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arXiv 0903.3029astro-ph.SR
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日出星极紫外成像光谱仪对非耀斑活动区热等离子体的观测

Hot Plasma in Non-Flaring Active Regions Observed by the Extreme-ultraviolet Imaging Spectrometer on Hinode

Yuan-Kuen Ko, George A. Doschek, Harry P. Warren, Peter R. Young

摘要:

Hinode航天器上的极紫外成像光谱仪在两个波长范围内获得太阳大气层的高分辨率光谱:170 - 210埃和250 - 290埃。这些波长区域包含覆盖来自色球/过渡区域的温度区域的大量发射线(例如,He II,Si VII)到耀斑温度(Fe XXIII,Fe XXIV)。对于理解日冕加热特别感兴趣的是在192.858埃处的Ca XVII线,其形成温度接近600万度。然而,这条线与两条Fe XI和六条O V线混合。在本文中,我们讨论了一个具体的程序,以提取钙XVII线的共混物。我们对五个活动区域和一个肢体耀斑的光栅数据执行了该程序,并证明如果Ca XVII通量占混合物的至少~10%,则可以从混合物中满意地提取Ca XVII线。我们展示了由Ca XVII发射描绘的高温日冕的例子,并发现Ca XVII发射在这些活动区域中具有三个形态特征-- 1)“胖”中等大小的环被限制在比100万度日冕更小的空间中,2)围绕这些环的较弱的扩散发射遍布活动区域的核心,以及3)强Ca XVII环的位置在由1百万度等离子体形成的线发射中通常较弱。我们发现,使用Ca XVII到Fe XI线强度比作为代理,在活动区域的核心中,600万度等离子体相对于较冷的100万度等离子体的发射测量比可以高达10。在活跃区核心之外,100万度环是丰富的,该比率的上限约为0.5。

英文摘要:

The Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft obtains high resolution spectra of the solar atmosphere in two wavelength ranges: 170 - 210 and 250 - 290 angstroms. These wavelength regions contain a wealth of emission lines covering temperature regions from the chromosphere/transition region (e.g., He II, Si VII) up to flare temperatures (Fe XXIII, Fe XXIV). Of particular interest for understanding coronal heating is a line of Ca XVII at 192.858 angstroms, formed near a temperature of 6 million degrees. However, this line is blended with two Fe XI and six O V lines. In this paper we discuss a specific procedure to extract the Ca XVII line from the blend. We have performed this procedure on the raster data of five active regions and a limb flare, and demonstrated that the Ca XVII line can be satisfactorily extracted from the blend if the Ca XVII flux contributes to at least ~10% of the blend. We show examples of the high-temperature corona depicted by the Ca XVII emission and find that the Ca XVII emission has three morphological features in these active regions -- 1) `fat' medium-sized loops confined in a smaller space than the 1 million degree corona, 2) weaker, diffuse emission surrounding these loops that spread over the core of the active region, and 3) the locations of the strong Ca XVII loops are often weak in line emission formed from the 1 million degree plasma. We find that the emission measure ratio of the 6 million degree plasma relative to the cooler 1 million degree plasma in the core of the active regions, using the Ca XVII to Fe XI line intensity ratio as a proxy, can be as high as 10. Outside of the active region core where the 1 million degree loops are abundant, the ratio has an upper limit of about 0.5.

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