共查询到20条相似文献，搜索用时 15 毫秒
1.
Solar gamma-ray lines, produced from nuclear reactions of accelerated particles interacting with the solar atmospheric medium, are the most direct diagnosis for the acceleration and transportation of energetic electrons and ions in solar flares. Much information about composition, spectrum, and angular distribution of the accelerated ions, as well as the elemental abundances of the ambient solar atmosphere can be derived from solar gamma-ray line spectra. A new gamma-ray calculation program has been developed by using an efficient nuclear code − TALYS. The theory of gamma-ray production in solar flares is treated in detail. The characteristics of gamma-ray spectrum are also presented. 相似文献
2.
Observations of gamma-ray lines from solar flares by SMM demonstrated that energetic protons and heavy ions are accelerated during the impulsive phase. In order to understand the acceleration mechanism for gamma-ray producing protons and heavy ions, we have studied the characteristics of the flares from which gamma-ray lines were observed by SMM In order to identify the characteristics unique to the gamma-ray line flares, we have also studied intense hard X-ray flares with no gamma-ray line emissions. We have found the following characteristics: 1) Most of the gamma-ray line flares produced intense radio bursts of types II and IV. 2) For most of the gamma-ray line flares, the time profiles of high-energy (? 300 keV) hard X-rays are delayed by order of several seconds with respect to those of low-energy hard X-rays. The delay times seem to be correlated with the spatial sizes of the flares. 3) In Hα importance, the gamma-ray line flares range from sub-flares to importance-3 flares. 4) The hard X-ray spectra of the gamma-ray line flares are generally flatter (harder) than those of flares with no gamma-ray line emission. From these characteristics, we conclude that the first-order Fermi acceleration operating in a flare loop is likely to be the acceleration mechanism for energetic protons and heavy ions as well as relativistic electrons. 相似文献
3.
Some interesting results on gamma-ray line emission and its time profiles observed by Hinotori are presented. Possible explanations of gamma-ray line and hard X-ray emissions for the impulsive and gradual flares are discussed. Relationship between the gamma-ray line emission and acceleration and escape of the solar particles is also studied. 相似文献
4.
Doing space Astronomy on lunar surface has several advantages. We present here feasibility of an All Sky Monitoring Payload for Spectro-photometry
in X-rays (SPHINX) which can be placed on a lander on the moon or in a space craft orbiting around the moon. The Si–PIN photo-diodes
and CdTe crystals are used to detect solar flares, bright gamma bursts, soft gamma-ray repeaters from space and also X-ray
fluorescence (XRF) from lunar surface. We present the complete Geant4 simulation to study the feasibility of such an instrument
in presence of Cosmic Diffused X-Ray Background (CDXRB). We find that the signal to noise ratio is sufficient for moderate
to bright GRBs (above 5 keV), for the quiet sun (up to 100 keV), solar flares, soft gamma-ray repeaters, X-ray Fluorescence
(XRF) of lunar surface etc. This is a low-cost system which is capable of performing multiple tasks while stationed at the
natural satellite of our planet. 相似文献
5.
A detailed review of nuclear processes and particle acceleration in solar flares has been completed recently (Ramaty and Murphy, 1987). Included in this review were a comprehensive discussion of the theory of gamma-ray and neutron production, as well as the results of comparisons of calculations with gamma-ray, neutron and charged-particle observations of solar flares. The implications of these comparisons on particle energy spectra, total numbers, anisotropies and electron-to-proton ratios, as well as on acceleration mechanisms and the interaction site were also discussed. In addition, elemental and isotopic abundances of the ambient gas, derived from gamma-ray observations, were compared to abundances obtained from observations of escaping accelerated particles and other sources. The present paper is a synopsis of this review 相似文献
6.
A detailed review of nuclear processes and particle acceleration in solar flares has been completed recently (Ramaty and Murphy, 1987). Included in this review were a comprehensive discussion of the theory of gamma-ray and neutron production, as well as the results of comparisons of calculations with gamma-ray, neutron and charged-particle observations of solar flares. The implications of these comparisons on particle energy spectra, total numbers, anisotropies and electron-to-proton ratios, as well as on acceleration mechanisms and the interaction site were also discussed. In addition, elemental and isotopic abundances of the ambient gas, derived from gamma-ray observations, were compared to abundances obtained from observations of escaping accelerated particles and other sources. The present paper is a synopsis of this review
相似文献7.
