共查询到20条相似文献，搜索用时 140 毫秒
1.
根据不同的发射波模以及偏振态（偏振度与偏振方向）的快速时变特征,对１９９３年１０月２日０７：４４：３４－０．７：４４：５２：９９ＵＴ期间的太阳射电事件进行了证认,认为这是一个由两群、总数约为４０个尖峰（ｓｐｉｋｅ０结构组成的罕见的宽带事件,它的总带宽〉３００ＭＨｚ、相对带宽〈５％,根据它们在２．５４５ＧＨｚ,２．６４５ＧＨｚ,２．６９５ＧＨｚ和２．８４０ＧＨｚ上的流量资料,首次对一些ｓｐｉｋｅ结构 相似文献
2.
给出1999年3月12日至6月8日,使用国家天文观测中心乌鲁木齐南山站25m射电望远镜在0．327GHZ,1．5GHZ,2．3GHZ,4．8GHZ和8．4GHZ频段,对脉冲星PSRB0329＋54进行的多波段观测结果．PSRB0329＋54的辐射呈幂律谱,并出现频谱转折现象,低频段谱指数为1．59,高频段为2．45,平均谱指数为1．72．五个频段上的平均脉冲轮廓的角宽度和二个弱成分峰值间的角宽度都随频率的增加而减小． 相似文献
3.
本文简述了1991年5月16日叠加在一个47GB微波大爆发上的快速精细结构(FFS)和spike群的偏振状态.在相隔100MHz的2645、2545MHz两频率上,spike的偏振状态随时间或随频率在50～100ms量级短时标内发生快速交替变化.我们认为这可能与小尺度空间内spike辐射源区的等离子体密度出现短时标的波动及磁场强度的起伏有关.这种波动和起伏使得等离子体频率与磁迴旋频率的比值(ω_p/Q_e)在2~(1/2)附近起伏变化,从而造成电磁波X波模和O波模的电子迴旋脉塞不稳定性增长率交替支配着电磁波的辐射,产生spike 辐射偏振状态的逆转. 相似文献
4.
利用日本YOHKOH卫星HXT提供的HXR爆发资料,和中国科学院北京天文台的太阳射电宽频带动态频谱仪（10－2．0GHZ,2．6-3．8GHZ）提供的微波爆发资料,对共生事件进行了初步统计分析,并对其中两例典型事件：1997年11月28日0503UT事件及1998年5月9日0340UT事件与共生的HXR爆发进行了详细比较,给出了几点有意义的结果及理论解释． 相似文献
5.
本文研究了寻常波和非常波在线性传播条件下，对快速毫秒级spike的时延、频漂和偏振逆转的影响．计算表明，在（20－40）×Baumbach－Alien的电子密度分布下，由于传播产生的时延，偏振逆转等约为30－300ms，这与观测结果在量级上是一致的．这说明在快速活动中传播效应是一个重要的因素． 相似文献
6.
CygX-1 X辐射的功率谱 总被引：1，自引：1，他引：0
运用自回归功率谱研究CygX－1X辐射的频谱特征,结果显示CygX－1转换态和高／软态时变频谱的连续成分,可以统一由有截断的幂律加噪声成分描述,转换态存在小于3Hz的宽峰结构及准周期振荡（QPO）成分（4－12Hz）,而高／软态完全可由截断幂律谱描述,不存在显著的QPO．截断频率在各态都相当稳定,在不同态的演化与平流为主的吸积流模型（ADAF）预期的情形一致．本文结果表明,自回归功率港分析是研究X射线双星光变特征的一个有效的方法． 相似文献
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8.
本文作者用美国ＮＲＡＯ，ＧｒｅｅｎＢａｎｋ４３ｍ和中国科学院紫金山天文台德令哈１３．７ｍ射电望远镜，对新近发现的水６１６—５２３脉泽相隔约１年的三次观测结果作了本地静止标准速度时变的研究，在分析实测结果时采用了参量ＬＳＲ速度延展（Ｖｓｐｄ），相继两历元观测的谱征峰值速度极差（ＤＶ）和速度位移（ＤＶ）．结果表明可将分析样本归纳为两类：Ａ类，微弱多数样本的速度时变给出的谱征位移显示脉泽结的替代效应．这种情况是在观测波束内存在若干未分解的脉泽斑引起的，主要受制于共同激发源的简单运动；Ｂ类，余下的样本给出较大的速度极差，呈现脉泽结整体的运动，涉及激发源的加速和减速以及抽运机制． 相似文献
9.
