MHD Wave Coupling From Photosphere To Corona
Decay-less kink oscillations as a signature of resonantly driven Alfvénic turbulence
Patrick Antolin
Ineke De Moortel, Tom Van Doorsselaere, Takaaki Yokoyama
University of St Andrews, School of Mathematics and Statistics
Recent statistical studies in active regions with imaging instruments such as SDO/AIA indicate the ubiquitous presence of low amplitude kink oscillations with a surprising decay-less character, in apparent contradiction with the resonant absorption mechanism. Combining 3D MHD simulations with forward modelling we have shown recently that transverse MHD waves can lead to fine-scale structure, braiding, heating, characteristic Doppler motions and line broadening through the combination of resonant absorption and dynamic instabilities. In the present work we show how the coherency in the generated Alfvénic turbulence, namely a periodic brightening and the ensemble motion of vortices impulsed by resonant absorption, combined with line-of-sight effects at low spatial resolution can lead to an apparent decay-less oscillation of the entire flux tube. The decay-less kink oscillations in the observations may therefore correspond to the torsional Alfvén waves that are resonantly coupled to the global kink mode and that become unstable. 


13:30 - 15:00
EX - C3 (150)