行星际闪烁（IPS）单站观测对太阳风速度的诊断

借助于弱散射理论和模式拟合方法，单站行星闪烁观测可以诊断太阳风速度，本讨论了太阳风参数和射电源角尺度对闪烁谱的影响，以及太阳速度的积分效应，结果表明，闪烁谱的特征是与视经下距太阳最近处的太阳风速度直接相关的。     

解读空间天气网站

太阳高层大气日冕中主要包含电子和质子,它们具有极高的动能和温度,可以摆脱太阳引力的作用,像风一样吹向行星际空间,称为太阳风。太阳风物质（等离子体）的温度、密度及速度随时间和太阳经度不同而变化。太阳风的速度—般在350～750Km／sec之间。     

太阳风的电波传播观测研究

本文以行星际空烁为主，综述了通过电波传播的观测来研究太阳风的方法及近３０年的观测结果。概述了这种方法的优缺点，基本假设和基础理论，讨论了这种方法所得到的太阳风电子密度谱，太阳风三维结构以及与太阳活动周的关系，特别是肯定了闪烁测量在研究太阳风加速区问题中的作用。并且结合当前的国际日地物理计划指出了９０年代的研究重点。最后，简述了北京天文台密云站射电天文设备用于行星际闪烁观测的可能性及特点。     

太阳风研究的新进展：略谈“尤里西斯”观测

太阳风研究的新进展：略谈“尤里西斯”观测藻间由太阳向外“吹”出的电子和离子组成的等离子体在局部行星际介质中占据一个巨大的腔。这些等离子体称为太阳风。它起源于具有百万度高温的太阳外层大气─—日冕。由于日冕温度很高，太阳风等离子体在克服太阳引力，以３００...     

行星际闪烁(IPS)研究新进展

太阳风行星际闪烁（ｉｎｔｅｒｐｌａｎｅｔａｒｙ ｓｃｉｎｔｉｌｌａｔｉｏｎ,ＩＰＳ）研究在太阳物理,日地空间物理和空间天气学研究中具有重要科学意义,经过近３０年重点研究太阳风后,从９０年代初开始,ＩＰＳ研究在太阳风与日球观测的对比分析、行星际扰动与地磁活动预报,观测数据的层析分析三方面都取得了新的进展。     

行星际闪烁单站单频数据处理

太阳风是日地空间的主要物质来源,太阳风的观测对日地空间环境及地球物理的研究具有重要意义。地基行星际闪烁观测是监测太阳风风速,测量太阳风等离子体不规则结构,研究遥远致密射电源角径的重要且有效的方法。介绍了行星际闪烁地基观测的单站单频模式的基本理论,针对单站单频模式观测的数据处理及自编软件。本文的工作是为行星际闪烁单站双频系统数据分析处理作前期准备。     

太阳风、高能暴粒子、太阳高能粒子和太阳宇宙线的谱指数研究

本文根据卫星提供的1963—1978年太阳风实验资料,将太阳风中的质子流作为极低能宇宙线,则能得到0.3—4kev的质子积分通量—动能曲线,使低能宇宙线的能谱向前推进了约三个数量级。所得的极低能宇宙线能谱亦呈幂律谱,即:J(>E)=A_sE~(-γ),具有双幂指数,约在1kev处发生转折,与低能太阳宇宙线能谱非常类似。 最近,卫星ISEE—3观测到46次与行星际激波相联系的高能暴粒子(ESP)事例,在能域35—53kev的各次质子峰值强度恰好绘于联结两能谱的虚线之中。这样,从太阳风、ESP、太阳高能粒子(SEP)到太阳低能宇宙线的能谱都被连接了起来,对于它们的起源,也能获得合理地很好地解释。     

太阳风离子尺度湍流与太阳风加热

太阳风源自太阳大气,在行星际空间传播过程中被持续加热,然而究竟是何种能量加热了太阳风至今未研究清楚.太阳风普遍处于湍动状态,其湍动能量被认为是加热太阳风的重要能源.然而,太阳风湍流通过何种载体、基于何种微观物理机制加热了太阳风尚不明确,这是相关研究的关键问题.将回顾人类对太阳风加热问题的研究历史,着重介绍近年来我国学者在太阳风离子尺度湍流与加热方面取得的研究进展,展望未来在太阳风加热研究中有待解决的科学问题和可能的研究方向.     