周树荣 《中国天文和天体物理学报》1996,(3)
本文研究结果表明：同一黑子群在日面期间的顺或反时针方向的旋转运动会先后并存．质子耀斑前1～2无，黑子群的旋转角速度达到极大．耀斑后，磁绳的松弛，黑子群可能会反向旋转，强的剪切过程和质子耀斑可能会再度出现．强质子耀斑活动区的共同特征是：（1）形态为单个团状结构δ型黑子，即众多异极性本影核紧锁在同一黑子半影中；（2）黑子面积＞1000×10－6半球面积，日面跨度＞10°；（3）黑子群都有快速的旋转运动．这类活动区，如果在日面西部活动性明显地增强，那么这个活动区在未来转到日面边缘及其背后、或再次从日面东边缘转出时，定能再次爆发耀斑和伴随较强质子事件。 相似文献
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11.
Location and parameters of a microwave millisecond spike event 总被引：1，自引：0，他引：1
A typical microwave millisecond spike event on November 2, 1997 was observed by the radio spectrograph of National Astronomical
Observatories (NAOs) at 2.6–3.8 GHz with high time and frequency resolution. This event was also recorded by Nobeyama Radio
Polarimeters (NoRP) at 1–35 GHz and Radio Heliograph (NoRH) at 17 GHz. The source at 17 GHz is located in one foot-point of
a small bright coronal loop of YOHKOH SXT and SOHO EIT images with strong photospheric magnetic field in SOHO MDI magnetograph.
It is assumed that the electron cyclotron maser instability and gyro-resonance absorption dominate, respectively, the rising
and decay phase of the spike event. For different harmonic number of gyro-frequency or magnetic field strength, a fitting
program with free plasma parameters is used to minimize the difference between the observational and theoretical values of
the exponential growth and decay rates for a given spike. The plasma parameters at third harmonic number are more comparable
to their typical values in solar corona. Hence, it is able to provide a diagnosis for the source parameters (magnetic field,
density, and temperature), the properties of radiations (wave vector and propagation angle), and the properties of non-thermal
electrons (density, pitch angle, and energy). The results are also comparable with the diagnosis of the gyro-synchrotron radiation
model, the frequency drift rates and a dipole magnetic field model, as well as the YOHKOH SXT and SOHO MDI data.
This study is supported by the NFSC project nos. 10333030 and 10273025, and “973” program with no. G2000078403. 相似文献
12.
Arnold O. Benz Christian Monstein Michael Beverland Hansueli Meyer Bruno Stuber 《Solar physics》2009,260(2):375-388
A new multichannel spectrometer, Phoenix-3, is in operation having capabilities to observe solar flare radio emissions in the 0.1?–?5 GHz range at an unprecedented spectral resolution of 61.0 kHz with high sensitivity. The present setup for routine observations allows measuring circular polarization, but requires a data compression to 4096 frequency channels in the 1?–?5 GHz range and to a temporal resolution of 200 ms. First results are presented by means of a well observed event that included narrowband spikes at 350?–?850 MHz. Spike bandwidths are found to have a power?–?law distribution, dropping off below a value of 2 MHz for full width at half maximum (FWHM). The narrowest spikes have a FWHM bandwidth less than 0.3 MHz or 0.04% of the central frequency. The smallest half-power increase occurs within 0.104 MHz at 443.5 MHz, which is close to the predicted natural width of maser emission. The spectrum of spikes is found to be asymmetric, having an enhanced low-frequency tail. The distribution of the total spike flux is approximately an exponential. 相似文献
13.
