Analysis of Overtones in Transverse Oscillations of Coronal Loops of an Active Region

IF 2.7 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Solar Physics Pub Date : 2024-12-18 DOI:10.1007/s11207-024-02411-x
Safna Banu K., Ram Ajor Maurya
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Abstract

We investigate the fundamental mode and overtones in the transverse oscillations of coronal loops associated with an active region using intensity observations taken by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The fundamental periods of the two selected coronal loops are found to be 17.0 minutes and 15.2 minutes, respectively. The first loop oscillated in the first and second overtones, with periods of around 6.9 minutes and 4.3 minutes, respectively. However, the second loop was detected only with the first overtone of approximately 7.7 minutes period. The period ratios of the fundamental to the first overtones of these loops are 1.24 and 0.99, respectively, while the fundamental-to-second-overtone period ratio of the first loop is 1.33. Thus, the deviation of period ratios from unity helps estimate the density scale height and the loop expansion factor. We obtained a density scale height of 11 Mm for the second loop and a loop expansion factor of 1.5 for the first coronal loop, considering that coronal loops have a greater effect on the loop expansion factor than on longitudinal density stratification associated with a sigmoidal active region. Using their lengths and periods of oscillations, we estimated a reasonable average magnetic field strength within a range of \(20-30\) G in the coronal loops.

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活动区日冕环横向振荡中的泛音分析
我们利用太阳动力学观测台(SDO)上的大气成像组件(AIA)进行的强度观测,研究了与活动区相关的日冕环横向振荡的基本模式和泛音。发现两个选定日冕环的基本周期分别为 17.0 分钟和 15.2 分钟。第一个环在第一和第二泛音中振荡,周期分别约为 6.9 分钟和 4.3 分钟。然而,第二个环路只在第一个泛音中检测到,周期约为 7.7 分钟。这些环路的基音与第一个泛音的周期比分别为 1.24 和 0.99,而第一个环路的基音与第二个泛音的周期比为 1.33。因此,周期比与统一值的偏差有助于估算密度尺度高度和环路扩展因子。考虑到日冕环路对环路扩展因子的影响比对与正弦活动区相关的纵向密度分层的影响更大,我们得出第二个环路的密度尺度高度为 11 毫米,第一个日冕环路的环路扩展因子为 1.5。利用它们的长度和振荡周期,我们估算出了日冕环中在\(20-30\)G范围内的合理平均磁场强度。
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来源期刊
Solar Physics
Solar Physics 地学天文-天文与天体物理
CiteScore
5.10
自引率
17.90%
发文量
146
审稿时长
1 months
期刊介绍: Solar Physics was founded in 1967 and is the principal journal for the publication of the results of fundamental research on the Sun. The journal treats all aspects of solar physics, ranging from the internal structure of the Sun and its evolution to the outer corona and solar wind in interplanetary space. Papers on solar-terrestrial physics and on stellar research are also published when their results have a direct bearing on our understanding of the Sun.
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