EVIDENCE OF WIDESPREAD HOT PLASMA IN A NONFLARING CORONAL ACTIVE REGION FROM HINODE/X-RAY TELESCOPE
EVIDENCE OF WIDESPREAD HOT PLASMA IN A NONFLARING CORONAL ACTIVE REGION FROM HINODE/X-RAY TELESCOPE
复制标题
来自 HINODE/X 射线望远镜的证据表明，在非耀斑日冕活动区域存在广泛的热等离子体
DOI：
10.1088/0004-637x/698/1/756
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Susanna Parenti
中科院分区：
文献类型：
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作者：
F. Reale;P. Testa;J. Klimchuk;Susanna Parenti
纳米耀斑是一种在空间上无法分辨的磁束中产生的短而强的热脉冲，现在被认为是解决日冕加热问题的主要候选物质。然而，纳米耀斑的频繁发生要求耀斑热等离子体始终存在于日冕中。到目前为止，它的探测一直难以捉摸，部分原因是它的强度预计非常微弱。在这里，我们报告了2006年11月Hinode/ x射线望远镜（XRT）用五个滤光片观测到的一个活跃区域的分析。我们已经使用滤波比方法来推导温度和发射测量（EM）的软和硬比值图。这些图是近似的，因为假设等离子体沿着每条视线都是等温的。尽管如此，最困难的比值揭示了等离子体在10 MK左右的清晰存在。为了获得关于等离子体特性的更详细信息，我们进行了蒙特卡罗模拟，假设了各种非等温EM沿视线分布。我们发现观测到的滤光率意味着双峰分布，由一个较冷的（log T ~ 6.3−6.5）分量和一个较弱的（几个百分点）和较热的（6.6 < log T < 7.2）分量组成。这些数据与沿所有视线（即整个活动区域）的双峰分布一致。我们还发现，从过滤比推断的等温温度敏感地依赖于冷组分的精确温度。这个分量的轻微移动会导致热分量在硬比测量中被遮挡。因此，以硬、软比值绘制的温度图往往是反相关的。我们的结论是，这一观察结果支持在活动区域广泛存在的纳米燃烧活动。
Nanoflares, short and intense heat pulses within spatially unresolved magnetic strands, are now considered a leading candidate to solve the coronal heating problem. However, the frequent occurrence of nanoflares requires that flare-hot plasma be present in the corona at all times. Its detection has proved elusive until now, in part because the intensities are predicted to be very faint. Here, we report on the analysis of an active region observed with five filters by Hinode/X-Ray Telescope (XRT) in 2006 November. We have used the filter ratio method to derive maps of temperature and emission measure (EM) both in soft and hard ratios. These maps are approximate in that the plasma is assumed to be isothermal along each line of sight. Nonetheless, the hardest available ratio reveals the clear presence of plasma around 10 MK. To obtain more detailed information about the plasma properties, we have performed Monte Carlo simulations assuming a variety of nonisothermal EM distributions along the lines of sight. We find that the observed filter ratios imply bi-modal distributions consisting of a strong cool (log T ∼ 6.3 − 6.5) component and a weaker (few percent) and hotter (6.6 < log T < 7.2) component. The data are consistent with bi-modal distributions along all lines of sight, i.e., throughout the active region. We also find that the isothermal temperature inferred from a filter ratio depends sensitively on the precise temperature of the cool component. A slight shift of this component can cause the hot component to be obscured in a hard ratio measurement. Consequently, temperature maps made in hard and soft ratios tend to be anti-correlated. We conclude that this observation supports the presence of widespread nanoflaring activity in the active region.
影响因子：
2.8
作者：
Kosugi, T.;Matsuzaki, K.;Golub, L.
通讯作者：
Golub, L.
DOI：
--
发表时间：
2007
期刊：
Science 318
影响因子：
--
作者：
Reale;et. al.
通讯作者：
et. al.