The 26 December 2001 Solar Eruptive Event Responsible for GLE63. II. Multi-Loop Structure of Microwave Sources in a Major Long-Duration Flare

Solar Physics - We have examined the more than 1100 drawings of the solar disk made by the German amateur astronomer Johann Caspar Staudach during 1749?–?1799 and counted the...     

The 26 December 2001 Solar Eruptive Event Responsible for GLE63: III. CME,Shock Waves,and Energetic Particles

The SOL2001-12-26 moderate solar eruptive event (GOES importance M7.1, microwaves up to 4000 sfu at 9.4 GHz, coronal mass ejection (CME) speed 1446 km?s^?1) produced strong fluxes of solar energetic particles and ground-level enhancement (GLE) of cosmic-ray intensity (GLE63). To find a possible reason for the atypically high proton outcome of this event, we study multi-wavelength images and dynamic radio spectra and quantitatively reconcile the findings with each other. An additional eruption probably occurred in the same active region about half an hour before the main eruption. The latter produced two blast-wave-like shocks during the impulsive phase. The two shock waves eventually merged around the radial direction into a single shock traced up to \(25~\mathrm{R}_{\odot}\) as a halo ahead of the expanding CME body, in agreement with an interplanetary Type II event recorded by the Radio and Plasma Wave Investigation (WAVES) experiment on the Wind spacecraft. The shape and kinematics of the halo indicate an intermediate regime of the shock between the blast wave and bow shock at these distances. The results show that i) the shock wave appeared during the flare rise and could accelerate particles earlier than usually assumed; ii) the particle event could be amplified by the preceding eruption, which stretched closed structures above the developing CME, facilitated its lift-off and escape of flare-accelerated particles, enabled a higher CME speed and stronger shock ahead; iii) escape of flare-accelerated particles could be additionally facilitated by reconnection of the flux rope, where they were trapped, with a large coronal hole; and iv) the first eruption supplied a rich seed population accelerated by a trailing shock wave.     

Two-dimensional solar mapping at 5.2 cm with the Siberian Solar Radio Telescope

We present two-dimensional solar maps at 5.2 cm computed from one-dimensinal observations with the Siberian Solar Radio Telescope (SSRT), using Earth rotation aperture synthesis techniques. The resolution attained with the E-W branch of the instrument is 15 by 45 for a solar declination of about 23°. Maps during the period of June 8 to 13, 1988 clearly show the quiet-Sun background, sunspot and plage associated emission as well as compact sources above the neutral line in some active regions. We found that the latter disappear as the gradient of the longitudinal magnetic field decreases. We also detected emission associated with active regions behind the limb, apparently from unresolved loops, extending up to 40. The prospects of the SSRT, as a dedicated solar instrument, are discussed.     

Some results of solar radio emission observations at the Siberian Solar Radio Telescope

This paper gives the main characteristics of the Siberian Solar Radio Telescope as well as some results derived by investigating the s-component sources and radio bursts on the Sun using the SSRT.     

Estimation of Solar Observations with the Five-hundred-meter Aperture Spherical Radio Telescope(FAST)

We present the estimation of solar observation with the Five-hundred-meter Aperture Spherical radio Telescope(FAST). For both the quiet Sun and the Sun with radio bursts, when pointing directly to the Sun, the total power received by FAST would be out of the safe operational range of the signal chain, even resulting in damage to the receiver. As a conclusion, the Sun should be kept at least ～2° away from the main beam during observations at～1.25 GHz. The separation for lower frequency should be ...     

The Siberian Solar Radio Telescope: the current state of the instrument,observations, and data

The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in 1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec. Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive prominences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument. We compare SSRT observations at 5.7 GHz, including computed `light curves', both morphologically and quantatively, with observations made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray observations, and dynamic radio spectra.     