太阳耀斑伽玛射线能谱是加速粒子与太阳大气介质原子碰撞的结果,它是研究太阳耀斑中加速粒子和高能电子最为直接的手段.通过分析伽玛射线能谱,可以获得耀斑过程中加速粒子的成分、能谱、角分布及太阳大气元素丰度等重要信息.TALYS程序是一套模拟核反应的软件,对核反应过程中的所有信息均能完整地描述.利用TALYS计算得到了完整的太阳耀斑伽玛射线的核反应截面数据,开发了一套新的耀斑伽玛射线谱计算程序.详细介绍了耀斑伽玛射线计算的理论模型,并简单探讨了耀斑伽玛射线的特性,为未来的耀斑伽玛射线能谱分析奠定了理论基础. 相似文献
8.
S. N. Kuznetsov V. G. Kurt I. N. Myagkova B. Yu. Yushkov K. Kudela 《Solar System Research》2006,40(2):104-110
The SONG instrument onboard the CORONAS-F satellite recorded gamma-ray emission with energy above 500 keV in 28 solar flares over three years of its in-orbit operation. According to the GOES classification, the X-ray importance of these flares lay within the range M1.4-X28. The gamma-ray energy recorded by SONG exceeded 4 MeV in 16 flares. Gamma-ray emission with energy up to 100 MeV was recorded in three events, more specifically, on August 25, 2001, October 28, 2003, and November 4, 2003. Increases in the count rate in the SONG channels that recorded neutrons with energies above 20 MeV were found during these three events. The energies of the recorded neutrons were estimated for the neutron increases. The time dependence of the neutron increases was compared with data from high-altitude ground-based neutron monitors that could, in principle, record the arrival of high-energy neutrons from the Sun. It should be noted that we detected series of flares with gamma-ray emission generated by the same active region (AR). The series in the last decade of August 2002 (AR NOAA 0069), the end of May 2003 (AR NOAA 0365), and the famous period of extreme solar activity in October–November 2003 associated with AR NOAA 0486 and AR NOAA 0501 are quite revealing. The catalog can be of use for future statistical and correlation analyses of solar flares. 相似文献
9.
I. V. Arkhangelskaja A. I. Arkhangelsky Yu. D. Kotov S. N. Kuznetsov A. S. Glyanenko 《Solar System Research》2006,40(2):133-141
The AVS-F apparatus onboard the CORONAS-F satellite (operated from July 31, 2001, to December 6, 2005) was intended for investigation of solar hard X-ray and gamma-ray radiation and for registration of gamma-ray bursts. The AVS-F apparatus constitutes a system for processing the data from two detectors: SONG-D (a CsI(Tl) scintillation detector 200 mm in diameter and 100 mm in height, fully surrounded by plastic anticoincidence shield) and RPS-1 (a solid state CdTe detector 4.9 mm × 4.9 mm in size). Over 60 solar flares stronger than M1.0 class by GOES classification were registered during the period from August 2001 to February 2005. Most flares showed gamma-ray emission during the periods when a rise in the X-ray flux was observed by the GOES instruments. Some flares produced gamma-rays only at maximum X-ray emission; for some flares, the durations of gamma-ray and X-ray emissions were the same. Up to six complexes of spectral lines were detected in some solar flares. The AVS-F instrument analyzes temporal profiles of low-energy gamma-ray emission with a temporal resolution of 1 ms within the first 4.096 seconds of solar flares. The preliminary analysis of such temporal profiles for seven solar flares revealed time regularities with scales from 7 to 35 ms in the 0.1-to 20-MeV energy range only for the flare of January 20, 2005, at a confidence level of 99%. 相似文献
10.
The study of nuclear line spectra from solar flares holds a rich promise for elucidating the properties of both the accelerated particles and the interaction or target region. We review the observations and the analysis of the large nuclear line rich flare which occurred near the west limb starting at 08:03 UT on 27 April, 1981. The observed spectrum from this flare contains three intense and isolated gamma-ray lines which can be analyzed in a model independent way. The measured energies are 1.628 ± 0.008, 4.430 ± 0.011, and 6.147 ± 0.022 MeV, identifying them as the de-excitation lines of 20Ne (1.634 MeV), 12C (4.438 MeV), and 16O (6.129 MeV). Elemental abundances of the ambient gas at the site of gamma-ray line production in the solar atmosphere are deduced using these gamma-ray line observations. The resultant abundances are different from local galactic abundances which are thought to be similar to photospheric abundances.Resident Research Associate at NRL under the NRC Associateship Program. 相似文献
11.
