Damping Scenarios of Kink Oscillations of Solar Coronal Loops

Evolution of impulsively excited oscillations described by a randomly driven harmonic oscillator with a linear damping term. The damping coefficient is δ=0.7. The red and blue oscillatory curves correspond to different initial amplitudes. The thick curves show the exponential damping of the oscillation envelopes with the characteristic time 2/δ.

Nakariakov V. M.; Yelagandula N. V.

The transition from the large-amplitude rapidly-decaying regime of kink oscillations of plasma loops observed in the corona of the Sun to the low-amplitude decayless oscillations is modelled. In this study, the decayless regime is associated with the energy supply from coronal plasma flows, i.e., self-oscillations, or random movements of footpoints of the oscillating loop. The damping is attributed to the linear effect of resonant absorption. We demonstrate that the decay of an impulsively excited kink oscillation to the self-oscillatory stationary amplitude differs from the exponential decay. The damping time is found to depend on the oscillation amplitude to the power of a negative constant whose magnitude is less than unity. In this scenario, a better model for the damping seems to be super-exponential. In the separately considered case of the decayless oscillatory regime supported by a random driver, the oscillation amplitude experiences an exponential decay to the decayless level. Implications of this finding for magnetohydrodynamic seismology of the solar corona based on the effect of resonant absorption are discussed.