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Title: MAGNETOHYDRODYNAMIC SEISMOLOGY OF A CORONAL LOOP SYSTEM BY THE FIRST TWO MODES OF STANDING KINK WAVES

Abstract

We report the observation of the first two harmonics of the horizontally polarized kink waves excited in a coronal loop system lying southeast of AR 11719 on 2013 April 11. The detected periods of the fundamental mode (P {sub 1}), its first overtone (P {sub 2}) in the northern half, and that in the southern one are 530.2 ± 13.3, 300.4 ± 27.7, and 334.7 ± 22.1 s, respectively. The periods of the first overtone in the two halves are the same considering uncertainties in the measurement. We estimate the average electron density, temperature, and length of the loop system as (5.1 ± 0.8) × 10{sup 8} cm{sup –3}, 0.65 ± 0.06 MK, and 203.8 ± 13.8 Mm, respectively. As a zeroth-order estimation, the magnetic field strength, B = 8.2 ± 1.0 G, derived by the coronal seismology using the fundamental kink mode matches with that derived by a potential field model. The extrapolation model also shows the asymmetric and nonuniform distribution of the magnetic field along the coronal loop. Using the amplitude profile distributions of both the fundamental mode and its first overtone, we observe that the antinode positions of both the fundamental mode and its first overtone shiftmore » toward the weak field region along the coronal loop. The results indicate that the density stratification and the temperature difference effects are larger than the magnetic field variation effect on the period ratio. On the other hand, the magnetic field variation has a greater effect on the eigenfunction of the first overtone than the density stratification does for this case.« less

Authors:
; ; ; ;  [1];  [2]; ;  [3]
  1. School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210046 (China)
  2. Solar Physics and Space Plasma Research Center (SP2RC), School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH (United Kingdom)
  3. Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)
Publication Date:
OSTI Identifier:
22364387
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; EIGENFUNCTIONS; ELECTRON DENSITY; EXTRAPOLATION; HARMONICS; MAGNETIC FIELDS; POTENTIALS; SEISMOLOGY; SOLAR CORONA; STRATIFICATION; SUN; VARIATIONS; WAVE PROPAGATION

Citation Formats

Guo, Y., Hao, Q., Cheng, X., Chen, P. F., Ding, M. D., Erdélyi, R., Srivastava, A. K., and Dwivedi, B. N., E-mail: guoyang@nju.edu.cn. MAGNETOHYDRODYNAMIC SEISMOLOGY OF A CORONAL LOOP SYSTEM BY THE FIRST TWO MODES OF STANDING KINK WAVES. United States: N. p., 2015. Web. doi:10.1088/0004-637X/799/2/151.
Guo, Y., Hao, Q., Cheng, X., Chen, P. F., Ding, M. D., Erdélyi, R., Srivastava, A. K., & Dwivedi, B. N., E-mail: guoyang@nju.edu.cn. MAGNETOHYDRODYNAMIC SEISMOLOGY OF A CORONAL LOOP SYSTEM BY THE FIRST TWO MODES OF STANDING KINK WAVES. United States. doi:10.1088/0004-637X/799/2/151.
Guo, Y., Hao, Q., Cheng, X., Chen, P. F., Ding, M. D., Erdélyi, R., Srivastava, A. K., and Dwivedi, B. N., E-mail: guoyang@nju.edu.cn. Sun . "MAGNETOHYDRODYNAMIC SEISMOLOGY OF A CORONAL LOOP SYSTEM BY THE FIRST TWO MODES OF STANDING KINK WAVES". United States. doi:10.1088/0004-637X/799/2/151.
@article{osti_22364387,
title = {MAGNETOHYDRODYNAMIC SEISMOLOGY OF A CORONAL LOOP SYSTEM BY THE FIRST TWO MODES OF STANDING KINK WAVES},
author = {Guo, Y. and Hao, Q. and Cheng, X. and Chen, P. F. and Ding, M. D. and Erdélyi, R. and Srivastava, A. K. and Dwivedi, B. N., E-mail: guoyang@nju.edu.cn},
abstractNote = {We report the observation of the first two harmonics of the horizontally polarized kink waves excited in a coronal loop system lying southeast of AR 11719 on 2013 April 11. The detected periods of the fundamental mode (P {sub 1}), its first overtone (P {sub 2}) in the northern half, and that in the southern one are 530.2 ± 13.3, 300.4 ± 27.7, and 334.7 ± 22.1 s, respectively. The periods of the first overtone in the two halves are the same considering uncertainties in the measurement. We estimate the average electron density, temperature, and length of the loop system as (5.1 ± 0.8) × 10{sup 8} cm{sup –3}, 0.65 ± 0.06 MK, and 203.8 ± 13.8 Mm, respectively. As a zeroth-order estimation, the magnetic field strength, B = 8.2 ± 1.0 G, derived by the coronal seismology using the fundamental kink mode matches with that derived by a potential field model. The extrapolation model also shows the asymmetric and nonuniform distribution of the magnetic field along the coronal loop. Using the amplitude profile distributions of both the fundamental mode and its first overtone, we observe that the antinode positions of both the fundamental mode and its first overtone shift toward the weak field region along the coronal loop. The results indicate that the density stratification and the temperature difference effects are larger than the magnetic field variation effect on the period ratio. On the other hand, the magnetic field variation has a greater effect on the eigenfunction of the first overtone than the density stratification does for this case.},
doi = {10.1088/0004-637X/799/2/151},
journal = {Astrophysical Journal},
number = 2,
volume = 799,
place = {United States},
year = {Sun Feb 01 00:00:00 EST 2015},
month = {Sun Feb 01 00:00:00 EST 2015}
}
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  • So far, the straight flux tube model proposed by Edwin and Roberts is the most commonly used tool in practical coronal seismology, in particular, to infer values of the (coronal) magnetic field from observed, standing kink mode oscillations. In this paper, we compare the period predicted by this basic model with three-dimensional (3D) numerical simulations of standing kink mode oscillations, as the period is a crucial parameter in the seismological inversion to determine the magnetic field. We perform numerical simulations of standing kink modes in both straight and curved 3D coronal loops and consider excitation by internal and external drivers.more » The period of oscillation for the displacement of dense coronal loops is determined by the loop length and the kink speed, in agreement with the estimate based on analytical theory for straight flux tubes. For curved coronal loops embedded in a magnetic arcade and excited by an external driver, a secondary mode with a period determined by the loop length and external Alfvén speed is also present. When a low number of oscillations is considered, these two periods can result in a single, non-resolved (broad) peak in the power spectrum, particularly for low values of the density contrast for which the two periods will be relatively similar. In that case (and for this particular geometry), the presence of this additional mode would lead to ambiguous seismological estimates of the magnetic field strength.« less
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