太阳活动周期的小波分析

运用小波技术对太阳射电流量2800 MHz,太阳黑子数和太阳黑子面积数周期进行分析．其结果表明: (1)这3个系列的数据显示最显著的周期是10．69年,其他周期并不明显．(2)小波功率谱给出了全部时间-周期范围的功率谱变化,它显示了在某个周期处于某个时段的局部功率的变化,小波功率谱分析表明,小于1年的周期仅仅在太阳活动最大期附近比较明显．(3)太阳射电2800 MHz,太阳黑子数和太阳黑子面积数的几个周期(10．69年,5．11年, 155．5天)的小波功率谱比较相似,出现峰值的时间相同;曲线的起伏相似,周期越小,曲线起伏的频率越大．     

相似射电爆发和它们的激励函数

本文从时域、频域及激励函数三方面讨论了发生在1989年8月28日的四个射电爆发的相似性。从讨论可看出,如果两个射电爆发相似,那么它们的上升相、下降相及爆发总持续时间的比是近似的,它们的激励函数可能也同样具有这种特点,而且它们的富     

双向Ⅲ型漂移爆发的多波段观测

分析了国家天文台云南天文台射电频谱仪在230～300MHz、625～1500MHz、1000～2000MHz和2600～3800MHz记录到的11对具有双向漂移结构的Ⅲ型爆发.对双向Ⅲ型爆发的半功率持续时间、频率漂移率、偏振度等观测特征与普通Ⅲ型爆发作了比较,与Hα耀斑的关系也作了详细分析.得到这些事件的显著特征,并对双向Ⅲ型爆发作了定性解释.     

云南天文台9375MHz、3653MHz、2902MHz1981年11月—1982年12月太阳射电观测精度分析

本文将云台9375MHz、3653MHz和2902MHz1981年11月—1982年12月期间观测到的太阳天线温度同USAF的Sagamore Hill系统进行了相关分析。分析结果表明:9375MHz、3653MHz和2902MHz总流量密度的均方差分别为±4.9％、±4.6％和±4.8％。爆发资料同紫台作了相关分析:9375MHz和2902MHz的均方差分别为±15.9％和19.9％。峰值时间精度校准在±0~m.1。     

一个复杂大爆发的分析

本文分析了2002.7.23国家天文台云南天文台射电频谱仪在625～1500 MHz、2600～3800 MHz和5200～7600 MHz记录到的复杂型大爆发,将此爆发与Hα耀斑、日冕物质抛射(CME)、硬X射线爆发及地球物理参数作了相关分析,得到这个事件的一些显著特征,认为这一事件电子的加速区在日冕的外层,接近625 MHz的地方,并且多次发生磁重联.磁重联以后的衰变相是湍流加速过程.     

一次形态复杂的微波大爆发——1980年10月14日射电爆发

1980年10月14日0542—0613—0734UT.,在位于日面S10W15的黑子区(M.W No.21811、AR2725)发生了一个3B级大耀斑。北京天文台的色球望远镜取得了比较完整的Hα观测资料,观测发现在耀斑爆发过程中存在喷焰(Spray)现象及扰动沿弧形轨迹运动的现象。北京天文台的3.2厘米(9395MHz),10.6厘米(2840MHz)总强度射电望远镜取得了完整的总辐射流量密度的时变曲线,参考云南天文台的8.2厘米及日本东京天文台2厘米,Tykw的15厘米,30厘米及S.G.D上的频谱资料对这一形态复杂的微波爆发作一初步的形态分析,与Hα资料作了比较,利用文献中的硬x线资料与射电资料作了初步的对比。     

1988年12月16日太阳射电大爆发的快速精细结构(英文)

