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arXiv 1906.07534astro-ph.SR
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行星际太阳射电型IV发射的截止特征

Cut-off features in interplanetary solar radio type IV emission

Silja Pohjolainen, Nasrin Talebpour Sheshvan

摘要:

太阳射电IV型爆发有时会表现出方向性,因此当源区域远离太阳盘中心时不会观测到爆发。这一点最近也从空间观测中得到了证实,在十亿分之一波长上,使用STEREO和Wind卫星对太阳进行了三维观测。目前还不清楚方向性是由发射机制引起的,还是由朝向某些方向的无线电波形成减少引起的,还是由沿视线的无线电波的吸收/阻挡引起的。我们在这里提出的三个IV型爆发事件,发生在2004年7月23日,25日和29日,起源于同一个活动区的意见。第一次事件的源位置在太阳盘中心附近,第三次事件在西翼附近。我们的分析表明,在过去的两个事件中,IV型爆发经历了部分切断,在他们的排放,这与冲击波相关的II型爆发的外观相吻合。II型爆发形成于传播的日冕物质抛射(CME)的侧翼和前缘。这些事件支持了向II型冲击区所在方向吸收的建议。

英文摘要:

Solar radio type IV bursts can sometimes show directivity, so that no burst is observed when the source region in located far from the solar disk center. This has recently been verified also from space observations, at decameter wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is unclear whether the directivity is caused by the emission mechanism, by reduced radio wave formation toward certain directions, or by absorption/blocking of radio waves along the line of sight. We present here observations of three type IV burst events that occurred on 23, 25, and 29 July 2004, and originated from the same active region. The source location of the first event was near the solar disk center and in the third event near the west limb. Our analysis shows that in the last two events the type IV bursts experienced partial cut-offs in their emission, that coincided with the appearance of shock-related type II bursts. The type II bursts were formed at the flanks and leading fronts of propagating coronal mass ejections (CMEs). These events support the suggestion of absorption toward directions where the type II shock regions are located.

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