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．     

日食的射电观测

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台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年太阳射电日食观测及其主要结果。     

太阳低频射电干涉阵的构建仿真

介绍了低频射电干涉阵的发展情况、研究领域,讨论了国际上的LOFAR、LWA和MWA等低频射电项目.借鉴当今的低频射电项目,结合云南的地理和太阳射电优势,设想在云南省内构建一个太阳低频射电干涉阵,观测频率在30 MHz～250 MHz范围内,文中仿真了太阳低频射电干涉阵(4台站),比较和分析了通过优化算法得到的阵列的UV覆盖、脏束(Dirty beam);讨论了低频射电干涉阵的观测模式、射电干扰、低频射电成像等问题;分析低频射电阵在观测太阳爆发性活动产生的日冕物质抛射(Coronal Mass Ejections,CME)、耀斑、射电爆发的可能性;通过上述的仿真和分析构建太阳低频射电干涉阵面临的问题,可以为今后建立阵列提供依据.     

来自6538活动区的太阳射电米波事件

利用云南天文台声光频谱仪在1991年3月记录到的太阳射电米波辐射事件、光学活动及相关事件作了分析，得到来自6538活动区太阳射电米波事件的一些基本特征。     

太阳二十二周峰年云南天文台四波段射电同步观测结果

本文主要介绍云南天文台“四波段太阳射电高时间分辨率同步观测系统”１９８９年１２月至１９９３年４月观测事件的统计结果，对１０２个射电爆发进行了初步分析，着重揭示几个类别典型事件的时间轮廓，说明射电高时间分辨率观测的意义。     

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，激发束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．     

来自6538活动区的太阳射电米波事件

利用云南天文台声光频谱仪在1991年3月记录到的太阳射电米波辐射事件、光学活动及相关事件作了分析，得到来自6538活动区太阳射电米波事件的一些基本特性。     

同步-自康普顿谱的相关性分析

有一些射电源同时观测到射电辐射和紫外-X射线辐射,某些作者认为这两种辐射起源于同步一自康普顿效应。本文给出该效应中同步射电谱与康普顿紫外-X射线谱的一系列相关性。分析这些相关性,可以提供一些半定量的理论判据,用以检验同步一自康普顿效应的正确性。这种分析也有利于估计源的各种物理参量。     

毫米波太阳射电的观测研究

综述了毫米波太阳射电的观测研究概况，着重介绍一些中，大型的毫米波太阳射电观测设备最新的观测结果。     

太阳射电辐射的第四种成份——太阳射电快变分量

太阳射电天文学从1942年诞生到现在,人们已经观测到并证实了的太阳射电基本辐射成份有三种:它们是太阳射电爆发分量、太阳射电缓变分量和太阳射电宁静分量。 本文报导的是,在经过太阳活动22周峰年的国内联合观测以及参加Fares22和Max’91 Compaign国际联合观测中,我们已经观测到并从大量观测资料中证实了的是,太阳上存在有第四种射电辐射成份——太阳射电快速变化分量。     

Solar radio spectrography in Europe

Recent technical progress of solar radio spectrography is concerned with digital data recording, the achievement of high time and frequency resolution, and with an improved coverage of the radio range at short and long wavelengths. A spatially-distributed network of radio spectrographs allows for complementary information about solar events and periods of activity selected for detailed investigation.By modern radio spectrographs a wealth of not yet adequately classified spectral fine structures can be observed, some of them potentially intimately related to effects of fragmentation of flare energy and/or to processes related to coronal heating. Requirements for the choice of technical parameters of solar spectrographs for checking theoretical models of fundamental processes of energy release are reflected in modern instruments. Prospects for future observations are briefly included.     

Solar, interplanetary, planetary, and related extra-solar system science for LOFAR

The low frequency array (LOFAR) radiotelescope will be a powerful instrument for answering fundamental, unresolved scientific questions concerning solar system radio phenomena and related emissions from nearby stellar systems. This paper reviews the phenomena, emission mechanisms, open scientific questions, and LOFAR's capabilities. LOFAR will detect metric solar radio bursts in the corona and interplanetary medium, out to distances of order 10 solar radii, as well as Jovian radio emissions. Arguments are given that LOFAR may be sufficiently sensitive to detect stellar analoges of solar type II and III bursts, and may detect cyclotron-maser emissions from extra-solar planets. LOFAR may also aid space weather research, by passively detecting coronal mass ejections (CMEs) via scintillation and Faraday rotation effects, or by detecting radar signals bounced off CMEs and coronal density structures if a suitable solar radar is developed.     

Using Laser Beacons for Daytime Adaptive Optics

This article examines the use of Laser Beacons for daytime astronomical observations. There are two potential applications: the diffraction limited observation of (1) the structure in the solar corona at all wavelengths, and (2) non-solar astronomical objects in the thermal infrared part of the spectrum. We examine the brightness of the Laser Beacon required as well as the limitations imposed by the daytime sky brightness and sky/telescope thermal emission on the observable magnitude limits. For both applications the use of Laser Beacon adaptive optics in daytime results in important research opportunities.     

