Numerical studies of the Kelvin-Hemholtz instability in a coronal jet

Kelvin-Hemholtz (K-H) instability in a coronal EUV jet is studied via 2.5D MHD numerical simulations. The jet results from magnetic reconnection due to the interaction of the newly emerging magnetic field and the pre-existing magnetic field in the corona. Our results show that the Alfvén Mach number...

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Bibliographic Details
Published in:Research in astronomy and astrophysics 2018-04, Vol.18 (4), p.45
Main Authors: Zhao, Tian-Le, Ni, Lei, Lin, Jun, Ziegler, Udo
Format: Article
Language:English
Subjects:
Computer simulation
Corona
Current sheets
guide-field
High temperature
Instability
Islands
Kelvin-Helmholtz instability
Kelvin-Hemholtz instability
Kinetic energy
Mach number
Magnetic fields
Magnetic islands
Magnetic reconnection
method: numerical simulations
Numerical simulations
Outflow
Stability
Sun: corona jet
Vortex structure
Vortices
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Summary:Kelvin-Hemholtz (K-H) instability in a coronal EUV jet is studied via 2.5D MHD numerical simulations. The jet results from magnetic reconnection due to the interaction of the newly emerging magnetic field and the pre-existing magnetic field in the corona. Our results show that the Alfvén Mach number along the jet is about 5-14 just before the instability occurs, and it is even higher than 14 at some local areas. During the K-H instability process, several vortex-like plasma blobs with high temperature and high density appear along the jet, and magnetic fields have also been rolled up and the magnetic configuration including anti-parallel magnetic fields forms, which leads to magnetic reconnection at many X-points and current sheet fragments inside the vortex-like blob. After magnetic islands appear inside the main current sheet, the total kinetic energy of the reconnection outflows decreases, and cannot support the formation of the vortex-like blob along the jet any longer, then the K-H instability eventually disappears. We also present the results about how the guide field and flux emerging speed affect the K-H instability. We find that a strong guide field inhibits shock formation in the reconnecting upward outflow regions but helps secondary magnetic islands appear earlier in the main current sheet, and then apparently suppresses the K-H instability. As the speed of the emerging magnetic field decreases, the K-H instability appears later, the highest temperature inside the vortex blob gets lower and the vortex structure gets smaller.
ISSN:1674-4527
DOI:10.1088/1674-4527/18/4/45