由对偶的Ⅲ型射电爆发观测探讨日冕双向电子束的起源问题

THE EXPLORATION OF BIDIRECTIONAL ELECTRON BEAMS ORIGINATING IN THE SOLAR CORONA WITH PAIRS OF TYPE Ⅲ RADIO BURSTS

介绍云南和北京天文台射电频谱仪观测到的 3个对偶的米波———微波Ⅲ型爆发 ,估计了双向电子束起源的频率和高度 ,3个事件分别揭示了在正向和反向漂移爆发之间的分界频率 (约为 2 50 ,1 30 0和 2 90 0MHz) ,它们指出了一个致密的电子加速源 ,在这个源中产生了向上和向下两个方向注入的电子束 ,从这些事例可以表明不同事件的双向电子束的分界频率有一个相当大的范围 (2 50 - 2 90 0MHz) ,而它们的起源范围却是在一个很小的 (大约 4-1 0 0MHz)和不同的频段范围内 .最后讨论了日冕磁结构的拓扑范围、电子加速源构造的空间尺度、电子束运动速度和对偶Ⅲ型爆发的产生机制 .

Three pairs of type Ⅲ radio bursts from metric to microwave regions observed with radio spectrometers at Yunnan and Beijing Observatories are investigated. The frequencies and heights of bidirectional electron beams are estimated. Three events reveal a separatrix frequency (at about 250, 1300 and 2900 MHz) between normal and reverse drifting radio bursts. They indicate a compact acceleration source where electron beams are injected in both the upward and downward directions. These cases may indicate that the separatrix frequency region of bidirectional electron beams are within a large braodband from 250 to 2900 MHz and the originating ranges (frequency band of separatrix) are in a very small (4 to 100 MHz) and different bands. Finally, the magnetic structure topology range, the spatial organization size of the electron acceleration source, the motion velocity of electron beam and the mechanism of pair of type Ⅲ bursts are discussed.