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1.
Following many solar flares, electrons with kinetic energy > 40 keV appear in interplanetary space. There are two classes of such electrons: prompt electrons which arrive within an hour of the flare and delayed electrons which arrive about a day following the flare. The promptly arriving electrons are found to be of two types: Simple (S) events are associated with solar flares which occur in the absence of large area Type I radio noise storm and the complex (C) events resulting from flares beneath these large radio noise regions. The propagation of energetic solar flare electrons to the earth is best described in terms of cones of propagation. In the S-events the cones have about 30° opening angle whereas in the C-type events the cones open to about 90° full angle. Outside the boundaries of these cones the electron flux is much reduced. Within the cones there is a net streaming of the electrons away from the sun. Solar flare electron fluxes do not show filamentary structure even at times when protons from the same flare do. This suggests that the electrons are injected into the interplanetary field from regions distinct from the proton injection region. The delayed solar electron events are accompanied by large fluxes of protons > 500 keV. These events are sometimes closely related to a sudden commencement. 相似文献
2.
Energetic solar electrons in the interplanetary medium 总被引：3，自引：0，他引：3
R. P. Lin 《Solar physics》1985,100(1-2):537-561
ISEE-3 measurements extending down to 2 keV energy have provided a new perspective on energetic solar electrons in the interplanetary medium. Impulsive solar electron events are observed, on average, several times a day near solar maximum, with 40% detected only below 15 keV. The electron energy spectra have a nearly power-law shape extending smoothly down to 2 keV, indicating that the origin of these events is high in the corona. These coronal flare-like events often produced 3He-rich particle events.In large solar flares which accelerate electrons and ions to relativistic energies, the electron spectrum appears to be modified by a second acceleration which results in a double power-law shape above 10 keV with a break near 100 keV and flattening from 10–100 keV. Large flares result in long-lived (many days) streams of outflowing electrons which dominate the interplanetary fluxes at low energies. Even in the absence of solar activity, significant fluxes of low energy electrons flow out from the Sun.Solar type-III radio bursts are produced by the escaping 2–102 keV electrons through a beam-plasma instability. The detailed ISEE-3 measurements show that electron plasma waves are generated by the bump-on-tail distribution created by the faster electrons running ahead of the slower ones. These plasma waves appear to be converted into radio emission by nonlinear wave-wave interactions. 相似文献
3.
R. P. Lin 《Solar physics》1970,12(2):266-303
Observations of prompt 40 keV solar flare electron events by the IMP series of satellites in the period August, 1966 to December, 1967 are tabulated along with prompt energetic solar proton events in the period 1964–1967. The interrelationship of the various types of energetic particle emission by the sun, including relativistic energy electrons reported by Cline and McDonald (1968) are investigated. Relativistic energy electron emission is found to occur only during proton events. The solar optical, radio and X-ray emission associated with these various energetic particle emissions as well as the propagation characteristics of each particle species are examined in order to study the particle acceleration and emission mechanisms in a solar flare. Evidence is presented for two separate particle acceleration and/or emission mechanisms, one of which produces 40 keV electrons and the other of which produces solar proton and possibly relativistic energy electrons. It is found that solar flares can be divided into three categories depending on their energetic particle emission: (1) small flares with no accompanying energetic phenomena either in particles, radio or X-ray emission; (2) small flares which produce low energy electrons and which are accompanied by type III and microwave radio bursts and energetic ( 20 keV) X-ray bursts; and (3) major solar flare eruptions characterized by energetic solar proton production and type II and IV radio bursts and accompanied by intense microwave and X-ray emission and relativistic energy electrons. 相似文献
4.
