Detection of three periodicities in a single oscillating coronal loop
Detection of three periodicities in a single oscillating coronal loop
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DOI：
10.1051/0004-6361/200912753
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发表时间：
2009-12
影响因子：
6.5
通讯作者：
T. Doorsselaere;D. Birtill;G. R. Evans
中科院分区：
文献类型：
--
作者：
T. Doorsselaere;D. Birtill;G. R. Evans
上下文De Moortel &布雷迪（2007）研究了2001年5月13日TRACE 171\AA{}\$的横向环振荡观测。他们发现在这一事件中存在三个周期的迹象。目标。本文的目的是改进分析，更准确地测量周期，以便进行冠状地震学。方法.我们创建多个（x，t）切片的循环，并确定这些切片内的振荡参数。然后，我们使用统计方法来减少测量的振荡参数的误差。结果我们发现两个种群有明显不同的时期。环顶种群的周期为895 pm2 ~{\rm s}$，环腿种群的周期为452 pm 1 ~{\rm s}$.这两个周期的比值大约为2，问题的几何形状表明观察到两个谐波。在残留物中，我们确认存在的三次谐波与周期309\pm15 ~{\rm s}$使用两个单独的数据分析技术。这三个时期，然后用来做一个地震学估计的环路扩展和密度规模的高度。
Context. TRACE $171~\AA{}$ observations of transverse loop oscillations on May 13, 2001 have been studied by De Moortel & Brady (2007). They found hints of 3 periodicities present in this event. Aims. The aim of this article is to improve the analysis, and measure the periodicities more accurately in order to do coronal seismology. Methods. We create multiple (x,t)-slices across the loop, and determine the oscillatory parameters within those slices. We then use statistical methods to reduce the errors on the measured oscillations parameters. Results. We find two populations with a clearly distinct period. The population at the loop top has a period of $895\pm2~{\rm s}$, while the population in the loop leg has a period of $452\pm1~{\rm s}$. The fact that the ratio of these two periods is roughly 2 and the geometry of the problem suggests that two harmonics are observed. In the residues, we confirm the presence of a 3rd harmonic with period $309\pm15~{\rm s}$ using two separate data analysis techniques. The three periods are then used to do a seismological estimate of the loop expansion and the density scale height.