ARTEMIS IV Radio Observations of the 14 July 2000 Large Solar Event

In this report we present a complex metric burst, associated with the 14 July 2000 major solar event, recorded by the ARTEMIS-IV radio spectrograph at Thermopylae. Additional space-borne and Earth-bound observational data are used, in order to identify and analyze the diverse, yet associated, processes during this event. The emission at metric wavelengths consisted of broad-band continua including a moving and a stationary type IV, impulsive bursts and pulsating structures. The principal release of energetic electrons in the corona was 15–20 min after the start of the flare, in a period when the flare emission spread rapidly eastwards and a hard X-ray peak occurred. Backward extrapolation of the CME also puts its origin in the same time interval, however, the uncertainty of the extrapolation does not allow us to associate the CME with any particular radio or X-ray signature. Finally, we present high time and spectral resolution observations of pulsations and fiber bursts, together with a preliminary statistical analysis.     

Hard x-ray and Metric/Decimetric Radio Observations of the 20 February 2002 Solar Flare

The GOES C7.5 flare on 20 February 2002 at 11:07 UT is one of the first solar flares observed by RHESSI at X-ray wavelengths. It was simultaneously observed at metric/decimetric wavelengths by the Nançay radioheliograph (NRH) which provided images of the flare between 450 and 150 MHz. We present a first comparison of the hard X-ray images observed with RHESSI and of the radio emission sites observed by the NRH. This first analysis shows that: (1) there is a close occurrence between the production of the HXR-radiating most energetic electrons and the injection of radio-emitting non-thermal electrons at all heights in the corona, (2) modifications with time in the pattern of the HXR sources above 25 keV and of the decimetric radio sources at 410 MHz are observed occurring on similar time periods, (3) in the late phase of the most energetic HXR peak, a weak radio source is observed at high frequencies, overlying the EUV magnetic loops seen in the vicinity of the X-ray flaring sites above 12 keV. These preliminary results illustrate the potential of combining RHESSI and NRH images for the study of electron acceleration and transport in flares.     

2840MHz太阳射电辐射流量计的升级改造

叙述了国家天文台升级改造后的2 840 MHz太阳射电辐射流量计的设计特点、性能、结构及观测结果。升级改造后的太阳射电辐射流量计将在较高时间分辨率上实时得到2 840 MHz频率上的太阳流量,为太阳物理研究积累丰富的观测数据,是太阳活动监测和预报的重要参数之一。     

10m口径射电望远镜天线计算机远程控制系统

本文从当前天文观测所受自然环境的影响入手 ,提出远程控制观测是解决目前观测所遇到的困扰的好方法 ,并介绍了中科院云南天文台太阳射电组的 1 0m口径抛物面天线的计算机远程控制系统。本文着重讨论了远程控制的实施方案 ,包括天线当前的性能测试、如何安全地做到远程通信、前端控制 (即现场控制 )等问题 ,把TCP/IP协议族原理和Client/Server原理与模糊逻辑控制思想相结合 ,对 1 0m口径天线实施自动控制 ,并开发了用于现场控制、远程控制的网络控制软件。     

云南天文台40米射电望远镜河外射电源观测

为了在云南天文台40 m天线上开展射电天文研究,使用它进行了河外射电源流量试观测。通过对河外致密源进行ON/OFF跟踪观测,得到射电源的流量变化曲线。但数据质量并不理想,说明系统存在一些问题。随后,根据对该望远镜系统的稳定性及其无线电环境干扰现状的考察,以及对现存问题的分析,提出了相应的解决方法。     

太阳和月球射电辐射对40m天线数据接收影响分析

利用标准射电源和标准噪声源,对宁静太阳和月球射电辐射的噪声温度进行了测量,估计它们对40m天线接收绕月卫星信号的影响,结论是:(1)40m天线指向偏离太阳超过2°时,能够满足正常数据接收要求;(2)40m天线指向月球时,系统接收的噪声温度增加值为87.1K, 此时系统的总噪声温度能够满足正常数据接收要求.     

Ultraviolet Observations of a Dynamic Event in the Solar Corona

The Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) observations show high Doppler shifts and temporal variations in profiles of ultraviolet lines from low temperature gas in the corona above the active region NOAA 7974. The profiles indicate 100 km s^-1 flows coming from an almost stationary source that appears bright in the lines of N III and Si III. The variations in line-of-sight velocities and intensities suggest small knots of cooling plasma emanating from a small region high in the corona. A few arc sec sunward of the region where the cool flows are seen is an elongated region of enhanced higher temperature, low velocity Ne VI and Mg VI line emission.     

