Unusual Solar Radio Burst Observed at Decameter Wavelengths

An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s^?1) at frequencies higher than 22 MHz and negative (100 kHz?s^?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈10³ s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.     

Some Observed Results of Solar Radio Spectrometer at 4.5—7.5GHz

A new instrument of broadband solar radio spectrometer working at waveband 4.5-7.5GHz was developed at Purple Mountain Observatory for Solar Maximum 23. Some new results of spectral observation have been obtained since August 1999.Two typical type Ⅲμbursts with rich fine structures are presented and some interesting features discussed.     

1989年4月9日射电爆发中的准周期振荡特征

本文对1989年4月9日在2840 MHz上观测到的微波爆发进行分析,发现该爆发存在几十到几百秒的准周期振荡现象。这种现象可能与磁环的准周期现象有关,应遵从磁流体力学规律。通过简单初步分析,获得一些有意义的结果。     

A Type IV Radio Burst Associated with Type III Burst,Pulsation and Spike Emissions

A type IV radio burst accompanied by several normal- and reverse-drifting type III bursts, multiple long-term quasi-periodic pulsations and spikes was observed with the radio spectrometers (1.0–2.0 and 2.6–3.8 GHz) at National Astronomical Observatories of China (NAOC) on 23 September 1998. In combination with the images of Siberian Solar Radio Telescope (SSRT) of Russia, the complex and multiple magnetic structures inferred from the radio bursts reveal the existence of both large-scale and small-scale magnetic structures. This event suggests that the geometries of coronal magnetic fields contain multiple discrete electron acceleration/injection sites at different heights, and extended open and closed magnetic field lines. It can be shown that the energetic electrons gain access to open, diverging and closed field lines thus producing different types of radio bursts. From the characteristics of position, polarization, dispersion and displacement of the sources, the model of the type IV event is supported, which involves synchrotron emission from the electrons confined by the rapid scattering through the interaction of hydromagnetic wave with particles.     

一个含有丰富快速精细结构的射电大爆发

本文对１９９０年７月３０日云南天文台四波段（１．４２ＧＨｚ、２．００ＧＨｚ、２．８４ＧＨｚ和４．００ＧＨｚ）太阳射电高时间分辨率同步观测系统［１，２］所观测到的太阳射电大爆发进行了分析，对在１．４２ＧＨｚ、２．００ＧＨｚ、２．８４ＧＨｚ三个波段上观测到的大量尖峰辐射（ｍｓ—ｓｐｉｋｅｓ）作了关于寿命和强度的统计，最后，针对本次爆发中的ｍｓ—ｓｐｉｋｅｓ的特点做了一些讨论。     

太阳分米波射电快速精细结构的观测分析

通过分析云南天文台(YNO)0.7～1.5GHz太阳射电频谱仪2000年9月至2001年9月取得的158个射电爆发,发现其中约有65%存在4类不同类型的快速精细结构(FFS):毫秒尖峰辐射、Ⅲ型爆发、准周期脉动、慢漂移结构。给出了其中6个典型精细结构的介绍和相关的初步解释。     

基于卷积神经网络的快速射电暴候选体分类

针对目前从海量的快速射电暴(Fast Radio Burst, FRB)候选体中人工筛选FRB事件难以为继的现状,提出了一种基于卷积神经网络(Convolutional Neural Networks, CNN)的FRB候选体分类方法.首先,通过真实的观测数据和仿真FRB组成训练和测试样本集.其次,建立了二输入的深度卷积神经网络模型,并对其进行训练、测试和优化,获取FRB候选体分类器.最后,利用来自脉冲星的单脉冲数据对该分类器的有效性和性能进行了验证.实验结果表明,该方法可以快速从大量候选体中准确识别出单脉冲事件,极大地提高了FRB候选体的处理速率和效率.     

