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空间甚低频太阳射电Ⅲ型暴研究进展
谭宝林
中国科学院国家天文台
摘要:
太阳耀斑和日冕物质抛射是太阳系所发生的最猛烈的爆发事件,能向行星际空间释放出三大类扰动源:强烈的电磁波辐射增强、抛出大量磁化等离子体云团、发射巨量的非热高能粒子流。它们在行星际空间产生剧烈扰动,传播到近地空间时,将触发一系列灾害性空间天气事件,严重干扰各种高技术系统的安全运行。其中,与太阳活动密切相关的非热高能粒子流是产生灾害性空间天气事件最主要的驱动源之一。太阳非热高能粒子流的主要观测特征便是具有快速频率漂移特征的射电Ⅲ型暴。但是,当它们传播到超过太阳表面以上5-10倍太阳半径的行星际空间以后,由于等离子体密度非常稀薄,辐射频率降低到大约30MHz以下的空间甚低频波段(SVLF),这时地基射电望远镜已经无法给出有效探测和追踪。空间或月基甚低频太阳射电探测器可以对频率低于80MHz的射电辐射信号进行有效的频谱观测,在该频段出现的射电Ⅲ型暴能有效探测和跟踪非热高能粒子流在广阔的行星际空间中的传播和演变特征,为灾害性空间天气事件预报提供直接依据。本文主要介绍了国际上在空间甚低频波段太阳射电Ⅲ型暴的观测和研究进展和存在的主要问题,并讨论了空间甚低频射电探测器的观测数据在太阳射电Ⅲ型暴研究方面的主要科学目标和前景。
关键词:  太阳活动;太阳射电;射电观测;空间天气
DOI:
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基金项目:
Research Advances of Solar Radio Type III Bursts at Space Very Low Frequencies
tanbaolin
Abstract:
Solar flares and coronal mass ejections (CME) are the most powerful explosions in the solar system, which may generate three kinds of violent disturbance in the interplanetary space: bursts of electromagnetic waves, magnetized plasma clouds, and great number of non-thermal high-energy particles. When such disturbance propagates to the space near the Earth, it creates serious perturbations to the terrestrial environment and greatly affects the safe operations of various kinds of high-tech systems in our society. Among the three types of disturbance, the non-thermal particles are the one of the main triggering sources of the disastrous space weather events. The main observational behavior of the non-thermal high-energy particles is the radio Type III bursts with fast frequency drifting rate. However, when the non-thermal particles flows are flying in interplanetary space beyond about 5-10 solar radii, the background plasma becomes very tenuous and the emission frequency is below 30 MHz (generally known as space very low frequency, SVLF) which cannot be detected by the ground-based solar radio telescope. The space-based or moon-based solar SVLF spectral polarimeter can observe effectively solar radio type III bursts at frequency of <80 MHz with high temporal and spectral resolutions, and can detect and track the propagation and evolution of the non-thermal particle streams produced by the solar eruption. These observations provide a robust service for the prediction of the disastrous space weather event. This paper introduces the main research advances and the existing problems of radio Type III bursts at SVLF, and discuss the main scientific objectives of the space-based or moon-based solar SVLF spectral polarimeter.
Key words:  solar activity;solar radio;radio observations; space weather