Microwave Neutral Line Associated Source and a Current Sheet
Microwave Neutral Line Associated Source and a Current Sheet
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微波中性线相关源和电流表
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
H. Nakajima
中科院分区：
文献类型：
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作者：
A. Uralov;V. Grechnev;G. Rudenko;I. G. Rudenko;H. Nakajima
中性线伴源（NLS）是投射到光球磁场中性线附近的准静止微波源。NLS通常是强大耀斑的前兆，但其性质尚不清楚。我们奋进揭示NLS的结构，并分析这样一个源的能量释放在日冕以上的NOAA 10488（2003年10月/11月）的网站之间的物理连接。该AR的演化包括两个双极磁结构的出现和碰撞、主磁选机的上升以及下方NLS的出现。NLS出现在太阳黑子碰撞的接触点上，黑子的相对运动继续进行，导致沿切线沿着的大切变。然后新生的NLS成为AR中微波起伏的主要来源。在17 GHz的NLS发射主要是由一个类似环的结构，一个NLS环，连接两个碰撞的太阳黑子的足点或顶部。在相当长的一段时间内，发射在NLS环的脚点上占主导地位，那里的磁场更强。在那时，NLS类似于一个通常的与太阳黑子相关的射电源，其亮度中心向太阳黑子的外围移动。X2.7耀斑的微波辐射主要集中在一个上升的耀斑环中，最初与NLS环重合。这个环的顶部位于软X射线中可见的非均匀棒状结构的底部，在耀斑开始时为34 GHz。我们揭示了i）向上延长的这个酒吧之前，耀斑发作，ii）的运动的顶部明显上升耀斑环沿着轴的酒吧，和iii）非热微波源，其下降沿着酒吧与发射的日冕喷射。我们连接的酒吧与一个几乎垂直的扩散区，一个网站内的扩展前耀斑电流片的最大能量释放的可能位置。NLS循环的顶部位于该区域的底部。NLS环和扩散区的结合构成了准稳态微波NLS的骨架。
Neutral Line associated Sources (NLSs) are quasi-stationary microwave sources projected onto vicinities of the neutral line of the photospheric magnetic field. NLSs are often precursors of powerful flares, but their nature is unclear. We endeavor to reveal the structure of an NLS and to analyze a physical connection between such a source with a site of energy release in the corona above NOAA 10488 (October/November 2003). Evolution of this AR includes emergence and collision of two bipolar magnetic structures, rise of the main magnetic separator, and the appearance of an NLS underneath. The NLS appears at a contact site of colliding sunspots, whose relative motion goes on, resulting in a large shear along a tangent. Then the nascent NLS becomes the main source of microwave fluctuations in the AR. The NLS emission at 17 GHz is dominated by either footpoints or the top of a loop-like structure, an NLS loop, which connects two colliding sunspots. During a considerable amount of time, the emission dominates over that footpoint of the NLS loop, where the magnetic field is stronger. At that time, the NLS resembles a usual sunspot–associated radio source, whose brightness center is displaced towards the periphery of a sunspot. Microwave emission of an X2.7 flare is mainly concentrated in an ascending flare loop, initially coinciding with the NLS loop. The top of this loop is located at the base of a non-uniform bar-like structure visible in soft X-rays and at 34 GHz at the flare onset. We reveal i) upward lengthening of this bar before the flare onset, ii) the motion of the top of an apparently ascending flare loop along the axis of this bar, and iii) a non-thermal microwave source, whose descent along the bar was associated with the launching of a coronal ejection. We connect the bar with a probable position of a nearly vertical diffusion region, a site of maximal energy release inside an extended pre-flare current sheet. The top of the NLS loop is located at the bottom of this region. A combination of the NLS loop and diffusion region constitutes the skeleton of a quasi-stationary microwave NLS.