R. P. Lin 《Solar physics》1970,15(2):453-478
Electrons of ~ 40 keV energy observed at 1 AU are used as tracers to map the emission structure of a large active region, McMath plage 8905, which crossed the visible disk in July–August, 1967.The acceleration of 10–100 keV electrons is found to be a property of active regions with a certain stage of development, and is signaled by the emission of 20 keV X-rays. The emission of electrons into the interplanetary medium may be separate from the acceleration of the electrons. Type III radio emission at long wavelengths appears to indicate the escape of the electrons into the interplanetary medium.The subsequent electron propagation in the interplanetary medium is essentially scatter-free, and the profile of the electron appears to be determined predominantly by transport/storage processes in the solar corona. The emission structure for active region McMath plage 8905 consists of (1) an open cone of ~ 70° extent in solar longitude where electrons have direct access to interplanetary field lines; (2) a cone of propagation of 100° width in solar longitude, surrounding and including the open cone in which impulsive electron events are observed; and (3) an overall ~ 200° extent of solar longitude over which low, non-impulsive fluxes from the active region are observed. A model is presented to account for the observed structure. This type of emission structure may be present in other electron-active regions. 相似文献
5.
Coherent synchrotron deceleration of 100 keV electrons is proposed as the mechanism by which type II and III solar radio bursts are generated. This mechanism directly excites the transverse electromagnetic radiation by a linear mechanism at the relativistic electron cyclotron frequency and at the first harmonic thereof if the energy spread of the exciting component is sufficiently narrow. Higher cyclotron harmonics are excluded by the energy spread in the 100 keV exciting electron component. This mechanism appears to fit the observational data concerning these emissions some-what better than the existing theory based on the non-linear interaction of electrostatic plasma waves. 相似文献
6.
A new series of solar flare energetic X-ray events has been detected by an ionization chamber on the OGO-I and OGO-III satellites in free space. These X-rays lie in the range 10–50 keV, and a study has been made of their relationship to 3 and 10 cm radio bursts and with the emission of electrons and protons observed in space. The onset times, times of maximum intensity and total duration are very similar for the radio and X-ray emission. Also, the average decay is similar and usually follows an exponential type behavior. However, this good correlation applies most often to the flash phase of flares, whereas subsequent surges of activity from the same eruption may produce microwave emission or further X-ray bursts not closely correlated. An approximate proportionality is found between the total energy content of the X-rays and of the 3 and 10 cm integrated radio fluxes. These measurements suggest that the X-ray and microwave emission have a common energizing process which determines the time profile of both. The recording of electrons greater than 40 keV by the Interplanetary Monitoring Probe (IMP satellite) has been found to correlate very well with flares producing X-ray and microwave emission provided the propagation path to the sun is favorable. There is evidence that the acceleration of solar protons may not be closely associated with the processes responsible for the production of microwaves, X-rays, and interplanetary electrons.The OGO ionization chamber responds to energies (10–50 keV) intermediate between the soft X-rays giving SID disturbances (1–10 keV) and energetic quanta previously measured with balloons (50–500 keV). Proposed source mechanisms should be capable of covering this range of energies including the most energetic quanta occasionally observed. 相似文献
7.
Solar radio bursts at long wavelengths provide information on solar disturbances such as coronal mass ejections (CMEs) and shocks at the moment of their departure from the Sun. The radio bursts also provide information on the physical properties (density, temperature and magnetic field) of the medium that supports the propagation of the disturbances with a valuable cross-check from direct imaging of the quiet outer corona. The primary objective of this paper is to review some of the past results and highlight recent results obtained from long-wavelength observations. In particular, the discussion will focus on radio phenomena occurring in the outer corona and beyond in relation to those observed in white light. Radio emission from nonthermal electrons confined to closed and open magnetic structures and in large-scale shock fronts will be discussed with particular emphasis on its relevance to solar eruptions. Solar cycle variation of the occurrence rate of shock-related radio bursts will be discussed in comparison with that of interplanetary shocks and solar proton events. Finally, case studies describing the newly-discovered radio signatures of interacting CMEs will be presented. 相似文献
8.
We describe the radio signatures that led up to and concluded the solar eruptive event of 14 July 2000 (Bastille Day Event).