We briefly discuss the observed features including the high flux density, short duration, narrow emission band, fast frequency drift, quasi-periodic oscillation and fast variation of polarized components, of 51 spike emission events observed at 2545/2645 MHz in the solar activity peak year, 1991 January–December, and carry out correlation analysis between these events and optical flares, magnetic field intensity and configuration of flare regions, and sunspot evolution types of active regions. In view of the fact that the observed and statistical characteristics of the spike emissions are very different from those of known types of solar radio burst and known solar radio components, we think that the spike emission in the peak years is probably a new type of radio burst excited by electron cyclotron maser instability under wave-particle resonance, or a new solar radio component. 相似文献
14.
统计分析了国家天文台2．6-3．8 GHz高时间分辨率射电动态频谱仪在23周峰年期间(1998．4—2003．1)观测到的266个III型爆发．对这些事件的频率漂移、持续时间、偏振、带宽、开始和结束频率做了详细分析．开始和结束频率的统计分析表明,开始频率在一个非常大的范围,从小于2．6 GHz到大于3．8 GHz,而结束频率的截止区相对集中,从2．82-3．76 G．Hz．这些现象说明,电子加速的高度相当分散,在观测频率范围内具有正、负漂移率的III型爆发数基本相等,这可能意味着被加速的向上和向下传播的电子束在2．6—3．8 GHz范围有相同的比例．统计结果表明,微波III型爆发的辐射机制主要是等离子体辐射和电子回旋脉泽辐射过程． 相似文献
15.
OJ 287是存在着剧烈活动的低峰频BL Lac天体,其低频段的能谱与另两个TeV BL Lac天体(0716+714和BL Lacertae)在低频段的能谱很相似,但是切仑科夫望远镜却没能探测到它的TeV射线.利用这3个天体的观测数据,比较它们在22 GHz、37 GHz和B波段的最小光变周期及延迟的异同,进一步寻找没有观测到OJ 287的TeV伽马射线的可能原因.分析结果显示:(1)最小光变周期方面,OJ 287在37 GHz和B波段的周期偏小,在22 GHz,OJ 287与0716+714的结果相当,但与BL Lacertae相比要小很多,OJ 287的周期更短表明其活动性更强,却没有探测到来自OJ 287的TeV伽马射线,这表明OJ 287在TeV波段的辐射与这3个低能波段最小光变周期之间可能没有联系;(2)延迟方面,OJ 287在B波段相对于37 GHz的延迟要长于0716+714,短于BL Lacertae;在37 GHz相对于22 GHz的延迟要短于0716+714,而BL Lacertae在37 GHz相对于22 GHz的时延为负值,表明22 GHz要超前于37 GHz.通过对延迟的比较分析,并没有发现OJ 287与0716+714和BL Lacertae之间存在明显的差异;从能谱来看,很可能是由于OJ 287在TeV波段的能谱较陡造成切仑科夫望远镜没有探测到来自OJ 287的伽马辐射,但TeV能段较陡的能谱对低能段光变的影响目前还不是很清楚. 相似文献
16.
We present a special solar radio burst detected on 5 January 1994 using the multi-channel (50) spectrometer (1.0–2.0 GHz) of the Beijing Astronomical Observatory (BAO). Sadly, the whole event could not be recorded since it had a broader bandwidth than the limit range of the instrument. The important part was obtained, however. The event is composed of a normal drift type III burst on the lower frequency side and a reverse drift type III burst appearing almost simultaneously on the high side. We call the burst type III a burst pair. It is a typical characteristic of two type III bursts that they are morphologically symmetric about some frequency from 1.64 GHz to 1.78 GHz on the dynamic spectra records, which indicates that there are two different electron beams from the same acceleration region travelling simultaneously in opposite directions (upward and downward). A magnetic reconnection mode is a nice interpretation of type III burst pair since the plasma beta 0.01 is much less than 1 and the beams have velocity of about 1.07×108 cm s–1 after leaving the reconnection region if we assume that the ambient magnetic field strength is about 100 G. 相似文献
17.
