints
of the magnetic arch are beams of electrons accelerated in field-aligned currents induced by the Hall electric field generated
in the current sheet. Both the hard X-rays detected above the active region and the type III radio emission are radiated by
electrons accelerated in the field-aligned currents induced by Alfven waves. The solar cosmic rays are emitted promptly at
the instant of the flare. It is important that the Lorentz electric field accelerates protons along the singular magnetic
X line. The relativistic protons propagate along the interplanetary magnetic field. These protons have exponential spectra,
typical for acceleration occurring in current sheets. A mechanism that is relevant for the generation of delayed cosmic rays,
which demonstrate significant anisotropy and a power-law spectrum with γ ∼5, is also discussed. 相似文献
3.
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
4.
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
5.
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
6.
New data for the energy and location of the hard-emission centers of a solar flare agree with an electrodynamic model of a solar flare based on the idea of the accumulation of free magnetic energy in the field of a current sheet. Three-dimensional MHD simulations are used to show that the energy stored in the preflare magnetic field of the current sheet is sufficient for the development of a flare and a coronal mass ejection. The flare and coronal mass ejection result from the explosive decay of the current sheet. The position of the brightness-temperature maximum of the radio emission during the flare coincides with the maximum of the current in the current sheet. The exponential spectrum of relativistic protons generated during the flare is consistent with acceleration by the electric field during the current-sheet decay. 相似文献
7.
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
8.
The correlation between the magnetic flux in an active solar region and associated powerful solar flares is studied. The behavior
of the active regions AR 10486 and AR 10365 is considered. These regions produced a series of class X flares as they crossed
the solar disk. The flares appeared when the magnetic flux exceeded 1022 Mx. The magnetic flux remained constant during all the flares except for one. During this flare, the flux decreased by about
10%; this impulsive decrease of the flux was also recorded in the absence of flares. No energy flux from the photosphere to
the corona at the time of the flare was observed. The behavior of the photospheric field in AR 10486 and AR 10365 is consistent
with a slow accumulation of energy in the corona and the explosive release of energy stored in the magnetic field of a current
sheet above an active region during the flare. 相似文献
9.
A. M. Gal’per B. I. Luchkov Yu. V. Ozerov S. B. Rinchinov A. M. Khodarovich 《Astronomy Reports》2000,44(6):389-400
We present an analysis of the temporal and spectral characteristics of high-energy (E>30 MeV) gamma-ray emission from solar flares in the 22nd solar-activity cycle obtained in the Gamma-1 experiment. The powerful flares of March 26, June 15, and October 27, 1991, are examined, as well as the weaker events of October 29 and December 8, 1991. Two emission phases are revealed in these flares: an active phase with individual, short bursts of radiation and a slow phase without such bursts. A qualitative scenario for the development of a solar gamma-ray flare is presented, based on the common temporal and spectral features of the observed flares and of simulation results. 相似文献
10.
Yu. A. Shchekinov 《Astronomy Reports》2005,49(4):269-273
Arguments are presented in support of the idea that the total energy losses of cosmic rays passing through molecular clouds can exceed the energy production due to the action of shocks in supernovae. Galactic cosmic rays interacting with the surface layers of molecular clouds can be efficiently reflected, so that they do not penetrate into the depths of the clouds. Low-energy cosmic rays (E < 1 GeV) that can produce the primary ionization of the molecular-cloud gas can be generated inside such clouds by numerous shocks arising due to supersonic turbulence. 相似文献
11.
12.
M. A. Livshits V. A. Chernetskii I. G. Mitrofanov A. S. Kozyrev M. L. Litvak A. B. Sanin V. I. Tret’yakov W. Boynton K. Shinohara D. Hamara 《Astronomy Reports》2005,49(11):916-931
We present the first results of data on solar flares detected by the HEND instrument onboard the 2001 Mars Odyssey interplanetary spacecraft during its flight to Mars and in orbit around Mars. The instruments carried by the spacecraft, which was developed at the Space Research Institute of the Russian Academy of Sciences, included a scintillation detector with two crystals, enabling the detection of photons with energies from tens of keV to 2.5 MeV with high time resolution. Several dozen flares were detected on both the sides visible from the Earth and back side of the Sun, supplementing other available data in a number of cases. A joint analysis of the HEND data together with data obtained in near-Earth orbits enabled the detection of variations in the integrated fluxes of photons with energies exceeding 80 keV during observations of flares near the limb from various directions. Two events were analyzed in great detail: the setting of a region displaying frequent very short flares on May 20, 2001, and the rising of the group 10486, which displayed numerous flare phenomena on the limb followed by extremely high activity in October–November 2003. These variations appear in simultaneous observations of limb M flares made at angles differing by only 8°–10°. Analyses of observations of rising sources obtained on two spacecraft lead to similar results. This indicates that the vast majority of emission at energies exceeding 80 keV arises at altitudes of no higher than seven to ten thousand kilometers. We briefly consider the powerful solar-disk gamma-ray flare of August 25, 2001. In this case, there are some differences in the behavior of the hard radiation in the decay phase for observations made at angles differing by 25°, which is most likely due to differences in the instrumental responses to radiation with this spectrum. The absence of hard radiation at great heights in the region of the “cusp” places some constraints on our picture of the physical processes occurring in powerful solar flares. 相似文献
13.
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
14.
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
15.