These radio signatures provide a means of remotely sensing the associated solar activity and transient phenomena. For many
days prior to the Bastille Day Event kilometric Type III radio storm emissions were observed that were presumably associated
with the active region NOAA 9077. These storm emissions continued until the X5.7 flare at ∼ 10 UT on 14 July 2000 that characterized
the Bastille Day Event, then ceased abruptly. The Bastille Day Event itself produced very intense, complex, long-duration
Type III-like radio emissions, which appear to have been associated with electrons generated (accelerated) deep in the solar
corona. The coronal mass ejection (CME) associated with the Bastille Day Event generated decametric to kilometric Type II
radio emissions as the CME propagated through the solar corona and interplanetary medium. The frequency drift of these Type II
radio emissions are related to the dynamics of the propagating CME and indicate that the CME experienced significant deceleration
as it propagated from the high corona into the interplanetary medium. 相似文献
9.
IMP-6 spacecraft observations of low frequency radio emission, fast electrons, and solar wind plasma are used to examine the dynamics of the fast electron streams which generate solar type-III radio bursts. Of twenty solar electron events observed between April, 1971 and August, 1972, four were found to be amenable to detailed analysis. Observations of the direction of arrival of the radio emission at different frequencies were combined with the solar wind density and velocity measurements at 1 AU to define an Archimedean spiral trajectory for the radio burst exciter. The propagation characteristics of the exciter and of the fast electrons observed at 1 AU were then conpared. We find that: (1) the fast electrons excite the radio emission at the second harmonic; (2) the total distance travelled by the electrons was between 30 and 70% longer than the length of the smooth spiral defined by the radio observations; (3) this additional distance travelled is the result of scattering of the electrons in the interplanetary medium; (4) the observations are consistent with negligible true energy loss by the fast electrons. 相似文献
10.
《Chinese Astronomy and Astrophysics》1981,5(2):157-161
An attempt is made to account for the decimetre portion of the Type-IV solar radio bursts by plasma emission. Non-thermal electrons (E ～ 500 keV) trapped in a magnetic mirror (IVdm, burst source) having loss-cone gap distribution excite plasma waves which are transformed into transverse waves through non-linear scattering by ions. A good agreement was reached between the calculated spectrum and the observed fluxes for the event of 1972 August 2. A distribution of the number of non-thermal electrons with height, and a total number of 1032, were obtained. Also it was found that the Langmuir waves can accelerate some background thermal electrons to the MeV range. 相似文献
11.
An extensive study of the IMP-6 and IMP-8 plasma and radio wave data has been performed to try to find electron plasma oscillations associated with type III radio noise bursts and low-energy solar electrons. This study shows that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. In nearly four years of observations only one event was found in which electron plasma oscillations are clearly associated with solar electrons. For this event the plasma oscillations appeared coincident with the development of a secondary maximum in the electron velocity distribution functions due to solar electrons streaming outwards from the Sun. Numerous cases were found in which no electron plasma oscillations with field strengths greater than 1 μV m?1 could be detected even though electrons from the solar flare were clearly detected at the spacecraft. For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare the electric field strength is relatively small, only about 100 μV m?1. This field strength is about a factor of ten smaller than the amplitude of electron plasma oscillations generated by electrons streaming into the solar wind from the bow shock. Electromagnetic radiation, believed to be similar to the type III radio emission, is also observed coming from the region of the more intense electron plasma oscillations upstream of the bow shock. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation. Possible ways of resolving these difficulties are discussed. 相似文献
12.
