arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1709.06252astro-ph.SR
收藏

耀斑SOL2012-07-06:17 GHz和34 GHz之间圆极化反转的起源

Flare SOL2012-07-06: on the origin of the circular polarization reversal between 17 GHz and 34 GHz

A. Altyntsev, N. Meshalkina, I. Myshyakov, V. Pal`shin, G. Fleishman

摘要:

新一代高空间分辨率多波长射电日像仪将采用微波成像分光偏振法来恢复耀斑源和波传播路径上的耀斑拓扑结构和等离子体参数。记录的偏振取决于发射机制和发射机制(光学厚或薄),发射粒子的属性和传播效应。在这里,我们报告了一个不寻常的耀斑,SOL 2012 -07- 06 T01:37,其光学薄的回旋同步辐射的主源显示出明显的普通模式意义上的偏振与经典理论,有利于非凡的模式。这次耀斑产生了大量的硬X射线和高达80 GHz的高频微波的非热辐射。发现主耀斑源对应于两个大小相差很大的环的相互作用部位。我们研究了圆极化传感的三个可能的已知原因-反模耦合、正电子贡献和波束角分布的影响。我们排除了由于正电子的贡献而导致的极化反转,因为在X射线发射中没有相关的响应。我们发现,一个束状的电子分布可以产生所观察到的极化行为,但源的热密度必须远远高于估计从X射线数据。我们的结论是,在光学薄模式的视寻常波发射是由于无线电波传播通过准横向(QT)层。在磁场值高且横向于视线的日冕中,可以实现相当低的异常高的过渡频率(高于35 GHz)。这将微波源放置在该QT层下方,即在日冕中非常低。

英文摘要:

The new generations of multiwavelength radioheliographs with high spatial resolution will employ microwave imaging spectropolarimetry to recover flare topology and plasma parameters in the flare sources and along the wave propagation paths. The recorded polarization depends on the emission mechanism and emission regime (optically thick or thin), the emitting particle properties, and propagation effects. Here, we report an unusual flare, SOL2012-07-06T01:37, whose optically thin gyrosynchrotron emission of the main source displays an apparently ordinary mode sense of polarization in contrast to the classical theory that favors the extraordinary mode. This flare produced copious nonthermal emission in hard X-rays and in high-frequency microwaves up to 80 GHz. It is found that the main flare source corresponds to an interaction site of two loops with greatly different sizes. We have investigated the three possible known reasons of the circular polarization sense reversal - mode coupling, positron contribution, and the effect of beamed angular distribution. We excluded polarization reversal due to contribution of positrons because there was no relevant response in the X-ray emission. We find that a beam-like electron distribution can produce the observed polarization behavior, but the source thermal density must be much higher than the estimate from to the X-ray data. We conclude that the apparent ordinary wave emission in the optically thin mode is due to radio wave propagation across the quasi-transverse (QT) layer. The abnormally high transition frequency (above 35 GHz) can be achieved reasonably low in the corona where the magnetic field value is high and transverse to the line of sight. This places the microwave source below this QT layer, i.e. very low in the corona.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