UK-SOSS next talk – 21st January 2021

January 11, 2021, from Chris Nelson

Dear all,

I have the pleasure of announcing the next instalment of the UK-SOSS which will take place at 10am (GMT) on 21st January 2021. Our speaker will be Prof. Valery Nakariakov from the University of Warwick. I look forward to welcoming you all to the talk at that time. The zoom link is:

Please find all other relevant details below.

All the best,
Chris Nelson (on behalf Marianna Korsos and Jiajia Liu)

“Magnetohydrodynamic Seismology of the Solar Coronal Plasma with Kink Oscillations”

Professor Valery M Nakariakov
(Centre for Fusion, Space & Astrophysics, University of Warwick, United Kingdom)

Standing transverse oscillations of the plasma loops of the solar corona have been intensively studied for the last 20 years as a tool for the diagnostics of the coronal magnetic field. Those oscillations are confidently interpreted as standing fast magnetoacoustic kink modes of the plasma non-uniformities. Statistical analysis demonstrates that, in the majority of cases, the oscillations are excited by a mechanical displacement of the loop from an equilibrium by a low coronal eruption. Standing kink oscillations are observed to operate in two regimes: rapidly decaying large amplitude oscillations and undamped small amplitude oscillations. In both these regimes, different loops oscillate with different periods that scale with the oscillating loop length. The oscillation amplitude does not show dependence on the loop length or the oscillation period. In the decayless regime the damping should be compensated by energy supply which allows the loop to perform almost monochromatic oscillations with almost constant amplitude and phase. We developed a low-dimensional model explaining the undamped kink oscillations as a self-oscillatory process caused by the effect of negative friction, which is analogous to producing a tune by moving a bow across a violin string. The period of self-oscillations is determined by the frequency of the kink mode. The ubiquity of decayless kink oscillations makes them an excellent tool for MHD seismology, in particular, for probing free magnetic energy in preflaring active regions.