作为异常太阳射电爆发源的终止激波
Termination shock as a source of unusual solar radio bursts
摘要：
利用2003年11月18日和2004年9月12日耀斑的厘米波和分米波太阳射电光谱观测资料，讨论了两次米波类Ⅱ型爆发。射电爆发表明，从高频到低频的普通频率漂移减慢并停止，出现从低频到高频的频率漂移。对相应耀斑的所有数据的分析提供了形成准静止快模激波（终止激波，TS）的证据。TS能够产生高能电子，导致新的硬X射线辐射源的出现，并产生快速射电暴（尖峰）、纤维和斑马结构。具有异常频率漂移的射电辐射带的源位于耀斑后环顶部（TS下部）或与爆发的日珥或日冕物质抛射（CME，TS上部）有关。估算了太阳耀斑中普通等离子体参数的临界马赫数，给出了在耀斑事件中容易实现的值1.3。产生不寻常的射电暴的必要条件可能发生在日冕中的头盔形磁结构中。
英文摘要：
Using centimeter wave and decimeter wave solar radio spectral observations of the flares of November 18, 2003 and September 12, 2004, we have discussed two type II like bursts at the meter waves. The radio bursts show that the ordinary frequency drift from high to low frequencies slows down and stops, and a frequency drift from low to high frequencies appears. An analysis of all data on the corresponding flares provides evidence of formation of quasi standing fast mode shocks (termination shocks, TS). TS are able to generate energetic electrons, responsible for the appearance of new sources of hard X ray radiation and generation of fast radio bursts (spikes), fibers and zebra structures. The sources of the radio emission bands with the unusual frequency drift are situated above the top of the post flare loops (lower TS) or are connected with the erupting prominence or coronal mass ejection (CME, upper TS). Estimations of the critical Mach numbers for the ordinary plasma parameters in the solar flares give the values 1.3 easily realized in the flare events. The conditions necessary for generation of unusual radio bursts are likely to occur in the helmet shaped magnetic structures in the solar corona.
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