Current-sheet Oscillations Caused by the Kelvin–Helmholtz Instability at the Loop Top of Solar Flares

• Published in: Astrophysical journal. Letters 2022-06, Vol.931 (2), p.L32
• Main Authors: Wang, Yulei, Cheng, Xin, Ren, Zining, Ding, Mingde
• Format: Article
• Language: English
• Subjects: Current sheets; Emission measurements; Field strength; Kelvin-Helmholtz instability; Magnetic fields; Magnetic reconnection; Magnetohydrodynamical simulations; Measurement methods; Oscillations; Perturbation; Phase velocity; Solar flares; Solar magnetic reconnection; Transverse waves
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ac715a

Current sheets (CSs), long stretching structures of magnetic reconnection above solar flare loops, are usually observed to oscillate; their origins, however, are still puzzled at present. Based on a high-resolution 2.5D MHD simulation of magnetic reconnection, we explore the formation mechanism of CS oscillations. We find that large-amplitude transverse waves are excited by the Kelvin–Helmholtz instability at the highly turbulent cusp-shaped region. The perturbations propagate upward along the CS with a phase speed close to local Alfvén speed thus resulting in the CS oscillations we observe. Though the perturbations damp after propagating for a long distance, the CS oscillations are still detectable. In terms of detected CS oscillations, with a combination of differential emission measure techniques, we propose a new method for measuring the magnetic field strength of the CS and its distribution in height.