本文介绍用“三波段太阳射电高时间分辨率同步观测系统”所观测到的1988年12月16日三波段(1420MHz、2840MHz、4000MHz)太阳射电大爆发中毫秒级精细结构的观测特征,指出太阳射电快速活动在射电爆发的不同阶段具有不同的特征,首先在爆发的上升沿出现2840MHz的毫秒尖峰辐射群,继而在1420MHz上出现毫秒级尖峰辐射群,并且还在以后的几个爆发次峰上陆续出现,在长达两小时的大爆发过程中,在4000MHz上始终未产生毫秒级尖峰辐射,这也反应了射电尖峰辐射现象存在着一定的带宽。特别引起注意的是毫秒级尖峰辐射群均出现在射电爆发的峰值附近,在其它时间的记录中尚未发现毫秒尖峰辐射。 三波段的秒级射电爆发曲线如图1所示。毫秒级精细结构如图2所示。由图2可见,单个尖峰辐射的持续随频率的减小而增加,2840MHz多为10—20ms,1420MHz多为30—170ms;所产生的尖峰辐射群强度不大,而且很少有孤立的尖峰;2840MHz尖峰辐射的强度一般为450—900sfu,1420MHz一般为500—1770sfu(1sfu=10~(-22)WM~(-2)Hz~(-1));还特别引起注意的是在2840MHz上当所出现的尖峰辐射群结束时,往往出现持续时间为100ms的流量下降现象,(此种现象在以往的观测中未曾见过),详见图2b和2c;关于事件尖峰辐射的丰度,仅对几个尖峰辐射群作了统计如下: 在1420M     

米波太阳射电频谱仪的科学目标和技术方案

介绍了70～700MHz低频太阳射电频谱仪的科学目标和技术方案,给出了11m 网状抛物面天线、接收系统、数字频谱终端的技术指标.并对系统的整机噪声系数、灵敏度、最小可测流量密度、LNA输入端的噪声功率进行了估计.系统频谱分辨率优于0.2MHz,时间分辨率最高可达2 ms.     

ON2西部区域OH1612 MHz脉泽的新观测

利用法国巴黎天文台的南锡射电望远镜对ON2西部区域OH16 12MHz脉泽首次进行观测 ,观测结果表明 ,西部区域的OH16 12MHz脉泽的辐射频谱为典型的单峰结构。结合模型对西部区域的OH16 12MHz脉泽谱线频谱图进行分析和研究。利用薄盘模型 ,得到相应于ON2西部区域的OH16 12MHz脉泽单峰脉泽斑的位置在r =112 .5AU ,Y =7.6AU ,其Keplerian运动速度为Ur=10 .6km s ,Vt =- 9.4km s .     

食变星狮子座XY的双色光电光变曲线和周期变化

我们测得XY Leo的B、V两色光电光变曲线.新光电光变曲线同1956年R.H.Koch的光变曲线比较,发现其形状有明显的变化.测出了一个主极小时刻和二个次极小时刻,收集了过去所测的极小时刻并计算出周期变化的O-C图,进一步验证了该食变星的周期是有周期性变化的.     

On the correlation between exciter duration and decay constant of solar decameter type III radio bursts

It is observed that while there exists a strong correlation between the decay constant and the exciter duration for isolated type III radio bursts, it is absent for those type III radio bursts which are preceded by type IIIb radio bursts. A possible theoretical explanation for the presence of correlation in one case and lack of it in the other is proposed.     

Type III solar radio burst storms observed at low frequencies

Storms of type III solar radio bursts observed from 5.4 to 0.2 MHz, indicate the quasicontinuous production of type III events observable for a half solar rotation but persisting in some cases for well over a complete rotation. The characteristics of these storms, including the dependance of occurrence and apparent drift rates on the disc position of the associated active region are discussed. The drift rate dependance is shown to be a consequence of the propagation time of emission from the source to the observer. The occurrence rate of a burst every 10 sec observed near CMP implies that if this level of activity persists, then about a quarter of a million exciter packets are released into the interplanetary plasma during a complete rotation. Storm bursts are less intense than most isolated type III's and occur over a more limited frequency range. There appears to be a very close relation between these storms and decametric continuum.     

Type III solar radio burst storms observed at low frequencies

Storms of type III solar radio bursts observed from 5.4 ot 0.2 MHz consist of a quasi-continuous production of type III events observable for half a solar rotation but persisting in some cases for well over a complete rotation (Fainberg and Stone, 1970). The observed burst drift rates are a function of the heliographic longitude of the associated active region. This apparent drift rate dependence is a consequence of the radio emission propagation time from source to observer. Based on this dependence, a least squares analysis of 2500 drift rates between frequencies in the 2.8 to 0.7 MHz range yields an average exciter speed of 0.38 c for the height range from approximately 11 to 30 R . In conjunction with the available determinations of exciter speeds of 0.33 c close to the sun, i.e. less than 3 R , and with in situ measurements of 40 keV solar electrons by space probes, the present results suggest that the exciters are electron packets which propagate with little deceleration over distances of at least 1 AU.     

