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Kinematic oscillations of post-CME blobs detected by K-Cor on 2017 September 10
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Lee, Jae-Ok, Cho , Kyung-Suk, Nakariakov, Valery M., Lee , Harim, Kim, Rok-Soon, Jang, Soojeong, Yang, Heesu, Kim, Sujin and Kim, Yeon-Han (2021) Kinematic oscillations of post-CME blobs detected by K-Cor on 2017 September 10. Journal of The Korean Astronomical Society, 54 (2). pp. 61-70. doi:10.5303/JKAS.2021.54.2.61
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WRAP-Kinematic-oscillations-post-CME-blobs-detected-K-Cor-2017-September-10-2021.pdf - Published Version - Requires a PDF viewer. Available under License Creative Commons: Attribution-Share Alike 4.0. Download (795Kb) | Preview |
Official URL: https://doi.org/10.5303/JKAS.2021.54.2.61
Abstract
We investigate 20 post-coronal mass ejection (CME) blobs formed in the post-CME current sheet (CS) that were observed by K-Cor on 2017 September 10. By visual inspection of the trajectories and projected speed variations of each blob, we find that all blobs except one show irregular "zigzag" trajectories resembling transverse oscillatory motions along the CS, and have at least one oscillatory pattern in their instantaneous radial speeds. Their oscillation periods are ranging from 30 to 91 s and their speed amplitudes from 128 to 902 km s-1. Among 19 blobs, 10 blobs have experienced at least two cycles of radial speed oscillations with different speed amplitudes and periods, while 9 blobs undergo one oscillation cycle. To examine whether or not the apparent speed oscillations can be explained by vortex shedding, we estimate the quantitative parameter of vortex shedding, the Strouhal number, by using the observed lateral widths, linear speeds, and oscillation periods of the blobs. We then compare our estimates with theoretical and experimental results from MHD simulations and fluid dynamic experiments. We find that the observed Strouhal numbers range from 0.2 to 2.1, consistent with those (0.15-3.0) from fluid dynamic experiments of bluff spheres, while they are higher than those (0.15-0.25) from MHD simulations of cylindrical shapes. We thus find that blobs formed in a post-CME CS undergo kinematic oscillations caused by fluid dynamic vortex shedding. The vortex shedding is driven by the interaction of the outward-moving blob having a bluff spherical shape with the background plasma in the post-CME CS.
| Item Type: | Journal Article | ||||||||||||||||||
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| Subjects: | Q Science > QB Astronomy | ||||||||||||||||||
| Divisions: | Faculty of Science > Physics | ||||||||||||||||||
| Library of Congress Subject Headings (LCSH): | Coronal mass ejections, Sun -- Corona, Magnetohydrodynamics, Heliosphere (Astrophysics) | ||||||||||||||||||
| Journal or Publication Title: | Journal of The Korean Astronomical Society | ||||||||||||||||||
| Publisher: | The Korean Astronomical Society | ||||||||||||||||||
| ISSN: | 1225-4614 | ||||||||||||||||||
| Official Date: | 30 April 2021 | ||||||||||||||||||
| Dates: |
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| Volume: | 54 | ||||||||||||||||||
| Number: | 2 | ||||||||||||||||||
| Page Range: | pp. 61-70 | ||||||||||||||||||
| DOI: | 10.5303/JKAS.2021.54.2.61 | ||||||||||||||||||
| Status: | Peer Reviewed | ||||||||||||||||||
| Publication Status: | Published | ||||||||||||||||||
| Access rights to Published version: | Open Access | ||||||||||||||||||
| RIOXX Funder/Project Grant: |
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