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arXiv 1307.3501astro-ph.SR
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长持续时间太阳耀斑中的小尺度微波爆发

Small Scale Microwave Bursts in Long-duration Solar Flares

Baolin Tan

摘要:

太阳小尺度微波爆发(SMBs)包括微波点、尖峰和窄带III型爆发,具有时间尺度短、频带窄和亮温高的特点。本文利用怀柔太阳宽带射电频谱仪的超高频率分辨率观测资料,对2005年1月14-21日发生在活动区NOAA 10720的几次耀斑中的中小尺度射电暴进行了详细的研究。特别是长持续时间的耀斑,SMB不仅发生在耀斑的早期上升和脉冲阶段,而且还发生在耀斑的衰减阶段,甚至在耀斑结束之后。这些SMB都是强爆发,推测亮度温度至少为8.18*10^11 - 1.92*10^13 K,寿命很短,为5-18 ms,相对频率带宽为0.7- 3.5%,频率漂移率超高。这些SMB与背景辐射(安静的太阳和其下的耀斑宽带连续谱)的偏振明显不同,它们应该是独立的强相干爆发,与小尺度源区的一些非热能释放和高能粒子产生有关。这些事实表明耀斑极大期后存在着小尺度强的非热能释放活动,这对空间天气的预报具有重要意义。物理分析表明,等离子体机制可能是最有利的候选人形成的SMB。从等离子体机制出发,可以推导出快电子的速度和动能,并跟踪电子加速的区域。

英文摘要:

Solar small scale microwave bursts (SMBs), including microwave dot, spike, and narrow band type III bursts, are characterized with very short timescales, narrow frequency bandwidth, and very high brightness temperatures. Based on observations of the Chinese Solar Broadband Radio Spectrometer at Huairou with superhigh cadence and frequency resolution, this work presents an intensive investigation of SMBs in several flares occurred in active region NOAA 10720 during 2005 Jan 14-21. Especially long-duration flares, SMBs occurred not only in early rising and impulsive phase, but also in the flare decay phase, and even in time of after the flare ending. These SMBs are strong bursts with inferred brightness temperature at least 8.18*10^11 - 1.92*10^13 K, very short lifetime of 5-18 ms, relative frequency bandwidths of 0.7-3.5%, and superhigh frequency drifting rates. Together with their obviously different polarizations from the background emission (the quiet Sun, and the underlying flaring broadband continuum), such SMBs should be individual independent strong coherent bursts which is related to some non-thermal energy releasing and production of energetic particles in small scale source region. These facts show the existence of small scale strong non-thermal energy releasing activities after the flare maxima, which is meaningful to the prediction of space weather. Physical analysis indicates that plasma mechanism may be the most favorable candidate for the formation of SMBs. From plasma mechanism, the velocities and kinetic energy of fast electrons can be deduced, and the region of electron acceleration can also be tracke.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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