共查询到20条相似文献，搜索用时 859 毫秒
1.
The Source Regions of Impulsive Solar Electron Events 总被引：1，自引：0，他引：1
Benz Arnold O. Lin Robert P. Sheiner Olga A. Krucker Säm Fainberg Joe 《Solar physics》2001,203(1):131-144
Low-energy (2–19 keV) impulsive electron events observed in interplanetary space have been traced back to the Sun, using their interplanetary type III radiation and metric/decimetric radio-spectrograms. For the first time we are able to study the highest frequencies and thus the radio signatures closest to the source region. All the selected impulsive solar electron events have been found to be associated with an interplanetary type III burst. This allows to time the particle events at the 2 MHz plasma level and identify the associated coronal radio emissions. Except for 5 out of 27 cases, the electron events were found to be associated with a coronal type III burst in the metric wavelength range. The start frequency yields a lower limit to the density in the acceleration region. We also search for narrow-band spikes at the start of the type III bursts. In about half of the observed cases we find metric spikes or enhancements of type I bursts associated with the start of the electron event. If interpreted as the plasma emission of the acceleration process, the observed average frequency of spikes suggests a source density of the order of 3×108 cm–3 consistent with the energy cut-off observed. 相似文献
2.
On the high-speed plasma streams,stormtime sudden commencements and cosmic-ray intensity: Relation amongst them during epoch 1978 to 1982 总被引：3，自引：0，他引：3
A new spectrometer has been put into operation that registers solar flare radio emission in the 0.1 to 3 GHz band. It is a frequency-agile system which can be fully programmed to measure both senses of circular polarization at any frequency within that range at selectable bandwidth. The time resolution has to be compromized with the number of frequency channels and can be in the range of 0.5 ms to 250 ms for 1 to 500 channels. First results mainly from the 1–3 GHz band are presented, a spectral region that has never been observed with high-resolution spectrometers. Most noteworthy are the frequent appearances of myriads of narrowband, fast-drifting bursts (microwave type III), diffuse patches of continuum emission, and broad clusters of millisecond spikes sometimes extending from 0.3 to 3 GHz. 相似文献
3.
We present statistics relating shock-associated (SA) kilometric bursts (Cane et al., 1981) to solar metric type II bursts. An SA burst is defined here to be any 1980 kHz emission temporally associated with a reported metric type II burst and not temporally associated with a reported metric type III burst. In this way we extend to lower flux densities and shorter durations the original SA concept of Cane et al. About one quarter of 316 metric type II bursts were not accompanied by any 1980 kHz emission, another quarter were accompanied by emission attributable to preceding or simultaneous type III bursts, and nearly half were associated with SA bursts. We have compared the time profiles of 32 SA bursts with Culgoora Observatory dynamic spectral records of metric type II bursts and find that the SA emission is associated with the most intense and structured part of the metric type II burst. On the other hand, the generally poor correlation found between SA burst profiles and Sagamore Hill Observatory 606 and 2695 MHz flux density profiles suggests that most SA emission is not due to energetic electrons escaping from the microwave emission region. These results support the interpretation that SA bursts are the long wavelength extension of type II burst herringbone emission, which is presumed due to the shock acceleration of electrons.Also: Department of Physics and Astronomy, University of Maryland, College Park, MD 20742, U.S.A. 相似文献
4.
The existence of a class of fast-drift, shock-associated (SA), kilometric radio bursts which occur at the time of metric type II emission and which are not entirely the kilometric continuation of metric type III bursts has been reported previously (Cane et al., 1981). In this paper, we establish unambiguous SA event criteria for the purpose of statistically comparing SA events with conventional kilometric type III bursts. We apply these criteria to all long-duration, fast-drift bursts observed by the ISEE-3 spacecraft during a 28-month interval and find that more than 70% of the events satisfying the criteria are associated with the radio signatures of coronal shocks. If a given event in our sample is associated with a metric type II or type IV burst, it is 13 times more likely to satisfy the SA criteria than an event associated only with metric type III activity. Compared with conventional kilometric type III bursts, the characteristics of these SA events are longer duration, higher maximum intensity, and a larger number of components. Differences in these characteristics for the two classes of events are not sufficient to distinguish all SA events from conventional type III bursts. The consistent lack of reported metric type III activity during the latter part of the candidate events suggests that some of the electrons are accelerated high in the corona, at or near the altitude of the shock. 相似文献
5.
