具有变化频率漂移率符号的Decomponent型III脉冲串
Decameter Type III Bursts with Changing Frequency Drift-Rate Signs
摘要：
我们讨论了III型爆发的性质，改变他们的漂移率从负到正，反之亦然的迹象。此外，这样的突发可以不止一次地改变它们的漂移速率的符号。这些特定的III型爆发是由UTR-2、URAN-2和NDA射电望远镜在8-41 MHz频段同时观测到的。这些爆发的负漂移率接近于通常的December III型爆发的负漂移率，变化范围为-0.84 ~-5.56MHz/s。特定III型爆发的正漂移率在0.44 MHz/s到12 MHz/s的较宽范围内变化。与倒U型爆发不同，尽管漂移率符号发生了变化，III型爆发仍然从高频向低频漂移。我们对这些III型爆发的正漂移率的基本解释不同于通常的假设，即III型爆发的正漂移率与电子束向太阳的传播有关。我们建议，即使电子束从太阳向外移动，他们可以产生III型爆发与正漂移率，如果在某些地区的日冕III型射电辐射的群速度低于电子束的速度。
英文摘要：
We discuss properties of type III bursts which change sign of their drift rate from negative to positive and vice versa. Moreover such bursts may change sign of their drift rates more than once. These specific type III bursts were observed simultaneously by radio telescopes UTR-2, URAN-2 and NDA in frequency band 8-41 MHz. The negative drift rates of these bursts are close to those of usual decameter type III bursts and variate from -0.84 MHz/s to -5.56 MHz/s. The positive drift rates of specific type III bursts vary in the wider range from 0.44MHz/s to 12 MHz/s. Unlike inverted U-bursts these type III bursts still drift from the high frequencies to the low frequencies in spite of the change of the drift rates signs. Our basic explanation of the positive drift rate of these type III burst differs from the common assumption that positive drift rates of Type III bursts are connected with electron beam propagation towards the Sun. We propose that, even if electron beams move outward from the Sun, they can generate type III bursts with positive drift rates if in some regions of the solar corona the group velocities of type III radio emissions are lower than the velocities of the electron beams.
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