Evolution of Kelvin-Helmholtz Instability in the Fan-spine Topology

TY - JOUR

T1 - Evolution of Kelvin-Helmholtz Instability in the Fan-spine Topology

AU - Mishra, Sudheer K.

AU - Singh, Balveer

AU - Srivastava, A. K.

AU - Kayshap, Pradeep

AU - Dwivedi, B. N.

N1 - Publisher Copyright: © 2021. The American Astronomical Society. All rights reserved.

PY - 2021/12/13

Y1 - 2021/12/13

N2 - We use multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to study the evolution of the Kelvin-Helmholtz (K-H) instability in a fan-spine magnetic field configuration. This magnetic topology exists near an active region AR12297 and is rooted in a nearby sunspot. In this magnetic configuration, two layers of cool plasma flow in parallel and interact with each other inside an elongated spine. The slower plasma flow (5 km s-1) is the reflected stream along the spine's field lines from the top, which interacts with the impulsive plasma upflows (114-144 km s-1) from below. This process generates a shear motion and subsequent evolution of the K-H instability. The amplitude and characteristic wavelength of the K-H unstable vortices increase, satisfying the criterion of the fastest-growing mode of this instability. We also describe how the velocity difference between two layers and the velocity of K-H unstable vortices are greater than the Alfvén speed in the second denser layer, which also satisfies the criterion of the growth of the K-H instability. In the presence of the magnetic field and sheared counterstreaming plasma as observed in the fan-spine topology, we estimate the parametric constant ? = 1, which confirms the dominance of velocity shear and the evolution of the linear phase of the K-H instability. This observation indicates that in the presence of complex magnetic field structuring and flows, the fan-spine configuration may evolve into rapid heating, while the connectivity changes due to the fragmentation via the K-H instability.

AB - We use multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to study the evolution of the Kelvin-Helmholtz (K-H) instability in a fan-spine magnetic field configuration. This magnetic topology exists near an active region AR12297 and is rooted in a nearby sunspot. In this magnetic configuration, two layers of cool plasma flow in parallel and interact with each other inside an elongated spine. The slower plasma flow (5 km s-1) is the reflected stream along the spine's field lines from the top, which interacts with the impulsive plasma upflows (114-144 km s-1) from below. This process generates a shear motion and subsequent evolution of the K-H instability. The amplitude and characteristic wavelength of the K-H unstable vortices increase, satisfying the criterion of the fastest-growing mode of this instability. We also describe how the velocity difference between two layers and the velocity of K-H unstable vortices are greater than the Alfvén speed in the second denser layer, which also satisfies the criterion of the growth of the K-H instability. In the presence of the magnetic field and sheared counterstreaming plasma as observed in the fan-spine topology, we estimate the parametric constant ? = 1, which confirms the dominance of velocity shear and the evolution of the linear phase of the K-H instability. This observation indicates that in the presence of complex magnetic field structuring and flows, the fan-spine configuration may evolve into rapid heating, while the connectivity changes due to the fragmentation via the K-H instability.

UR - https://www.scopus.com/pages/publications/85122875245

U2 - 10.3847/1538-4357/ac2a43

DO - 10.3847/1538-4357/ac2a43

M3 - Article

AN - SCOPUS:85122875245

SN - 0004-637X

VL - 923

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 72

ER -