太阳射电爆发(Solar Radio Burst, SRB)是太阳高能电子与背景等离子体相互作用产生的感应辐射现象,其多样的动力学谱类型及其复杂的精细结构反映了辐射源区磁等离子体结构状态丰富的物理信息,而相关辐射机制则是解读相关物理信息的关键工具.长期以来,在SRB辐射机制的研究中一直存在着争议不决的两种主要机制,即等离子体辐射机制和电子回旋脉泽(Electron Cyclotron Maser, ECM)辐射机制.近年来,针对传统的ECM辐射机制应用到SRB现象时遇到的一些主要困难,发展了由幂律谱电子低能截止驱动和包含快电子束自生阿尔文波效应的新型ECM驱动模型,并成功应用于解释各类不同SRB动力学谱的形成机制.基于这些新型的ECM辐射模型,系统地总结了ECM辐射机制在各种不同类型SRB现象中的应用,并对它们不同动力学谱结构的形成给出了一致统一的物理解释. 相似文献
13.
G. Mann H.-T. Classen U. Motschmann H. Kunow W. Dröge 《Astrophysics and Space Science》1998,264(1-4):489-496
Combined SOHO (Solar and Helisopheric Observatory) and ground based radio observations show evidently signatures of electrons
accelerated by a shock wave during the event on July 9, 1996. A solar type II radio burst has been received as a signature
of a coronal shock wave at 300 MHz on 9:10:54 UT. It was accompanied with electron beams appearing as type III radio bursts
below 80 MHz. Simultaneously, the COSTEP (Comprehensive Suprathermal and Energetic Particle Analyzer) instrument aboard SOHO
has measured enhanced electron fluxes in the range 30 keV – 3 MeV. This indicates that a coronal shock wave was able to produce
high energetic electrons. A mechanism of electron acceleration up to relativistic velocities is presented and compared with
the observations. The electron acceleration takes place at substructures of quasi-parallel collisionless shocks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Until recently, most of the information on particle acceleration processes in solar flares has been obtained from hard X-ray and cm-microwave observations. As a rule they provide information on electrons with energies below 300 keV. During recent years it became possible to measure the gamma-ray and millimeter radio emission with improved sensitivities. These spectral ranges carry information on much higher energy electrons. We studied the temporal and spectral behaviour of the radio burst emission at centimeter-millimeter wavelengths (8–50 GHz) by using the data from the patrol instruments of IAP (Bern University). We have analyzed more than 20 impulsive and long duration radio bursts (of 10 s to several 100 s duration).The main finding of the data analysis is the presence of spectral flattening throughout the bursts, which occurs always during the decay phase of flux peaks, at frequencies well above the spectral peak frequency and independently of burst duration. Furthermore, for some of the bursts, the flux maxima at higher frequencies are delayed. These findings can serve as evidence of the hardening of the electron spectrum at energies above some hundreds of keV during the decay phase of cm–mm flux peaks. As a most likely reason for such a hardening we consider Coulomb collisions of energetic electrons continuously injected and trapped in a flaring loop. 相似文献
15.
The GOES C7.5 flare on 20 February 2002 at 11:07 UT is one of the first solar flares observed by RHESSI at X-ray wavelengths. It was simultaneously observed at metric/decimetric wavelengths by the Nançay radioheliograph (NRH) which provided images of the flare between 450 and 150 MHz. We present a first comparison of the hard X-ray images observed with RHESSI and of the radio emission sites observed by the NRH. This first analysis shows that: (1) there is a close occurrence between the production of the HXR-radiating most energetic electrons and the injection of radio-emitting non-thermal electrons at all heights in the corona, (2) modifications with time in the pattern of the HXR sources above 25 keV and of the decimetric radio sources at 410 MHz are observed occurring on similar time periods, (3) in the late phase of the most energetic HXR peak, a weak radio source is observed at high frequencies, overlying the EUV magnetic loops seen in the vicinity of the X-ray flaring sites above 12 keV. These preliminary results illustrate the potential of combining RHESSI and NRH images for the study of electron acceleration and transport in flares. 相似文献
16.
In this paper, the 3B flare of February 4, 1986 is studied comprehensively. The escape electrons accelerated to 10–100 keV at the top of coronal loop are confirmed by III type bursts. The energetic electron beams moved downward trigger the eruptions in the low layer of solar atmosphere. The radio and soft X-ray bursts are interpreted, respectively, by the maser mechanism and evaporation effect. Finally, the important role of energetic electron beams in solar flares is pointed out. 相似文献
17.
