  We investigate the decayless regime of coronal kink oscillations recently
discovered in the Solar Dynamics Observatory (SDO)/AIA data. In contrast to
decaying kink oscillations that are excited by impulsive dynamical processes,
this type of transverse oscillations is not connected to any external impulsive
impact, such as a flare or CME, and does not show any significant decay.
Moreover the amplitude of these decayless oscillations is typically lower than
that of decaying oscillations. The aim of this research is to estimate the
prevalence of this phenomenon and its characteristic signatures. We analysed 21
active regions (NOAA 11637--11657) observed in January 2013 in the 171 A
channel of SDO/AIA. For each active region we inspected six hours of
observations, constructing time-distance plots for the slits positioned across
pronounced bright loops. The oscillatory patterns in time-distance plots were
visually identified and the oscillation periods and amplitudes were measured.
We also estimated the length of each oscillating loop. Low-amplitude decayless
kink oscillations are found to be present in the majority of the analysed
active regions. The oscillation periods lie in the range from 1.5 to
10~minutes. In two active regions with insufficient observation conditions we
did not identify any oscillation patterns. The oscillation periods are found to
increase with the length of the oscillating loop. The considered type of
coronal oscillations is a common phenomenon in the corona. The established
dependence of the oscillation period on the loop length is consistent with
their interpretation in terms of standing kink waves.
