摘要：Context. A sunspot acts as a waveguide in response to the dynamics of
the solar interior; the trapped waves and oscillations could reveal its thermal and
magnetic structures.
Aims. We study the oscillations in a sunspot intruded by a light bridge,
and the details of these oscillations could reveal the fine structure of the magnetic
topology.
Methods. We used the Solar Dynamics Observatory/Atmospheric Imaging
Assembly data to analyse the oscillations in the emission intensity of light bridge plasma
at different temperatures, and we investigated their spatial distributions.
Results. The extreme ultraviolet emission intensity exhibits two
persistent oscillations at five-minute and sub-minute ranges. The spatial distribution of
the five-minute oscillation follows the spine of the bridge, whereas the sub-minute
oscillations overlap with two flanks of the bridge. Moreover, the sub-minute oscillations
are highly correlated in spatial domain, however, the oscillations at the eastern and
western flanks are asymmetric with regard to the lag time. In the meantime, jet-like
activities are only found at the eastern flank.
Conclusions. Asymmetries in the form of oscillatory pattern and jet-like
activities are found between two flanks of a granular light bridge. Based on our study and
recent findings, we propose a new model of twisted magnetic field for a light bridge and
its dynamic interactions with the magnetic field of a sunspot.