加热日冕的磁毯

半个多世纪以来,天文学家一直在考虑太阳的外层大气,即日冕,为什么会这么热,超过一百万度,而太阳的表面（光球）温度却只有６０００℃。美国宇航局和欧洲空间局联合建立的太阳和太阳风层观测台（ＳＯＨＯ）的资料表明是磁能加热了日冕。斯坦福空间研究所的艾伦·蒂特...     

太阳风中阿尔文波的研究进展

阿尔文波在太阳风中普遍存在,对其中等离子体的加热与加速有重要意义.从太阳风中的结构、太阳风湍流、太阳风全球模型、等离子体不稳定性(参量衰变不稳定性和火蛇管不稳定性)、太阳风的加热与加速等方面,总结了近年来太阳风中阿尔文波相关的研究进展.结合目前的研究趋势,从亚阿尔文速太阳风、太阳风全球模型和太阳源区3个方向展望了未来阿尔文波的相关研究.     

Observations of Rapid Velocity Variations in the Slow Solar Wind

The technique of interplanetary scintillation (IPS) is the observation of rapid fluctuations of the radio signal from an astronomical compact source as the signal passes through the ever-changing density of the solar wind. Cross-correlation of simultaneous observations of IPS from a single radio source, received at multiple sites of the European Incoherent SCATter (EISCAT) radio antenna network, is used to determine the velocity of the solar wind material passing over the lines of sight of the antennas. Calculated velocities reveal the slow solar wind to contain rapid velocity variations when viewed on a time-scale of several minutes. Solar TErrestrial RElations Observatory (STEREO) Heliospheric Imager (HI) observations of white-light intensity have been compared with EISCAT observations of IPS to identify common density structures that may relate to the rapid velocity variations in the slow solar wind. We have surveyed a one-year period, starting in April 2007, of the EISCAT IPS observing campaigns beginning shortly after the commencement of full science operations of the STEREO mission in a bid to identify common density structures in both EISCAT and STEREO HI datasets. We provide a detailed investigation and presentation of joint IPS/HI observations from two specific intervals on 23 April 2007 and 19 May 2007 for which the IPS P-Point (point of closest approach of the line of sight to the Sun) was between 72 and 87 solar radii out from the Sun’s centre. During the 23 April interval, a meso-scale (of the order of 10⁵ km or larger) transient structure was observed by HI-1A to pass over the IPS ray path near the P-Point; the observations of IPS showed a micro-scale structure (of the order of 10² km) within the meso-scale transient. Observations of IPS from the second interval, on 19 May, revealed similar micro-scale velocity changes, however, no transient structures were detected by the HIs during that period. We also pose some fundamental thoughts on the slow solar wind structure itself.     

Comparison of single-site interplanetary scintillation solar wind speed structure with coronal features

Interplanetary Scintillation (IPS) Observations were made during the period 1984–1990 using a single radio telescope at 103 MHz situated at Thaltej (Ahmedabad), India. Solar wind speeds were estimated using a recently developed method based on matching the observed IPS spectra with model solar wind spectra for Kolmogorov turbulence. The best-fit speeds derived are traced back to a source surface, and average velocity maps are made for each year, averaging over a number of Carrington rotations. It is found that the resulting single-site, large-scale IPS speed structure agrees well with that derived from 3-site observations from earlier workers. The IPS speed structure during this period was compared with other coronal features. Nearly 85% of the observed high-speed regions were associated with coronal holes. At solar minimum, in 1986, a quasi-sinusoidal, narrow belt of slow solar wind was observed which matched well with the neutral line structure of the solar magnetic field and the belt of active centers. Near solar maximum, in 1990, the speed structure was chaotic, similar to that of the neutral line, with low speed regions appearing all over the source surface.     

