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arXiv 1508.02604astro-ph.SR
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太阳射电IV型爆发斑马斑图偏振的频率依赖性

Frequency Dependence of Polarization of Zebra Pattern in Type-IV Solar Radio Bursts

Kazutaka Kaneda, Hiroaki Misawa, Kazumasa Iwai, Fuminori Tsuchiya, Takahiro Obara

摘要:

研究了2011年6月21日AMATERAS观测到的IV型太阳射电爆发中斑马斑(ZP)的偏振特性,以评估ZP的产生过程。分析高分辨率的光谱和偏振数据揭示了圆偏振度的频率依赖性和两个偏振分量之间的延迟首次。圆偏振度为50%-70%的右旋,它几乎不随频率变化。互相关分析确定,在ZP的整个频率范围内,左手圆偏振分量相对于右手分量延迟50-70 ms,并且该延迟随频率增加。我们研究了所获得的极化特性,通过使用预先存在的ZP模型,并得出结论,ZP产生的双等离子体共振过程。我们的研究结果表明,ZP发射最初是在一个完全偏振态的O-模式,并在源附近部分转换成X-模式。随后,O模和X模的群速度之间的差异导致了时间延迟。

英文摘要:

We investigated the polarization characteristics of a zebra pattern (ZP) in a type-IV solar radio burst observed with AMATERAS on 2011 June 21 for the purpose of evaluating the generation processes of ZP. Analyzing highly resolved spectral and polarization data revealed the frequency dependence of the degree of circular polarization and the delay between two polarized components for the first time. The degree of circular polarization was 50-70 percent right-handed and it varied little as a function of frequency. Cross-correlation analysis determined that the left-handed circularly polarized component was delayed by 50-70 ms relative to the right-handed component over the entire frequency range of the ZP and this delay increased with the frequency. We examined the obtained polarization characteristics by using pre-existing ZP models and concluded that the ZP was generated by the double plasma resonance process. Our results suggest that the ZP emission was originally generated in a completely polarized state in the O-mode and was partly converted into the X-mode near the source. Subsequently, the difference between the group velocities of the O-mode and X-mode caused the temporal delay.

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