Electron and proton acceleration in reconnecting current sheets in electron-rich solar flares is considered. A significant three-dimensional magnetic field is assumed in the current sheet where the particles are accelerated by the DC electric field. The tearing instability of a pre-flare current sheet leads to the formation of multiple singular lines of magnetic field where the electric and magnetic fields are coaligned. Magnetized electrons are shown to be accelerated to a few tens of MeV before they leave the vicinity of a singular line. The acceleration time is estimated to be less than 10–3 s. By contrast, much heavier protons are unmagnetized and their energy gain is more modest. The model explains a high electron-to-proton ratio and the unusually intense gamma-ray continuum above 1 MeV observed in the electron-rich flares. 相似文献
12.
Electron-dominated episodes or events during solar flares are characterized by a flattening of the electron bremsstrahlung continuum above about 1 MeV. This flattening leads to a dominance of the continuum at MeV energies over nuclear emissions. We analyzed events recorded by the gamma-ray spectrometer on SMM with the aim to determine the nuclear contribution in the energy range between 4 and 8 MeV. We find that for comparable continuum fluences it is less by about an order of magnitude than for other flares. The spectral index of the best-fit power law of the > 1 MeV continuum with a median at –1.84 turns out to be independent of the heliocentric angle of the events, implying that the degree of anisotropy of the radiating particles was low. It is of interest to note that a value of –1.5 seems to be a limit. The spectral index of the continuum between 0.3 and 1 MeV does not differ significantly from that of other flares. Only measurements with detectors sensitive up to at least 10 MeV can, therefore, sort out electron dominated episodes during solar flares. 相似文献
13.
《Chinese Astronomy and Astrophysics》1983,7(2):124-129
Starting with the quasi-linear equation of the distribution function of particles in a regular electric field, a combined diffusion coefficient in the momentum space conbining the effects of the regular field and a turbulent field is obtained and a combined mechanism of acceleration by the regular and turbulent fields in the neutral sheet of solar proton flares is proposed. It is shown by calculation that conditions in solar proton flares are such that the charged particles can be effectively accelerated to tens of MeV, even ~1 GeV. It is shown that the combined acceleration by a regular electric field and ion-acoustic turbulence pumps the protons and other heavy ions into ranges of energy where they can be accelerated by Langmuir turbulence. By considering the combined acceleration by Langmuir turbulence and the regular electric field, the observed spectrum of energetic protons and the power-law spectrum of energetic electrons can be reproduced. 相似文献
14.
The temporal histories of three intense and impulsive gamma-ray flares, for which also white-light emission had been observed, are analyzed in order to test the role of high-energy particles- electrons and protons - in powering the optical continuum. By comparing the light curves at optical wavelengths and at X-ray and gamma-ray energies, we find a good correlation of the main peaks of emission, which confirms previous findings that the continuum emission is most likely associated with the energy loss of energetic particles. The power carried by the greater-than-50 keV nonthermal electrons may be sufficient to balance the optical emission. The power residing in protons or ions with energies greater than 1 MeV depends largely on the spectral shape of the particle distribution. Only if this is similar to a power law, may the energy carried by these high-energy particles be sufficient to balance the white-light flare emission.Operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. Partial support for the National Solar Observatory is provided by the USAF under a Memorandum of Understanding with the NSF. 相似文献
15.
I. G. Mitrofanov 《Astrophysics and Space Science》1989,155(1):141-143
The possibility of microsecond flares from cosmic gamma-ray sources is considered taking into account theoretical models. Several observations effects resulted from these flares are also presented. 相似文献
16.