M. J. Aschwanden A. O. Benz R. A. Schwartz R. P. Lin R. M. Pelling W. Stehling 《Solar physics》1990,130(1-2):39-55
We present observations of the solar flare on 1980 June 27, 16:14–16:33 UT, which was observed by a balloon-borne 300 cm2 phoswich hard X-ray detector and by the IKARUS radio spectrometer. This flare shows intense hard X-ray (HXR) emission and an extreme productivity of (at least 754) type III bursts at 200–400 MHz. A linear correlation was found between the type III burst rate and the HXR fluence, with a coefficient of 7.6 × 1027 photons keV–1 per type III burst at 20 keV. The occurrence of 10 type III bursts per second, and also the even higher rate of millisecond spikes, suggests a high degree of fragmentation in the acceleration region. This high quantization of injected beams, assuming the thick-target model, shows up in a linear relationship between hard X-ray fluence and the type III rate, but not as fine structures in the HXR time profile.The generation of a superhot isothermal HXR component in the decay phase of the flare coincides with the fade-out of type III production.Universities Space Research Associates.ST Systems Corporation. 相似文献
6.
根据1994年lslike＆Benz给出的1－3GHz频带上的微波III型爆发和微波尖峰辐射的分类定义,分析北京天文台26－3．8GHz频带上观测到的微波爆发的精细结构．通过分析发现该定义有局限性．本文重新定义了该波段上的微波III型爆发和微波尖峰辐射,并讨论了这种分类定义与设备时间分辨率的关系 相似文献
7.
Using the observed data for metric and hectometric type III radio bursts, the dependence of burst characteristics on the solar longitude has been examined over a wide frequency range. It is found that there exists an east-west asymmetry for the extension of metric type III bursts into hectometric wavelength range. In particular, hectometric bursts are rarely observed for solar flares associated with metric bursts eastward solar longitude 60°E. Furthermore, for eastern longitudes, the low frequency radio observations show a large dispersion in drift time interval. 相似文献
8.
Properties of electron acceleration in flares, especially the density structure in the acceleration region, are deduced from a correlation study between decimetric type III, spike, and hard X-ray (HXR) bursts. The high association rate found (71%) strongly suggests that spikes also originate from energetic electrons. Spikes and type III bursts have been found to be easily identified by their different polarizations. The two types of emission generally do not overlap in frequency. A reliable lower limit to the density is derived from the starting frequency of type III and U bursts. The spike emission very likely yields an upper limit. The density inhomogeneity in the acceleration region spans more than one order of magnitude and is more than one order of magnitude larger in the associated type U sources. A peak-to-peak correlation does not always exist between type III, spike and HXR bursts. This discrepancy can be interpreted in terms of the different source conditions and propagation properties. Whereas spikes need special conditions to become visible, type III and peaks of HXR may be the product of many elementary accelerations.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985. 相似文献
9.
《天文和天体物理学研究(英文版)》2021,(6)
Solar radio spikes are one of the most intriguing spectral types of radio bursts. Their very short lifetimes, small source size and super-high brightness temperature indicate that they should be involved in some strong energy release, particle acceleration and coherent emission processes closely related to solar flares. In particular, for the microwave spike bursts, their source regions are much close to the related flaring source region which may provide the fundamental information of the flaring process. In this work,we identify more than 600 millisecond microwave spikes which recorded by the Solar Broadband Radio Spectrometer in Huairou(SBRS/Huairou) during an X3.4 solar flare on 2006 December 13 and present a statistical analysis about their parametric evolution characteristic. We find that the spikes have nearly the same probability of positive and negative frequency drifting rates not only in the flare rising phase, but also in the peak and decay phases. So we suppose that the microwave spike bursts should be generated by shockaccelerated energetic electrons, just like the terminational shock(TS) wave produced by the reconnection outflows near the loop top. The spike bursts occurred around the peak phase have the highest central frequency and obviously weak emission intensity, which imply that their source region should have the lowest position with higher plasma density due to the weakened magnetic reconnection and the relaxation of TS during the peak phase. The right-handed polarization of the most spike bursts may be due to the TS lying on the top region of some very asymmetrical flare loops. 相似文献
10.
