太阳射电宽带动态频谱仪步研究进展

介绍了围绕我国近年完成的太阳射电宽带动态频亦仪展开的研究工作进展，并提出了今后的努力方向，以期庐设备能在我国第23周太阳活动峰年研究中发展更大作用。     

一个宽带的太阳射电尖峰事件

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07：44：34-07：44：52：99UT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（spike）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2B40GHZ上的流量资料,首次对一些spike结构作了谱分析．发现spike结构谱的峰值频率,第一群呈现为随时间由高频向低频漂移的倾向,第二群基本上位于2．695GHZ上．Spike谱的这些观测特征,可定性地用非热电子束流平均能量的时变特性来解释．对于第二群具有相同峰值频率的spike辐射,可能来自同一电子回旋脉泽不稳定区域．     

世界各国太阳射电望远镜概况

详细汇总了国内太阳射电望远镜的技术性能及原理框图。收集了部分国外太阳射电望远镜技术指标。对射电望远镜系统参数灵敏度、信噪比、交叉计划隔离度的计算方法作了介绍。     

日食的射电观测(英)

日食为射电天文提供了一维高空间分辨率太阳射电观测机会．日食射电观测在太阳射电物理的发展上起过重要的作用．文中对日食射电观测的若干重要因素作了介绍和分析．日食射电观测在我国太阳射电天文发展上也起了重要作用．文中简要介绍了在我国组织观测的1958年、1968年、1980年及1987年的太阳射电日食观测及其主要结果．     

22.6--3.8 GHz 太阳射电动态频谱仪

给出北京天文台 ２．６—３．８ ＧＨ_(ｚ)太阳射电动态频谱仪的性能、结构及初步观测结果．     

Scintillation of Solar Radio Sources: Implication for Spikes

Possible scattering regimes of the emission from a solar radio source due to dielectric permitivity fluctuations of an extended coronal plasma co-rotating with the Sun are discussed. The exact and approximate expressions are given for the spectrum of temporal intensity fluctuations in the regime of weak scattering. The frequency, at which the spectrum shows a bend, is determined by the location of the effective scattering screen if the source size is not too large. In the regime of strong scattering of the emission from a broadbanded nonimpulsive radio source, the formation of random intensity spikes, namely millisecond, narrowbanded spike bursts is a possibility. Their apparent size can be quite significant. However, the sources with very small true sizes are required in order to produce strong spikes.     

太阳射电分米波尖峰辐射和米波射电爆发

本文分析了云南天文台四波段快速采样射电望远镜在1990年1月至1991年3月间记录到的毫秒级尖峰辐射事件。结合此期间S.G.D.公布的米波射电大爆发资料,给出了毫秒级尖峰辐射的各种特征,总结出毫秒级尖峰辐射同Ⅲ型、Ⅱ型和Ⅳ型太阳射电爆发的关系,最后做出了相应的解释和讨论。     

1-2GHz太阳射电动态频谱仪

本文描述了北京天文台研制的１－２ＧＨｚ太阳射电动态频谱仪的性能、结构、初步观测结果及进一步改进计划．     

一种用于射电频谱分析的高速FFT实现算法

提出了一种用于高速射电频谱分析的FFT实现算法,基于奇偶分开的FFT变换算法.采用N点FFT变换来实现4N点实信号的FFT变换,从而在FPGA(现场可编程门阵列)硬件里实现了高速FFT变换算法.仿真分析表明,新算法得到了良好的效果,明显地提高了硬件的利用效率.     

