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首页> 外文期刊>The Astrophysical journal >STUDIES OF MICROFLARES IN RHESSI HAKD X-RAY, BIG BEAR SOLAR OBSERVATORY Hα, AND MICHELSON DOPPLER IMAGER MAGNETOGRAMS
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STUDIES OF MICROFLARES IN RHESSI HAKD X-RAY, BIG BEAR SOLAR OBSERVATORY Hα, AND MICHELSON DOPPLER IMAGER MAGNETOGRAMS

机译：瑞西哈德X射线，大熊太阳观测Hα和米歇尔·多普勒成像仪中的微火星研究

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摘要

In this paper, we present a study of the morphology of 12 microflares jointly observed by RHESSI in the energy range from 3 to 15 keV and by Big Bear Solar Observatory (BBSO) at the Hα line. They are A2-B3 events in GOES classification. From their time profiles, we find that all of these microflares are seen in soft X-ray, hard X-ray, and Hα wavelengths, and their temporal evolution resembles that of large flares. Co-aligned hard X-ray, Hα, and magnetic field observations show that the events all occurred in active regions and were located near magnetic neutral lines. In almost all of the events, the hard X-ray sources are elongated structures connecting two Hα bright kernels in opposite magnetic fields. These results suggest that, similar to large flares, the X-ray sources of the microflares represent emission from small magnetic loops and that the Hα bright kernels indicate emission at footpoints of these flare loops in the lower atmosphere. Among the 12 microflares, we include five events that are clearly associated with type Ⅲ radio bursts as observed by the radio spectrometer on board Wind. Spectral fitting results indicate the nonthermal origin of the X-ray emission at over ~10 keV during the impulsive phase of all the events, and the photon spectra of the microflares associated with type Ⅲ bursts are generally harder than those without type Ⅲ bursts. TRACE observations at EUV wavelengths are available for five events in our list, and in two of these, coincident EUV jets are clearly identified to be spatially associated with the microflares. Such findings suggest that some microflares are produced by magnetic reconnection, which results in closed compact loops and open field lines. Electrons accelerated during the flare escape along the open field lines to interplanetary space.
机译：在本文中，我们对RHESSI在3至15 keV的能量范围内和由大熊太阳观测台（BBSO）在Hα线处共同观察到的12个微耀斑的形态进行了研究。它们是GOES分类中的A2-B3事件。从它们的时间分布图中，我们发现所有这些微耀斑都是在软X射线，硬X射线和Hα波长中看到的，它们的时间演化类似于大耀斑。对准的硬X射线，Hα和磁场观测表明，这些事件都发生在活动区域​​中，并且位于磁性中性线附近。在几乎所有事件中，硬X射线源都是细长结构，它们在相反的磁场中连接两个Hα亮核。这些结果表明，类似于大火炬，微火炬的X射线源表示来自小磁环的发射，而Hα亮核表明在较低大气层中这些火炬环的脚点发射。在12个微耀斑中，我们包括5个事件，这些事件显然与Wind上的无线电光谱仪观察到的Ⅲ型无线电爆发有关。光谱拟合结果表明，在所有事件的脉冲阶段，X射线发射的非热源都超过10 keV，并且与Ⅲ型爆发有关的微光斑的光子光谱通常比没有Ⅲ型爆发的微火炬更难。在我们列表中的五个事件中，可以使用EUV波长的TRACE观测，其中两个事件中，重合的EUV射流被明确标识为与微耀斑在空间上相关。这些发现表明，通过磁重新连接会产生一些微火炬，这会导致闭合的紧凑环路和开放磁场线。在耀斑中加速的电子沿着开放磁场线逃逸到行星际空间。

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