A Study on the Technique of Observing Interplanetary Scintillation with Simultaneous Dual-Frequency Measurements

Ground-based observation of Interplanetary Scintillation(IPS)is an important ap- proach of monitoring solar wind speed.We describe both the principle and method of ob- serving the solar wind speed by using the normalized cross-spectrum of simultaneous dual- frequency IPS measurement.The effects of the solar wind properties and the angular size of the scintillation source on the measurement of solar wind speed are investigated by numerical analysis.We carry out a comparison of this method with the traditional single station-single frequency method.We outline a new IPS observation system using this method now under construction at the National Astronomical Observatories,CAS(NAOC).     

A bimodal model of the solar wind speed

Until the ULYSSES spacecraft reached high latitude, the only means for measuring the solar wind velocity in the polar regions was from radio scattering observations (IPS), and these remain the only way to measure the velocity near the sun. However, IPS, like many remote sensing observations, is a line-of-sight integrated measurement. This integration is particularly troublesome when the line-of-sight passes through a fast stream but that stream does not occupy the entire scattering region. Observations from the HELIOS spacecraft have shown that the solar wind has a bimodal character which becomes more pronounced near the sun. Recent observations from ULYSSES have confirmed that this structure is clear at high latitudes even at relatively large solar distances. We have developed a method of separating the fast and slow contributions to an IPS observation which takes advantage of this bimodal structure. In this paper I will describe the technique and its application to IPS observations made using the receiving antennas of the EISCAT incoherent backscatter radar observatory in northern Scandinavia.     

Analysis of Solar Wind Events Using Interplanetary Scintillation Remote Sensing 3D Reconstructions and Their Comparison at Mars

Interplanetary Scintillation (IPS) allows observation of the inner heliospheric response to corotating solar structures and coronal mass ejections (CMEs) in scintillation level and velocity. With colleagues at STELab, Nagoya University, Japan, we have developed near-real-time access of STELab IPS data for use in space-weather forecasting. We use a 3D reconstruction technique that produces perspective views from solar corotating plasma and outward-flowing solar wind as observed from Earth by iteratively fitting a kinematic solar wind model to IPS observations. This 3D modeling technique permits reconstruction of the density and velocity structure of CMEs and other interplanetary transients at a relatively coarse resolution: a solar rotational cadence and 10° latitudinal and longitudinal resolution for the corotational model and a one-day cadence and 20° latitudinal and longitudinal heliographic resolution for the time-dependent model. This technique is used to determine solar-wind pressure (“ram” pressure) at Mars. Results are compared with ram-pressure observations derived from Mars Global Surveyor magnetometer data (Crider et al. 2003, J. Geophys. Res. 108(A12), 1461) for the years 1999 through 2004. We identified 47 independent in situ pressure-pulse events above 3.5 nPa in the Mars Global Surveyor data in this time period where sufficient IPS data were available. We detail the large pressure pulse observed at Mars in association with a CME that erupted from the Sun on 27 May 2003, which was a halo CME as viewed from Earth. We also detail the response of a series of West-limb CME events and compare their response observed at Mars about 160° west of the Sun – Earth line by the Mars Global Surveyor with the response derived from the IPS 3D reconstructions.     

