太阳运动Ⅳ型射电爆发的相干辐射模型

A Coherent Emission Model for Solar Moving Type Ⅳ Radio Bursts

为解释太阳运动Ⅳ型射电爆发的相干辐射机制提出一个理论模型。从耀斑中产生的高能电子,可以被扩展上升的太阳磁流管俘获。在磁流管顶部,这些高能电子的速度分布形成为类束流速度分布,激发束流等离子体的不稳定性,并且主要直接放大O模电磁波。不稳定性增长率敏锐地依赖了日冕等离子体参数f_(pe)/f_(ce)和射束温度T_b,这能定性解释在太阳运动Ⅳ型射电爆发中观测到的高亮温度和高偏振度,以及宽频谱的特性。

A theoretical model is suggested here, in order to explain the coherent emis- sion mechanism of solar moving type IV radio bursts. The energetic electrons from flare can be trapped into an expanding solar magnetic arch. Their velocity distribution forms a beam--like velocity distribution in the top of the magnetic loop. A beam-plasma instability can be excited by this beam, it may amplify mainly O mode electromagnetic waves. It is found that the growth rate of instability depends sensitively on the coronal plasma param- eter f_(pe)/f_(ce) and beam temperature T_b. It may explain qualitatively the characters of high brightness temperature and high polarization, as well as broad spectrum, observed in the solar moving type IV radio bursts.