Low-amplitude decayless kink oscillations of coronal loops
MHD Wave Coupling From Photosphere To Corona
Sergey Anfinogentov
Valery Nakariakov (University of Warwick)
University of Warwick
Kink oscillations of coronal loops are found to occur in two regimes: rapidly decaying and decay-less. The former is excited by an eruptive event and characterised by large displacement amplitude (> 1Mm) and a clearly decaying profile. The latter regime was recently discovered with SDO/AIA. In contrast to the decaying oscillations, this type of transverse oscillations is not connected to any impulsive events, such as a flare or a coronal mass ejection. Decayless oscillations are found to be a common phenomenon of the non-eruptive corona. Their oscillation period is found to scale linearly with the loop length, supporting their interpretation as standing fast magnetoacoustic modes of coronal loops. It provides us with an excellent opportunity for the diagnostics of the magnetic field in the host active regions. However, analysis of these oscillations is a challenging task because of their small displacements amplitude, less than the pixel size of SDO/AIA. This issue is addressed with the motion magnification technique. It acts like a microscope for low amplitude transverse motions in image sequences (i.e. AIA data cubes), allowing for artificial magnification of low-amplitude quasi-periodic transverse displacements which become much better visible in time-distance plots and animations. This approach is found to give good results for harmonic oscillations, including amplitude and period modulated signals, and multi-modal signals. We applied the motion magnification to the SDO/AIA observations of a non-flaring active region, and obtained a clearly demonstration of the presence of low-amplitude decay-less oscillations in the majority of loops associated with the active region.


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