Detalles de publicación
PP 025076
Identification of Nonlinear Damping of Transverse Loop Oscillations by KHI-induced Turbulence
1 Department of Mathematics and Statistics, University of Exeter, UK
2 Instituto de Astrofísica de Canarias, Spain
3 Departmento de Astrofísica, Universidad de La Laguna, Spain
Kink oscillations in coronal loops have been extensively studied for their potential contributions
to coronal heating and their role in plasma diagnostics through coronal seismology. A key focus
is the strong damping of large-amplitude kink oscillations, which observational evidence suggests is
nonlinear. However, directly identifying the nonlinearity is a challenge. This work presents an analytic
formula describing nonlinear standing kink oscillations dissipated by turbulence, characterised by a
time-varying damping rate and period drift. We investigate how the damping behaviour depends
on the driving amplitude and loop properties, showing that the initial damping time τ is inversely
proportional to the velocity disturbance over the loop radius, Vi/R. Using MCMC fitting with Bayesian
inference, the nonlinear function better fits an observed decaying kink oscillation than traditional
linear models, including exponential damping, suggesting its nonlinear nature. By applying a Bayesian
model comparison, we establish regimes in which nonlinear and linear resonant absorption mechanisms
dominate based on the relationship between the damping rate τ/P and Vi/R. Additionally, analysis
of two specific events reveals that while one favours the nonlinear model, the other is better explained
by the linear model. Our results suggest that this analytical approximation of nonlinear damping due
to turbulence provides a valid and reliable description of large-amplitude decaying kink oscillations in
coronal loops.
to coronal heating and their role in plasma diagnostics through coronal seismology. A key focus
is the strong damping of large-amplitude kink oscillations, which observational evidence suggests is
nonlinear. However, directly identifying the nonlinearity is a challenge. This work presents an analytic
formula describing nonlinear standing kink oscillations dissipated by turbulence, characterised by a
time-varying damping rate and period drift. We investigate how the damping behaviour depends
on the driving amplitude and loop properties, showing that the initial damping time τ is inversely
proportional to the velocity disturbance over the loop radius, Vi/R. Using MCMC fitting with Bayesian
inference, the nonlinear function better fits an observed decaying kink oscillation than traditional
linear models, including exponential damping, suggesting its nonlinear nature. By applying a Bayesian
model comparison, we establish regimes in which nonlinear and linear resonant absorption mechanisms
dominate based on the relationship between the damping rate τ/P and Vi/R. Additionally, analysis
of two specific events reveals that while one favours the nonlinear model, the other is better explained
by the linear model. Our results suggest that this analytical approximation of nonlinear damping due
to turbulence provides a valid and reliable description of large-amplitude decaying kink oscillations in
coronal loops.