Origin of the Submillimeter Radio Emission During the Time-Extended Phase of a Solar Flare

Solar flares observed in the 200 – 400 GHz radio domain may exhibit a slowly varying and time-extended component which follows a short (few minutes) impulsive phase and can last for a few tens of minutes to more than one hour. The few examples discussed in the literature indicate that such long-lasting submillimeter emission is most likely thermal bremsstrahlung. We present a detailed analysis of the time-extended phase of the 27 October 2003 (M6.7) flare, combining 1 – 345 GHz total-flux radio measurements with X-ray, EUV, and Hα observations. We find that the time-extended radio emission is, as expected, radiated by thermal bremsstrahlung. Up to 230 GHz, it is entirely produced in the corona by hot and cool materials at 7 – 16 MK and 1 – 3 MK, respectively. At 345 GHz, there is an additional contribution from chromospheric material at a few 10⁴ K. These results, which may also apply to other millimeter–submillimeter radio events, are not consistent with the expectations from standard semiempirical models of the chromosphere and transition region during flares, which predict observable radio emission from the chromosphere at all frequencies where the corona is transparent.     

太阳射电频谱观测数据分析系统方案设计

中国太阳射电宽带动态频谱仪(solar Broadband Radio Spectrometer)在太阳物理研究和国际合作交流中发挥了重要作用.为进一步扩大该设备观测数据的国际交流和共享、挖掘数据的深层信息、加快科学产出,有必要开发一套与SSW(Solar Soft Ware)兼容的数据分析系统.该系统具有以下主要特点:(1)按SSW规范设计编写,既可以在SSW环境下运行也可以独立安装使用;(2)新界面设计更易于用户上手,也可以进行复杂深层的数值分析;(3)规范明晰的功能模块和流程设计减少了漏洞和排错时间,定标和特征信息提取等多种亟需功能的完善为科学研究开拓了空间,节省了时间;(4)利用MySQL关系数据库管理系统建设一个安全稳定、易于升级管理的数据库,便于浏览搜索和批量下载.此外,该数据分析系统的开发将为正在研制的中国太阳射电频谱日像仪积累经验和储备技术,并为国内其它台站提供模式和经验.     

2000Mc太阳射电望远镜本机振荡器改造

本文介绍了２０００Ｍｃ太阳射电望远镜本机振荡器改造的基本原理，以及本机振荡器的主要技术指标进行检测的结果，结果表明主要技术参数达到了原设计指标。     

Numerical Simulation of a Solar Active Region. I: Bastille Day Flare

We present three-dimensional unsteady modeling and numerical simulations of a coronal active region, carried out within the compressible single-fluid MHD approximation. We focus on AR 9077 on 14 July 2000, and the triggering of the X5.7 GOES X-ray class “Bastille Day” flare. We simulate only the lower corona, although we include a virtual photosphere and chromosphere below. The boundary conditions at the base of this layer are set using temperature maps from line intensities and line-of-sight magnetograms (SOHO/MDI). From the latter, we generate vector magnetograms using the force-free approximation; these vector magnetograms are then used to produce the boundary condition on the velocity field using a minimum energy principle (Longcope, Astrophys. J. 612, 1181, 2004). The reconnection process is modeled through a dynamical hyper-resistivity which is activated when the current exceeds a critical value (Klimas et al., J. Geophys. Res. 109, 2218, 2004). Comparing the time series of X-ray fluxes recorded by GOES with modeled time series of various mean physical variables such as current density, Poynting energy flux, or radiative loss inside the active region, we can demonstrate that the model properly captures the evolution of an active region over a day and, in particular, is able to explain the initiation of the flare at the observed time.     

Solar System Observations with MIRI, The Mid InfraRed Instrument on the James Webb Space Telescope

MIRI is the Mid InfraRed Instrument for the James Webb Space Telescope (JWST) and will provide imaging, coronography and integral field spectroscopy in the range between 4.9 and 28.6  $\upmu \hbox{m}.$ We summarise solar system observations which may be possible with this instrument, drawing on examples of observations made with previous space missions such as IRAS, ISO and Spitzer.