We investigate the 2005 August 22 flare event(00:54 UT) exploiting hard X-ray(HXR) observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager(RHESSI) and microwave(MW) observations from the Nobeyama Solar Radio Observatory. The HXR time profile exposes well-damped quasi-periodic pulsations with four sequential peaks, and the MW time profile follows the corresponding peaks.Based on this feature, we derive the time relationship of HXRs and MWs with multifrequency data from the Nobeyama Radio Polarimeter, and the spatially resolvable data from RHESSI and the Nobeyama Radioheliograph. We find that both frequency dependent delays in MWs and energy dependent delays in HXRs are significant.Furthermore, MW emissions from the south source are delayed with respect to those from the north source at both 17 GHz and 34 GHz, but no significant delays are found in HXR emissions from the different sources at the same energies. To better understand all these long time delays, we derive the electron fluxes of different energies by fitting the observed HXR spectra with a single power-law thick-target model, and speculate that these delays might be related to an extended acceleration process. We further compare the time profile of a MW spectral index derived from 17 and 34 GHz fluxes with the flux densities, and find that the spectral index shows a strong anticorrelation with the HXR fluxes. 相似文献
18.
Many solar microwave bursts presenting fine structures were recorded at high temporal resolution (8 ms) by the 2.6–3.8 GHz
spectrometer of National Astronomical Observatories of China (NAOC). Here we present data that were recorded on 15 April 1998.
After data processing, more than one hundred spikes were detected in the interval 07:59:29.622–07:59:50.362 UT. Some of the
spikes were single, while others were grouped in clusters. We report the observational characteristics including lifetime,
frequency bandwidth, drift rate and polarization degree, as well as duration of spike clusters. Afterwards we discuss the
difference between the lifetime of the spikes presented here (near 3 GHz) and those reported formerly at frequency up to 1 GHz,
the probable source density and dimension, the brightness temperature and some other characteristics. 相似文献
19.
We analyze the high-frequency drift radio structures observed by the spectrometer at Purple Mountain Observatory (PMO) over
the frequency range of 4.5 – 7.5 GHz during the 18 March 2003 solar flare. The drifting structures take place before the soft
X-ray maximum, almost at the maximum of hard X-ray flux at 25 – 50 keV. For the first time, the positive drift in this kind
of radio structures is detected in such a high frequency range. Their global drifting rate is roughly estimated as 3.6 GHz s−1. They appear in four groups, lasting in total for less than 6 s, and have a broad bandwidth of more than 2 GHz but a smaller
ratio of the bandwidth of the drifting structures to mean frequency than that of the lower frequency range. The lifetime of
each individual burst in this event can be derived by using the high temporal resolution of the spectrometer at PMO and has
an average value of 36.3 ms. Since the negative drifting structures observed in the 0.6 – 4.5 GHz frequency range were interpreted
to be a radio signature of a plasmoid ejected upward (moving out of the Sun), the present observation may imply that it is
possible for a plasmoid to move downward during a solar flare. However, for a confirmation of this suggestion direct radio
imaging observation would be needed. 相似文献
20.
Takeo Kosugi 《Solar physics》1981,71(1):91-105
A well-developed multiple impulsive microwave burst occurred on February 17, 1979 simultaneously with a hard X-ray burst and a large group of type III bursts at metric wavelengths. The whole event is composed of several subgroups of elementary spike bursts. Detailed comparisons between these three classes of emissions with high time resolution of 0.5 s reveal that individual type III bursts coincide in time with corresponding elementary X-ray and microwave spike bursts. It suggests that a non-thermal electron pulse generating a type III spike burst is produced simultaneously with those responsible for the corresponding hard X-ray and microwave spike bursts. The rise and decay characteristic time scales of the elementary spike burst are 1 s, 1 s and 3 s for type III, hard X-ray and microwave emissions respectively. Radio interferometric observations made at 17 GHz reveal that the spatial structure varies from one subgroup to others while it remains unchanged in a subgroup. Spectral evolution of the microwave burst seems to be closely related to the spatial evolution. The spatial evolution together with the spectral evolution suggests that the electron-accelerating region shifts to a different location after it stays at one location for several tens of seconds, duration of a subgroup of elementary spike bursts. We discuss several requirements for a model of the impulsive burst which come out from these observational results, and propose a migrating double-source model. 相似文献