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．     

A Composite Model for GHz Peaked Spectra of Radio Sources

GHz-Peaked Spectrum (GPS) radio sources are powerful and compact sources with convex spectra. With increasing observational findings, it has been realized that either Synchrotron Self-Absorption (SSA) alone or Free-Free Absorption (FFA) alone is not enough to account for all the spectral features. We present a model consisting of an SSA region partially covered by FFA plasma, and derive a composite spectral formula. By applying the model to a sample of 19 GPS sources having strong absorption, it is found that the external FFA process makes the SSA peak frequency linearly shift to a higher (observed) peak frequency. The shift indicates that the FFA does play a role at the frequency close to the observed peak frequency.     

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．     

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.     

A Solar Stationary Type IV Radio Burst and Its Radiation Mechanism

A stationary Type IV (IVs) radio burst was observed on September 24, 2011. Observations from the Nançay RadioHeliograph (NRH) show that the brightness temperature (\(T_{\mathrm{B}}\)) of this burst is extremely high, over \(10^{11}\) K at 150 MHz and over \(10^{8}\) K in general. The degree of circular polarization (\(q\)) is between \(-60\% \sim -100\%\), which means that it is highly left-handed circularly polarized. The flux–frequency spectrum follows a power-law distribution, and the spectral index is considered to be roughly \(-3 \sim -4\) throughout the IVs. Radio sources of this event are located in the wake of the coronal mass ejection and are spatially dispersed. They line up to present a formation in which lower-frequency sources are higher. Based on these observations, it is suggested that the IVs was generated through electron cyclotron maser emission.     

A Fast Radio Burst Backend for the Tianlai Dish Pathfinder Array

The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish antennas. The original digital backend integration time is at the seconds level, designed for H I intensity mapping experiment. A new digital backend with millisecond response is added to enable it to search for fast radio burst during its observations. The design and calibration of this backend, and the real time search pipeline for it are described in this paper. It is capable of forming 16 digita...     

A Solar Radio Spectrometer at 5.2–7.6 GHz

The properties, structure and performance of a Solar Radio Spectrometer working at 5.2–7.6 GHz developed by National Astronomical Observatories/Beijing and Hebei Semiconductor Research Institute are described. The spectrometer has a spectral resolution of 20 MHz and a temporal resolution of 5 ms, with an instantaneous detectable range from 2% to 10 times flux of the quiet Sun. It can measure both left and right circular polarizations with an accuracy of 10% of polarization degree. Some results of preliminary observations are presented.     

A Radio Burst and Its Associated CME on March 17, 2002

In this study, we present a detailed analysis, based on multiwavelength observations and magnetic field extrapolation, of a radio and X-ray event observed on March 17, 2002. This event was accompanied by a Coronal Mass Ejection (CME) observed by the Large-Angle Spectrometric Coronagraph (LASCO) aboard SOHO. During the main event, the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) mission observed a hard X-ray emission correlated in time with the development of a type III burst group. The CME development, the hard X-ray emission, and the type III burst group appear to be closely associated. The multifrequency Nançay Radioheliograph (NRH) shows that the type III bursts are produced at a distance from the active region that progressively increases with time. Their emitting sources are distributed along the western edge of the CME. We conclude the type III electron beams propagate in the interface region between the ascending CME and the neighboring open field lines. Due to the development of the CME, this region becomes progressively highly compressed. By measuring, at each frequency, the shift versus time of the type III positions, we estimate that the electron density in this compression region increased roughly by a factor of 10 over a few minutes. Another signature of this compression region is a narrow white light feature interpreted as a coronal shock driven by the CME lateral expansion.     