Yu. V. Balabin É. V. Vashenyuk O. V. Mingalev A. I. Podgorny I. M. Podgorny 《Astronomy Reports》2005,49(10):837-846
Analysis of the relativistic proton spectra of solar flares occurring in the 23rd solar activity cycle derived from data of a worldwide neutron monitor network and numerical modeling both provide evidence for the acceleration of charged particles by an electric field that arises in coronal current sheets during reconnection. The method used to obtain the spectra is based on simulating the response of a neutron monitor to an anisotropic flux of relativistic solar protons with specified parameters and determining the characteristics of the primary relativistic solar protons by fitting model responses to the observations. Studies of the dynamics of the energy spectra distinguish two populations of relativistic protons in solar cosmic-ray events: the so-called fast component, which arrives at the flux front of the solar cosmic rays, followed by the delayed slow component. The fast component is characterized by strong anisotropy and an exponential energy spectrum, in agreement with the spectrum yielded by mathematical modeling of particle acceleration by an electric field directed along the X line of the magnetic field. The slow component, whose propagation is probably diffusive, has a power-law spectrum. 相似文献
16.
Semi-empirical models for three kernels emitting in the continuum during the pre-impulsive and impulsive phases of the white-light flare of August 9, 2011 have been calculated, based on observations of the continuum brightness near 6579 Å, Hα profiles, and photospheric iron lines. These computations show that, in order to achieve agreement between the computed and observed profiles and the contrast of the continuum emission of the impulsive kernels of the white-light flare, the temperature must be increased in both the lower chromosphere and the upper photosphere. The most efficient heating is located deeper in the photosphere in the pre-impulsive than in the impulsive phase, and chromospheric heating is negligible in the pre-impulsive phase. Spectral data and the results of model computations indicate that it is difficult to explain the emission of the white-light flare kernels as the effect of heating by energy transported from the corona into lower-lying, deep layers of the atmosphere by canonical transport mechanisms. 相似文献
17.
The locations of sites of primary energy release of solar flares are studied. Magnetic singularities revealed earlier—self-intersections
(reconnections) of F = 0 surfaces, where F is a differential factor determining the structural singularity in a potential magnetic field—are considered as possible
sites of energy release. Six flare events demonstrating paired sources of non-thermal hard X-rays emission observed on March
17, 2002, July 17, 2002, April 6, 2004, November 4, 2004, November 6, 2004, and December 1, 2004 are analyzed for probable
singularities. In each event analyzed, each source of non-thermal hard X-rays emission can be associated with an individual
magnetic singularity; in other words, there is a magnetic-field line passing near the singularity and ending near (i.e. within
about 10″) the source located on the photosphere (in the chromosphere). For the homologous flares observed on November 4 and
6, 2004, the same magnetic singularity is responsible for the source of non-thermal hard X-rays emission observed in the eastern
sector of the flare region on November 4 and the source observed in the western part on November 6. A proposed interpretation
associates these observations with a reversal of the electric field generated in the magnetic singularity on November 6, compared
with the electric field generated on November 4, attributed to corresponding changes occurring in the photospheric magnetic
field. 相似文献
18.
N Bhandari 《Journal of Earth System Science》1988,97(2):117-125
The rates of production of21Ne and22Ne in spallation reactions, both due to solar as well as galactic cosmic rays, in some major meteoritic minerals, e.g. olivines, feldspars and pyroxenes, are calculated using their energy spectra and excitation functions. The production profiles of21Ne and22Ne due to galactic cosmic rays, and the22Ne/21Ne ratio depend upon the size of the meteoroid. The22Ne/21Ne ratio is very sensitive to the abundance of sodium and consequently its depth profile is distinctly different in feldspars, the ratio increasing with depth rather than decreasing as in pyroxenes and olivines. In the near-surface regions, up to a depth of 2cm, production due to solar flare protons dominates, giving rise to a steep gradient in isotopic production as well as in the22Ne/21Ne ratio. Composite production profiles are given and compared with measurements in some meteorites. 相似文献
19.
Recent observations indicate that relatively strong plasma ejections are accompanied by the formation of systems of coronal loops with two glowing ribbons near their footpoints. However, while two-ribbon flares can sometimes last for many hours, for example, soft X rays, they sometimes decay within tens of minutes. We study here factors affecting the durations of flares using four major flares occurring in July 15–18, 2002, as examples. Various ground-based and satellite observations are used to show that short-duration events involved collimated (narrow) plasma ejections directed to the north and the subsequent formation of compact loops in the leading part of the active region. During one event, a powerful eastward ejection in a wide solid angle was followed by the formation of an extended arch system in the trailing part, which determined the long duration of the flare. It is proposed that in events involving collimated jets and corresponding narrow features in coronal mass ejections (CMEs), systems of coronal loops do form, but post-eruptive energy release either does not occur or is expressed very faintly. So the energy does not go downward from this region, and the plasma is emitted free in the coronal loops. In contrast to such rapid flares, wide ejections and bright, large-scale CMEs are accompanied by the formation and prolonged existence of an extended arch system. Thus, powerful nonstationary solar processes involve a large-scale CME and the flare itself, with the pattern of a particular event determined by the reconnection scenario and the evolution of the ejected plasma. 相似文献
20.
O. G. Den 《Astronomy Reports》2008,52(11):931-936
We analyze the flare events of October 28 and May 27, 2003 to examine the possible connection of solar flares with singularities in the differential characteristics of solar magnetic fields. The relation between flares and the behavior of F indicators (which describe structural singularities of the magnetic fields) introduced earlier is analyzed. It is shown that the generation of flares can be associated with self-intersections (or reconnection) of the F = 0 curves, where magnetic reconnection can occur. Consequently, the current sheets generated in such regions can be sources of energy release. 相似文献