A Broadband Solar Radio Spectrometer and Some New Observational Results

A broadband solar radio spectrometer with a bandwidth of about 7 GHz has been developed in China for solar maximum 23. This work is a cooperative project of Beijing Astronomical Observatory (BAO), Purple Mountain Observatory (PMO), Yunnan Observatory (YNO), and Nanjing University. The spectrometer of PMO worked in the waveband of 4.5–7.5 GHz, that of BAO in 1–2 GHz, 2.6–3.8 GHz, and 5.2–7.6 GHz, and that of YNO in 0.7–1.5 GHz. The spectrometer of PMO is a multichannel and frequency-agile one with a time resolution of 1–5 ms and a frequency resolution of 10 MHz. It started to operate in August 1999 and since then more than 300 spectral events have been observed, and some type III or type III-like structures have also been found. In this paper, some selected typical events, for example, the events on 25 August 1999 and 27 October 1999, are presented, and some new observed features are also described and discussed.     

Bidirectional Type III Solar Radio Bursts

Bidirectional coronal type III bursts are modeled by combining a model of coronal electron heating and beam generation via time-of-flight effects with semiquantitative estimates of quasilinear relaxation. Electromagnetic emissivities are estimated by extending the recently developed theory of interplanetary type III bursts to coronal emissions, including its features of stochastic Langmuir-wave growth and three-wave interactions. The results are investigated for heating on open and closed coronal field lines and are compared with observations of normal, reverse-slope, bidirectional, and inverted-J and -U coronal type III radio bursts. Harmonic emission is predicted to dominate at plasma frequencies above roughly 100 MHz where the efficiency of fundamental emission falls off steeply, while its free-free reabsorption rises. The model also explains the observed trends in the likelihood of occurrence of normal, reverse-slope, and bidirectional coronal type III bursts.     

Multiple Type II Solar Radio Bursts

We report on the detailed analysis of a set of 38 multiple type II radio bursts observed by Culgoora radio spectrograph from January 1997 to July 2003. These events were selected on the basis of the following criteria: (i) more than one type II were reported within 30 min interval, (ii) both fundamental and harmonic were identified for each of them. The X-ray flares and CMEs associated with these events are identified using GOES, Yohkoh SXT, SOHO/EIT, and SOHO/LASCO data. From the analysis of these events, the following physical characteristics are obtained: (i) In many cases, two type IIs with fundamental and harmonic were reported, and the time interval between the two type IIs is within 15 min; (ii) The mean values of starting frequency, drift rate, and shock speed of the first type II are significantly higher than those of the second type II; (iii) More than 90% of the events are associated with both X-ray flares and CMEs; (iv) Nearly 75% of the flares are stronger than M1 X-ray class and 50% of CMEs have their widths larger than 200^∘ or they are halo CMEs; (v) While most of the first type IIs started within the flare impulsive phase, 22 out of 38 second type IIs started after the flare impulsive phase. Weak correlations are found between the starting and ending frequencies of these type II events. On the other hand, there was no correlation between two shock speeds between the first and the second type II. Since most of the events are associated with both the flares and CMEs, and there are no events which are only associated with multiple impulsive flares or multiple mass ejections, we suggest that the flares and CMEs (front or flank) both be sources of multiple type IIs. Other possibilities on the origin of multiple type IIs are also discussed.     

A Method of Forecasting Solar Activity Based on Radio Astronomical Observations

We present the results of forecasting flare activity based on the data from microwave spectropolarimetric observations of active regions (ARs) obtained with the RATAN-600 radio telescope and the X-ray data from the GOES satellite as well as monitoring data. The method is designed for short-term (1–3-days) flare forecasts. Proton events are considered as part of the general flare problem. Obtaining a reliable forecast is a difficult process in view of the multi-parameter and multi-dimensional system of plasma parameter variations and multiple non-linear interconnections.We used a modified Tanaka–Enome criterion, as well a database of observational material collected over many years. The forecasting efficiency was analyzed depending on the threshold values of the criterion. We show that the quality of the radio astronomical forecast is determined by the level of sensitivity of the detector at short centimeterwavelengths and by the solar activity level.     

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.     