A Highly Circularly Polarized Solar Radio Emission Component Observed at Hectometric Wavelengths

We report here the observation of a rare solar radio event at hectometric wavelengths that was characterized by essentially 100% circularly polarized radiation and that was observed continuously for about six days, from May 17 to 23, 2002. This was the first time that a solar source with significantly polarized radiation was detected by the WAVES experiment on the Wind spacecraft. From May 19 to 22, the intense polarized radio emissions were characterized by quasi-periodic intensity variations with periods from one to two hours and with superposed drifting, narrowband, fine structures. The bandwidth of this radiation extended from about 400 kHz to 7 MHz, and the peak frequency of the frequency spectrum slowly decreased from 2 MHz to about 0.8 MHz over the course of four days. The radio source, at each frequency, was observed to slowly drift from east to west about the Sun, as viewed from the Earth and was estimated to lie between 26 and 82R_⊙ (R_⊙ = 696 000 km). We speculate that this unusual event may represent an interplanetary manifestation of a moving type IV burst and discuss possible radio emission mechanisms. The ISEE-3 spacecraft may possibly have detected a similar event some 26 years ago.     

Decameter Type IV Burst Associated with a Behind-the-limb CME Observed on 7 November 2013

We report on the results of observations of a type IV burst made by the Ukrainian Radio interferometer of the Academy of Sciences (URAN-2) in the frequency range 22?–?33 MHz. The burst is associated with a coronal mass ejection (CME) initiated by a behind-the-limb active region (N05E151) and was also observed by the Nançay Decameter Array (NDA) radio telescope in the frequency band 30?–?60 MHz. The purpose of the article is the determination of the source of this type IV burst. After analysis of the observational data obtained with the URAN-2, the NDA, the Solar-Terrestrial Relations Observatory (STEREO) A and B spacecraft, and the Solar and Heliospheric Observatory (SOHO) spacecraft, we come to the conclusion that the source of the burst is the core of a behind-the-limb CME. We conclude that the radio emission can escape the center of the CME core at a frequency of 60 MHz and originates from the periphery of the core at a frequency of 30 MHz that is due to occultation by the solar corona at the corresponding frequencies. We find plasma densities in these regions assuming the plasma mechanism of radio emission. We show that the frequency drift of the start of the type IV burst is governed by an expansion of the CME core. The type III bursts that were observed against this type IV burst are shown to be generated by fast electrons propagating through the CME core plasma. A type II burst was registered at frequencies of 44?–?64 MHz and 3?–?16 MHz and was radiated by a shock with velocities of about \(1000~\mbox{km}\,\mbox{s}^{-1}\) and \(800~\mbox{km}\,\mbox{s}^{-1}\), respectively.     

快速射电暴光学对应体在中国未来大视场望远镜中的可探测性分析

快速射电暴是近年来发展最快的天文学科之一. 理论上, 快速射电暴可能存在毫秒到小时时标的光学\lk对应体. 快速射电暴光学对应体有可能在中国未来大视场望远镜中探测到, 例如: 中国空间站工程巡天望远\lk镜(China Space Station Telescope, CSST)、中国科学技术大学和紫金山天文台合作的2.5m大视场巡天望远镜(Wide Field Survey Telescope, WFST)和地球2.0 (Earth 2.0, ET)等. 快速射电暴光学对应体通常分为毫秒时标光学对应体、小时时标光学对应体和光学余辉. 前两者可产生于快速射电暴的高能外延或是快速射电暴的射电辐射与高能电子的逆康普顿散射, 探测率与光学-射电流量比$\eta_\nu$关系密切. 对于毫秒时标光学对应体, 最理想情况下WFST、CSST和ET的探测率可以达到每年上百个. 当$\eta_\nu$~10^-3时, WFST、CSST的年探测率仅 为1个的量级, ET的年探测率为19.5个. 对于小时时标光学对应体, 最理想情况下超新星遗迹的年龄为5年且$\eta_\nu$约为10^-6时, 年探测率可到100以上. FRB 200428的X射线对应体表明, 快速射电暴可能产生相对论性外流并且与星际介质相互作用产生光学余辉. 结合快速射电暴的能量、在宇宙中的分布以及标准余辉模型, 可以对快速射电暴余辉的可探测性进行研究. 当总能量-射电能量比与FRB 200428类似(ζ = 10⁵)时, CSST、WFST和ET的 年探测率分别为1.3、1.0和67个.     

A New Solar Radio Spectrometer at 1.10-2.06 GHz and First Observational Results

An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented.