1989年8月17日太阳射电尖峰事件的准周期脉动及EFB分析

Quasi-Periodic Pulsition and the Elementary Flare Bursts of the Radio Spike Event of August 17,1989

本文分析了云南天文台１０ｍ射电望远镜在２ｌｃｍ波段上观测到的一次尖峰辐射事件，这次事件发生在５６２９活动区（Ｓ１６Ｗ１０９），它伴随了Ｘ２·９／ＳＦ耀斑及边缘耀斑环，并且有质子流量的上升和一次罕见的地磁场突然反相脉冲与之对应．我们从耀斑环的Ｈβ照片可以看出，在尖峰辐射发生前，原先存在的耀斑环的顶部开始变亮，而尖峰开始后环顶亮度达到极大，说明这次尖峰辐射与耀斑环顶部增亮有关，辐射很可能来自环顶．从尖峰事件的时间轮廓得到的ＦＦＴ功率谱表明存在１５０ｍｓ的准周期脉动．按照Ｍｃｌｅａｎ等人的模型，即脉动是由俘获在磁通管内的电子的径向振荡引起，可以推断，这次尖峰辐射与Ｆｅｒｍｉ机制激发快速电子有关，且尖峰的发生需要被俘获的电子．此外，我们将这次尖峰事件分解为几百个元耀斑爆发（ＥＦＢ），并且讨论了这些ＥＦＢ的性质．

A rapid fluctuation event(spike emission) of 1426 MHz radio microwave emission on August 17,1989 is discussed in this paper.The event was observed with time resolution of 8 ms by 10-meter radio telescope at Yunnan Observatory.The producer of the spike was AR 5629(S16W109).A powerful X2.g/SF flare and flaring limb loops accompanied with the spikes,in addition,the energetic proton flux rising and a rare inverted sudden impulse of the geomagnetic field occurred in response to the flare.We could see from Hβ images of the flare that the existed loop tops had turned brighter before the spike emission,and reached the maximum brightness when the spike just began.This situation shows that the microwave emission at 21 cm in the flare was related to the loop top's increasing brightness,and the emission probably came from the loop tops.The FFT power spectrum deduced from the time profile of the event indicates that a quasi-periodic pulsation of 150 ms existed in the microwave emission.According to the model proposed by McLean et al.,i.e.the radio pulsation was radial oscillations which was caused by energetic particles trapped in magnetic loops,it can be inferred that the spike emission is related to the speed electrons which were accelerated by Fermi mechanism, and the occurrence of the spike requires the trapped electrons. We have decomposed the microwave emission of August 17,into 642 EFBs,and discussed the properties of the EFB(elementary flare burst).