  Solar coronal loops are commonly subject to oscillations. Observations of
coronal oscillations are used to infer physical properties of the coronal
plasma using coronal seismology. Excitation and evolution of oscillations in
coronal loops is typically studied using highly idealised models of magnetic
flux-tubes. In order to improve our understanding of coronal oscillations, it
is necessary to consider the effect of realistic magnetic field topology and
evolution. We study excitation and evolution of coronal oscillations in
three-dimensional self-consistent simulations of solar atmosphere spanning from
convection zone to solar corona using radiation-MHD code Bifrost. We use
forward-modelled EUV emission and three-dimensional tracing of magnetic field
to analyse oscillatory behaviour of individual magnetic loops. We further
analyse the evolution of individual plasma velocity components along the loops
using wavelet power spectra to capture changes in the oscillation periods.
Various types of oscillations commonly observed in the corona are present in
the simulation. We detect standing oscillations in both transverse and
longitudinal velocity components, including higher order oscillation harmonics.
We also show that self-consistent simulations reproduce existence of two
distinct regimes of transverse coronal oscillations: rapidly decaying
oscillations triggered by impulsive events and sustained small-scale
oscillations showing no observable damping. No harmonic drivers are detected at
the footpoints of oscillating loops. We show that coronal loop oscillations are
abundant in self-consistent 3D MHD simulations of the solar atmosphere. The
dynamic evolution and variability of individual magnetic loops suggest we need
to reevaluate our models of monolithic and static coronal loops with constant
lengths in favour of more realistic models.