IPRT/AMATERAS: A New Metric Spectrum Observation System for Solar Radio Bursts

A new radio spectropolarimeter for solar radio observation has been developed at Tohoku University and installed on the Iitate Planetary Radio Telescope (IPRT) at the Iitate observatory in Fukushima prefecture, Japan. This system, named AMATERAS (the Assembly of Metric-band Aperture TElescope and Real-time Analysis System), enables us to observe solar radio bursts in the frequency range between 150 and 500 MHz. The minimum detectable flux in the observation frequency range is less than 0.7 SFU with an integration time of 10 ms and a bandwidth of 61 kHz. Both left and right polarization components are simultaneously observed in this system. These specifications are accomplished by combining the large aperture of IPRT with a high-speed digital receiver. Observational data are calibrated and archived soon after the daily observation. The database is available online. The high-sensitivity observational data with the high time and frequency resolutions from AMATERAS will be used to analyze spectral fine structures of solar radio bursts.     

Wavelet Decomposition of Submillimeter Solar Radio Bursts

We present the results of wavelet decomposition of fast-time structures during four solar flares observed by the Solar Submillimeter-wave Telescope at 212 GHz. The result of the analysis shows (1) observational evidence on the existence of submm-emission time variations in the range from a few tens of millisecond up to few seconds during solar flares, and (2) that when a solar flare is in progress the time scales reduce as the bulk of the emission flux time variations is increasing.     

Wavelet Cleaning of Solar Dynamic Radio Spectrograms

By applying the state-of-the-art mathematical apparatus, the wavelet transformation, we explore the possibillity of a dynamic cleaning of raw data obtained with the Chinese solar radio spectrographs over a wide wavelength range (from 0.7 to 7.6 GHz). We consider the problem of eliminating the interference caused by combination rates of data sampling (10-20ms), and the low-frequency interference (4-30s) caused by the receiving equipment changing its characteristics with time. It is shown that the best choice to reconstruct a signal suffering from amplitude, frequency and phase instabilities, is by means of wavelet transformation at both high and low frequencies. We analysed observational data which contained interferences of nonsolar origin such as instrumental effects and other man-made signals. A subsequent comparison of the reference data obtained with the acoustooptical receiver of the Siberian Solar Radio Telescope (SSRT) with the “cleaned” spectra confirms the correctness of this approach.     

太阳运动Ⅳ型射电爆发的相干辐射模型

为解释太阳运动Ⅳ型射电爆发的相干辐射机制提出一个理论模型.从耀斑中产生的高能电子,可以被扩展上升的太阳磁流管俘获.在磁流管顶部,这些高能电子的速度分布形成为类束流速度分布,激发柬流等离子体的不稳定性,并且主要直接放大O模电磁波.不稳定性增长率敏锐地依赖了日冕等离子体参数fpe/fce和射束温度Tb,这能定性解释在太阳运动Ⅳ型射电爆发中观测到的高亮温度和高偏振度,以及宽频谱的特性.     

Quasi-Periodic Long-Term Solar Radio Pulsations During A Decimetric Type IV Burst

Long-periodic pulsations with a period of tens of seconds associated with a Type IV solar radio emission are found at 1420 and 2000 MHz. Some features (such as the bandwidth, periodicity, frequency drift, amplitude, and relative amplitude) of the pulsations are introduced and discussed in this paper.     

Fine Time Structures in Solar Radio Bursts: A Summary of Observations at Four Frequencies

29 fine time structures (FTS) are found in 103 radio bursts observed with YRSOS of high temporal resolution of 1 ms at 4 frequencies (1.42, 2.00 (or2.13), 2.84 and 4.00 (or 4.26) GHz) from January 1990 to January 1994. The various morphologies of FTSs occurring in different phases of flares and the different FTS in the same event may reflect the transitional property of the low-frequency microwave bursts. Most FTSs are probably consisted with the four characteristics observed previously in literatures. The typical and representative events of FTSs and occurrence frequency of each kind are presented in order to explain the multiplicity, breadth and observational characteristics of FTSs in the range of long centimeter to short decimeter wavelengths. This revised version was published online in July 2006 with corrections to the Cover Date.