Two-Station Interplanetary Scintillation Measurements of Solar Wind Speed near the Sun Using the X-band Radio Signal of the Nozomi Spacecraft

Interplanetary scintillation (IPS) measurements of the solar wind speed for the distance range between 13 and 37 R _S were carried out during the solar conjunction of the Nozomi spacecraft in 2000?–?2001 using the X-band radio signal. Two large-aperture antennas were employed in this study, and the baseline between the two antennas was several times longer than the Fresnel scale for the X-band. We successfully detected a positive correlation of IPS from the cross-correlation analysis of received signal data during ingress, and estimated the solar wind speed from the time lag corresponding to the maximum correlation by assuming that the solar wind flows radially. The speed estimates range between 200 and 540?km?s^?1 with the majority below 400?km?s^?1. We examined the radial variation in the solar wind speed along the same streamline by comparing the Nozomi data with data obtained at larger distances. Here, we used solar wind speed data taken from 327 MHz IPS observations of the Solar-Terrestrial Environment Laboratory (STEL), Nagoya University, and in?situ measurements by the Advanced Composition Explorer (ACE) for the comparison, and we considered the effect of the line-of-sight integration inherent to IPS observations for the comparison. As a result, Nozomi speed data were proven to belong to the slow component of the solar wind. Speed estimates within 30 R _S were found to be systematically slower by 10?–?15 % than the terminal speeds, suggesting that the slow solar wind is accelerated between 13 and 30 R _S.     

Remote sensing of the heliospheric solar wind using radio astronomy methods and numerical simulations

The ground-based radio astronomy method of interplanetary scintillations (IPS) and spacecraft observations have shown, in the past 25 years, that while coronal holes give rise to stable, reclining high speed solar wind streams during the minimum of the solar activity cycle, the slow speed wind seen more during the solar maximum activity is better associated with the closed field regions, which also give rise to solar flares and coronal mass ejections (CME’s). The latter events increase significantly, as the cycle maximum takes place. We have recently shown that in the case of energetic flares one may be able to track the associated disturbances almost on a one to one basis from a distance of 0.2 to 1 AU using IPS methods. Time dependent 3D MHD models which are constrained by IPS observations are being developed. These models are able to simulate general features of the solar-generated disturbances. Advances in this direction may lead to prediction of heliospheric propagation of these disturbances throughout the solar system.     

Disturbances in the solar wind from IPS measurements in August 1972

From IPS and spacecraft measurements of the solar wind combined with geomagnetic observations, we identify the passage of three main disturbances through the solar wind from solar flares on August 2, 4 and 7. From a detailed study of the IPS data covering the third event, we conclude that the extent of the disturbance front at 1 AU covered about ±60° in longitude and more than 30° in latitude from the flare normal. If interpreted as a blast wave according to the model of De Young and Hundhausen (1971), the disturbance was ejected from the Sun into a cone of half-angle 45°±15°.     

Synoptic Maps of Solar Wind: Comparison of IPS Data and the NOAA/SEC Version of the Wang and Sheeley Model

Since the 1970s, the Solar-Terrestrial Environment Laboratory, Japan, has been publishing synoptic maps of solar wind velocity prepared using the technique of interplanetary scintillation. These maps, known as V-maps, are useful to study the global distribution of solar wind in the heliosphere. As the Earth-orbiting satellites are unable to probe regions outside the ecliptic, it is important to exploit the scope of interplanetary scintillation to study the solar wind properties at these regions and their relation with coronal features. It has been shown by Wang and Sheeley that there exists an inverse correlation between rate of magnetic flux expansion and the solar wind velocity. The NOAA/Space Environment Center daily updated version of the Wang and Sheeley model has been used to produce synoptic maps of solar wind velocity and magnetic field polarity for individual Carrington rotations. The predictions of the model at 1 AU have been found to be in good agreement with the observed values of the same. The present work is a comparison of the synoptic maps on the source surface using the interplanetary scintillation measurements from Japan and the NOAA/SEC version of the Wang and Sheeley model. The two results agree near the equatorial regions and the slow solar wind locations are consistent most of the times. However, at higher latitudes within ±60°, the wind velocities differ considerably. In the Wang and Sheeley model the highest speed obtained is 600 km s^–1 whereas in the IPS results velocities as high as 800 km s^–1 have been detected. The paper discusses the possible causes for this discrepancy and suggestion to improve the agreement between the two results.