Yu. Yurovsky 《Solar physics》2001,201(2):389-392
It is shown that for burst bandwidth B considered in the time-frequency domain, the distribution of w(B
−1) is the probability density of radiation of radio emission of a given relative frequency bandwidth, while the distribution
w(B) is the density of bursts, arrangement on axis B. Using this remark, we find that solar decimetric spikes and type III bursts, and metric noise storms, have a `radiation
probability' approximately 10 times higher for large-bandwidth bursts than for small-bandwidth bursts. 相似文献
11.
We analyze the radioheliograph and SMM-C/P observations of 1986 November 3 mass ejection event. The metric radio emissions are the only detected activity associated with the mass ejection, but are adequate to study the evolution of the event. The start time of the ejection seems to precede a possible flare behind the limb indicated by the early type III bursts. We discuss the physical relation between various types of bursts and the CME. We interpret moving type IV bursts as a plasma emission process. It is also shown using white-light coronagraph data that the density in the source region of the moving type IV is sufficient to support second harmonic plasma emission at the observed frequency of 50 MHz. 相似文献
12.
Zongjun Ning Qijun Fu Yihua Yan Yuying Liu Quankang Lu 《Astrophysics and Space Science》2001,277(4):615-624
The 2.60–3.80 GHz spectrometer at the Beijing Astronomical Observatory (BAO) recorded a ‘decimetric pulsation’ event (DCIM)
around the time 1999 0216 0300. At the beginning and end of this DCIM, two groups of reverse slope type III bursts (RS-III)
are also detected; meanwhile, metric type II bursts are recorded by CULG and HIRA during the same time. These solar radio
bursts on that day might be caused by the same active region 8458 and a same flare. We present a plausible qualitative model
for all of them.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
In previous attempts to show one-to-one correlation between type III bursts and X-ray spikes, there have been ambiguities as to which of several X-ray spikes are correlated with any given type III burst. Here, we present observations that show clear associations of X-ray bursts with RS type III bursts between 16:46 UT and 16:52 UT on July 9, 1985. The hard X-ray observations were made at energies above 25 keV with HXRBS on SMM and the radio observations were made at 1.63 GHz using the 13.7m Itapetinga antenna in R and L polarization with a time resolution of 3 ms. Detailed comparison between the hard X-ray and radio observations shows:
- In at least 13 cases we can identify the associated hard X-ray and decimetric RS bursts.
- On average, the X-ray peaks were delayed from the peak of the RS bursts at 1.6 GHz by ～ 400 ms although a delay as long as 1 s was observed in one case.
14.
本文介绍了云南天文台四波段（１．４２,２．１３,２．８４和４．２６ＧＨｚ）太阳射电高时间分辩率同步观测得到的五个微波ＩＩ型爆发事件,它们具有宽频带、长和短寿命、内向和外向快速频漂等特征．观测事例表明,非热电子束引起的等离子体辐射和电子回旋脉泽辐射两种机制都可能发生．这些观测特征既不完全同于米波—分米波ＩＩ型爆发,也不完全同于微波高频段ＩＩ型爆发,说明在微波低频段可能存在二重性或过渡现象 相似文献
15.
Out of 120 solar type IV events recorded at the Trieste Astronomical Observatory, we have selected 15 groups of spike bursts. We analyze their properties, concentrating on the characteristics of their polarization. We find that the polarization of the spikes varies over a wide range, but that within a particular group of spikes it remains almost constant. Sometimes groups of spikes with different degrees of polarization occur almost contemporaneously, probably indicating that more than one source is active at nearly the same time.Occasionally spike bursts accompany type III bursts. Then, unlike the case with type IV-associated events, the polarization of the spikes varies greatly.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985. 相似文献
16.
The relationship between metric type II radio bursts and solar flares is studied. Well-defined correlations between the properties of type II bursts and the characteristics of associated microwave and soft X-ray bursts are established in two entirely independent data sets. It is shown that the correlations are strongly affected by the wide range of coronal Alfvén velocities involved, comprising values from only 150 up to 800 km s–1, with a typical value of 400 km s–1. After careful data analysis it was inferred that type II bursts are more closely related to the soft X-ray bursts than they are to microwave bursts. The correlations indicate that type II burst shocks are preferably generated by flares with a relatively strong thermal component, and that the shocks are probably ignited by the plasma expansion associated with the 'evaporation' process in the transition region. Although the results imply that the majority of metric type II bursts are caused by flares, a simple geometrical consideration shows that a fraction of non-flare type II bursts cannot be explained by behind-limb events and that roughly 10% of metric type II bursts should be attributed to non-flare coronal mass ejections. 相似文献
17.
