Standing Kink Waves in Sigmoid Solar Coronal Loops: Implications for Coronal Seismology
Abstract
Using full threedimensional magnetohydrodynamic numerical simulations, we study the effects of magnetic field sigmoidity or helicity on the properties of the fundamental kink oscillation of solar coronal loops. Our model consists of a single denser coronal loop, embedded in a plasma with dipolar forcefree magnetic field with a constant αparameter. For the loop with no sigmoidity, we find that the numerically determined oscillation period of the fundamental kink mode matches the theoretical period calculated using WKB theory. In contrast, with increasing sigmoidity of the loop, the actual period is increasingly smaller than the one estimated by WKB theory. Translated through coronal seismology, increasing sigmoidity results in magnetic field estimates that are increasingly shifting toward higher values, and even surpassing the average value for the highest α value considered. Nevertheless, the estimated range of the coronal magnetic field value lies within the minimal/maximal limits, proving the robustness coronal seismology. We propose that the discrepancy in the estimations of the absolute value of the forcefree magnetic field could be exploited seismologically to determine the free energy of coronal loops, if averages of the internal magnetic field and density can be reliably estimated by other methods.
 Publication:

The Astrophysical Journal
 Pub Date:
 May 2020
 DOI:
 10.3847/20418213/ab8e36
 arXiv:
 arXiv:2004.14083
 Bibcode:
 2020ApJ...894L..23M
 Keywords:

 1964;
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 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 doi:10.3847/20418213/ab8e36