Scaling-laws of Radio Spike Bursts and Their Constraints on New Solar Radio Telescopestwo

Radio observation is one of important methods in solar physics and space science. Sometimes, it is almost the sole approach to observe the physical processes such as the acceleration, emission, and propagation of non-thermal energetic particles, etc. So far, more than 100 solar radio telescopes have been built in the world, including solar radiometers, dynamic spectrometers, and radioheliographs. Some of them have been closed after the fulfillment of their primary scientific objectives, or for their malfunctions, and thus replaced by other advanced instruments. At the same time, based on some new technologies and scientific ideas, various kinds of new and much more complicated solar radio telescopes are being constructed by solar radio astronomers and space scientists, such as the American E-OVSA and the solar radio observing system under the framework of Chinese Meridian Project II, etc. When we plan to develop a new solar radio telescope, it is crucial to design the most suitable technical parameters, e.g., the observing frequency range and bandwidth, temporal resolution, frequency resolution, spatial resolution, polarization degree, and dynamic range. Then, how do we select a rational set of these parameters? The long-term observation and study revealed that a large strong solar radio burst is frequently composed of a series of small bursts with different time scales. Among them, the radio spike burst is the smallest one with the shortest lifetime, the narrowest bandwidth, and the smallest source region. Solar radio spikes are considered to be related to a single magnetic energy release process, and can be regarded as an elementary burst in solar flares. It is a basic requirement for the new solar radio telescope to observe and discriminate these solar radio spike bursts, even though the temporal and spatial scales of radio spike bursts actually vary with the observing frequency. This paper presents the scaling laws of the lifetime and bandwidth of solar radio spike bursts with respect to the observing frequency, which provide some constraints for the new solar radio telescopes, and help us to select the rational telescope parameters. Besides, we propose a spectrum-image combination mode as the best observation mode for the next-generation solar radio telescopes with high temporal, spectral, and spatial resolutions, which may have an important significance for revealing the physical essence of the various non-thermal processes in violent solar eruptions.     

X-ray spectroscopy of stellar coronae: History - present - future

Since in 1948 X-rays were detected from the solar corona, stellar coronae were among the first predicted non-solar X-ray sources. However, because of their relatively low X-ray luminosity, the first non-solar stellar corona was not detected in X-rays until 1974 - twelve years after the discovery of the first non-solar X-ray source. After the 1980s, with the advent of sensitive X-ray imaging instruments on board the EINSTEIN, EXOSAT, and later the ROSAT observatories, the study of stellar coronae has become a vastly growing field of research. These X-ray observations have demonstrated that X-ray emitting coronae are a common feature among stars on the cool side of the Hertzsprung-Russell diagram, with the probable exception of single very cool giant and supergiant stars and A-type dwarfs. The instruments on board these satellites provided for the first time a taste of what can be achieved with X-ray spectroscopy and with the advent of the EUVE (1992) and ASCA (1993), detailed spectroscopy of stellar coronae in the EUV and X-ray regimes got off to a real start. The observations have permitted the identification of coronal material at different temperatures whose existence relates to a range of possible magnetic loop structures in the hot outer atmospheres of stars. The higher spectral resolution of the next generation of spectrometers on board NASA's AXAF (1998), ESA's XMM (1999), and the Japanese ASTRO-E (2000) will improve the determination of coronal temperature structure, abundances, and densities from which loop geometries can be derived and will enable velocity diagnostics. This paper reviews our present knowledge of observational stellar X-ray spectroscopy up to EUVE and ASCA and briefly discusses the perspectives for coronal diagnostics offered by AXAF, XMM, and ASTRO-E.Dedicated to Cornelis de Jager     

2009年7月22日昆明日偏食太阳色球观测

阐述了云南天文台太阳全日面Hα色球望远镜对特殊天象日食的观测及资料情况。同时为局部射电源特征分析研究、CME理论、地球物理效应等相关学科研究提供资料共享信息。     

GPS/LEO掩星方法中的电离层延迟量对太阳射电辐射流量的响应

对无线电信号在电离层中的传播路径进行了数值模拟;针对掩星观测中的五组实际卫星轨道数据(包括GPS和LEO卫星),给出了在太阳射电辐射流量(FLUX)分别为0,70,160和240等几种情况下的电离层延迟量对10.7cm波长的太阳辐射流量的响应结果;这分别对应着无太阳辐射、太阳射电辐射处于活动低谷、平静期和高峰期等几种情形。从中可以发现,掩星观测中电离层延迟量对10.7cm波长的太阳射电辐射流量的响应表现为如下特性:电离层延迟同参数FLUX的大小有明显的对应关系,即FLUX越大,则掩星观测中的电离层延迟越大;对于上升掩星情况而言,掩星观测中电离层延迟量起先逐渐增加,然后达到某一峰值,其后逐渐下降;在掩星观测的初期和中期,太阳射电辐射处于活动低谷、平静期和高峰期等几种情形之间的电离层延迟量差异都较为显著,而在掩星观测的后期,几种情形相互间电离层延迟量的差异都比较小。     

关于太阳射电快速活动真伪信号识别问题

本文列举了云南天文台四波段太阳射电实测中得到的几种干扰实例及确认的太阳快速信号，在认识到太阳射电和干扰信号十分相似的基础上，探讨如何识别真伪信号问题。     

LSTM neural network for solar radio spectrum classification

A solar radio spectrometer records solar radio radiation in the radio waveband. Such solar radio radiation spanning multiple frequency channels and over a short time period could provide a solar radio spectrum which is a two dimensional image. The vertical axis of a spectrum represents frequency channel and the horizontal axis signifies time. Intrinsically, time dependence exists between neighboring columns of a spectrum since solar radio radiation varies continuously over time. Thus, a spectrum can be treated as a time series consisting of all columns of a spectrum, while treating it as a general image would lose its time series property. A recurrent neural network(RNN) is designed for time series analysis. It can explore the correlation and interaction between neighboring inputs of a time series by augmenting a loop in a network.This paper makes the first attempt to utilize an RNN, specifically long short-term memory(LSTM), for solar radio spectrum classification. LSTM can mine well the context of a time series to acquire more information beyond a non-time series model. As such, as demonstrated by our experimental results, LSTM can learn a better representation of a spectrum, and thus contribute better classification.