Characteristics of type III exciters derived from low frequency radio observations

Low frequency radio observations (2.8 MHz-67 kHz) from the RAE-1 and IMP-6 satellites allow the tracking of type III solar burst exciters out to large distances from the Sun (of the order of 1 AU). A study of the interaction processes between the exciter and the interplanetary medium was made using the time-intensity profiles of the radio emission. We have investigated the change in exciter length with distance from the Sun, and the resulting exciter velocity dispersion which can be deduced from this change. From detailed measurements on 35 simple bursts we have found that the exciter length increases at a faster rate than a constant velocity dispersion would give. We have also investigated the damping of the radio emission and have concluded that some current theories of the damping mechanism give results which are not consistent with the low frequency observations.Work performed while a NRC/NAS Postdoctoral Resident Research Associate.     

Initial Results of the Ichon Solar Radio Spectrograph

A new solar radio spectrograph to observe solar radio bursts has been installed at the Ichon branch of the Radio Research Laboratory, Ministry of Information and Communication, Korea. The spectrograph consists of three different antennas to sweep a wide band of frequencies in the range of 30 MHz ∼ 2500 MHz. Its daily operation is fully automated and typical examples of solar radio bursts have been successfully observed. In this paper we describe briefly its hardware and data processing methods. Then we present coronal shock speeds estimated for 34 type II bursts from May 1998 to November 2000 and compare them with those from other observatories. We also present the close relationship between onset time of type II bursts and X-ray flares as well as their associations with coronal mass ejections.     

Fast solar electrons,interplanetary plasma and km-wave type-III radio bursts observed from the IMP-6 spacecraft

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.     

Type II solar radio events observed in the interplanetary medium

Fifteen type II solar radio events have been identified in the 2 MHz to 30 kHz frequency range by the radio astronomy experiment on the ISEE-3 satellite over the period from September 1978 to December 1979. These data provide the most comprehensive sample of type II radio bursts hitherto observed at kilometer wavelengths. Dynamic spectra of a number of events are presented. Where possible, the 15 events have been associated with an initiating flare, ground-based radio data, the passage of a shock at the spacecraft and the sudden commencement of a geomagnetic storm. The general characteristics of kilometric type II bursts are discussed.Research Associate, University of Maryland, U.S.A.     

Exponential decay and exciter profile of fast pulses in type IV events

Some fast bursts occurring at 237 MHz during type IV events in association with sawtooth pulsations have been studied. These bursts, when occurring sufficiently isolated from the adjacent pulsating activity, appear to have an exponential decay phase similar to that of fast type III bursts.A computational procedure, based on Fourier transform techniques, has been applied; it allows the computation, for every observed point in the time profile, of the corresponding value for the logarithmic derivative and for the exciter function. The results so far obtained show that the time decay value is of the same order observed for normal type III's. As the bursts studied appear clearly not to be type III's (mainly for their total polarization), but isolated components of pulsation groups, this result may be an interesting indicator of the emission mechanism (plasma waves excitation and its abrupt stop) involved in type IV decimetric pulsations.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.     

Flare-time sudden enhancements of low frequency field strength and associated meter wave solar radio bursts

A number of meter wavelength solar radio bursts of spectral Type-III have been observed by means of a solar radio spectroscope (40–240 MHz) simultaneously with sudden enhancements of low frequency (164 KHz) field strength (SES's) of Radio Tashkent which are known to take place due to the enhancements of D-layer ionization caused by flare-time solar X-rays.The association between the solar X-ray flares as detected by the SES's and the Type-III meter-wave solar bursts is discussed. It is found that the association of SES's and meter wave solar bursts, which implies the ejection of flare-time electrons towards the photosphere as well as corona, is about 72%.     

由对偶的Ⅲ型射电爆发观测探讨日冕双向电子束的起源问题

介绍云南和北京天文台射电频谱仪观测到的3个对偶的米波－－微波Ⅲ型爆发，估计了双向电子束起源的频率和高度，3个事件分别揭示了在正向和反向漂移爆发之间的分界频率（约为250，1300和2900MHz),它们指出了一个致密的电子加速源，在这个源中产生了向上和向下两个方向注入的电子束，从这些事例可以表明不同事件的双向电子束的分界频率有一个相当大的范围（250－2900MHz)，而它们的起源范围却是在一个很小的（大约4－100MHz)和不同的频段范围内。最后讨论了日冕磁结构的拓扑范围、电子加速源构造的空间尺度、电子束运动速度和对偶Ⅲ型爆发的产生机制。