太阳米波噪暴:哨声模式

SOLAR METER NOISE STORM:WHISTLER MODEL

本文以日冕活动区磁结构演化为噪暴现象的驱动力,并假定日冕活动区在磁学上是不均匀的——存在强磁场纤维,提出了太阳米波噪暴的哨声模式.活动区磁结构的演化将在冕弧中产生弱激波.当弱激波通过强磁场纤维时,加热部分电子,被加热的电子在强磁场纤维中形成损失锥分布.在日冕的噪暴区域中,快速电子的损失锥分布将产生高亮度的哨声波和朗缪尔波.通过感应散射,朗缪尔波滑向低波区域时将与哨声波发生强烈的互作用而产生窄束电磁辐射(Ⅰ型爆发).强磁场纤维及相应的场位形决定了Ⅰ型爆发的频宽和持续时间.而噪暴连续谱则采用通常认为的各同向电子产生的朗缪尔波与低频波耦合的产物.

In this paper, a storm model is presented taking the magnetic field ecolution of a coronal active region as the driving force of the noise storm phenomena. And it has been assumed that a coronal active region is inhomogeneous in magnetics, there are' strong magnetic field fibers in it. The evolution of the magneic structure of an active region will produce weak shocks. When the shocks pass a coronal arch, a fraction of electrons is heated. The, heated fast electrons form a local loss-cone distribution in strong magnetic fibers. The fast electron loss-cone instabilities will generate Langmuir wave and whistler wave with high temperature. When the Langmuir wave spectrum slip towards smaller wave number ranges due to differential transfer, it will strongly act with whistler wave to produce electromagnetic wave with high frequency in a narrow beam (type-1 buist). A strong field and associated configuiation determine the frequency band width and duration of a type-1 burst. And continuum is due to the coupling between the Langmuir wave from a fast electron isotropic distribution and an other low frequency wave.It is thought that the strong directivity of type-1 bursts is the intrinsic characteristics of them. To distinguish which low frequency disturbance will couple with a high frequency wave to generate a trasverse electromagnetic wave, the directivity should be referred to as a critical factor. And that is one of the differences of this model from others.