Transverse loop oscillations via vortex shedding: a self oscillating process

Abstract

Identifying the underlying mechanisms behind the excitation of transverse oscillations in coronal loops is essential for their role as diagnostic tools in coronal seismology and their potential use as wave heating mechanisms of the solar corona. In this paper, we explore the concept of these transverse oscillations being excited through a self-sustaining process, caused by Alfvénic vortex shedding from strong background flows interacting with coronal loops. We show for the first time in 3D simulations that vortex shedding can generate transverse oscillations in coronal loops, in the direction perpendicular to the flow due to periodic "pushing" by the vortices. By plotting the power spectral density we identify the excited frequencies of these oscillations. We see that these frequencies are dependent both on the speed of the flow, as well as the characteristics of the oscillating loop. This, in addition to the fact that the background flow is constant and not periodic, makes us treat this as a self-oscillating process. Finally, the amplitudes of the excited oscillations are near constant in amplitude, and are comparable with the observations of decay-less oscillations. This makes the mechanism under consideration a possible interpretation of these undamped waves in coronal loops.

8 pages, 8 figures, accepted for publication in ApJL

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• Decayless oscillations in solar coronal bright points
• What drives decayless kink oscillations in active region coronal loops on the Sun?
• High frequency decayless waves with significant energy in Solar Orbiter/EUI observations
• Two-Spacecraft Detection of Short-period Decayless Kink Oscillations of Solar Coronal Loops
• Traveling kink oscillations of coronal loops launched by a solar flare
• A Statistical Investigation of Decayless Oscillations in Small-scale Coronal Loops Observed by Solar Orbiter/EUI
• Cut-off of transverse waves through the solar transition region
• 30-min Decayless Kink Oscillations in a Very Long Bundle of Solar Coronal Plasma Loops
• Decayless oscillations in 3D coronal loops excited by a power-law driver
• Forward Modeling of Simulated Transverse Oscillations in Coronal Loops and the Influence of Background Emission
• Uniturbulence and Alfven wave solar model
• Kelvin-Helmholtz instability and heating in oscillating loops perturbed by power-law transverse wave drivers
• Effects of external flow on resonant absorption of coronal loop kink oscillations driven by an external fast wave: Selective excitation problem
• Acoustic wave properties in footpoints of coronal loops in 3D MHD simulations
• Polarization of decayless kink oscillations in a 3D MHD coronal loop model
• Spectra of standing kink waves in loops and the effects of the lower solar atmosphere