An extensive study of the IMP-6 and IMP-8 plasma and radio wave data has been performed to try to find electron plasma oscillations associated with type III radio noise bursts and low energy solar electrons. This study shows that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. In nearly four years of observations only one event was found in which electron plasma oscillations are clearly associated with solar electrons. Numerous cases were found in which no electron plasma oscillations with field strengths greater than 1 V/m could be detected even though electrons from the solar flare were clearly detected at the spacecraft.For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare, the electric field strength is very small, only about 100 V/m. This field strength is about a factor of ten smaller than the amplitude of electron plasma oscillations generated by electrons streaming into the solar wind from the bow shock. Electromagnetic radiation, believed to be similar to the type III radio emission, is also observed coming from the region of more intense electron plasma oscillations upstream of the bow shock. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation. Possible ways of resolving these difficulties are discussed. 相似文献
18.
Radio noise storms show that suprathermal electrons (a few tens of keV) are present in the vicinity of active regions during several hours or even a few days. Where and how these electrons are energized is not yet well known. A flare-like sudden energy release in the active region is in general observed at the onset of noise storms, either as a fully developed flare or, more often, as a soft X-ray brightening without conspicuous H signature. In order to investigate to what extent electrons energized in the active region contribute to the noise-storm emission in the overlying coronal structures, we combine radio imaging (Nançay radioheliograph) with X-ray spectral observations at photon energies of a few keV (GOES) and - for the first time - around 10 keV (WATCH/GRANAT). In two of four studied events the WATCH data show a significant excess of the deka-keV count rate above the expectation from an isothermal fit to the GOES fluxes. Although the electron population producing the deka-keV X-ray emission would be energetic enough to power the simultaneous radio noise storm, the much longer duration of the radio emission requires time-extended particle acceleration. The acceleration probably occurs in the corona overlying the X-ray emitting region, triggered by the processes which give rise to the X-ray brightenings. 相似文献
19.
We review recent progress on our understanding of radio emission from solar flares and coronal mass ejections (CMEs) with emphasis on those aspects of the subject that help us address questions about energy release and its properties, the configuration of flare?–?CME source regions, coronal shocks, particle acceleration and transport, and the origin of solar energetic particle (SEP) events. Radio emission from electron beams can provide information about the electron acceleration process, the location of injection of electrons in the corona, and the properties of the ambient coronal structures. Mildly relativistic electrons gyrating in the magnetic fields of flaring loops produce radio emission via the gyrosynchrotron mechanism, which provides constraints on the magnetic field and the properties of energetic electrons. CME detection at radio wavelengths tracks the eruption from its early phase and reveals the participation of a multitude of loops of widely differing scale. Both flares and CMEs can ignite shock waves and radio observations offer the most robust tool to study them. The incorporation of radio data into the study of SEP events reveals that a clear-cut distinction between flare-related and CME-related SEP events is difficult to establish. 相似文献
20.
《天文和天体物理学研究(英文版)》2019,(11)
Hard X-ray Imager(HXI) is one of the three scientific instruments onboard the Advanced Spacebased Solar Observatory(ASO-S) mission, which is proposed for the 25th solar maximum by the Chinese solar community. HXI is designed to investigate the non-thermal high-energy electrons accelerated in solar flares by providing images of solar flaring regions in the energy range from 30 keV to 200 keV. The imaging principle of HXI is based on spatially modulated Fourier synthesis and utilizes about 91 sets of bi-grid sub-collimators and corresponding LaBr_3 detectors to obtain Fourier components with a spatial resolution of about 3 arcsec and a time resolution better than 0.5 s. An engineering prototype has been developed and tested to verify the feasibility of design. In this paper, we present background, instrument design and the development and test status of the prototype. 相似文献