Detailed statistics and analysis of 264 type III bursts observed with the 625–1500 MHz spectrograph during the 23rd solar
cycle (from July 2000 to April 2003) are carried out in the present article. The main statistical results are similar to those
of microwave type III bursts presented in the literature cited, such as the correlation between type III bursts and flares,
polarization, duration, frequency drift rate (normal and reverse slopes), distribution of type III bursts and frequency bandwidth.
At the same time, the statistical results also point out that the average values of the frequency drift rates and degrees
of polarization increase with the increase in frequency and the average value of duration decreases with the increase in frequency.
Other statistical results show that the starting frequencies of the type III bursts are mainly within the range from 650 to
800 MHz, and most type III bursts have an average bandwidth of 289 MHz. The distributions imply that the electron acceleration
and the place of energy release are within a limited decimetric range. The characteristics of the narrow bandwidth possibly
involve the magnetic configuration at decimetric wavelengths, the location of electron acceleration in the magnetic field
nearto the main flare, the relevant runaway or trapped electrons, or the coherent radio emission produced by some secondary
shock waves. In addition, the number of type III bursts with positive frequency drift rates is almost equal to that with negative
frequency drift rates. This is probably explained by the hypothesis that an equal number of electron beams are accelerated
upwards and downwards within the range of 625 to 1500 MHz. The radiation mechanism of type III bursts at decimetric wavelengths
probably includes these microwave and metric mechanisms and the most likely cause of the coherent plasma radiation are the
emission processes of the electron cyclotron maser. 相似文献
18.
68 groups of type III bursts recorded with the dynamic spectrograph (from1 to 2 GHz) at the Beijing Astronomical Observatory
are statistically analyzed in this present article, with the frequency drift, duration, bandwidth and polarization of each
of these events being analyzed in detail. These observational features are different from those of metric, decimetric and
microwave high frequency type III bursts, showing that there possibly exist transition phenomena in the microwave low frequency
band and the microwave type III bursts at low frequencies are possibly produced by the harmonic plasma radiation caused by
nonthermal electronic beams and by the electron gyro-maser radiation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
We have searched for nonthermal radio signatures in the form of metric type III bursts in conjunction with two-sided-loop-type X-ray jets observed by the Yohkoh/SXT experiment. We have found no evidence of type III bursts in association with this particular type of X-ray jets in contrast to the positive evidence of type III's in association with anemone-type X-ray jets. This result is consistent with the simulation results of Yokoyama and Shibata (1995), which show that anemone-type jets are produced by vertical/oblique plasma flow whereas the two-sided-loop-type jets are produced by horizontal plasma flow. 相似文献
20.
Gennady P.Chernov 《中国天文和天体物理学报》2010,10(9)
This review covers the most recent experimental results and theoretical research on zebra patterns(ZPs)in solar radio bursts.The basic attention is given to events with new peculiar elements of zebra patterns received over the last few years.All new properties are considered in light of both what was known earlier and new theoretical models.Large-scale ZPs consisting of small-scale fiber bursts could be explained by simultaneous inclusion of two mechanisms when whistler waves"highlight"the levels of double plasma resonance(DPR).A unique fine structure was observed in the event on 2006 December 13: spikes in absorption formed dark ZP stripes against the absorptive type Ⅲ-like bursts.The spikes in absorption can appear in accordance with well known mechanisms of absorptive bursts.The additional injection of fast particles filled the loss-cone(breaking the loss-cone distribution),and the generation of the continuum was quenched at these moments.The maximum absorptive effect occurs at the DPR levels.The parameters of millisecond spikes are determined by small dimensions of the particle beams and local scale heights in the radio source.Thus,the DPR model helps to understand several aspects of unusual elements of ZPs.However,the simultaneous existence of several tens of the DPR levels in the corona is impossible for any realistic profile of the plasma density and magnetic field.Three new theories of ZPs are examined.The formation of eigenmodes of transparency and opacity during the propagation of radio waves through regular coronal inhomogeneities is the most natural and promising mechanism.Two other models(nonlinear periodic space-charge waves and scattering of fast protons on ion-sound harmonics)could happen in large radio bursts. 相似文献