Flares and coronal mass ejections (CMEs) contribute to the acceleration and propagation of solar energetic particles (SEP) detected in the interplanetary space, but the exact roles of these phenomena are yet to be understood. We examine two types of energetic particle tracers related with 15 CME-less flares that emit bright soft X-ray bursts (GOES X class): radio emission of flare-accelerated electrons and in situ measurements of energetic electrons and protons near 1 AU. The CME-less flares are found to be vigorous accelerators of microwave-emitting electrons, which remain confined in low coronal structures. This is shown by unusually steep low-frequency microwave spectra and by lack of radio emission from the middle and high corona, including dm?–?m wave type IV continua and metre-to-hectometre type III bursts. The confinement of the particles accelerated in CME-less flares agrees with the magnetic field configuration of these events inferred by others. Two events produced isolated metric type II bursts revealing coronal shock waves. None of the seven flares in the western hemisphere was followed by enhanced particle fluxes in the GOES detectors, but one, which was accompanied by a type II burst, caused a weak SEP event detected at SoHO and ACE. Three of the CME-less flares were followed within some hours by SEP-associated flares from the same active region. These SEP-producing events were clearly distinct from the CME-less ones by their association with fast and broad CMEs, dm?–?m wave radio emission, and intense DH type III bursts. We conclude that radio emission at decimetre and longer waves is a reliable indication that flare-accelerated particles have access to the high corona and interplanetary space. The absence of such emission can be used as a signal that no SEP event is to be expected despite the occurrence of a strong soft X-ray burst. 相似文献
17.
A. R. Rao J. P. Malkar M. K. Hingar V. K. Agrawal Sandip K. Chakrabarti Anuj Nandi D. Debnath T. B. Kotoch R. Sarkar T. R. Chidambaram P. Vinod S. Sreekumar Y. D. Kotov A. S. Buslov V. N. Yurov V. G. TyshkeVich A. I. Arkhangelsky R. A. Zyatkov 《Solar System Research》2011,45(2):123-134
The RT-2 Experiment onboard the CORONAS-PHOTON satellite is designed to study the spectral, temporal, and spatial details of solar hard X-ray flares in the 15–150 keV range. Above this energy (and upto 1000 keV), it also acts as an omni-directional gamma-ray detector with a capability to study gamma-ray bursts (GRB), bright solar flares, and X-ray pulsars. With an ensemble of hard X-ray detectors with different fields of view and coding devices, it also has the capability to investigate the spectrum of Cosmic Diffuse X-ray Background. The performance of the detectors from 2009 February to November is described in this paper. Results obtained on a few GRBs and solar flares are also briefly discussed. 相似文献
18.
Stefano Gabici Felix A. Aharonian Pasquale Blasi 《Astrophysics and Space Science》2007,309(1-4):365-371
It is believed that the observed diffuse gamma-ray emission from the galactic plane is the result of interactions between
cosmic rays and the interstellar gas. Such emission can be amplified if cosmic rays penetrate into dense molecular clouds.
The propagation of cosmic rays inside a molecular cloud has been studied assuming an arbitrary energy and space dependent
diffusion coefficient. If the diffusion coefficient inside the cloud is significantly smaller compared to the average one
derived for the galactic disk, the observed gamma-ray spectrum appears harder than the cosmic ray spectrum, mainly due to
the slower penetration of the low energy particles towards the core of the cloud. This may produce a great variety of gamma-ray
spectra. 相似文献
19.
The Fermi LAT provides a continuous and uniform monitoring of the Universe in the gamma-ray band. During the first year many gamma-ray blazar flares, some unidentified transients and emission by the Sun while in a quiet state were promptly detected. This is mainly due to the design of the mission, featuring a detector, the LAT with a wide field of view, and to the operation of the spacecraft itself, that can cover every region of the sky every 3 hours. Nevertheless, the scientific exploitation of this monitoring is more fruitful when early information about transients reaches a broader community. In this respect, the indefatigable activity of flare advocates, who worked on weekly shifts to validate the results and quickly broadcast information about flares and new detections, was the key to most scientific results. 相似文献
20.
Y. Ogawara T. Takano T. Kato T. Kosugi S. Tsuneta T. Watanabe I. Kondo Y. Uchida 《Solar physics》1991,136(1):1-16
The SOLAR-A spacecraft is to be launched by the Institute of Space and Astronautical Science, Japan (ISAS) in August, 1991. As a successor of HINOTORI, this mission is dedicated principally to the study of solar flares, especially of high-energy phenomena observed in the X- and gamma-ray ranges. The SOLAR-A will be the unique space solar observatory during the current activity maximum period (1989–1992). With a coordinated set of instruments including hard X-ray and soft X-ray imaging telescopes as well as spectrometers with advanced capabilities, it will reveal many new aspects of flares and help better understand their physics, supporting international collaborations with ground-based observatories as well as theoretical investigations. An overview of this mission, including the satellite, its scientific instruments, and its operation, is given in this paper. Also the scientific objectives are briefly discussed.After the launch the name of SOLAR-A has been changed to YOHKOH. 相似文献